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The introduction of poly-ADP ribose polymerase (PARP) inhibitors (PARPi) has completely changed the treatment landscape of breast cancer susceptibility 1-2 (BRCA1-BRCA2)-mutant cancers and generated a new avenue of research in the fields of DNA damage response and cancer therapy. Despite this, primary and secondary resistances to PARPi have become a challenge in the clinic, and novel therapies are urgently needed to address this problem. After two decades of research, a unifying model explaining sensitivity of cancer cells to PARPi is still missing. Here, we review the current knowledge in the field and the increasing evidence pointing to a crucial role for replicative gaps in mediating sensitization to PARPi in BRCA-mutant and 'wild-type' cancer cells. Finally, we discuss the challenges to be addressed to further improve the utilization of PARPi and tackle the emergence of resistance in the clinical context., (© 2025 The Author(s).)

Centella asiatica (L.) Urban, one of the authentic medicinal materials from Guizhou Province in China, has been traditionally applied for the treatment of contusions and fractures, as well as for promoting wound healing. Preliminary research suggests that asiaticoside-nitric oxide hydrogel (ACNO) exhibits the potential to enhance the healing of diabetic wounds (DWs); however, the underlying molecular mechanisms require further elucidation. Here, we aim to identify ACNO's anti-apoptotic targets and its mode of action in DWs treatment. ACNO was applied topically on db/db and db/m mice with DWs. Wound healing was evaluated through photography, histology, and molecular analyses including molecular docking, RT-qPCR, and western blotting. The impact of ACNO on cell migration and apoptosis was assessed in hyperglycosylated HFF-1 cells using CCK-8, scratch, and cloning assays, with molecular mechanisms confirmed using a Bcl-2 inhibitor. ACNO hydrogel promotes wound epithelialization and angiogenesis in diabetic mice, and also regulates abnormal apoptosis of wound cells. In vitro studies showed that ACNO promoted the proliferation and migration of hyperglycosylated HFF-1 cells and enhanced their anti-apoptotic capacity in vitro. Further experimental studies showed that ACNO hydrogel enhances the healing process of DWs by modulating the Bcl-2/Bax/Caspase-3/PARP signaling cascade, which stimulates cell growth and movement, encourages the formation of new blood vessels, and diminishes cell death. This discovery presents a pioneering approach to harnessing the potential of traditional chinese medicine for the management of persistent and challenging injuries, including DWs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Mono(ADP-ribosyl)ation (MARylation) is emerging as a critical regulator of ribosome function and translation. Herein, we demonstrate that RACK1, an integral component of the ribosome, is MARylated by the mono(ADP-ribosyl) transferase (MART) PARP14 in ovarian cancer cells. MARylation of RACK1 is required for stress granule formation and promotes the colocalization of RACK1 in stress granules with G3BP1, eIF3η, and 40S ribosomal proteins. In parallel, we observed reduced translation of a subset of mRNAs, including those encoding key cancer regulators (e.g., AKT). Treatment with a PARP14 inhibitor or mutation of the sites of MARylation on RACK1 blocks these outcomes, as well as the growth of ovarian cancer cells in culture and in vivo. To reset the system after prolonged stress and recovery, the ADP-ribosyl hydrolase TARG1 deMARylates RACK1, leading to the dissociation of the stress granules and the restoration of translation. Collectively, our results demonstrate a therapeutically targetable pathway that controls polysome assembly, translation, and stress granule dynamics in ovarian cancer cells., (© 2025 Challa et al.)

Poly(ADP-ribosyl)ation (PARylation), catalyzed by poly(ADP-ribose) polymerases (PARPs) and hydrolyzed by poly(ADP-ribose) glycohydrolase (PARG), is an important reversible post-translational protein modification in all eukaryotes, including plant pathogenic fungi. Previously, we revealed that FonPARP1, an active PARP, is crucial for the pathogenicity of Fusarium oxysporum f. sp. niveum (Fon), the causative agent of watermelon Fusarium wilt. This study explores the enzymatic activity and substrates of FonPARP1 in regulating Fon pathogenicity. FonPARP1 is localized in nuclei of Fon macroconidia and hyphae. Essential conserved domains and a key glutamic acid residue at position 729 are critical for FonPARP1 enzyme activity and pathogenicity function in Fon. FonPARP1 interacts with protein disulfide isomerase FonPdi1 and PARylates it at 13 glutamic acid residues, affecting the interaction ability, PDI activity, ER homeostasis, and pathogenicity function. FonPARG1, interacting with both FonPARP1 and FonPdi1, hydrolyzes poly(ADP-ribose) chains from auto-PARylated FonPARP1 and FonPARP1-PARylated FonPdi1. These findings underscore the role of FonPARP1-catalyzed PARylation in regulating Fon pathogenicity and its significance in plant pathogenic fungi., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Cancer cells exploit mechanisms to evade immune detection triggered by aberrant self-nucleic acids (NA). PARP7, a key player in this immune evasion strategy, has emerged as a potential target for cancer therapy. PARP7 inhibitors reactivate NA sensing, resulting in type I interferon (IFN) signaling, programmed cell death, anti-tumor immunity, and tumor regression. Cancer cells with elevated IFN-stimulated gene (ISG) scores, representing a viral mimicry-primed state, are particularly sensitive to PARP7 inhibition. This review focuses on the endogenous sources of NA in cancer and the potential to exploit elevated aberrant self-NA in cancer therapy. We describe strategies to increase cytoplamic NA levels, including targeting epigenetic control, DNA damage response, and mitochondrial function. We also discuss targeting RNA processing pathways, such as splicing and RNA editing, to enhance the immunostimulatory potential of existing NA. Combining PARP7 inhibitors with NA elevating strategies may improve cancer immunotherapy, especially for tumors with high ISG scores., (© 2024 The Author(s). BioEssays published by Wiley Periodicals LLC.)

Viral manipulation of posttranslational modifications (PTMs) is critical to enable control over host defenses. Evidence suggests that one such PTM, adenosine 5'-diphosphate (ADP)-ribosylation, is important for viral replication, but the host and viral components involved are poorly understood. Here, we demonstrate that several human poly(ADP-ribose) polymerase (PARP) proteins, including the zinc-finger domain containing PARP7 (TiPARP) and PARP12, directly ADP-ribosylate the alphaviral nonstructural proteins (nsPs), nsP3 and nsP4. These same human PARP proteins inhibit alphavirus replication in a manner that can be antagonized by the ADP-ribosylhydrolase activity of the virally encoded macrodomain. Last, we find that knockdown of any of the three CCCH zinc-finger domain containing PARPs, PARP7, PARP12, or the enzymatically inactive PARP13 (ZAP/ZC3HAV1), attenuates the antiviral effects of interferon-γ on alphavirus replication. Combined with evolutionary analyses, these data suggest that zinc-finger PARPs share an ancestral antiviral function that can be antagonized by the activity of viral macrodomains, indicative of an ongoing evolutionary conflict between host ADP-ribosylation and viruses.

Background: Programmed cell death 1 (PD-1) signaling blockade by immune checkpoint inhibitors (ICI) effectively restores immune surveillance to treat melanoma. However, chronic interferon-gamma (IFNγ)-induced immune homeostatic responses in melanoma cells contribute to immune evasion and acquired resistance to ICI. Poly ADP ribosyl polymerase 14 (PARP14), an IFNγ-responsive gene product, partially mediates IFNγ-driven resistance. PARP14 inhibition prolongs PD-1 blockade responses in preclinical models, but fails to achieve full tumor clearance, suggesting the involvement of additional resistance mechanisms., Methods: We identified a robust PARP14 catalytic inhibitor gene signature and evaluated its association with patient survival. Using preclinical models and single-cell RNA sequencing, we investigated immune and tumor cell adaptations to PARP14 inhibition combined with PD-1 blockade., Results: Combining PARP14 inhibition and PD-1 blockade suppressed tumor-associated macrophages while increasing proinflammatory memory macrophages. Moreover, this combination mitigated the terminal exhaustion of cytotoxic T cells by inducing a quiescent state, thereby preserving functionality. Despite the enhanced immune responses, tumor cells developed adaptive resistance by engaging alternative immune evasion pathways., Conclusions: Although adaptive resistance mechanisms re-emerge, PARP14 inhibition combined with PD-1 blockade offers a promising strategy to enhance treatment outcomes and overcome ICI resistance in melanoma, as immune cells are primed for further therapeutic interventions that leverage the quiescent state., Competing Interests: Competing interests: The authors declare the following competing interests: DTI and MN were employees and shareholders of Ribon Therapeutics at the time of data collection. AH received research sponsorship from Ribon Therapeutics. All other authors declare no competing interests., (© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.)

To tolerate oxidative stress, cells enable DNA repair responses often sensitive to poly(ADP-ribose) (PAR) polymerase 1 and 2 (PARP1/2) inhibition-an intervention effective against cancers lacking BRCA1/2. Here, we demonstrate that mutating the CHD6 chromatin remodeler sensitizes cells to PARP1/2 inhibitors in a manner distinct from BRCA1, and that CHD6 recruitment to DNA damage requires cooperation between PAR- and DNA-binding domains essential for nucleosome sliding activity. CHD6 displays direct PAR-binding, interacts with PARP-1 and other PAR-associated proteins, and combined DNA- and PAR-binding loss eliminates CHD6 relocalization to DNA damage. While CHD6 loss does not impair RAD51 foci formation or DNA double-strand break repair, it causes sensitivity to replication stress, and PARP1/2-trapping or Pol ζ inhibitor-induced γH2AX foci accumulation in S-phase. DNA repair pathway screening reveals that CHD6 loss elicits insufficiency in apurinic-apyrimidinic endonuclease (APEX1) activity and genomic abasic site accumulation. We reveal APEX1-linked roles for CHD6 important for understanding PARP1/2-trapping inhibitor sensitivity., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Breast cancer represents the primary cause of death of women under 65 in developed countries, due to the acquisition of multiple drug resistance mechanisms. The PI3K/AKT pathway is one of the major regulating mechanisms altered during the development of endocrine resistance and inhibition of steps in this signalling pathway are adopted as a key strategy to overcome this issue. ADP-ribosylation is a post-translational modification catalysed by PARP enzymes that regulates essential cellular processes, often altered in diseases. PARP12, a member of this family, has been associated with the onset of drug resistance in oestrogen receptor-positive breast cancers, making this enzyme a promising drug target. The molecular basis underlying its involvement in the acquisition of resistance are unknown to date. Here, we demonstrate that PARP12-mediated mono-ADP-ribosylation of AKT is required for AKT activation whilst the absence of PARP12 leads to apoptosis induction in a subset of oestrogen receptor-positive breast cancer cells. Our data show that transcriptional inhibition of PARP12 correlates with an increased DNA-damage induction, mirrored by augmented p53 nuclear localisation and enhanced p53-AKT interaction. Under these conditions, AKT is functionally incompetent towards its downstream targets FOXO, hence favouring cell death. This is achieved by increasing protein levels of the FOXO1 transcription factor, that in turn activates the apoptotic cascade. Overall, we show a novel regulation step of AKT activation and apoptosis relying on PARP12-mediated mono-ADP-ribosylation and propose PARP12 as a potential pharmacological target to be exploited as an innovative therapeutical strategy to overcome endocrine resistance., Competing Interests: Declarations. Conflict of interest: The authors have no financial interests to disclose. Consent for publication: All authors have approved this publication. Ethical approval and consent to participate: Not applicable to this publication., (© 2025. The Author(s).)

Non-covalent interactions of poly(ADP-ribose) (PAR) facilitate condensate formation, yet the impact of these interactions on condensate properties remains unclear. Here, we demonstrate that PAR-mediated interactions through PARP13, specifically the PARP13.2 isoform, are essential for modulating the dynamics of stress granules-a class of cytoplasmic condensates that form upon stress, including types frequently observed in cancers. Single amino acid mutations in PARP13, which reduce its PAR-binding activity, lead to the formation of smaller yet more numerous stress granules than observed in the wild-type. This fragmented stress granule phenotype is also apparent in PARP13 variants with cancer-associated single-nucleotide polymorphisms (SNPs) that disrupt PAR binding. Notably, this fragmented phenotype is conserved across a variety of stresses that trigger stress granule formation via diverse pathways. Furthermore, this PAR-binding mutant diminishes condensate dynamics and impedes fusion. Overall, our study uncovers the important role of PAR-protein interactions in stress granule dynamics and maturation, mediated through PARP13., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal forms of cancer, and despite low incidence rates, it remains the sixth leading cause of cancer related deaths worldwide. Immunotherapy, which aims to enhance the immune system's ability to recognize and eliminate cancer cells, has emerged as a promising approach in the battle against PDAC. PARP7, a mono-ADP-ribosyltransferase, is a negative regulator of the type I interferon (IFN-I) pathway and has been reported to reduce anti-tumour immunity., Methods: We used murine pancreatic cancer cells, CR705, CRISPR/Cas9, in vivo tumour models and spectral flow cytometry to determine the role of PARP7 in pancreatic tumour growth., Results: Loss of Parp7 elevated the levels of interferon stimulated gene factor 3 (ISGF3) and its downstream target genes, even in the absence of STING. Cancer cells knocked out for Parp7 (CR705Parp7KO) produced smaller tumours than control cells (CR705Cas9) when injected into immunocompetent mice. Transcriptomic analyses revealed that CR705Parp7KO tumours had increased expression of genes involved in immunoregulatory interactions and interferon signalling pathways. Characterization of tumour infiltrating leukocyte (TIL) populations showed that CR705Parp7KO tumours had higher proportions of natural killer cells, CD8+ T cells and a lower proportion of anti-inflammatory macrophages (M2). The overall TIL profile of CR705Parp7KO tumours was suggestive of a less suppressive microenvironment., Conclusions: Our data show that loss of Parp7 reduces PDAC tumour growth by increasing the infiltration of immune cells and enhancing anti-tumour immunity. These findings provide support to pursue PARP7 as a therapeutic target for cancer treatment., Competing Interests: JM was a consultant for Duke Street Bio Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 Kannen, Rasmussen, Das, Giuliana, Izzati, Choksi, Erlingsson, Olafsen, Åhrling, Cappello, Teino, Maimets, Jaudzems, Gulbinas, Dambrauskas, Edgar, Grant and Matthews.)

PARP (poly-ADP ribose polymerase) has received widespread attention in cancer treatment. Research has shown that PARP plays a crucial role in DNA damage repair and has become a popular target for drug design. Based on the mechanism of "synthetic lethality", multiple PARPis (PARP inhibitors) have been launched for the treatment of BRCA deficient tumors. For example, the approved PARPis have shown significant potential in cancer treatment, particularly in breast cancer and cancers associated with BRCA1/BRCA2 deficiencies. However, the clinical efficacy and safety of PARP inhibitors in different cancers remain issues that cannot be overlooked. The design of PARPis aims to eliminate their resistance and broaden their application scope. Designing selective PARP-1 inhibitors is also a potential strategy. PROTACs (Proteolysis Targeting Chimeras) to degrade PARP have become a potential novel cancer treatment strategy.

Small-molecule inhibitors of the mono (ADP) ribosyl transferase PARP7 are being evaluated asmonotherapy for tumors overexpressing PARP7 and in combination with immune checkpoint blockade. We previously showed that sensitivity to the PARP7 inhibitor (PARP7i) RBN-2397 could be enhanced by cotreatment with agonists of the aryl hydrocarbon receptor (AHRa) in cell lines that show strong intrinsic sensitivity to RBN-2397. In this study, we demonstrated that a range of tumor cell lines that are relatively insensitive to PARP7i or AHRa as individual agents are unexpectedly profoundly sensitive to their combination. Our data show that this synergistic response is dependent on the AHR/AHR nuclear translocator and is associated with increased levels of nuclear AHR and increased transcription of AHR target genes. In some hormone receptor-positive cell lines, we find that combination treatment is associated with proteasomal turnover of the steroid hormone receptors, androgen receptor and estrogen receptor. Both wild-type and hormone-resistant mutant forms of these receptors are degraded upon treatment with AHRa and PARP7i in breast and prostate cancer models. These results suggest that combining PARP7i with AHRa may extend the utility of these drugs to a wider range of tumors, including those that are refractory to hormone therapy., (©2024 American Association for Cancer Research.)

Protein PARylation is a reversible post-translational modification; however, its role in fungal virulence has remained elusive. Recently, Gao et al. demonstrated that PARylation of two 14-3-3 regulatory proteins by poly(ADP-ribose) polymerase is essential for the virulence of rice blast fungus, highlighting the critical regulatory function of PARylation in fungal pathogenicity., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Apoptosis is a type of programmed cell death which can be induced by thyroid hormone in pituitary and other cell models. This process is characterized by several biochemical changes, including modifications in plasma membrane lipid composition, mitochondrial membrane dysfunction, and DNA fragmentation, among others. These cellular alterations can be measured using western blotting and flow cytometry techniques. Here we describe the method to detect cleavage of poly-ADP ribose polymerase by western blotting, as well as different flow cytometry-based methods to quantify the sub-G1 hypodiploid cell population, the redistribution of phosphatidylserine to the outer leaflet of plasma membrane, and the loss of the mitochondrial inner membrane potential., (© 2025. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Poly(ADP-ribose) polymerase (PARP) is a superfamily of enzymes involved in cell survival. Both PARP1 and PARP14 are overexpressed in malignancies. No clinically approved PARP14 inhibitors are available, and PARP1 inhibitors are generally nonspecific, resulting in a need for a more diverse library of selective PARP1 and PARP14 inhibitors., Materials and Methods: Based on the previous lead compounds 1 and 2 , 26 novel compounds were designed, synthesized, and screened against PARP1 and PARP14. Compounds with the best in vitro inhibitory results were further screened against PARP2, PARP3, PARP5a, PARP7, and PARP15., Results and Conclusion: The 26 novel compounds demonstrated a lesser inhibitory effect than the lead compounds. Compounds 1 and 2 were further investigated using in vitro cell viability assays, which revealed that cells treated with either lead PARP inhibitor and cisplatin in combination had significantly lower survival rates than those treated with cisplatin alone. At 10 µM, the combination showed more significant cell survival reduction, suggesting greater inhibition of PARP increases lethality, particularly in HeLa and PC-3 cell lines at 96 h and beyond.

Nicaraven has been reported to inhibit the activity of poly (ADP-ribose) polymerase (PARP). In this study, we investigated the probable ability of nicaraven to attenuate cancer radioresistance during fractionated radiotherapy. Tumor models were established in C57BL/6 mice and BALB/c nude mice by subcutaneous injection of Lewis mouse lung carcinoma cancer cells and A549 human lung cancer cells, respectively. When the tumors had grown to approximately 100 mm 3 , we initiated fractionated radiotherapy. Nicaraven or saline was administered immediately after each irradiation exposure. Compared to saline treatment, nicaraven administration significantly induced gamma-H2AX foci formation and cell apoptosis in tumors at 1 or 3 days after an additional challenge exposure to 10 Gy and inhibited tumor growth during the short-term follow-up period, suggesting increased radiosensitivity of cancer cells. Moreover, the expression of PARP in tumor tissue was decreased by nicaraven administration. Our data suggest that nicaraven likely attenuates the acquired radioresistance of cancers through PARP inhibition., Competing Interests: Declarations. Competing interests: The authors have no relevant financial or nonfinancial interests to disclose. Ethical approval: All animal experiments were approved by the Institutional Animal Care and Use Committee of Nagasaki University (No.2107071730-7) and performed following institutional and national guidelines. The mice were sacrificed under anesthesia, and all efforts were made to minimize suffering., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Cerebral amyloid angiopathy (CAA) is a neurological disorder in the elderly, involving the deposition of vascular amyloid-β (Aβ). Sleep deprivation (SD) causes memory deficits during CAA. Lysine specific demethylase 6B (KDM6B) is a histone H3 lysine 27-specific demethylase associated with neuronal injury and inflammation. However, the role of KDM6B in CAA has yet to be studied. In the current study, the multi-platform over-water method was used to induce chronic SD in APP/PS1 mice. Pathological analysis revealed that SD exacerbated vascular lesions in this model, as manifested by extensive formation of Aβ-positive deposits. In addition, SD led to a significant increase in the expression of KDM6B in the cerebral cortex of APP/PS1 mice. Next, the effect of KDM6B on CAA progression was explored through loss of function. Further experiments illustrated that KDM6B knockdown diminished SD-induced memory impairment, neuronal injury and vascular lesions in vivo. Additionally, isolated primary cortical neurons were treated with 10 µM Aβ 1-42 for 48 h to induce the cell model. As expected, knockdown of KDM6B inhibited the Aβ 1-42 -induced cytotoxicity in primary neurons. Mechanistically, our results demonstrated that KDM6B knockdown downregulated poly (ADP-ribose) polymerase16 (PARP16) expression by increasing trimethylated lysine 27 on histone 3 (H3K27me3) levels, indicating that KDM6B epigenetically regulated PARP16 expression. Function recovery experiment results further proved that PARP16 overexpression negated the effect of KDM6B knockdown on Aβ 1-42 -induced cytotoxicity. Overall, our findings uncover an unanticipated role of KDM6B in CAA, and KDM6B may serve as a potential therapeutic target for CAA. Abbreviations: CAA, cerebral amyloid angiopathy; Aβ, amyloid-β; SD, sleep deprivation; KDM6B, lysine specific demethylase 6B; AD, Alzheimer's disease; H3K27me3, trimethylated lysine 27 on histone 3; PARP16, poly (ADP-ribose) polymerase16; AAV2, adeno-associated virus 2; CHIP, chromatin immunoprecipitation; ANOVA, one-way analysis of variance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The ADP-ribosyl hydrolases PARG and ARH3 counteract PARP enzymatic activity by removing ADP-ribosylation. PARG and ARH3 activities have a synthetic lethal effect; however, the specific molecular mechanisms underlying this response remain unknown. Here, we show that the PARG and ARH3 synthetic lethality is enhanced further in the presence of DNA alkylating agents, suggesting that the inability to revert ADP-ribosylation primarily affects the repair of alkylated DNA bases. ARH3 knockout cells, treated with PARG inhibitor and alkylating genotoxins, accumulated single-stranded DNA and DNA damage, resulting in G2/M cell cycle arrest and apoptosis. Furthermore, we reveal a reduction in PARP1/PARP2 levels in ARH3-deficient cells treated with PARG inhibitor due to excessive ADP-ribosylation, which may contribute to alkylating agents' vulnerability. Collectively, these results uncover the potential of targeting ADP-ribosyl hydrolases in combination with alkylating agents for cancer therapy and provide insights into the mechanisms underlying the synthetic lethal effect., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Background: Gastric cancer (GC) is a highly malignant gastrointestinal tumor characterized by difficult early diagnosis and poor prognosis. Therefore, it is imperative to explore potential therapeutic targets for gastric cancer. PARP9 is abnormally expressed in a variety of tumors and is associated with tumor cell apoptosis and DNA damage. However, its relationship with GC has not been fully studied., Methods: The expression and prognostic significance of PARP9 in gastric cancer (GC) were examined using bioinformatics approaches. Cell lines with either knockdown or overexpression of PARP9 were established through lentiviral transduction, and the role of PARP9 in the malignant phenotypes of GC cells was validated via CCK8 assays, wound healing assays, clonogenic assays, and Transwell migration experiments. Finally, alterations in downstream targets and signaling pathways following changes in PARP9 expression were analyzed through RNA sequencing., Results: PARP9 is highly expressed in GC tissues and is associated with poor prognosis. PARP9 knockdown can significantly inhibit the proliferation, invasion and migration of GC cells, and increase the apoptosis and DNA damage of GC cells. The therapeutic process of PARP9 in GC may be realized by synergistic interaction with SOX6 through MAPK signaling pathway., Conclusions: Our study reveals a potential link between PARP9 and GC, providing a new target for the treatment of GC., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Poly (ADP-ribose) polymerase family member 11 (PARP11) has important immune regulatory functions in viral infection and tumor immune response. Particularly, PARP11 showed protumor activities in multiple preclinical murine models. However, no systematic pan-cancer analysis has been conducted to explore PARP11 function. In this study, we used multiple databases to assess PARP11 expression, which is associated with clinical outcomes, immune checkpoint factors, prognostic significance, genomic characteristics, and immunological aspects. The analysis revealed varying expression levels of PARP11 across different cancer types and a significant correlation between its expression and immune cell infiltration. Insights from the CellMiner database suggest a strong link between PARP11 expression and sensitivity to anticancer drugs, highlighting its potential as a therapeutic target. Moreover, PARP11 expression correlates with patient survival during anti-PD1 and anti-CTLA4 treatments, suggesting that PARP11 would be a predictor of immune checkpoint inhibitor treatment. In summary, PARP11 would be a potential immunoregulatory target and a diagnosis and prognosis marker for certain types of cancers. The detailed mechanisms of PARP11 in tumor immune responses need to be further investigated., Competing Interests: Conflict of interest. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

PARP enzymes transfer ADP-ribose from NAD + onto proteins as a covalent modification that regulates multiple aspects of cell biology. Here, we identify an undiscovered catalytic activity for human PARP1: de novo generation of free PAR molecules that are not attached to proteins. Free PAR production arises when a molecule of NAD + or ADP-ribose docks in the PARP1 acceptor site and attaches to an NAD + molecule bound to the donor site, releasing nicotinamide and initiating ADP-ribose chains that emanate from NAD + /ADP-ribose rather than protein. Free PAR is also produced by human PARP2 and the PARP enzyme Tankyrase. We demonstrate that free PAR in cells is generated mostly by PARP1 de novo synthesis activity rather than by PAR-degrading enzymes PAR glycohydrolase (PARG), ARH3, and TARG1 releasing PAR from protein. The coincident production of free PAR and protein-linked modifications alters models for PAR signaling and broadens the scope of PARP enzyme signaling capacity., Competing Interests: Declaration of interests J.M.P. is a co-founder of Hysplex with interests in PARP inhibitor development., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Therapeutic strategies targeting the DNA damage response, such as poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi), have revolutionized cancer treatment in tumors deficient in homologous recombination (HR). However, overcoming innate and acquired resistance to PARPi remains a significant challenge. Here, we employ a genome-wide CRISPR knockout screen and discover that the depletion of ubiquitin-activating enzyme E1 (UBA1) enhances sensitivity to PARPi in HR-proficient ovarian cancer cells. We show that silencing or pharmacological inhibition of UBA1 sensitizes multiple cell lines and organoid models to PARPi. Mechanistic studies uncover that UBA1 inhibition not only impedes HR repair to sensitize cells to PARP inhibition but also increases PARylation, which may subsequently be targeted by PARP inhibition. In vivo experiments using patient-derived xenografts demonstrate that combining PARP and UBA1 inhibition provided significant survival benefit compared to individual therapies with no detectable signs of toxicity, establishing this combination approach as a promising strategy to extend PARPi benefit., Competing Interests: Declaration of interests M.T.L. is a founder and limited partner in StemMed Ltd. and a manager in StemMed Holdings, its general partner. He is a founder and equity stakeholder in Tvardi Therapeutics Inc. Some PDXs are exclusively licensed to StemMed Ltd. resulting in royalty income to M.T.L. L.E.D. is a compensated employee of StemMed Ltd. Some PDXs are exclusively licensed to StemMed Ltd. resulting in royalty income to L.E.D. A.K.S. discloses the following competing interests: consulting (Merck, GSK, ImmunoGen, Iylon, Kiyatec, AstraZeneca, and Onxeo), shareholder (BioPath), and patent (EGFL6 antibody). T.A.Y. is Vice President and Head of Clinical Development in the Therapeutics Discovery Division at University of Texas MD Anderson Cancer Center, which has a commercial interest in DDR and other inhibitors; receives institutional research support funded by Acrivon, Artios, AstraZeneca, Bayer, Beigene, BioNTech, Blueprint, BMS, Clovis, Constellation, Cyteir, Eli Lilly, EMD Serono, Forbius, F-Star, GSK, Genentech, Haihe, Ideaya, ImmuneSensor, Ionis, Ipsen, Jounce, Karyopharm, KSQ, Kyowa, Merck, Mirati, Novartis, Pfizer, Ribon Therapeutics, Regeneron, Repare, Rubius, Sanofi, Scholar Rock, Seattle Genetics, Tesaro, Vivace, and Zenith; is a consultant for AbbVie, AstraZeneca, Acrivon, Adagene, Aduro, Almac, Amphista, Artios, Athena, Atrin, Avoro, Axiom, Baptist Health Systems, Bayer, Beigene, Boxer, BMS, C4 Therapeutics, Calithera, Cancer Res. UK, Clovis, Cybrexa, Diffusion, EMD Serono, F-Star, Genmab, Glenmark, GLG, Globe Life Sciences, GSK, Guidepoint, Idience, Ignyta, I-Mab, ImmuneSensor, Impact, Institut Gustave Roussy, Intellisphere, Jansen, Kyn, MEI Pharma, Mereo, Merck, Natera, Nexys, Novocure, OHSU, OncoSec, Ono Pharma, Pegascy, PER, Pfizer, Piper Sandler, Prolynx, Repare, resTORbio, Roche, Schrodinger, Theragnostics, Varian, Versant, Vibliome, XinThera, Zai Labs, and ZielBio; and holds stock from Seagen., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The poly(adenosine diphosphate-ribose) polymerase inhibitors (PARPi) have demonstrated efficacy in ovarian, breast, and prostate cancers, but current biomarkers do not consistently predict clinical benefit. 18 F-fluorthanatrace ( 18 F-FTT) is an analog to rucaparib, a clinically approved PARPi, and is a candidate biomarker for PARPi response. This study intends to characterize 18 F-FTT pharmacokinetics in breast cancer and optimize image timing for clinical trials. A secondary aim is to determine whether 18 F-FTT uptake in breast cancer correlates with matched frozen surgical specimens as a reference standard for PARP-1 protein. Methods: Thirty prospectively enrolled women with a new diagnosis of breast cancer were injected with 18 F-FTT and imaged dynamically 0-60 min after injection over the chest, with an optional static scan over multiple bed positions starting around 70 min. Kinetic analysis of lesion uptake was performed using blood-pool activity with population radiometabolite corrections. Normal breast and normal muscle reference tissue models were compared with PARP-1 protein expression in 10 patients with available tissue. Plasma radiometabolite concentrations and uptake in tumor and normal muscle were investigated in mouse xenografts. Results: Pharmacokinetics of 18 F-FTT were well fit by Logan plot reference region models of reversible binding. However, fits of 2-tissue compartment models assuming negligible metabolite uptake were unstable. Rapid metabolism of 18 F-FTT was demonstrated in mice, and similar uptake of radiometabolites was found in tumor xenografts and normal muscle. Tumor 18 F-FTT distribution volume ratios relative to normal muscle reference tissue correlated with tissue PARP-1 expression ( P < 0.02, n = 10). The tumor-to-normal muscle ratio from a 5-min frame between 50 and 60 min after injection, a potential static scan protocol, closely corresponded to the distribution volume ratio relative to normal muscle and correlated to PARP-1 expression ( P < 0.02, n = 10). Conclusion: This study of PARPi analog 18 F-FTT showed that uptake kinetics in vivo corresponded to expression of PARP-1 and that 18 F-FTT quantitation is influenced by radiometabolites that are increasingly present late after injection. Radiometabolites can be controlled by using optimal image acquisition timing or normal muscle reference tissue modeling in dynamic imaging or a tumor-to-normal muscle ratio. Optimal image timing for tumor-to-normal muscle quantification in humans appears to be between 50 and 60 min after injection. Therefore, a clinically practical static imaging protocol commencing 45-55 min after injection may sufficiently balance 18 F-FTT uptake with background clearance and radiometabolite interference for quantitative interpretation of PARP-1 expression in vivo., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

The coenzyme NAD + is consumed by signalling enzymes, including poly-ADP-ribosyltransferases (PARPs) and sirtuins. Ageing is associated with a decrease in cellular NAD + levels, but how cells cope with persistently decreased NAD + concentrations is unclear. Here, we show that subcellular NAD + pools are interconnected, with mitochondria acting as a rheostat to maintain NAD + levels upon excessive consumption. To evoke chronic, compartment-specific overconsumption of NAD + , we engineered cell lines stably expressing PARP activity in mitochondria, the cytosol, endoplasmic reticulum or peroxisomes, resulting in a decline of cellular NAD + concentrations by up to 50%. Isotope-tracer flux measurements and mathematical modelling show that the lowered NAD + concentration kinetically restricts NAD + consumption to maintain a balance with the NAD + biosynthesis rate, which remains unchanged. Chronic NAD + deficiency is well tolerated unless mitochondria are directly targeted. Mitochondria maintain NAD + by import through SLC25A51 and reversibly cleave NAD + to nicotinamide mononucleotide and ATP when NMNAT3 is present. Thus, these organelles can maintain an additional, virtual NAD + pool. Our results are consistent with a well-tolerated ageing-related NAD + decline as long as the vulnerable mitochondrial pool is not directly affected., Competing Interests: Competing interests: M.Z. is chief scientist at Blue Helix Health AS. All other authors declare no competing of interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Diffuse large B-cell lymphoma (DLBCL) is the most common pathological type of non-Hodgkin lymphoma, and is closely associated with hepatitis B virus (HBV) infection status and hepatitis B X (HBx) gene integration. This project investigated the cellular biological effects and molecular mechanisms responsible for lymphomagenesis and the progression of HBx integration in DLBCL. The data showed that clinical DLBCL cells demonstrated HBx integration, and the sequencing analysis of integrated sites validated HBx integration in the constructed HBx-transfected cells. Compared with control cells, HBx-transfected cells had a significantly reduced proportion of mitochondrial membrane potential, signals of chromosomal DNA breaks, and proportion of apoptotic cells. Further studies found that this decreased apoptosis level was associated with a significant reduction of cleaved Caspase-3 and downstream poly ADP-ribose polymerase (PARP) proteins, revealing the molecular mechanisms of HBx-associated apoptosis in DLBCL. Animal experiments also demonstrated that the protein expression of cleaved Caspase-3 and PARP was prominently reduced in HBx-transfected cells from subcutaneous tumors in mice. Furthermore, the HBx-integrated cells in clinical tissues had significantly lower cleaved PARP levels than the HBx-negative samples. Therefore, HBx integration inhibits cell apoptosis through the Caspase-3-PARP pathway in DLBCL indicating a potential biomarker and therapeutic target in HBV related DLBCL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Pterosin B (PB) exhibits strong neuroprotective effects in vitro, but its therapeutic effect and underlying mechanism on Alzheimer's disease (AD) remain elusive., Purpose: This study aimed to investigate the anti-AD effect and mechanism of PB., Study Design: The therapeutic effect and mechanism of PB were investigated in APP/PS1 mice and lipopolysaccharide (LPS)-induced BV-2 cells., Methods: After 8 weeks of oral administration of PB or donepezil, the cognitive function was assessed using behavioral tests. Pathological damage was evaluated using histological analysis and immunohistochemical staining. Flow cytometry was applied to detect M1/M2 polarization. The expression levels of glycolysis- and oxidative phosphorylation-related proteins as well as enzyme activities were determined using Western blot and biochemical kits, respectively. The levels of inflammatory cytokines and Kruppel-like factor 5 (Klf5) were measured using enzyme-linked immunosorbent assay. AD biomarkers in serum were analyzed using single-molecular array. RNA sequencing identified the downstream molecules of Klf5, and interaction was evaluated using dual-luciferase reporter assay., Results: Our findings demonstrated that PB effectively ameliorated cognitive impairment and reduced pathological damage in APP/PS1 mice. Furthermore, PB facilitated the transition of the phenotype of LPS-induced BV-2 cells from M1 to M2 by modulating metabolic reprogramming. Additionally, Klf5 had high expression levels in the serum of patients with AD, which strongly correlated with cognitive performance and AD biomarkers. PB downregulated Klf5 expression both in vitro and in vivo. Subsequently, poly-ADP ribosyl polymerase 14 (Parp14) was identified as a downstream molecule of Klf5 involved in regulating metabolic reprogramming, and PB regulated microglia M1/M2 polarization by inhibiting the Klf5/Parp14 pathway., Conclusion: The findings suggested that PB ameliorated cognitive dysfunction in AD by modulating microglia M1/M2 polarization via inhibiting Klf5/Parp14 pathway., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Background: Vascular leakage is a deadly complication of severe infections, ranging from bacterial sepsis to malaria. Worldwide, septicemia is among the top 10 causes of lethality because of the shock and multiorgan dysfunction that arise from the host vascular response. In the monoclonal gammopathy-associated capillary leak syndrome (MG-CLS), even otherwise mundane infections induce recurrent septic-like episodes of profound microvascular hyperpermeability and shock. There are no defined genetic risk factors for MG-CLS or effective treatments for acute crises., Methods: We characterized predicted loss-of-function mutations in PARP15 (poly[ADP-ribose] polymerase 15), a protein of unknown function that is absent in mice, in patients with MG-CLS. We analyzed barrier function in PARP15-deficient vascular endothelial cells and vascular leakage in mice engineered to express wild-type or loss-of-function variant human PARP15., Results: We discovered several loss-of-function PARP15 variants associated with MG-CLS. These mutations severely reduced PARP15 enzymatic function. The presence of the most frequently detected variant (G628R) correlated with clinical markers of severe vascular leakage. In human microvascular endothelial cells, PARP15 suppressed cytokine-induced barrier disruption by ADP-ribosylating the scaffold protein JIP3 (c-Jun N-terminal kinase-interacting protein 3) and inhibiting p38 MAP (mitogen-activated protein) kinase activation. Mice expressing enzymatically inactive human PARP15(G628R) were significantly more prone to inflammation-associated vascular leakage than mice expressing wild-type PARP15 in a p38-dependent fashion., Conclusions: PARP15 represents a previously unrecognized genetic susceptibility factor for MG-CLS. PARP15-mediated ADP ribosylation is an essential and genetically determined mechanism of the human vascular response to inflammation., Competing Interests: None.

Epithelial-to-mesenchymal transition (EMT) allows cancer cells to metastasize while acquiring resistance to apoptosis and chemotherapeutic agents with significant implications for patients' prognosis and survival. Despite its clinical relevance, the mechanisms initiating EMT during cancer progression remain poorly understood. We demonstrate that DNA damage triggers EMT and that activation of poly (ADP-ribose) polymerase (PARP) and the PARP-dependent chromatin remodeler ALC1 (CHD1L) was required for this response. Our results suggest that this activation directly facilitates access to the chromatin of EMT transcriptional factors (TFs) which then initiate cell reprogramming. We also show that EMT-TFs bind to the RAD51 promoter to stimulate its expression and to promote DNA repair by homologous recombination. Importantly, a clinically relevant PARP inhibitor reversed or prevented EMT in response to DNA damage while resensitizing tumor cells to other genotoxic agents. Overall, our observations shed light on the intricate relationship between EMT, DNA damage response, and PARP inhibitors, providing potential insights for in cancer therapeutics., Competing Interests: Conflicts of interests: The authors declare no financial conflict of interest.

The presented study covers testicular tissue and epididymal spermatozoa cryopreservation processes in bulls and aims to investigate the effects of these applications on spermatological parameters, cell viability in testicular tissue, and the expression of the PARP-1 gene, a DNA repair enzyme. Testes of 20 bulls over 2 years old, slaughtered in a slaughterhouse, were used in the study. After spermatological evaluations, the semen obtained from the cauda epididymis was frozen in liquid nitrogen vapor according to the straw method and stored in liquid nitrogen (-196 °C). Testicular tissue pieces obtained from the testicles were frozen by the slow freezing method in cryotubes in diluents containing Dimethylsulfoxide (DMSO) and Ethylene Glycol (EG) cryoprotectants and stored in liquid nitrogen (-196 °C). The total motility (TM) (85.89 ± 12.83 %), progressive motility (PM) (54.02 ± 15.77 %), and kinematic parameter values of fresh sperm were significantly higher compared to the TM (57.62 ± 13.13 %), PM (29.60 ± 10.76 %), and kinematic parameter values after thawing (P < 0.05). Significant decreases in plasma membrane integrity (PMI) and viability and an increase in chromatin condensation and morphological disorders in the head, middle part, and tail regions were observed in post-thaw semen samples (P < 0.05). When the effects of DMSO and EG on cell viability after thaw in frozen testicular tissue were evaluated, it was observed that the cell viability values of testicular tissues frozen with EG (45.70 ± 10.00) were statistically significantly lower than those frozen with DMSO (51.20 ± 7.70) (P < 0.05). When the effects of both cryoprotectants on gene expression in tissue and semen samples were examined, it was determined that gene expression increased on average 0.19 ± 0.27 times in the tissue samples in the DMSO group compared to fresh tissue samples and 0.17 ± 0.19 times in the tissue samples in the EG group. It was determined that gene expression levels increased by an average of 1.20 ± 1.08 times in post-thaw epididymal spermatozoa samples compared to fresh semen samples. The results show that cryopreservation can activate cellular repair mechanisms by stimulating PARP-1 gene expression and affect gene expression by activating specific pathways in tissues and cells., Competing Interests: Declaration of competing interest None of the authors have any conflict of interest to declare., (Copyright © 2024 Society for Cryobiology. Published by Elsevier Inc. All rights reserved.)

Poly(ADP-ribose) polymerase 1 (PARP1) is a crucial member of the PARP family, which modifies targets through ADP-ribosylation and plays key roles in a variety of biological processes. PARP inhibitors (PARPis) hinder ADP-ribosylation and lead to the retention of PARP1 at the DNA lesion (also known as trapping), which underlies their toxicity. However, inhibitors and mutations that make PARP1 inactive do not necessarily correlate with trapping potency, challenging the current understanding of inactivation-caused trapping. Recent studies on mouse models indicate that both trapping and non-trapping inactivating mutations of PARP1 lead to embryonic lethality, suggesting the unexpected toxicity of the current inhibition strategy. The allosteric model, complicated automodification, and various biological functions of PARP1 all contribute to the complexity of PARP1 inactivation., Competing Interests: Declaration of interests The authors declare no conflicts of interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Poly-ADP-ribose polymerase-14 (PARP14) can modify proteins and nucleic acids by the reversible addition of a single ADP-ribose molecule. Aberrant PARP14 functions have been related to cancer and inflammation, and its domains are involved in processes related to viral infection. Previous research indicates that PARP14 functions might be mediated via a multitude of target proteins. In vitro studies of this large multidomain enzyme have been complicated by difficulties to obtain biochemical quantities of pure protein. Here we present a strategy that allows bacterial expression and purification of a functional multidomain construct of PARP14. We substituted an internal KH domain and its neighboring unstructured region with a SUMO domain to obtain a protein construct that encompasses three macrodomains, a WWE domain, and a PARP catalytic domain. We show that the resulting construct retains both ADP-ribosyltransferase and de-MARylase activities. This construct will be useful in structural and functional studies of PARP14., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Taking into account involvement of the RNA-binding proteins in regulation of activity of poly(ADP-ribose) polymerase 1 (PARP1), a key factor of DNA repair, the effect of the intrinsically disordered protein Sam68 (Src-associated substrate during mitosis of 68 kDa) on catalytic activity of this enzyme was studied. Plasmid containing coding sequence of the Sam68 protein was obtained. Using the obtained construct, conditions for the Sam68 expression in Escherichia coli cells were optimized and procedure for protein purification was developed. It was found that Sam68 is able to regulate catalytic activity of PARP1, stimulating auto-poly(ADP-ribosyl)ation of PARP1, interacting with the damaged DNA and purified poly(ADP-ribose) (PAR). Based on the experimental data, a hypothesis on the mechanism of PARP1 activity stimulation by the Sam68 protein was proposed, which involves formation of a complex of Sam68 with poly(ADP-ribosyl)ated PARP1. Sam68 interacts with PAR, shielding its negative charge, which increases the time of PARP1 in the complex with damaged DNA and the overall yield of PAR synthesized by this enzyme.

Ischemic stroke is a high-mortality disease that urgently requires new therapeutic strategies. Insufficient cerebral blood supply can induce poly (ADP-ribose) polymerase (PARP) activation and mitochondrial dysfunction, leading to tissue damage and motor dysfunction. We demonstrate that the expression of TCDD inducible PARP (TIPARP) is elevated in ischemic stroke patients and mice. Knockdown of Tiparp reduces brain infarction and promotes recovery of motor function in ischemic stroke mice. A rationally designed TIPARP inhibitor, XG-04-B1, promotes repair of brain injury and recovery of motor function in ischemic stroke mice. Mechanistically, XG-04-B1 increases neuronal plasticity and inhibits astrocyte activation in ischemic stroke mice. In addition, eukaryotic translation initiation factor 3 subunit B (EIF3B) is a direct target of TIPARP. TIPARP interacts with EIF3B through nucleoplasmic redistribution, leading to mitochondrial dysfunction. Knockdown of Tiparp and inhibition of TIPARP via XG-04-B1 restore mitochondrial homeostasis in ischemic stroke mice. Taken together, TIPARP activation contributes to mitochondrial dysfunction and subsequent brain injury, and is therefore a promising therapeutic target for stroke., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Breast cancer is the most common malignant tumor and a major cause of mortality among women worldwide. Atramacronoid A (AM-A) is a unique natural sesquiterpene lactone isolated from the rhizome of Atractylodes macrocephala Koidz (known as Baizhu in Chinese). Our study demonstrated that AM-A triggers a specific form of cell death resembling PANoptosis-like cell death. Further analysis indicated that AM-A-induced PANoptosis-like cell death is associated with the CASP-3/PARP-GSDMD-MLKL pathways, which are mediated by mitochondrial dysfunction. These results suggest the potential of AM-A as a lead compound and offer insights for the development of therapeutic agents for breast cancer from natural products.

Host plants and various fungicides combat plant pathogens by triggering the release of excessive ROS, leading to DNA damage and subsequent cell death. The mechanisms by which the Phytophthora sojae mitigates ROS stress induced by plant immune responses and fungicides are not well understood. This study investigates the role of PsPARP1A-mediated poly (ADP-ribosylation) (PARylation) in ROS-induced DNA damage responses (DDR). Mechanistically, Phytophthora sojae poly (ADP-ribose) polymerase (PsPARP1A) interacts with meiotic recombination 11 (PsMRE11) to facilitate the accumulation of histone H2Ax phosphorylated on serine 137 (γH2Ax) in response to plant ROS-induced DNA damage. The PARylation of PsMRE11 by PsPARP1A at E5, D7, D8, and E12 is critical for the nuclear localization of PsMRE11 and the subsequent accumulation of γH2Ax during DNA damage induced by host defense-generated ROS stress in P. sojae. These findings underscore the pivotal role of the PsPARP1A-PsMRE11 axis in DNA damage repair and adaptation to ROS, thereby contributing to the virulence of P. sojae. Our study highlights the novel functions of PsPARP1/PsMRE11 in pathogenic oomycetes, linking PARylation-dependent DDR processes to their development and virulence., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Poly(ADP-ribose) polymerases 1 and 2 (PARP1 and PARP2) play a key role in DNA repair. As major sensors of DNA damage, they are activated to produce poly(ADP-ribose). PARP1/PARP2 inhibitors have emerged as effective drugs for the treatment of cancers with BRCA deficiencies. Here, we explored aminomethylmorpholino and aminomethylmorpholino glycine nucleosides as inhibitors of PARP1 and PARP2, using different enzymatic assays. The compounds bearing thymine or 5-Br(I)-uracil bases displayed the highest inhibition potency, with all of them being more selective toward PARP1. Interaction of the inhibitors with the NAD + binding cavity of PARP1 (PARP2) suggested by the mixed-type inhibition was demonstrated by molecular docking and the RoseTTAFold All-Atom AI-model. The best PARP1 inhibitors characterized by the inhibition constants in the range of 12-15 µM potentiate the cytotoxicity of hydrogen peroxide by displaying strong synergism. The inhibitors revealed no impact on PARP1/PARP2 affinity for DNA, while they reduced the dissociation rate of the enzyme-DNA complex upon the autopoly(ADP-ribosyl)ation reaction, thus providing evidence that their mechanism of action for PARP trapping is due primarily to catalytic inhibition. The most active compounds were shown to retain selectivity toward PARP1, despite the reduced inhibition potency in the presence of histone PARylation factor 1 (HPF1) capable of regulating PARP1/PARP2 catalytic activity and ADP-ribosylation reaction specificity. The inhibitors obtained seem to be promising for further research as potential drugs.

ADP-ribosylation is a reversible post-translational modification that plays a role as a signaling mechanism in various cellular processes. This modification is characterized by its structural diversity, highly dynamic nature, and short half-life. Hence, it is tightly regulated at many levels by cellular factors that fine-tune its formation, downstream signaling, and degradation that together impacts cellular outcomes. Poly-ADP-ribosylation is an essential signaling mechanism in the DNA damage response that mediates the recruitment of DNA repair factors to sites of DNA damage via their poly-ADP-ribose (PAR)-binding domains (PBDs). PAR readers, encoding PBDs, convey the PAR signal to mediate cellular outcomes that in some cases can be dictated by PAR structural diversity. Several PBD families have been identified, each with variable PAR-binding affinity and specificity, that also recognize and bind to distinct parts of the PAR chain. PARylation signaling has emerged as an attractive target for the treatment of specific cancer types, as the inhibition of PAR formation or degradation can selectively eliminate cancer cells with specific DNA repair defects and can enhance radiation or chemotherapy response. In this review, we summarize the key players of poly-ADP-ribosylation and its regulation and highlight PBDs as tools for studying PARylation dynamics and the expanding potential to target PARylation signaling in cancer treatment., (© 2024 Environmental Mutagenesis and Genomics Society.)

DNA-protein crosslinks (DPC) are common DNA lesions induced by various external and endogenous agents. One of the sources of DPC is the apurinic/apyrimidinic site (AP site) and proteins interacting with it. Some proteins possessing AP lyase activity form covalent complexes with AP site-containing DNA without borohydride reduction (suicidal crosslinks). We have shown earlier that tyrosyl-DNA phosphodiesterase 1 (TDP1) but not AP endonuclease 1 (APE1) is able to remove intact OGG1 from protein-DNA adducts, whereas APE1 is able to prevent the formation of DPC by hydrolyzing the AP site. Here we demonstrate that TDP1 can remove intact PARP2 but not XRCC1 from covalent enzyme-DNA adducts with AP-DNA formed in the absence of APE1. We also analyzed an impact of APE1 and TDP1 on the efficiency of DPC formation in APE1 -/- or TDP1 -/- cell extracts. Our data revealed that APE1 depletion leads to increased levels of PARP1-DNA crosslinks, whereas TDP1 deficiency has little effect on DPC formation., (© 2024 International Union of Biochemistry and Molecular Biology.)

Polyadenosine diphosphate-ribose polymerase 7 (PARP7) acts as a suppressor of the type I interferon (IFN) signaling pathway via suppressing TANK-binding protein 1 (TBK1). Research study indicates that inhibition of PARP7 could potentially regulate tumor immunity. However, the effect of PARP7 inhibition on innate antiviral immunity in macrophages as well as the underlying mechanism have not been demonstrated else well. We report herein that PARP7 inhibitor clinical candidate RBN-2397 could augment type I interferon (IFN-I) production in macrophages by elevating retinoic acid-inducible gene I (RIG-I) and stimulator of interferon genes (STING) signaling pathways. Treatment with RBN-2397 leads to increased pattern recognition ligands-induced interferon-β production in primary bone marrow-derived macrophages (BMDM) and RAW264.7 cells. Additionally, RBN-2397 suppresses viral replication efficiency in macrophages infected by vesicular stomatitis virus (VSV) and amplifies the expression of interferon-stimulated chemokine genes (ISGs). Mechanistically, RBN-2397 promotes TBK1 phosphorylation, consequently leading to the amplified activation of RIG-I and STING signaling pathways. Furthermore, RBN-2397 enhances the phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT2 induced by IFN-α/β and the expression of chemokine genes in macrophages in response to IFN stimulation. In vivo experiments demonstrated that RBN-2397 enhances innate antiviral immunity in mice infected with VSV, resulting in increased serum IFN-β levels, reduced viral loads, and alleviated pulmonary inflammatory responses of the VSV-infected mice. In conclusion, our findings highlight the potential of RBN-2397 as a promising antiviral therapeutic agent for enhancing the IFN-relative antiviral immune defense in host., (© 2024 Wiley Periodicals LLC.)

Purpose: Overexpression of Poly (ADP-ribose) polymerase (PARP) is associated with many diseases such as oncological diseases. Several PARP-targeting radiotracers have been developed to detect tumor in recent years. Two 18 F labelled probes based on Olaparib and Rucaparib molecular scaffolds have been evaluated in clinical trials, but their slow hepatic clearance hinders their tumor imaging performance. Although a number of positron emission tomography (PET) probes with lower liver uptake have been designed, the tumor to background ratios remains to be low. Therefore, we designed a probe with low lipid-water partition coefficient to solve this problem., Methods: A pyridine-containing quinazoline-2,4(1 H,3 H)-dione PARP-targeting group was rationally designed and used to conjugate with the chelator 2,2',2'',2'''-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) to prepare the lead compound named as SMIC-2001 for radiolabeling. In vitro experiments, the lipid-water partition coefficient, stability, binding affinity, and cellular uptake of [ 68 Ga]Ga-SMIC-2001 were determined. In vivo experiments, the U87MG xenograft models were used to evaluate its tumor imaging properties., Results: [ 68 Ga]Ga-SMIC-2001 showed a low Log D 7.4 (-3.82 ± 0.06) and high affinity for PARP-1 (48.13 nM). In vivo study revealed that it exhibited a high tumor-to-background contrast in the U87MG xenograft models and mainly renal clearance. And the ratios of tumor to main organs were high except for the kidney (e.g. tumor to liver ratio reached 2.20 ± 0.51) at 60 min p.i., Conclusion: In summary, pyridine-containing quinazoline-2,4(1 H,3 H)-dione is a novel PARP-targeting molecular scaffold for imaging probe development, and [ 68 Ga]Ga-SMIC-2001 is a highly promising PET probe capable of imaging tumors with PARP overexpression., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Vascular endothelial cytoskeletal disruption leads to increased vascular permeability and is involved in the pathogenesis and progression of various diseases. Oxidative stress can increase vascular permeability by weakening endothelial cell-to-cell junctions and decrease intracellular nicotinamide adenine dinucleotide (NAD + ) levels. However, it remains unclear how intracellular NAD + variations caused by oxidative stress alter the vascular endothelial cytoskeletal organization. In this study, we demonstrated that oxidative stress activates poly (ADP-ribose [ADPr]) polymerase (PARP), which consume large amounts of intracellular NAD + , leading to cytoskeletal disruption in vascular endothelial cells. We found that hydrogen peroxide (H 2 O 2 ) could transiently disrupt the cytoskeleton and reduce intracellular total NAD levels in human umbilical vein endothelial cells (HUVECs). H 2 O 2 stimulation led to rapid increase in ADPr protein levels in HUVECs. Pharmaceutical PARP inhibition counteracted H 2 O 2 -induced total NAD depletion and cytoskeletal disruption, suggesting that NAD + consumption by PARP induced cytoskeletal disruption. Additionally, supplementation with nicotinamide mononucleotide (NMN), the NAD + precursor, prevented both intracellular total NAD depletion and cytoskeletal disruption induced by H 2 O 2 in HUVECs. Inhibition of the NAD + salvage pathway by FK866, a nicotinamide phosphoribosyltransferase inhibitor, maintained H 2 O 2 -induced cytoskeletal disruption, suggesting that intracellular NAD + plays a crucial role in recovery from cytoskeletal disruption. Our findings provide further insights into the potential application of PARP inhibition and NMN supplementation for the treatment and prevention of diseases involving vascular hyperpermeability., Competing Interests: Declaration of competing interest The authors state no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Osteoarthritis (OA) is an age-related cartilage-degenerating joint disease. Mitochondrial dysfunction has been reported to promote the development of OA. Poly (ADP-ribose) polymerase family member 12 (PARP12) is a key regulator of mitochondrial function, protein translation, and inflammation. However, the role of PARP12 in OA-based cartilage degradation and the underlying mechanisms are relatively unknown. Here, we first demonstrated that PARP12 inhibits mitophagy and promotes OA progression in human OA cartilage and a monosodium iodoacetate-induced rat OA model. Using mass spectrometry and co-immunoprecipitation assay, PARP12 was shown to interact with ISG15, upregulate mitofusin 1 and 2 (MFN1/2) ISGylation, which downregulated MFN1/2 ubiquitination and SUMOylation, thereby inhibiting PINK1/Parkin-dependent chondrocyte mitophagy and promoting cartilage degradation. Moreover, inflammatory cytokine-induced interferon regulatory factor 1 (IRF1) activation was required for the upregulation of PARP12 expression, and it directly bound to the PARP12 promoter to activate transcription. XAV-939 inhibited PARP12 expression and suppressed OA pathogenesis in vitro and in vivo. Clinically, PARP12 can be used to predict the severity of OA; thus, it represents a new target for the study of mitophagy and OA progression. In brief, the IRF1-mediated upregulation of PARP12 promoted cartilage degradation by inhibiting PINK1/Parkin-dependent mitophagy via ISG15-based attenuation of MFN1/2 ubiquitylation and SUMOylation. Our data provide new insights into the molecular mechanisms underlying PARP12-based regulation of mitophagy and can facilitate the development of therapeutic strategies for the treatment of OA., (© 2024. The Author(s).)

Tumor hypoxia is a dynamic phenomenon marked by fluctuations in oxygen levels across both rapid (seconds to minutes) and slow (hours to days) time scales. While short hypoxia cycles are relatively well understood, the mechanisms behind longer cycles remain largely unclear. In this paper, we present a novel mechanistic mathematical model that explains slow hypoxia cycles through feedback loops involving vascular expansion and regression, oxygen-regulated tumor growth, and toxic cytokine production. Our study reveals that, for the emergence of slow hypoxia cycles, endothelial cells must adapt by decreasing receptor activation as ligand concentration increases. Additionally, the interaction between tumor cells and toxic cytokines influences frequency and intensity of these cycles. By examining the effects of pharmacological interventions, specifically poly (ADP-ribose) polymerase inhibitors, we also demonstrate how targeting cell proliferation can help regulate oxygen levels. Our findings enhance the understanding of hypoxia regulation and suggest PARP proteins as promising therapeutic targets., (© 2024. The Author(s).)

Poly (ADP-ribose) polymerase (PARP) 1 and 2 enzymatic inhibitors (PARPi) are promising cancer treatments. But recently, their use has been hindered by unexplained severe anemia and treatment-related leukemia. In addition to enzymatic inhibition, PARPi also trap PARP1 and 2 at DNA lesions. Here we report that, unlike Parp2 -/- mice, which develop normally, mice expressing catalytically inactive Parp2 (E534A and Parp2 EA/EA ) succumb to Tp53- and Chk2-dependent erythropoietic failure in utero, mirroring Lig1 -/- mice. While DNA damage mainly activates PARP1, we demonstrate that DNA replication activates PARP2 robustly. PARP2 is selectively recruited and activated by 5'-phosphorylated nicks (5'p-nicks), including those between Okazaki fragments, resolved by ligase 1 (Lig1) and Lig3. Inactive PARP2, but not its active form or absence, impedes Lig1- and Lig3-mediated ligation, causing dose-dependent replication fork collapse, which is detrimental to erythroblasts with ultra-fast forks. This PARylation-dependent structural function of PARP2 at 5'p-nicks explains the detrimental effects of PARP2 inactivation on erythropoiesis, shedding light on PARPi-induced anemia and the selection for TP53/CHK2 loss., Competing Interests: Declaration of interests D.M. is a scientific editor for Molecular Cell and therefore was not involved in the peer review or the decision-making process of this manuscript., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Pyruvate serves as a key metabolite in energy production and as an anti-oxidant. In our previous study, exogenous pyruvate starvation under high-glucose conditions induced IMS32 Schwann cell death because of the reduced glycolysis-tricarboxylic acid (TCA) cycle flux and adenosine triphosphate (ATP) production. Thus, this study focused on poly-(ADP-ribose) polymerase (PARP) to investigate the detailed molecular mechanism of cell death. Rucaparib, a PARP inhibitor, protected Schwann cells against cell death and decreased glycolysis but not against an impaired TCA cycle under high-glucose conditions in the absence of pyruvate. Under such conditions, reduced pyruvate dehydrogenase (PDH) activity and glycolytic and mitochondrial ATP production were observed but not oxidative phosphorylation or the electric transfer chain. In addition, rucaparib supplementation restored glycolytic ATP production but not PDH activity and mitochondrial ATP production. No differences in the increased activity of caspase 3/7 and the localization of apoptosis-inducing factor were found among the experimental conditions. These results indicate that Schwann cells undergo necrosis rather than apoptosis or parthanatos under the aforementioned conditions. Exogenous pyruvate plays a pivotal role in maintaining the flux in PARP-dependent glycolysis and the PARP-independent TCA cycle in Schwann cells under high-glucose conditions.

In response to DNA damage, the histone PARylation factor 1 (HPF1) regulates PARP1/2 activity, facilitating serine ADP-ribosylation of chromatin-associated factors. While PARP1/2 are known for their role in DNA single-strand break repair (SSBR), the significance of HPF1 in this process remains unclear. Here, we investigated the impact of HPF1 deficiency on cellular survival and SSBR following exposure to various genotoxins. We found that HPF1 loss did not generally increase cellular sensitivity to agents that typically induce DNA single-strand breaks (SSBs) repaired by PARP1. SSBR kinetics in HPF1-deficient cells were largely unaffected, though its absence partially influenced the accumulation of SSB intermediates after exposure to specific genotoxins in certain cell lines, likely due to altered ADP-ribosylation of chromatin. Despite reduced serine mono-ADP-ribosylation, HPF1-deficient cells maintained robust poly-ADP-ribosylation at SSB sites, possibly reflecting PARP1 auto-poly-ADP-ribosylation at non-serine residues. Notably, poly-ADP-ribose chains were sufficient to recruit the DNA repair factor XRCC1, which may explain the relatively normal SSBR capacity in HPF1-deficient cells. These findings suggest that HPF1 and histone serine ADP-ribosylation are largely dispensable for PARP1-dependent SSBR in response to genotoxic stress, highlighting the complexity of mechanisms that maintain genomic stability and chromatin remodeling., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Poly(ADP-ribose) polymerases (PARPs) are crucial nuclear proteins that play important roles in various cellular processes, including DNA repair, gene transcription, and cell death. Among the 17 identified PARP family members, PARP1 is the most abundant enzyme, with approximately 1-2 million molecules per cell, acting primarily as a DNA damage sensor. It has become a promising biological target for anticancer drug studies. Enhanced PARP expression is present in several types of tumors, such as melanomas, lung cancers, and breast tumors, correlating with low survival outcomes and resistance to treatment. PARP inhibitors, especially newly developed third-generation inhibitors currently undergoing Phase II clinical trials, have shown efficacy as anticancer agents both as single drugs and as sensitizers for chemo- and radiotherapy. This review explores the properties, characteristics, and challenges of PARP inhibitors, discussing their development from first-generation to third-generation compounds, more sustainable synthesis methods for discovery of new anti-cancer agents, their mechanisms of therapeutic action, and their potential for targeting additional biological targets beyond the catalytic active site of PARP proteins. Perspectives on green chemistry methods in the synthesis of new anticancer agents are also discussed.

Introduction: PRV infection in swine can cause devastating disease and pose a potential threat to humans. Advancing the interplay between PRV and host is essential to elucidate the pathogenic mechanism of PRV and identify novel anti-PRV targets., Methods: PARP11-KO PK-15 cells were firstly constructed by CRISPR/Cas9 technology. Next, the effect of PARP11-KO on PRV infection was determined by RT-qPCR, TCID50 assay, RNA-seq, and western blot., Results and Discussion: In this study, we identified PARP11 as a host factor that can significantly affect PRV infection. Inhibition of PARP11 and knockout of PARP11 can significantly promoted PRV infection. Subsequently, we further found that PARP11 knockout upregulated the transcription of NXF1 and CRM1, resulting in enhanced transcription of viral genes. Furthermore, we also found that PARP11 knockout could activate the autophagy pathway and suppress the mTOR pathway during PRV infection. These findings could provide insight into the mechanism in which PARP11 participated during PRV infection and offer a potential target to develop anti-PRV therapies., Competing Interests: Authors HY, DL, HO, DP, ZX were employed by Chongqing Jitang Biotechnology Research Institute Co., Ltd. Author HO was employed by Shenzhen Kingsino Technology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Qi, Zhao, Wang, Hu, Wang, Wu, Li, Zhou, Zhang, Qi, Huo, Tu, Zhong, Yuan, Lv, Yan, Ouyang, Pang and Xie.)

ADP-ribosylation (ADPRylation), which encompasses poly(ADP-ribosyl)ation and mono(ADP-ribosyl)ation, is an important post-translational modification catalysed by the poly(ADP-ribose) polymerase (PARP) enzyme superfamily. The process involves writers (PARPs) and erasers (ADP-ribose hydrolases), which work together to precisely regulate diverse cellular and molecular responses. Although the PARP-mediated synthesis of ADP-ribose (ADPr) has been well studied, ADPr degradation by degrading enzymes deserves further investigation. Nonetheless, recent studies have provided important new insights into the biology and functions of ADPr hydrolases. Notably, research has illuminated the significance of the poly(ADP-ribose) degradation pathway and its activation by the coordinated actions of poly(ADP-ribose) glycohydrolase and other ADPr hydrolases, which have been identified as key components of ADPRylation signalling networks. The degradation pathway has been proposed to play crucial roles in key cellular processes, such as DNA damage repair, chromatin dynamics, transcriptional regulation and cell death. A deep understanding of these ADPr erasing enzymes provides insights into the biological roles of ADPRylation in human health and disease aetiology and paves the road for the development of novel therapeutic strategies. This review article provides a summary of current knowledge about the biochemical and molecular functions of ADPr erasers and their physiological implications in human pathology.