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Mendelian disorders, arising from pathogenic variations within single genetic loci, often manifest as neurodevelopmental disorders (NDDs), affecting a significant portion of the pediatric population worldwide. These disorders are marked by atypical brain development, intellectual disabilities, and various associated phenotypic traits. Genetic testing aids in clinical diagnoses, but inconclusive results can prolong confirmation processes. Recent focus on epigenetic dysregulation has led to the discovery of DNA methylation signatures, or episignatures, associated with NDDs, accelerating diagnostic precision. Notably, TRIP12 and USP7, genes involved in the ubiquitination pathway, exhibit specific episignatures. Understanding the roles of these genes within the ubiquitination pathway sheds light on their potential influence on episignature formation. While TRIP12 acts as an E3 ligase, USP7 functions as a deubiquitinase, presenting contrasting roles within ubiquitination. Comparison of phenotypic traits in patients with pathogenic variations in these genes reveals both distinctions and commonalities, offering insights into underlying pathophysiological mechanisms. This review contextualizes the roles of TRIP12 and USP7 within the ubiquitination pathway, their influence on episignature formation, and the potential implications for NDD pathogenesis. Understanding these intricate relationships may unveil novel therapeutic targets and diagnostic strategies for NDDs. [ABSTRACT FROM AUTHOR]

The E3 ubiquitin ligase thyroid hormone receptor interacting protein 12 (TRIP12) has been implicated in pancreatic adenocarcinoma (PDAC) through its role in mediating the degradation of pancreas transcription factor 1a (PTF1a). PTF1a is a transcription factor essential for the acinar differentiation state that is notably diminished during the early steps of pancreatic carcinogenesis. Despite these findings, the direct involvement of TRIP12 in the onset of pancreatic cancer has yet to be established. In this study, we demonstrated that TRIP12 protein was significantly upregulated in human pancreatic preneoplastic lesions. Furthermore, we observed that TRIP12 overexpression varied within PDAC samples and PDAC‐derived cell lines. We further demonstrated that TRIP12 was required for PDAC‐derived cell growth and for the expression of E2F‐targeted genes. Acinar‐to‐ductal cell metaplasia (ADM) is a reversible process that reflects the high plasticity of acinar cells. ADM becomes irreversible in the presence of oncogenic Kras mutations and leads to the formation of preneoplastic lesions. Using two genetically modified mouse models, we showed that a loss of TRIP12 prevented acini from developing ADM in response to pancreatic injury. With two additional mouse models, we further discovered that a depletion of TRIP12 prevented the formation of KrasG12D‐induced preneoplastic lesions and impaired metastasis formation in the presence of mutated KrasG12D and Trp53R172H genes. In summary our study identified an overexpression of TRIP12 from the early stages of pancreatic carcinogenesis and proposed this E3 ubiquitin ligase as a novel regulator of acinar plasticity with an important dual role in initiation and metastatic steps of PDAC. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Mendelian disorders, arising from pathogenic variations within single genetic loci, often manifest as neurodevelopmental disorders (NDDs), affecting a significant portion of the pediatric population worldwide. These disorders are marked by atypical brain development, intellectual disabilities, and various associated phenotypic traits. Genetic testing aids in clinical diagnoses, but inconclusive results can prolong confirmation processes. Recent focus on epigenetic dysregulation has led to the discovery of DNA methylation signatures, or episignatures, associated with NDDs, accelerating diagnostic precision. Notably, TRIP12 and USP7, genes involved in the ubiquitination pathway, exhibit specific episignatures. Understanding the roles of these genes within the ubiquitination pathway sheds light on their potential influence on episignature formation. While TRIP12 acts as an E3 ligase, USP7 functions as a deubiquitinase, presenting contrasting roles within ubiquitination. Comparison of phenotypic traits in patients with pathogenic variations in these genes reveals both distinctions and commonalities, offering insights into underlying pathophysiological mechanisms. This review contextualizes the roles of TRIP12 and USP7 within the ubiquitination pathway, their influence on episignature formation, and the potential implications for NDD pathogenesis. Understanding these intricate relationships may unveil novel therapeutic targets and diagnostic strategies for NDDs.

Abstract Background Overexpressed EZH2 is oncogenically involved in the pathogenesis of different cancerous contexts including extranodal natural killer/T cell lymphoma (ENKTL). However, the underlying mechanisms of EZH2 upregulation have not been fully clarified and it is still difficult to target EZH2 in ENKTL. Results Current study identifies an E3 ligase TRIP12 that triggers K63-linked polyubiquitination of EZH2 in ENKTL and unexpectedly, stabilizes EZH2. As determined by gene expression profiling (GEP), TRIP12 and EZH2 levels correlate with each other in ENKTL patient samples. Aided by quantitative mass spectrometry (MS) and follow-up analysis, we identify K634 as the ubiquitination site of EZH2. Further study confirms that TRIP12-mediated EZH2 K634 ubiquitination enhances the interaction between EZH2 and SUZ12 or CDK1 and increases the level of EZH2 T487 phosphorylation. This study further demonstrates the TRIP12-EZH2 signaling might be regulated by cytoplasmic HSP60. Importantly, the TRIP12-EZH2 axis mediates ENKTL cell migration via accelerating epithelial-mesenchymal transition (EMT). Moreover, our study finds out dexamethasone treatment manipulates TRIP12-EZH2 signaling and may represent a novel therapeutic strategy against ENKTL metastasis. Conclusions Altogether, TRIP12 induces K63-linked site-specific polyubiquitination of EZH2 for stabilization, which promotes ENKTL cell migration and could be targeted by dexamethasone treatment.

Background: Overexpressed EZH2 is oncogenically involved in the pathogenesis of different cancerous contexts including extranodal natural killer/T cell lymphoma (ENKTL). However, the underlying mechanisms of EZH2 upregulation have not been fully clarified and it is still difficult to target EZH2 in ENKTL. Results: Current study identifies an E3 ligase TRIP12 that triggers K63-linked polyubiquitination of EZH2 in ENKTL and unexpectedly, stabilizes EZH2. As determined by gene expression profiling (GEP), TRIP12 and EZH2 levels correlate with each other in ENKTL patient samples. Aided by quantitative mass spectrometry (MS) and follow-up analysis, we identify K634 as the ubiquitination site of EZH2. Further study confirms that TRIP12-mediated EZH2 K634 ubiquitination enhances the interaction between EZH2 and SUZ12 or CDK1 and increases the level of EZH2 T487 phosphorylation. This study further demonstrates the TRIP12-EZH2 signaling might be regulated by cytoplasmic HSP60. Importantly, the TRIP12-EZH2 axis mediates ENKTL cell migration via accelerating epithelial-mesenchymal transition (EMT). Moreover, our study finds out dexamethasone treatment manipulates TRIP12-EZH2 signaling and may represent a novel therapeutic strategy against ENKTL metastasis. Conclusions: Altogether, TRIP12 induces K63-linked site-specific polyubiquitination of EZH2 for stabilization, which promotes ENKTL cell migration and could be targeted by dexamethasone treatment. [ABSTRACT FROM AUTHOR]

The Ku heterodimer, composed of subunits Ku70 and Ku80, is known for its essential role in repairing double-stranded DNA breaks via non-homologous end joining (NHEJ). We previously identified Ku70 S155 as a novel phosphorylation site within the von Willebrand A-like (vWA) domain of Ku70 and documented an altered DNA damage response in cells expressing a Ku70 S155D phosphomimetic mutant. Here, we conducted proximity-dependent biotin identification (BioID2) screening using wild-type Ku70, Ku70 S155D mutant, and Ku70 with a phosphoablative substitution (S155A) to identify Ku70 S155D-specific candidate proteins that may rely on this phosphorylation event. Using the BioID2 screen with multiple filtering approaches, we compared the protein interactor candidate lists for Ku70 S155D and S155A. TRIP12 was exclusive to the Ku70 S155D list, considered a high confidence interactor based on SAINTexpress analysis, and appeared in all three biological replicates of the Ku70 S155D-BioID2 mass spectrometry results. Using proximity ligation assays (PLA), we demonstrated a significantly increased association between Ku70 S155D-HA and TRIP12 compared to wild-type Ku70-HA cells. In addition, we were able to demonstrate a robust PLA signal between endogenous Ku70 and TRIP12 in the presence of double-stranded DNA breaks. Finally, co-immunoprecipitation analyses showed an enhanced interaction between TRIP12 and Ku70 upon treatment with ionizing radiation, suggesting a direct or indirect association in response to DNA damage. Altogether, these results suggest an association between Ku70 phospho-S155 and TRIP12. [ABSTRACT FROM AUTHOR]

Background: The MYC oncoprotein, also known as the master regulator of genes, is a transcription factor that regulates numerous physiological processes, including cell cycle control, apoptosis, protein synthesis and cell adhesion, among others. MYC is overexpressed in approximately 70% of human cancers. Given its pervasive role in cancer biology, MYC down‐regulation has become an attractive cancer treatment strategy. Methods: The CRISPR/Cas9 method was used to produce KO cell models. Western blot was used to analyzed the expressions of MYC and TATA‐binding proteinassociated factors 10 (TAF10) in cancer cells (MCF7, A549, HepG2 cells) Cell culture studies were performed to determine the mechanisms by which small molecules (Z363119456, Z363) affects MYC and TAF10 expressions and functions. Mouse studies were carried out to investigate the impact of Z363 regulation on tumor growth. Results: Z363 activate Thyroid hormone Receptor‐interacting Protein 12 (TRIP12), which phosphorylates MYC at Thr58, resulting in MYC ubiquitination and degradation and thereby regulating MYC target genes. Importantly, TRIP12 also induces TAF10 degradation, which reduces MYC protein levels. TRIP12, an E3 ligase, controls MYC levels both directly and indirectly by inhibiting MYC or TAF10 activity. Conclusions: In summary,these results demonstrate the anti‐cancer properties of Z363, a small molecule that is co‐regulated by TAF10 and MYC. [ABSTRACT FROM AUTHOR]

Clark–Baraitser syndrome is a rare autosomal dominant intellectual disability syndrome caused by pathogenic variants in the TRIP12 (Thyroid Hormone Receptor Interactor 12) gene. TRIP12 encodes an E3 ligase in the ubiquitin pathway. The ubiquitin pathway includes activating E1, conjugating E2 and ligating E3 enzymes which regulate the breakdown and sorting of proteins. This enzymatic pathway is crucial for physiological processes. A significant proportion of TRIP12 variants are currently classified as variants of unknown significance (VUS). Episignatures have been shown to represent a powerful diagnostic tool to resolve inconclusive genetic findings for Mendelian disorders and to re-classify VUSs. Here, we show the results of DNA methylation episignature analysis in 32 individuals with pathogenic, likely pathogenic and VUS variants in TRIP12. We identified a specific and sensitive DNA methylation (DNAm) episignature associated with pathogenic TRIP12 variants, establishing its utility as a clinical biomarker for Clark–Baraitser syndrome. In addition, we performed analysis of differentially methylated regions as well as functional correlation of the TRIP12 genome-wide methylation profile with the profiles of 56 additional neurodevelopmental disorders. [ABSTRACT FROM AUTHOR]

Free radicals produce in DNA a large variety of base and deoxyribose lesions that are corrected by the base excision DNA repair (BER) system. However, the C1′-oxidized abasic residue 2-deoxyribonolactone (dL) traps DNA repair lyases in covalent DNA-protein crosslinks (DPC), including the core BER enzyme DNA polymerase beta (Polβ). Polβ-DPC are rapidly processed in mammalian cells by proteasome-dependent digestion. Blocking the proteasome causes oxidative Polβ-DPC to accumulate in a ubiquitylated form, and this accumulation is toxic to human cells. In the current study, we investigated the mechanism of Polβ-DPC processing in cells exposed to the dL-inducing oxidant 1,10-copper-ortho-phenanthroline. Alanine substitution of either or both of two Polβ C-terminal residues, lysine-206 and lysine-244, enhanced the accumulation of mutant Polβ-DPC relative to the wild-type protein, and removal of the mutant DPC was diminished. Substitution of the N-terminal lysines 41, 61, and 81 did not affect Polβ-DPC processing. For Polβ with the C-terminal lysine substitutions, the amount of ubiquitin in the stabilized DPC was lowered by ∼40 % relative to wild-type Polβ. Suppression of the HECT domain-containing E3 ubiquitin ligase TRIP12 augmented the formation of oxidative Polβ-DPC and prevented Polβ-DPC removal in oxidant-treated cells. Consistent with the toxicity of accumulated oxidative Polβ-DPC, TRIP12 knockdown increased oxidant-mediated cytotoxicity. Thus, ubiquitylation of lysine-206 and lysine-244 by TRIP12 is necessary for digestion of Polβ-DPC by the proteasome as the rapid first steps of DPC repair to prevent their cytotoxic accumulation. Understanding how DPC formed with Polβ or other AP lyases are repaired in vivo is an important step in revealing how cells cope with the toxic potential of such adducts. • Ubiquitylation of K206 and K244 is required for proteolysis of Polβ-DPC. • TRIP12 E3 ubiquitin ligase targets Polβ-DPC for proteolysis. • TRIP12 protects cells from the cytotoxic effects of oxidative Polβ-DPC. [ABSTRACT FROM AUTHOR]

Wnt signaling is essential for both the development and homeostasis of diverse cellular lineages, including hematopoietic stem cells. Organism-wide, Wnt signals are tightly regulated, as overactivation of the pathway can lead to tumorigenesis. Although numerous Wnt ligands and Frizzled (Fzd) receptors exist, how particular Wnt/Fzd pairings are established and how their signals are regulated is poorly understood. We have previously identified the requirements of the cognate pairing of Wnt9a and Fzd9b for early hematopoietic stem cell proliferation. However, the specific signals governing activation, but equally important, the molecular mechanisms required to turn the signal 'off,' are unknown. Here, we show that the E3 ubiquitin ligase Trip12 (thyroid hormone receptor interactor 12) is specifically required to ubiquitinate the third intracellular loop of Fzd9b at K437, targeting it for lysosomal degradation. In contrast to other ubiquitin ligases described to regulate the cell surface availability of multiple Fzds broadly, our data indicate that Trip12 is selective for Fzd9b. We further demonstrate that this occurs through ubiquitination at K437 of Fzd9b in the third intracellular loop, ultimately leading to a decrease in Fzd9b receptor availability and in Wnt9a/Fzd9b signaling that impacts hematopoietic stem cell proliferation in zebrafish. Our results point to specific mechanisms driving the availability of different Fzd receptors. Determining how particular Fzd abundance is regulated at the membrane will be critical to developing specific therapies for human intervention.

Intellectual disability (ID) is a complicated and multifactorial condition often with an unclear cause. Advancements in diagnostic techniques have identified genetic causes in a significant proportion. Pathogenic variants in TRIP12, encoding for an E3 ligand in the ubiquitin‐protease pathway, have previously been identified as a cause of ID with autistic behavior and dysmorphic features. We report two unrelated patients with de novo mutations in TRIP12 and diagnoses of global developmental delay, autism spectrum disorder and dysmorphic features, as well as a range of other characteristics. Exome sequencing was utilized as part of an extensive genetic workup for both individuals. The genotypic and phenotypic data for both patients has been collated with previously reported data. Epilepsy was noted in about 20% published cases. One of our patents had epilepsy. These cases highlight the variable phenotypic presentations of TRIP12 variations while emphasizing the core features of ID and speech delay, with or without autistic features and epilepsy. [ABSTRACT FROM AUTHOR]

PARP inhibitors (PARPi) are increasingly used in breast cancer therapy, including high-grade triple-negative breast cancer (TNBC) treatment. Varying treatment responses and PARPi resistance with relapse currently pose limitations to the efficacy of PARPi therapy. The pathobiological reasons why individual patients respond differently to PARPi are poorly understood. In this study, we analyzed expression of PARP1, the main target of PARPi, in normal breast tissue, breast cancer, and its precursor lesions using human breast cancer tissue microarrays covering a total of 824 patients, including more than 100 TNBC cases. In parallel, we analyzed nuclear adenosine diphosphate (ADP)-ribosylation as a marker of PARP1 activity and TRIP12, an antagonist of PARPi-induced PARP1 trapping. Although we found PARP1 expression to be generally increased in invasive breast cancer, PARP1 protein levels and nuclear ADP-ribosylation were lower in higher tumor grade and TNBC samples than non-TNBCs. Cancers with low levels of PARP1 and low levels of nuclear ADP-ribosylation were associated with significantly reduced overall survival. This effect was even more pronounced in cases with high levels of TRIP12. These results indicate that PARP1-dependent DNA repair capacity may be compromised in aggressive breast cancers, potentially fueling enhanced accumulation of mutations. Moreover, the results revealed a subset of breast cancers with low PARP1, low nuclear ADP-ribosylation, and high TRIP12 levels, which may compromise their response to PARPi, suggesting a combination of markers for PARP1 abundance, enzymatic activity, and trapping capabilities might aid patient stratification for PARPi therapy., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

The deubiquitinating enzyme, USP7/ HAUSP (herpesvirus-associated ubiquitin-specific protease), is a key regulator of the tumor suppressor p53 and plays a major role in regulating genome stability. Here, we report that the protein stability of USP7 is regulated by the ubiquitin-proteasome pathway. We identified the thyroid hormone receptor interactor 12 (Trip12) as a ubiquitin E3 ligase for USP7. We also found that Trip12 affects USP7-mediated stabilization of p53 and the checkpoint proteins 53 BP1 and Chk1. Knockdown of Trip12 leads to an increased cell population in G1 phase, mimicking USP7 overexpression. In contrast, Trip12 overexpression increased the number of cells in intra-S-phase, phenocopying the USP7 knockdown phenotype. Therefore, our data reveal an important modulatory role for Trip12 in the USP7-dependent DNA damage response. [ABSTRACT FROM AUTHOR]

E3 ubiquitin ligases constitute a large family of enzymes that modify specific proteins by covalently attaching ubiquitin polypeptides. This post-translational modification can serve to regulate protein function or longevity. In spite of their importance in cell physiology, the biological roles of most ubiquitin ligases remain poorly understood. Here, we analyzed the function of the HECT domain family of E3 ubiquitin ligases in stem cell biology and tissue regeneration in planarians. Using bioinformatic searches, we identified 17 HECT E3 genes that are expressed in the Schmidtea mediterranea genome. Whole-mount in situ hybridization experiments showed that HECT genes were expressed in diverse tissues and most were expressed in the stem cell population (neoblasts) or in their progeny. To investigate the function of all HECT E3 ligases, we inhibited their expression using RNA interference (RNAi) and determined that orthologs of huwe1 , wwp1 , and trip12 had roles in tissue regeneration. We show that huwe1 RNAi knockdown led to a significant expansion of the neoblast population and death by lysis. Further, our experiments showed that wwp1 was necessary for both neoblast and intestinal tissue homeostasis as well as uncovered an unexpected role of trip12 in posterior tissue specification. Taken together, our data provide insights into the roles of HECT E3 ligases in tissue regeneration and demonstrate that planarians will be a useful model to evaluate the functions of E3 ubiquitin ligases in stem cell regulation. [ABSTRACT FROM AUTHOR]

Aberrant splicing events play important roles in the pathogenesis of acute myeloid leukemia (AML). To investigate the aberrant splicing events in AML during treatment, we carried out RNA sequencing in peripheral mononuclear cell samples from a patient with complete remission. In addition to the sequencing samples, selected splicing events were confirmed and validated with real-time quantitative RT-PCR in another seven pairs of samples. A total of 4.05 and 3.39 GB clean data of the AML and remission sample were generated, respectively, and 2,223 differentially expressed genes (DEGs) were identified. Integrated with gene expression profiling on T cells from AML patients compared with healthy donors, 82 DEGs were also differentially expressed in AML CD4 T cells and CD8 T cells. Twenty-three alternative splicing events were considered to be confidential, and they were involved in many biological processes, such as RNA processing, cellular macromolecule catabolic process, and DNA binding process. An exon3-skipping event in TRIP12 was detected in patients at remission and further validated in another three independent samples. TRIP12 is an ubiquitin ligase of ARF, which suppresses aberrant cell growth by activating p53 responses. The exon3-skipping isoform of TRIP12 increased significantly after treatment. Our results may provide new understanding of AML, and the confirmed alternative splicing event of TRIP12 may be used as potential target for future investigations. [ABSTRACT FROM AUTHOR]

Background: A sophisticated level of coordinated gene expression is necessary for skeletal muscle fibers to obtain their unique functional identities. We have previously shown that the transcription factor Sox6 plays an essential role in coordinating muscle fiber type differentiation by acting as a transcriptional suppressor of slow fiber-specific genes. Currently, mechanisms regulating the activity of Sox6 in skeletal muscle and how these mechanisms affect the fiber phenotype remain unknown. Methods: Yeast two-hybrid screening was used to identify binding partners of Sox6 in muscle. Small interfering RNA (siRNA)-mediated knockdown of one of the Sox6 binding proteins, Trip12, was used to determine its effect on Sox6 activity in C2C12 myotubes using quantitative analysis of fiber type-specific gene expression. Results: We found that the E3 ligase Trip12, a HECT domain E3 ubiquitin ligase, recognizes and polyubiquitinates Sox6. Inhibiting Trip12 or the 26S proteasome activity resulted in an increase in Sox6 protein levels in C2C12 myotubes. This control of Sox6 activity in muscle cells via Trip12 ubiquitination has significant phenotypic outcomes. Knockdown of Trip12 in C2C12 myotubes led to upregulation of Sox6 protein levels and concurrently to a decrease in slow fiber-specific Myh7 expression coupled with an increased expression in fast fiber-specific Myh4. Therefore, regulation of Sox6 cellular levels by the ubiquitin-proteasome system can induce identity-changing alterations in the expression of fiber type-specific genes in muscle cells. Conclusions: Based on our data, we propose that in skeletal muscle, E3 ligases have a significant role in regulating fiber type-specific gene expression, expanding their importance in muscle beyond their well-established role in atrophy. [ABSTRACT FROM AUTHOR]

Suggestion for a potential genetic basis to chronic rhinosinusitis (CRS) is afforded by degree of inheritability suggested from family and twin studies, existence of CRS in simple mendelian diseases, and development of sinusitis as part of the phenotype of certain gene 'knockout' murine models. Genetic association studies are expected to identify novel genes associated with CRS and suggest novel mechanisms implicated in disease development. Although these studies are subject to methodologic difficulties, associations of CRS and polymorphisms in more than 30 genes have been published, with single nucleotide polymorphisms in 3 ( IL1A, TNFA, AOAH) replicated. While the individual risk conferred by these single nucleotide polymorphisms remains modest, taken as a group, they suggest an important implication of pathways of innate immune recognition and in regulation of downstream signaling in the development of CRS. In a demonstration of these techniques' potential to identify new targets for research, the authors present a functional investigation of LAMB1, the top-rated gene from a pooling-based genome-wide association study of CRS. Upregulation of gene expression in LAMB1 and associated laminin genes in primary epithelial cells from CRS patients implicates the extracellular matrix in development of CRS and offers a new avenue for further study. [ABSTRACT FROM AUTHOR]

Abstract: Interstitial 2q36 deletion is a rare event. We report on a patient with a de novo del(2)(q36.2q36.3) interstitial deletion of the long arm of chromosome 2 diagnosed by classical banding. The phenotype comprised facial dysmorphism, enlarged kidneys with multiple renal cysts, abnormal minora labia, asymmetric lower limbs with dysplastic patella, and severe mental retardation. By physical mapping, using array-comparative genomic hybridisation (CGH) confirmed by Fluorescent In Situ Hybridisation (FISH), the breakpoints of the deletion were mapped and the size of the deletions was measured: 5.61±0.19Mb. A skin biopsy was analysed using electronic microscopy showing an alteration of the structure and organisation of the dermal and peri-neuronal basement membrane. The relation between the phenotype and the deletion of both COL4A4 and COL4A3 genes, located in 2q36.3 loci, as well as the disruption of TRIP12 were discussed. [Copyright &y& Elsevier]

Abstract: The NEDD8 pathway plays an essential role in various physiological processes, such as cell cycle progression and signal transduction. The conjugation of NEDD8 to target proteins is initiated by the NEDD8-activating enzyme composed of APP-BP1 and Uba3. In the present study, we show that APP-BP1 is degraded by ubiquitin-dependent proteolysis. To study biological functions of TRIP12, a HECT domain-containing E3 ubiquitin ligase, we used the yeast two-hybrid system and identified APP-BP1 as its binding partner. Immunoprecipitation analysis showed that TRIP12 specifically interacts with the APP-BP1 monomer but not with the APP-BP1/Uba3 heterodimer. Overexpression of TRIP12 enhanced the degradation of APP-BP1, whereas knockdown of TRIP12 stabilized it. In vitro ubiquitination assays revealed that TRIP12 functions as an E3 enzyme of APP-BP1 and additionally requires an E4 activity for polyubiquitination of APP-BP1. Moreover, neddylation of endogenous CUL1 was increased in TRIP12 knockdown cells, while complementation of the knockdown cells with TRIP12 lowered neddylated CUL1. Our data suggest that that TRIP12 promotes degradation of APP-BP1 by catalyzing its ubiquitination, which in turn modulates the neddylation pathway. [Copyright &y& Elsevier]

Simple Summary: Over the past two decades, there have been many published studies reporting high-copy SB transgenic lines in which the transposon allele includes both gene-trap and internal promoter elements to drive tumorigenesis in vivo. Cancer gene discovery from end-stage solid tumors in these studies performed by our labs and others has found few proto-oncogenic insertions. However, the question remains whether these tumors are initiated by SB insertions in proto-oncogenes to promote permissible phenotypes for tumor initiation, which become dispensable for tumor maintenance. Here, our study expands upon these indirect observations to demonstrate that high-copy SB transposon alleles designed with only gene-trap elements that inactivate genes (Onc2.3) can drive tumor initiation, progression, and maintenance to end-stage tumors in the absence of sensitizing mutations. A central challenge in cancer genomics is the systematic identification of single and cooperating tumor suppressor gene mutations driving cellular transformation and tumor progression in the absence of oncogenic driver mutation(s). Multiple in vitro and in vivo gene inactivation screens have enhanced our understanding of the tumor suppressor gene landscape in various cancers. However, these studies are limited to single or combination gene effects, specific organs, or require sensitizing mutations. In this study, we developed and utilized a Sleeping Beauty transposon mutagenesis system that functions only as a gene trap to exclusively inactivate tumor suppressor genes. Using whole body transposon mobilization in wild type mice, we observed that cumulative gene inactivation can drive tumorigenesis of solid cancers. We provide a quantitative landscape of the tumor suppressor genes inactivated in these cancers and show that, despite the absence of oncogenic drivers, these genes converge on key biological pathways and processes associated with cancer hallmarks. [ABSTRACT FROM AUTHOR]

The Thyroid hormone Receptor Interacting Protein 12 (TRIP12) protein belongs to the 28-member Homologous to the E6-AP C-Terminus (HECT) E3 ubiquitin ligase family. First described as an interactor of the thyroid hormone receptor, TRIP12's biological importance was revealed by the embryonic lethality of a murine model bearing an inactivating mutation in the TRIP12 gene. Further studies showed the participation of TRIP12 in the regulation of major biological processes such as cell cycle progression, DNA damage repair, chromatin remodeling, and cell differentiation by an ubiquitination-mediated degradation of key protein substrates. Moreover, alterations of TRIP12 expression have been reported in cancers that can serve as predictive markers of therapeutic response. The TRIP12 gene is also referenced as a causative gene associated to intellectual disorders such as Clark–Baraitser syndrome and is clearly implicated in Autism Spectrum Disorder. The aim of the review is to provide an exhaustive and integrated overview of the different aspects of TRIP12 ranging from its regulation, molecular functions and physio-pathological implications. [ABSTRACT FROM AUTHOR]