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[Display omitted] The excessive dosage of pesticides required for agronomic reality results in growing contamination of pesticide residues in environment, thus bringing high risks to crop production and human health. This study aims to unveil a novel mechanism for catabolism of two pesticides MTR and FSA facilitated by an uncharacterized Phase II reaction enzyme termed acetyltransferase-1 (ACE1) in rice and to make assessment of its potential for bioremediation to minimize the risks to crop production and food safety. We developed genetically improved cultivars overexpressing OsACE1 (OE) and knockout mutant lines by CRISPR-Cas9 technology to identify the MTR and FSA detoxic and metabolic functions and characterized their metabolites and conjugates by HPLC-LTQ-MS/MS. OsACE1 overexpression conferred rice resistance to toxicity of MTR/FSA compared to wild-type, manifested by improved plant elongation and biomass, attenuated cellular injury, and increased chlorophyll accumulation. The OE plants accumulated significantly less parent MTR/FSA and more degradative metabolites, and removed MTR/FSA from their growth medium by 1.38 and 1.61 folds over the wild-type. In contrast, knocking out OsACE1 led to compromised growth fitness and intensified toxic symptoms under MTR/FSA stress and accumulation of more toxic MTR and FSA in rice. The reduced metabolites of MTR and FSA detected in the Cas9 plants suggest the impaired capability of OsACE1 function. These results signified that OsACE1 expression is required for detoxifying the two poisoning chemicals in rice and plays a critical role in accelerating breakdown of the pesticides mainly through Phase II reaction mechanism pathways. [ABSTRACT FROM AUTHOR]

The histone acetyltransferase HBO1, also known as KAT7, is a major chromatin modifying enzyme responsible for H3 and H4 acetylation. It is found within two distinct tetrameric complexes, the JADE subunit-containing complex and BRPF subunit-containing complex. The HBO1-JADE complex acetylates lysine 5, 8 and 12 of histone H4, and the HBO1-BRPF complex acetylates lysine 14 of histone H3. HBO1 regulates gene transcription, DNA replication, DNA damage repair, and centromere function. It is involved in diverse signaling pathways and plays crucial roles in development and stem cell biology. Recent work has established a strong relationship of HBO1 with the histone methyltransferase MLL/KMT2A in acute myeloid leukemia. Here, we discuss functional and pathological links of HBO1 to cancer, highlighting the underlying mechanisms that may pave the way to the development of novel anti-cancer therapies. • HBO1 acetyltransferase, or KAT7, is a major chromatin modifying enzyme. • HBO1 catalyzes acetylation of histone H3 and H4. • HBO1 regulates gene transcription and genome stability. • HBO1 and MLL complexes cooperate and activate transcription in leukemogenesis. • HBO1 is a potential pharmacological target for a broad spectrum of cancers. [ABSTRACT FROM AUTHOR]

[Display omitted] Synthesis of proteolysis targeting chimeras (PROTACs) involves conjugation of an E3 ligase binding ligand to a ligand targeting a protein of interest via a rigid or flexible chemical linker. The choice of linker conjugation site on these ligands can be informed by structural analysis of ligand-target binding modes, the feasibility of synthetic procedures to access specific sites, and computational modeling of predicted ternary complex formations. Small molecules that target bromodomains - epigenetic readers of lysine acetylation - typically offer several potential options for linker conjugation sites. Here we describe how varying the linker attachment site (exit vector) on a CBP/p300 bromodomain ligand along with linker length affects PROTAC degradation activity and ternary complex formation. Using kinetic live cell assays of endogenous CBP and p300 protein abundance and bead-based proximity assays for ternary complexes, we describe the structure-activity relationships of a diverse library of CBP/p300 degraders (dCBPs). [ABSTRACT FROM AUTHOR]

New approaches to treat ovarian cancer, the fifth leading cause of cancer mortality among women, are being sought, with the targeting of epigenetic modulators now receiving much attention. The histone acetyltransferase HBO1 functions in regulating diverse molecular processes, including DNA repair, transcription and replication, and is highly expressed in primary ovarian cancer. Here we define both the molecular function and a role in cell biomechanics for HBO1 in ovarian cancer. HBO1 preferentially acetylates histone H4 through the concomitant overexpression of co-regulator JADE2, and is required for the expression of YAP1, an ovarian cancer oncogene and mechano-transductor signaling factor. HBO1 appears therefore to have a role in determining the mechano-phenotype in ovarian cancer cells, through both signal transduction processes, and the modulation of cell elasticity as observed using direct measurements on live cells via atomic force microscopy. The histone acetyltransferase HBO1 is overexpressed in ovarian cancer cell lines and exerts specific epigenetic regulation through the assembly and targeting of multi-protein complexes, which include JADE scaffolding subunits. This study showed that HBO1 preferentially targets histone H4 for acetylation, and has a significant involvement in the regulation of mechano-transduction pathways and cell elasticity in ovarian cancer cells. Unlabelled Image [ABSTRACT FROM AUTHOR]

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, Rox), a widely used organoarsenical feed additive, can enter soils and be further biotransformed into various arsenic species that pose human health and ecological risks. However, the pathway and molecular mechanism of Rox biotransformation by soil microbes are not well studied. Therefore, in this study, we isolated a Rox-transforming bacterium from manure-fertilized soil and identified it as Pseudomonas chlororaphis through morphological analysis and 16S rRNA gene sequencing. Pseudomonas chlororaphis was able to biotransform Rox to 3-amino-4-hydroxyphenylarsonic acid (3-AHPAA), N -acetyl-4-hydroxy- m -arsanilic acid (N-AHPAA), arsenate [As(V)], arsenite [As(III)], and dimethylarsenate [DMAs(V)]. The complete genome of Pseudomonas chlororaphis was sequenced. PcmdaB, encoding a nitroreductase, and PcnhoA, encoding an acetyltransferase, were identified in the genome of Pseudomonas chlororaphis. Expression of PcmdaB and PcnhoA in E. coli Rosetta was shown to confer Rox(III) and 3-AHPAA(III) resistance through Rox nitroreduction and 3-AHPAA acetylation, respectively. The PcMdaB and PcNhoA enzymes were further purified and functionally characterized in vitro. The kinetic data of both PcMdaB and PcNhoA were well fit to the Michaelis-Menten equation, and nitroreduction catalyzed by PcMdaB is the rate-limiting step for Rox transformation. Our results provide new insights into the environmental risk assessment and bioremediation of Rox(V)-contaminated soils. [Display omitted] • Pseudomonas chlororaphis was isolated as a Rox-transforming strain from soil. • A nitroreductase gene (PcmdaB) and an acetyltransferase gene (PcmdaB) were identified. • PcmdaB and PcnhoA expression confers Rox(III) and 3-AHPAA(III) resistance in E. coli. • PcMdaB and PcNhoA enzymes catalyze Rox nitroreduction and 3-AHPAA acetylation. • Nitroreduction is the rate-limiting step for Rox transformation. [ABSTRACT FROM AUTHOR]

Nα-acetyltransferase 10 protein (Naa10p) is known as the catalytic subunit of N-terminal acetyltransferases A (NatA) complex, associating with Naa15p to acetylate N-termini of the human proteome. Recent investigations have unveiled additional functions for Naa10p, encompassing lysine ε-acetylation and acetyltransferase-independent activities. Its pleiotropic roles have been implicated in diverse physiological and pathological contexts. Emerging evidence has implicated Naa10p in cancer progression, demonstrating dual attributes as an oncogene or a tumor suppressor contingent on the cancer type and acetyltransferase activity context. In this comprehensive review, we present a pan-cancer analysis aimed at elucidating the intricacies underlying Naa10p dysregulation in cancer. Our findings propose the potential involvement of c-Myc as a modulatory factor influencing Naa10p expression. Moreover, we provide a consolidated summary of recent advancements in understanding the intricate molecular underpinnings through which Naa10p contributes to cancer cell proliferation and metastasis. Furthermore, we delve into the multifaceted nature of Naa10p's roles in regulating cancer behaviors, potentially attributed to its interactions with a repertoire of partner proteins. Through an exhaustive exploration of Naa10p's functions, spanning its acetylation activity and acetyltransferase-independent functionalities, this review offers novel insights with implications for targeted therapeutic strategies involving this pivotal protein in the realm of cancer therapeutics. • Across multiple cancers, NAA10 expression in tumors is linked to poor or favorable survival predictions. • The comprehensive TCGA analysis across cancers suggests c-Myc as a potential regulator of NAA10 expression. • Naa10p drives cancer cell proliferation by influencing the cell cycle, apoptosis, autophagy, and related gene expressions. • Naa10p modulates cancer metastasis with diverse partners, including proteases and protease inhibitors. • NAA10 links to pathways involved in mitochondria, ribosomes, spliceosomes, and proteasomes, paving future research. [ABSTRACT FROM AUTHOR]

Abstract A simple and sensitive turn-off electrogenerated chemiluminescence (ECL) biosensor was designed for the analysis of histone acetyltransferases (HATs) activity and inhibitor evaluation based on the anti-hydrolysis ability of acetylated peptide and mimetic superoxide dismutase (SOD) features of tannic acid (TA) assembled gold nanoparticles (AuNPs) nanoprobes. In this strategy, after the acetylated reaction in the presence of HATs, the acetylated peptide on electrode was resistance to the hydrolysis of trypsin, and can absorb AuNPs@TA-Fe probe onto the electrode by the hydrophobic interaction and hydrogen bonding interaction. Thus, the ECL signal of the modified electrode in luminol solution decreased significantly owing to the mimetic SOD features of the TA assembled nanoprobe that can eliminate the reactive oxygen species. The ECL intensity changes can be utilized for sensitive HATs activities detection and inhibitor screening. The detection limit of the as-prepared ECL biosensor was 0.074 nM (S/N = 3). Moreover, the as designed ECL biosensor was also applied in MCF-7 cell lysates for HATs activity analysis and drug inhibition, which is feasible to HATs activity analysis and inhibitor screening, and presents highly promise in HAT-related clinical diagnostics. Highlights • A turn-off ECL biosensor for HATs activity analysis and inhibition was first designed. • Mimetic SOD features of TA assembled AuNPs nanoprobes was successfully prepared. • A strategy based on mimetic SOD nanoprobes was developed with sensitivity and selectivity. • The biosensor was applied in cell lysates and showed promise in HATs-related research. [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MELs) are biosurfactants produced from feedstocks by basidiomycetous yeasts. MELs exhibit different properties depending on their structures, such as the degree of acetylation or acylation and the chirality of the mannosylerythritol moiety. Pseudozyma tsukubaensis produces a diastereomer type of MEL-B (mono-acetylated MEL); therefore, deletion of an acetyltransferase could yield a diastereomer type of MEL-D (deacetylated MEL), which has only been produced in in vitro reactions of lipase using MEL-B as a substrate. Here, we deleted the gene PtMAT1 in P. tsukubaensis 1E5 encoding an acetyltransferase related to MEL biosynthesis via targeted gene deletion and generated a producer of the diastereomer type of MEL-D. The uracil auxotrophic mutant of P. tsukubaensis 1E5 (PtURA5 -mutant) was used as a host strain for gene deletion. The gene PtMAT1 was replaced with a PtURA5 cassette by homologous recombination using uracil auxotrophy as a selectable marker. According to thin-layer chromatography and nuclear magnetic resonation spectroscopy, we identified the strain Δ PtMAT1 as a producer of the diastereomer type of MEL-D instead of MEL-B. [ABSTRACT FROM AUTHOR]

Carnitine/choline acyltransferases play diverse roles in energy metabolism and neuronal signalling. Our knowledge of their evolutionary relationships, important for functional understanding, is incomplete. Therefore, we aimed to determine the evolutionary relationships of these eukaryotic transferases. We performed extensive phylogenetic and intron position analyses. We found that mammalian intramitochondrial CPT2 is most closely related to cytosolic yeast carnitine transferases (Sc-YAT1 and 2), whereas the other members of the family are related to intraorganellar yeast Sc-CAT2. Therefore, the cytosolically active CPT1 more closely resembles intramitochondrial ancestors than CPT2. The choline acetyltransferase is closely related to carnitine acetyltransferase and shows lower evolutionary rates than long chain acyltransferases. In the CPT1 family several duplications occurred during animal radiation, leading to the isoforms CPT1A, CPT1B and CPT1C. In addition, we found five CPT1-like genes in Caenorhabditis elegans that strongly group to the CPT1 family. The long branch leading to mammalian brain isoform CPT1C suggests that either strong positive or relaxed evolution has taken place on this node. The presented evolutionary delineation of carnitine/choline acyltransferases adds to current knowledge on their functions and provides tangible leads for further experimental research. [ABSTRACT FROM AUTHOR]

The aminoglycoside, 6′- N -acetyltransferase type Ib [AAC(6')-Ib] is the most widely distributed enzyme among AAC(6')-I-producing Gram-negative pathogens and confers resistance to clinically relevant aminoglycosides, including amikacin. This enzyme is therefore an ideal target for enzymatic inhibitors that could overcome resistance to aminoglycosides. The search for inhibitors was carried out using mixture-based combinatorial libraries, the scaffold ranking approach, and the positional scanning strategy. A library with high inhibitory activity had pyrrolidine pentamine scaffold and was selected for further analysis. This library contained 738,192 compounds with functionalities derived from 26 different amino acids (R1, R2 and R3) and 42 different carboxylic acids (R4) in four R–group functionalities. The most active compounds all contained S-phenyl (R1 and R3) and S-hydromethyl (R2) functionalities at three locations and differed at the R4 position. The compound containing 3-phenylbutyl at R4 (compound 206 ) was a robust enzymatic inhibitor in vitro, in combination with amikacin it potentiated the inhibition of growth of three resistant bacteria in culture, and it improved survival when used as treatment of Galleria mellonella infected with aac(6')-Ib -harboring Klebsiella pneumoniae and Acinetobacter baumannii strains. [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MELs) are produced by several smut fungi of the Ustilaginaceae family; they are promising microbial biosurfactants and have excellent surface-active and self-assembling properties. Pseudozyma hubeiensis is a candidate for abundant MEL production and produces large amounts of 4- O -[(4′-mono- O -acetyl-2′,3′-di- O -alkanoyl)-β- d -mannopyranosyl]- meso -erythritol (MEL-C). An acetyltransferase disruption mutant of P. hubeiensis , SY62-MM36, was obtained to selectively produce deacetylated 4- O -[(2′,3′-di- O -alkanoyl)-β- d -mannopyranosyl]- meso -erythritol (MEL-D), and the structures of the products were determined. Lower mobility of major spots of the mutant on silica gel thin-layer chromatography verified its more hydrophilic nature than that of wild-type MEL-A, B, and C. Structural analyses confirmed the product to be MEL-D, which comprises acyl chains of caproic acid (C6:0), capric acid (C10:0), and lauric acid (C12:0). The critical micelle concentration (CMC) and the surface tension (γCMC) of the MEL-D were 2.0 × 10 −5 M and 29.7 mN/m, respectively. SY62-MM36 also produced a minor product that was estimated as triacylated MEL-D. The triacylated MEL-D had a CMC of 3.5 × 10 −5 M and a γCMC of 29.6 mN/m. In water, MEL-D formed a lamella liquid crystal phase over a broad range of concentrations. By fed-batch cultivation, the mutant produced 91.6 ± 6.3 g/L of MEL-D for 7 days. [ABSTRACT FROM AUTHOR]

Among post-translational modifications of proteins, acetylation, phosphorylation, and ubiquitination are most extensively studied over the last several decades. Owing to their different target residues for modifications, cross-talk between phosphorylation with that of acetylation and ubiquitination is relatively less pronounced. However, since canonical acetylation and ubiquitination happen only on the lysine residues, an overlap of the same lysine residue being targeted for both acetylation and ubiquitination happens quite frequently and thus plays key roles in overall functional regulation predominantly through modulation of protein stability. In this review, we discuss the cross-talk of acetylation and ubiquitination in the regulation of protein stability for the functional regulation of cellular processes with an emphasis on transcriptional regulation. Further, we emphasize our understanding of the functional regulation of Super Elongation Complex (SEC)-mediated transcription, through regulation of stabilization by acetylation, deacetylation and ubiquitination and associated enzymes and its implication in human diseases. [ABSTRACT FROM AUTHOR]

l -arginine is used as a source of both carbon and nitrogen in Mycobacterium tuberculosis ( Mtb ) and its biosynthesis is essential for the pathogen's survival. Mtb ArgA (Rv2747) catalyzes the initial step in l -arginine biosynthesis by transferring an acetyl group from acetyl coenzyme A (AcCoA) to l -glutamate. Mtb ArgA is a class III N -acetylglutamate synthase (NAGS) with no structural information. Here, we solved the crystal structure of Mtb ArgA complexed with AcCoA and l -glutamate. The overall structure adopts a classic fold of the GCN5-related N -acetyltransferase (GNAT) family, characterized by a “V”-shaped cleft and β-bulge, but uses distinct residues for the binding and reaction of AcCoA. In particular, its activity depends on dimerization to form a deep, vast pocket for l -glutamate binding. Interestingly, in the structure, l -glutamate binds at a site far away from AcCoA, implying a mechanism of separate capture and catalysis. Additionally, based on a docking model of l -glutamate at the catalytic site, a one-step sequential mechanism was proposed for enzymatic catalysis. Important sites for substrate binding and catalysis were also evaluated by site-directed mutagenesis study and activity analysis. The unique features of the Mtb ArgA structure will provide useful insights for inhibitor design and anti-tuberculosis drug discovery. [ABSTRACT FROM AUTHOR]

Background: Ogden syndrome is a rare X-linked disorder caused by pathogenic variants in the NAA10 gene. This syndrome, reported in just over 20 children, has been associated with dysmorphic features, failure to thrive, developmental impairments, hypotonia, and cardiac arrhythmias.Patient Description: We describe a 14-year-old girl who presented in infancy with hypotonia, global developmental delay, and dysmorphic features. She later developed autism spectrum disorder, epileptic encephalopathy, extrapyramidal signs, early morning lethargy with hypersomnolence, and hypertension with left ventricular hypertrophy. Magnetic resonance imaging showed a thin corpus callosum and progressive white matter loss. Whole exome sequencing identified a de novo pathogenic variant in the NAA10 gene (c.247C>T, p.R83C). Much of her early presentation was in keeping with what has been previously described with Ogden syndrome.Conclusions: We have identified additional evolving neurological impairments in this, to date, oldest documented girl with Ogden syndrome. We recommend screening patients with Ogden syndrome for these newly identified features of early life trajectories to guide management. [ABSTRACT FROM AUTHOR]

Summary Although histone-modifying enzymes are generally assumed to function in a manner dependent on their enzymatic activities, this assumption remains untested for many factors. Here, we show that the Tip60 (Kat5) lysine acetyltransferase (KAT), which is essential for embryonic stem cell (ESC) self-renewal and pre-implantation development, performs these functions independently of its KAT activity. Unlike ESCs depleted of Tip60 , KAT-deficient ESCs exhibited minimal alterations in gene expression, chromatin accessibility at Tip60 binding sites, and self-renewal, thus demonstrating a critical KAT-independent role of Tip60 in ESC maintenance. In contrast, KAT-deficient ESCs exhibited impaired differentiation into mesoderm and endoderm, demonstrating a KAT-dependent function in differentiation. Consistent with this phenotype, KAT-deficient mouse embryos exhibited post-implantation developmental defects. These findings establish separable KAT-dependent and KAT-independent functions of Tip60 in ESCs and during differentiation, revealing a complex repertoire of regulatory functions for this essential chromatin remodeling complex. [ABSTRACT FROM AUTHOR]

Members of the Gcn5-related N -acetyltransferase (GNAT) superfamily catalyze the acetylation of a wide range of small molecule and protein substrates. Due to their abundance in all kingdoms of life and diversity of their functions, they are implicated in many aspects of eukaryotic and prokaryotic physiology. Although numerous GNATs have been identified thus far, many remain structurally and functionally uncharacterized. The elucidation of their structures and functions is critical for broadening our knowledge of this diverse and important superfamily. In this work, we present the structural and kinetic analyses of two previously uncharacterized bacterial acetyltransferases - SACOL1063 from Staphylococcus aureus strain COL and CD1211 from Clostridium difficile strain 630 . Our structures of SACOL1063 show substantial flexibility of a loop that is likely responsible for substrate recognition and binding compared to structures of other homologs. In the CoA complex structure, we found two CoA molecules bound in both the canonical AcCoA/CoA-binding site and the acceptor-substrate-binding site. Our work also provides initial clues regarding the substrate specificity of these two enzymes; however, their native function(s) remain unknown. We found both proteins act as N - rather than O -acetyltransferases and preferentially acetylate l -threonine. The combination of structural and kinetic analyses of these two previously uncharacterized GNATs provides fundamental knowledge and a framework on which future studies can be built to elucidate their native functions. [ABSTRACT FROM AUTHOR]

The protein lysine acetylation includes acetyl-CoA (AcCoA) or acetyl phosphate (AcP)-mediated nonenzymatic acetylation, and enzymatic acetylation. It is widespread in the proteomes but the acetylation levels of most sites are very low. A thorough understanding of the determinants of low acetylation levels is highly important for elucidating the physiological relevance of lysine acetylation. In this study, we constructed a non-native substrate library containing 24 synthesized polypeptides, and we showed that ATP could inhibit the AcCoA-mediated nonenzymatic acetylation of these polypeptides through LC-MS/MS analysis. The acetyltransferase PatZ could acetylated these non-native substrates, and the PatZ-catalyzed acetylation of the polypeptides was also inhibited by ATP. Furthermore, the Western blot showed that ATP also inhibited the nonenzymatic (AcCoA or AcP-mediated) and enzymatic (PatZ-catalyzed) acetylation of acetyl-CoA synthetase Acs, which is a native substrate for acetylation. ATP can also inhibit the autoacetylation of acetyltransferase PatZ. Besides, both ADP and AMP could enhance the AcP-mediated acetylation of Acs, but ADP slightly inhibited the AcCoA-mediated acetylation of Acs. However, both ADP and AMP had no evident inhibition on the PatZ-catalyzed acetylation of Acs. Based on these results, we proposed that ATP can act as an inhibitor of acetylation, and it may regulate the function of PatZ by inhibiting its autoacetylation and compensate for the function of deacetylase CobB. [ABSTRACT FROM AUTHOR]

Lysine acetyltransferase (KAT) enzymes including the p300, MYST, and GCN5 families play major roles in modulating the structure of chromatin and regulating transcription. Because of their dysregulation in various disease states including cancer, efforts to develop inhibitors of KATs have steadily gained momentum. Here we provide an overview of recent progress on the development of high quality chemical probes of the p300 and MYST family of KATs and how they are emerging as useful tools for basic and translational investigation. [ABSTRACT FROM AUTHOR]

Terpenoids and steroids are two large families of natural products with diverse biological activities. C3 oxidase and acetyltransferase are the key enzymes in the post-modification of terpenoids and steroids, while their discovery is of great importance for the efficient bioproduction and wide application of these natural products. In this review, we first explain the reaction mechanism of typical enzymes. Next, we summarize the current state-of-art strategies in the discovery of C3 oxidase and acetyltransferase, and discuss rational engineering of these enzymes with novel catalytic functions. Finally, we propose how to obtain an excellent biocatalyst of C3 oxidase and acetyltransferase by exploiting the discovery strategy and the reaction mechanism. • As the key enzymes in post-modification of terpenoids and steroids, discovery of C3 oxidase and acetyltransferase is extremely crucial for their efficient biosynthesis. • The reaction mechanism of typical C3 oxidase and acetyltransferase are discussed. • The strategies to discover C3 oxidase and acetyltransferase of terpenoids and steroids are thoroughly summarized in this review. [ABSTRACT FROM AUTHOR]

Acetylation is one of the major post-translational protein modifications in the cell, with manifold effects on the protein level as well as on the metabolome level. The acetyl group, donated by the metabolite acetyl-coenzyme A, can be co- or post-translationally attached to either the α-amino group of the N-terminus of proteins or to the ε-amino group of lysine residues. These reactions are catalyzed by various N-terminal and lysine acetyltransferases. In case of lysine acetylation, the reaction is enzymatically reversible via tightly regulated and metabolism-dependent mechanisms. The interplay between acetylation and deacetylation is crucial for many important cellular processes. In recent years, our understanding of protein acetylation has increased significantly by global proteomics analyses and in depth functional studies. This review gives a general overview of protein acetylation and the respective acetyltransferases, and focuses on the regulation of metabolic processes and physiological consequences that come along with protein acetylation. [ABSTRACT FROM AUTHOR]

The zinc finger protein GATA4 is a transcription factor involved in cardiomyocyte hypertrophy. It forms a functional complex with the intrinsic histone acetyltransferase (HAT) p300. The HAT activity of p300 is required for the acetylation and transcriptional activity of GATA4, as well as for cardiomyocyte hypertrophy and the development of heart failure. In the present study, we have identified Receptor for Activated Protein Kinase C1 (RACK1) as a novel GATA4-binding protein using tandem affinity purification and mass spectrometry analyses. We found that exogenous RACK1 repressed phenylephrine (PE)-induced hypertrophic responses, such as myofibrillar organization, increased cell size, and hypertrophy-associated gene transcription, in cultured cardiomyocytes. RACK1 physically interacted with GATA4 and the overexpression of RACK1 reduced PE-induced formation of the p300/GATA4 complex and the acetylation and DNA binding activity of GATA4. In response to hypertrophic stimulation in cultured cardiomyocytes and in the hearts of hypertensive heart disease model rats, the tyrosine phosphorylation of RACK1 was increased, and the binding between GATA4 and RACK1 was reduced. In addition, the tyrosine phosphorylation of RACK1 was required for the disruption of the RACK1/GATA4 complex and for the formation of the p300/GATA4 complex. These findings demonstrate that RACK1 is involved in p300/GATA4-dependent hypertrophic responses in cardiomyocytes and is a promising therapeutic target for heart failure. [ABSTRACT FROM AUTHOR]

Summary N-Terminal acetylation is a common and important protein modification catalyzed by N-terminal acetyltransferases (NATs). Six human NATs (NatA–NatF) contain one catalytic subunit each, Naa10 to Naa60, respectively. In contrast to the ribosome-associated NatA to NatE, NatF/Naa60 specifically associates with Golgi membranes and acetylates transmembrane proteins. To gain insight into the molecular basis for the function of Naa60, we developed an Naa60 bisubstrate CoA-peptide conjugate inhibitor, determined its X-ray structure when bound to CoA and inhibitor, and carried out biochemical experiments. We show that Naa60 adapts an overall fold similar to that of the catalytic subunits of ribosome-associated NATs, but with the addition of two novel elongated loops that play important roles in substrate-specific binding. One of these loops mediates a dimer to monomer transition upon substrate-specific binding. Naa60 employs a catalytic mechanism most similar to Naa50. Collectively, these data reveal the molecular basis for Naa60-specific acetyltransferase activity with implications for its Golgi-specific functions. [ABSTRACT FROM AUTHOR]

Summary N-acetylglucosamine-1-phosphate uridyltransferase (GlmU) is a pivotal bifunctional enzyme, its N and C terminal domains catalyzes uridyltransferase and acetyltransferase activities, respectively. Final product of GlmU catalyzed reaction, uridine-diphospho-N-acetylglucosamine (UDP-GlcNAc), acts as sugar donor providing GlcNAc residues in the synthesis of peptidoglycan and a disaccharide linker (D-N-GlcNAc-1-rhamnose), the key structural components of Mycobacterium tuberculosis ( M. tuberculosis ) cell wall. In the present study, we have searched new inhibitors against acetyltransferase activity of M. tuberculosis GlmU. A subset of 1607 synthetic compounds, selected through dual approach i.e., in-silico and whole cell screen against 20,000 compounds from ChemBridge library, was further screened using an in-vitro high throughput bioassay to identify inhibitors of acetyltransferase domain of M. tuberculosis GlmU. Four compounds were found to inhibit GlmU enzyme specific to acetyltransferase activity, with IC 50 values ranging from 9 to 70 μM. Two compounds (6624116, 5655606) also exhibited whole cell activity against drug susceptible as well as drug resistant M. tuberculosis . These two compounds also exhibited increased anti-TB activity when tested in combination with rifampicin, isoniazid and ethambutol, however 5655606 was cytotoxic to eukaryotic cell line. These results demonstrate that identified chemical scaffolds can be used as inhibitors of M. tuberculosis cell wall enzyme after optimizations for future anti-TB drug development program. [ABSTRACT FROM AUTHOR]

Excess copper (Cu) in environment affects the growth and metabolism of plants and green algae. However, the molecular mechanism for regulating plant tolerance to excess Cu is not fully understood. Here, we report a gene CrGNAT enconding an acetyltransferase in Chlamydomonas reinhardtii and identified its role in regulating tolerance to Cu toxicity. Expression of CrGNAT was significantly induced by 75–400 μM Cu. The top induction occurred at 100 μM. Transgenic algae overexpressing CrGNAT ( 35S::CrGNAT ) in C. reinhardtii showed high tolerance to excess Cu, with improved cell population, chlorophyll accumulation and photosynthesis efficiency, but with low degree of oxidation with regard to reduced hydrogen peroxide, lipid peroxides and non-protein thiol compounds. In contrast, CrGNAT knock-down lines with antisense led to sensitivity to Cu stress. 35S::CrGNAT algae accumulated more Cu and other metals (Zn, Fe, Cu, Mn and Mg) than wild-type, whereas the CrGNAT down-regulated algae ( 35S::AntiCrGNAT ) had moderate levels of Cu and Mn, but no effects on Zn, Fe and Mg accumulation as compared to wild-type. The elevated metal absorption in CrGNAT overexpression algae implies that the metals can be removed from water media. Quantitative RT-PCR analysis revealed that expression of two genes encoding N -lysine histone methyltransferases was repressed in 35S::CrGNAT algae, suggesting that CrGNAT -regulated algal tolerance to Cu toxicity is likely associated with histone methylation and chromatin remodeling. The present work provided an example a basis to develop techniques for environmental restoration of metal-contaminated aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Drought stress seriously inhibits crop growth and yields and constrains photosynthesis, which is a key biological process. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a key enzyme in the carbon assimilation process, and while its activity is reportedly significantly inhibited under drought stress, little is known about the underlying molecular mechanism. We identified a chloroplast-localized acetyltransferase, SlSNAT2, negatively regulates drought tolerance in tomato. The slsnat2 mutants were conduced to endogenous abscisic acid accumulation in tomato and could promote scavenging of reactive oxygen species through the enhanced activity of antioxidant enzymes. Knocking out this gene could therefore improve photosynthesis under drought stress. Moreover, SlSNAT2 could catalyze the Lys acetylation of rbcL, a large Rubisco subunit. And SlSNAT2 knockout lines were found to maintain higher levels of Rubisco activity under drought stress in the absence of SlSNAT2-catalyzed acetylation of rbcL than wild type plants. Our results demonstrate that SlSNAT2 functions as a negative regulator of drought tolerance. Accordingly, SlSNAT2 could be targeted in molecular designs for tomato breeding. • SlSNAT2 acetylates rbcL and negatively regulates Rubisco activity and endogenous ABA content in tomato. SlSNAT2 knockout lines stabilize photosynthesis in tomato under drought stress conditions. [ABSTRACT FROM AUTHOR]

While the cardioprotective functions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and omega-3 unsaturated fatty acids have been previously demonstrated, little is known about their effects on cardiomyocyte hypertrophy. In this study, we compared the effects of EPA and DHA on hypertrophic responses in cardiomyocytes and development of heart failure in rats with myocardial infarction (MI). Both EPA and DHA significantly suppressed phenylephrine- and p300-induced cardiomyocyte hypertrophy, transcription of hypertrophy response genes, and acetylation of histone H3K9 in cardiomyocytes. EPA and DHA directly inhibited p300-histone acetyltransferase activity (IC50: 37.8 and 30.6 μM, respectively). Further, EPA- and DHA-induced allosteric inhibition of histones and competitive inhibition of acetyl-CoA, and significantly prevented p300-induced hypertrophic responses. Rats with moderate MI (left ventricular fractional shortening [FS] <40%) were randomly assigned to three groups, namely, vehicle (saline), EPA (1 g/kg), and DHA (1 g/kg). One week after the operation, rats were orally administrated with test agents for 6 weeks. Echocardiographic analysis demonstrated that both EPA and DHA treatments preserved FS and prevented MI-induced left ventricular remodeling. Furthermore, EPA and DHA significantly suppressed the MI-induced increase in myocardial cell diameter, perivascular fibrosis, mRNA levels of hypertrophic markers, fibrosis, and acetylation of histone H3K9. The effects on hypertrophic responses and the development of heart failure were not different between EPA and DHA groups. Both EPA and DHA suppressed hypertrophic responses and the development of heart failure to the same extent through the inhibition of p300-HAT activity. [ABSTRACT FROM AUTHOR]

Lys- N ɛ -acetylation (PKA) has recently ascended from a post-translational modification (PTM) of limited distribution to one approaching the abundance of O -phosphorylation. Thousands of KAC proteins have been identified in Archaea, bacteria, and Eukarya, and the KAC system of acetyltransferases, deacetylases, and binding proteins is superficially comparable with the kinases, phosphatases, and phospho- (P-)protein binding-proteins of O -phosphorylation. Herein, we describe recent results and compare several aspects of these two major systems of PTM in plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Serotype 33A polysaccharide has the same backbone structure as serotype 33F. [•] Serotype 33A has two additional sites of O-acetylation compared to 33F. [•] The 33A/33F backbone with one common O-acetylation is proposed epitope for typing serum 33b. [•] A 5,6-di-O-acetylated →3)-β-d-Galf5,6Ac-(1→3)-β-d-Glcp-(1→ disaccharide is proposed epitope for typing serum 20b. [Copyright &y& Elsevier]

Abstract: AAC(6′)-Ib is an important aminoglycoside resistance enzyme to target with enzymatic inhibitors. An in silico screening approach was used to identify potential inhibitors from the ChemBridge library. Several compounds were identified, of which two of them, 4-[(2-{[1-(3-methylphenyl)-4,6-dioxo-2-thioxotetrahydro-5(2H)-pyrimidinylidene]methyl}phenoxy)methyl]benzoic acid and 2-{5-[(4,6-dioxo-1,3-diphenyl-2-thioxotetrahydro-5(2H)-pyrimidinylidene)methyl]-2-furyl}benzoic acid, showed micromolar activity in inhibiting acetylation of kanamycin A. These compounds are predicted to bind the aminoglycoside binding site of AAC(6′)-Ib and exhibited competitive inhibition against kanamycin A. [Copyright &y& Elsevier]

Abstract: Aminoglycosides (AGs) are broad-spectrum antibiotics whose constant use and presence in growth environments has led bacteria to develop resistance mechanisms to aid in their survival. A common mechanism of resistance to AGs is their chemical modification (nucleotidylation, phosphorylation, or acetylation) by AG-modifying enzymes (AMEs). Through evolution, fusion of two AME-encoding genes has resulted in bifunctional enzymes with broader spectrum of activity. Serratia marcescens, a human enteropathogen, contains such a bifunctional enzyme, ANT(3″)-Ii/AAC(6′)-IId. To gain insight into the role, effect, and importance of the union of ANT(3″)-Ii and AAC(6′)-IId in this bifunctional enzyme, we separated the two domains and compared their activity to that of the full-length enzyme. We performed a thorough comparison of the substrate and cosubstrate profiles as well as kinetic characterization of the bifunctional ANT(3″)-Ii/AAC(6′)-IId and its individually expressed components. [Copyright &y& Elsevier]

Abstract: Plants synthesize volatile alcohol esters on environmental insult or as metabolic induction during flower/fruit development. However, essential oil plants constitutively produce them as the oil constituents. Their synthesis is catalyzed by BAHD family enzymes called alcohol acyltransferases (AATs). However, no AAT has been characterized from plant foliage synthesizing acyclic monoterpenoids containing essential oils. Therefore, we have purified and biochemically characterized a geraniol: acetyl coenzyme A acetyltransferase (GAAT) from Palmarosa aroma grass (Cymbopogon martinii) leaf. MALDI-assisted proteomic study of the 43kDa monomeric enzyme revealed its sequence motif novelties e.g. relaxed conservation at Phe and Trp in DFGWG’. This suggests permissiveness of variations in the conserved motif without loss of catalytic ability. Also, some new conserved/semi-conserved motifs of AATs were recognized. The GAAT k cat/K m values (300–700M−1 s−1) were low (a generic characteristic for secondary metabolism enzyme) but higher than those of some floral AATs. Wide substrate acceptability for catalyzing acetylation of diverse primary alcohols (chain of ≥C6) implied its catalytic description as a ‘primary aliphatic alcohol acetyltransferase’. It signifies metabolic ability to deliver diverse aroma esters, should the acceptor alcohols be available in planta. To our knowledge, this is the first report of detailed kinetics of a vegetal monoterpenol acyltransferase. [Copyright &y& Elsevier]

Abstract: Caloric excess has been postulated to disrupt cardiac function via (i) the generation of toxic intermediates, (ii) via protein glycosylation and (iii) through the generation of reactive oxygen species. It is now increasingly being recognized that the nutrient intermediates themselves may modulate metabolic pathways through the post-translational modifications of metabolic enzymes. In light of the high energy demand of the heart, these nutrient mediated modulations in metabolic pathway functioning may play an important role in cardiac function and in the capacity of the heart to adapt to biomechanical stressors. In this review the role of protein acetylation and deacetylation in the control of metabolic programs is explored. Although not extensively investigated directly in the heart, the emerging data support that these nutrient mediated post-translational regulatory events (i) modulate cardiac metabolic pathways, (ii) integrate nutrient flux mediated post-translational effects with cardiac function and (iii) may be important in the development of cardiac pathology. Areas of investigation that need to be explored are highlighted. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection. [Copyright &y& Elsevier]

Abstract: In chromatin, gene transcription is regulated through posttranslational modifications on the histone N-terminal tail sequences, typically an acetyl group modification on lysine residues. To realize a simple model of the gene regulation of chromatin, we designed a hydrophilic polymer grafted with histone H3 tail peptides. The polyplex formed from the polymer and DNA suppressed the gene expression effectively although the polyplex was weaker than the polyplex of poly-l-lysine and DNA. This weaker polyplex afforded the acetylation of the lysine residue of the grafted peptides by histone acetyltransferase. Subsequently, the gene expression was activated due to the relaxation of the polyplex which was brought by a cationic charge decrease in the grafted peptides. This molecular system is the first functional model of the gene regulation of the chromatin. [Copyright &y& Elsevier]

Abstract: Aminoglycosides have been an essential component of the armamentarium in the treatment of life-threatening infections. Unfortunately, their efficacy has been reduced by the surge and dissemination of resistance. In some cases the levels of resistance reached the point that rendered them virtually useless. Among many known mechanisms of resistance to aminoglycosides, enzymatic modification is the most prevalent in the clinical setting. Aminoglycoside modifying enzymes catalyze the modification at different –OH or –NH2 groups of the 2-deoxystreptamine nucleus or the sugar moieties and can be nucleotidyltranferases, phosphotransferases, or acetyltransferases. The number of aminoglycoside modifying enzymes identified to date as well as the genetic environments where the coding genes are located is impressive and there is virtually no bacteria that is unable to support enzymatic resistance to aminoglycosides. Aside from the development of new aminoglycosides refractory to as many as possible modifying enzymes there are currently two main strategies being pursued to overcome the action of aminoglycoside modifying enzymes. Their successful development would extend the useful life of existing antibiotics that have proven effective in the treatment of infections. These strategies consist of the development of inhibitors of the enzymatic action or of the expression of the modifying enzymes. [ABSTRACT FROM AUTHOR]

Abstract: The 70kDa ribosomal protein S6 kinases (S6K1 and S6K2) play important roles in the regulation of protein synthesis, cell growth and survival. S6Ks are activated in response to mitogen stimulation and nutrient sufficiency by the phosphorylation of conserved serine and threonine residues. Here we show for the first time, that in addition to phosphorylation, S6Ks are also targeted by lysine acetylation. Following mitogen stimulation, S6Ks interact with the p300 and p300/CBP-associated factor (PCAF) acetyltransferases. S6Ks can be acetylated by p300 and PCAF in vitro and S6K acetylation is detected in cells expressing p300. Furthermore, it appears that the acetylation sites targeted by p300 lie within the divergent C-terminal regulatory domains of both S6K1 and S6K2. Acetylation of S6K1 and 2 is increased upon the inhibition of class I/II histone deacetylases (HDACs) by trichostatin-A, while the enhancement of S6K1 acetylation by nicotinamide suggests the additional involvement of sirtuin deacetylases in S6K deacetylation. Both expression of p300 and HDAC inhibition cause increases in S6K protein levels, and we have shown that S6K2 is stabilized in cells treated with HDAC inhibitors. The finding that S6Ks are targeted by histone acetyltransferases uncovers a novel mode of crosstalk between mitogenic signalling pathways and the transcriptional machinery and reveals additional complexity in the regulation of S6K function. [Copyright &y& Elsevier]

Abstract: Histone acetylation is a vital mechanism for the activation of chromatin and the corresponding expression of genes competing the action of histone deacetylation and leading to chromatin inactivation. Histone acetyltransferases (HATs) comprise a superfamily including the GNAT/MYST, CBP and TFII250 families. Histone acetyltransferases have been well studied in Arabidopsis but information from agronomically important crops is limited. In the present work three full-length sequences encoding members of the GNAT/MYST family, namely HvMYST, HvELP3 and HvGCN5, respectively, were isolated and characterized from barley (Hordeum vulgare L.), a crop of high economic value. Expression analysis of the barley GNAT/MYST genes revealed significant quantitative differences in different seed developmental stages and between cultivars with varying seed size and weight, suggesting an association of these genes with barley seed development. Furthermore, all three HvGNAT/MYST genes were inducible by the stress-related phytohormone abscisic acid (ABA) involved in seed maturation, dormancy and germination, implying a possible regulation of these genes by ABA, during barley seed development, germination and stress response. [Copyright &y& Elsevier]

Abstract: Protein acetylation is increasingly recognized as an important post-translational modification. Although a lot of protein acetyltransferases have been identified, a few putative acetyltransferases are yet to be studied. In this study, we identified a novel protein acetyltransferase, Patt1, which belongs to GNAT family. Patt1 exhibited histone acetyltransferase activity and auto-acetylation activity. Deletion and mutation analysis of the predicted acetyltransferase domain in Patt1 showed that the conserved Glu139 was an important residue for its protein acetyltransferase activity. Furthermore, we found that Patt1 was highly expressed in liver and significantly downregulated in hepatocellular carcinoma tissues. In addition, we showed that overexpression of Patt1 enhanced the apoptosis of hepatoma cells dependent on its acetyltransferase activity, whereas knockdown of Patt1 significantly protected Chang liver cells from apoptosis. These data suggest that Patt1 might be involved in the development of hepatocellular carcinoma, and could be served as a potential therapy target for hepatocellular carcinoma. [Copyright &y& Elsevier]

Abstract: Gene ACIAD1637 from Acinetobacter baylyi ADP1 encodes a 182 amino acid putative antibiotic resistance protein. The structure of this protein (termed acepita) has been solved in space group P2 to 2.35 Å resolution. Acepita belongs to the GCN5-related N-acetyltransferase (GNAT) family, and contains the four sequence motifs conserved among family members. The structure of acepita is compared with that of pita, its homologue from Pseudomonas aeruginosa. Acepita has a similar substrate profile to pita and performs a similar function. [Copyright &y& Elsevier]

Abstract: Histone lysine and arginine residues are subject to a wide array of post-translational modifications including methylation, citrullination, acetylation, ubiquitination, and sumoylation. The combinatorial action of these modifications regulates critical DNA processes including replication, repair, and transcription. In addition, enzymes that modify histone lysine and arginine residues have been correlated with a variety of human diseases including arthritis, cancer, heart disease, diabetes, and neurodegenerative disorders. Thus, it is important to fully understand the detailed kinetic and chemical mechanisms of these enzymes. Here, we review recent progress towards determining the mechanisms of histone lysine and arginine modifying enzymes. In particular, the mechanisms of S-adenosyl-methionine (AdoMet) dependent methyltransferases, FAD-dependent demethylases, iron dependent demethylases, acetyl-CoA dependent acetyltransferases, zinc dependent deacetylases, NAD+ dependent deacetylases, and protein arginine deiminases are covered. Particular attention is paid to the conserved active-site residues necessary for catalysis and the individual chemical steps along the catalytic pathway. When appropriate, areas requiring further work are discussed. [Copyright &y& Elsevier]

The cytotoxic mechanism of the histone deacetylase inhibitor (HDACI) Trichostatin A (TSA) was explored in a neuroblastoma (NB) model. TSA induces cell death in neuroblastic-type NB cells by increasing the acetylation of Ku70, a Bax-binding protein. Ku70 acetylation causes Bax release and activation, triggering cell death. This response to TSA depends on the CREB-binding protein (CBP) acetylating Ku70. TSA-induced cell death response correlates with CBP expression. In stromal-type NB cell lines with low levels of CBP and relative type resistance to TSA, increasing CBP expression disrupts Bax-Ku70 binding and sensitizes them to TSA. Reducing CBP expression in neuroblastic cell types causes resistance. Cytotoxic response to TSA is Bax-dependent. Interestingly, depleting NB cells of Ku70 also triggers Bax-dependent cell death, suggesting that conditions that leave Bax unbound to Ku70 result in cell death. We also show that CBP, Ku70, and Bax are expressed in human NB tumors and that CBP expression varies across cell types comprising these tumors, with the highest expression observed in neuroblastic elements. Together, these results demonstrate that CBP, Bax, and Ku70 contribute to a therapeutic response to TSA against NB and identify the possibility of using these proteins to predict clinical responsiveness to HDACI treatment. [ABSTRACT FROM AUTHOR]

Abstract: Over the past 10 years, much progress has been made to understand the roles of the similar, yet distinct yeast SAGA and SLIK coactivator complexes involved in histone post-translational modification and gene regulation. Many different groups have elucidated functions of the SAGA complexes including identification of novel components, which have conferred additional distinct functions. Together, recent studies demonstrate unique attributes of the SAGA coactivator complexes in histone acetylation, methylation, phosphorylation, and deubiquitination. In addition to roles in transcriptional activation with the 19S proteasome regulatory particle, recent evidence also suggests functions for SAGA in elongation and mRNA export. The modular nature of SAGA allows this ∼1.8MDa complex to organize its functions and carry out multiple roles during transcription, particularly under conditions of cellular stress. [Copyright &y& Elsevier]

Abstract: Aminoglycoside antibiotics act by binding to 16S rRNA. Resistance to these antibiotics occurs via drug modifications by enzymes such as aminoglycoside 6′-N-acetyltransferases (AAC(6′)s). We report here the regioselective and efficient synthesis of N-6′-acylated aminoglycosides and their use as probes to study AAC(6′)-Ii and aminoglycoside–RNA complexes. Our results emphasize the central role of N-6′ nucleophilicity for transformation by AAC(6′)-Ii and the importance of hydrogen bonding between 6′-NH2 and 16S rRNA for antibacterial activity. [Copyright &y& Elsevier]

Abstract: Trypanosomatids are widespread parasites that cause three major tropical diseases. In trypanosomatids, as in most other organisms, acetylation is a common protein modification that is important in multiple, diverse processes. This paper describes a new member of the Trypanosoma cruzi acetyltransferase family. The gene is single copy and orthologs are also present in the other two sequenced trypanosomatids, Trypanosoma brucei and Leishmania major. This protein (TcAT-1) has the essential motifs present in members of the GCN5-related acetyltransferase (GNAT) family, as well as an additional motif also found in some enzymes from plant and animal species. The protein is evolutionarily more closely related to this group of enzymes than to histone acetyltransferases. The native protein has a cytosolic cellular location and is present in all three life-cycle stages of the parasite. The recombinant protein was shown to have autoacetylation enzymatic activity. [Copyright &y& Elsevier]

Abstract: Activation of transcription by NF-κB requires association with coactivator proteins, including CBP/p300 and P/CAF. To identify new coregulatory proteins, a cytoplasmic two-hybrid screen was performed using the C-terminus of the p65 subunit as bait. Through this screen, the spermidine/spermine N1-acetyltransferase 2 (SSAT2) protein was identified as a potential modulator of NF-κB activity. SSAT2 was originally identified based on homology to SSAT1, a protein involved in polyamine catabolism. However both proteins contain an acetyltransferase domain that has similarity to the acetyltransferase domains of the GNAT superfamily of coactivators. Although SSAT2 is 46% identical to SSAT1, based on a recent report, SSAT2 does not appear to function in polyamine catabolism. Because of the similarity of SSAT2 to coactivators, we wanted to determine if SSAT2 could function as a coactivator for NF-κB. Coimmunoprecipitations confirmed the interaction between p65 and SSAT2. In transient transfection reporter gene assays, SSAT2 functions as a transcriptional coactivator for NF-κB and cooperates with CBP and P/CAF to enhance TNFα-induced NF-κB activity. Moreover, SSAT2 transiently associates with the promoters of the NF-κB-regulated cIAP2 and IL-8 genes in response to TNFα. Although the overall function of SSAT2 is not known, it appears that it can function as a transcriptional coactivator. [Copyright &y& Elsevier]

Abstract: N-Nitroso compounds, such as N-nitrosodiethylamine (NDEA), are a versatile group of chemical carcinogens, being suspected to be involved in gastrointestinal tumors in humans. The intestinal microflora can modify a wide range of environmental chemicals either directly or in the course of enterohepatic circulation. Nitroreductases from bacteria seem to have a wide spectrum of substrates, as observed by the reduction of several nitroaromatic compounds, but their capacity to metabolize N-nitroso compounds has not been described. To elucidate the participation of nitroreductase or acetyltransferase enzymes in the mutagenic activity of NDEA, the bacterial (reverse) mutation test was carried out with the strains YG1021 (nitroreductase overexpression), YG1024 (acetyltransferase overexpression), TA98NR (nitroreductase deficient), and TA98DNP6 (acetyltrasferase deficient), and YG1041, which overexpresses both enzymes. The presence of high levels of acetyltransferase may generate toxic compounds that must be eliminated by cellular processes or can lead to cell death, and consequently decrease the mutagenic effect, as can be observed by the comparison of strain TA98DNP6 with the strains TA98 and YG1024. The slope curves for TA98 strain were 0.66rev/μM (R 2 =0.51) and 52.8rev/μM (R 2 =0.88), in the absence and presence of S9 mix, respectively. For YG1024 strain, the slope curve, in the presence of S9 mix was 6897rev/μM (R 2 =0.78). Our data suggest that N-nitroso compounds need to be initially metabolized by enzymes such as cytochromes P450 to induce mutagenicity. Nitroreductase stimulates toxicity, while acetyltransferase stimulates mutagenicity, and nitroreductase can neutralize the mechanism of mutagenicity generating innoccuos compounds, probably by acting on the product generated after NDEA activation. [Copyright &y& Elsevier]

Abstract: The dynamic nature of the ovarian follicle makes it an ideal model to study the coordinated activation and inactivation of genes related to cell growth and differentiation. Much progress has been made in identifying transcription factors that promote the transcription of ovarian genes mediating gonadotropin action and steroidogenesis, but how these factors promote transcription in the context of chromatin is not well understood. Over the past 5 years, epigenetic regulation of ovarian genes through histone modifications has been the focus of an increasing number of studies. Several coactivators and corepressors associated with transcription factors are in fact histone acetyltransferases and histone deacetylases mediating the hyperacetylation and hypoacetylation of histones, respectively. Hyperacetylation of lysine residues in the core histone tails promotes chromatin alterations that favor transcription, whereas hypoacetylation of histones promotes gene silencing or repression. Not only does the acetylation status of the core histones determine whether chromatin remodeling occurs, but histone phosphorylation and methylation may serve equally important roles. For example, the combination of histone H3 phosphorylation and acetylation concertedly favors transcription. In addition, specific lysine methylations (e.g., K9 of histone H3) repress gene expression whereas other methylations promote gene expression. It is most likely the combination of histone modification events that regulate the initiation of transcription. Understanding how ovarian hormones control specific histone modifications will help us understand how follicular cells can switch from active gene pools governing cell proliferation to those gene groups controlling terminal differentiation. Progress in elucidating the ovarian specific regulation of histone modifying enzymes as well as identification of their target gene pools at different stages of the follicular cycle is expected in the next few years. [Copyright &y& Elsevier]

Abstract: N-terminal-ubiquitinylation (NTU) is a newly discovered protein degradation pathway initiated by ubiquitin-tagging of the N-terminal α-amino group. We have used data from recent genomic studies, especially those on humans, to up-date and re-interpret biochemical data to identify the sequence features associated with NTU. We compared a mini-proteome for which experimental protein sequence is available with large-scale genomic data. We conclude that N-α-acetylation involves less than 30%, and not the widely assumed 90%, of the proteins encoded by any higher eukaryote genome, greatly increasing thereby the number of possible targets for NTU-mediated degradation. Next, straightforward rules linking the first N-terminal residues of any nascent polypeptides to the nature of their processed N-termini are established and dedicated prediction tool is made available at http://www.isv.cnrs-gif.fr/Terminator/. We provide strong arguments indicating that the nature of the processed N-terminus is a major determinant factor of the half-life of the protein. We finally reveal that one third of the nuclear-encoded proteins starting with an unprocessed and unblocked methionine are at least one order of magnitude less stable than is average in higher eukaryotes. This appears to be the first common feature of proteins undergoing N-terminal ubiquitinylation. Hence, a pool of about 3000 proteins in each proteome could be unstable per se and tagged for rapid degradation via NTU. [Copyright &y& Elsevier]

Abstract: Antibiotic resistance can occur via three general mechanisms: prevention of interaction of the drug with target, efflux of the antibiotic from the cell, and direct destruction or modification of the compound. This review discusses the latter mechanisms focusing on the chemical strategy of antibiotic inactivation; these include hydrolysis, group transfer, and redox mechanisms. While hydrolysis is especially important clinically, particularly as applied to β-lactam antibiotics, the group transfer approaches are the most diverse and include the modification by acyltransfer, phosphorylation, glycosylation, nucleotidylation, ribosylation, and thiol transfer. A unique feature of enzymes that physically modify antibiotics is that these mechanisms alone actively reduce the concentration of drugs in the local environment; therefore, they present a unique challenge to researchers and clinicians considering new approaches to anti-infective therapy. This review will present the current status of knowledge of these aspects of antibiotic resistance and discuss how a thorough understanding of resistance enzyme molecular mechanism, three-dimensional structure, and evolution can be leveraged in combating resistance. [Copyright &y& Elsevier]

Abstract: Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; PAF) is a potent inflammatory mediator produced by cells in response to physical or chemical stress. The mechanisms linking cell injury to PAF synthesis are unknown. We used liquid chromatography-tandem mass spectrometry to investigate stress-induced PAF synthesis in human neutrophils. PAF synthesis induced by extracellular pH 5.4 correlated with the activation of a stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), and was blocked by the p38 MAPK inhibitor SB 203580. A key enzyme of PAF synthesis, acetyl-CoA:lysoPAF acetyltransferase, which we have previously shown is a target of p38 MAPK, was also activated in an SB 203580-sensitive fashion. Another MAPK pathway, extracellular signal-regulated kinase-1/2 (ERK-1/2), was also activated. Surprisingly, the pharmacological blockade of the ERK-1/2 pathway with PD 98059 did not block, but rather enhanced, PAF accumulation. Two unexpected actions of PD 98059 may underlie this phenomenon: an augmentation of stress-induced p38 MAPK phosphorylation and an inhibition of PAF catabolism. The latter effect did not appear to be due to a direct inhibition of PAF acetylhydrolase. Finally, similar results were obtained using another form of cellular stress, hypertonic sodium chloride. These data are consistent with a model in which stress-induced PAF accumulation is regulated positively by p38 MAPK and negatively by ERK-1/2. Such a model contrasts with the PAF accumulation induced by other forms of stimulation, which we and others have found is up-regulated by both p38 MAPK and ERK-1/2. [Copyright &y& Elsevier]