Reversible Acetylation Research Articles

AtHDA15 binds directly to COP1 positively regulating photomorphogenesis

Reversible histone acetylation and deacetylation play crucial roles in modulating light-regulated gene expression during seedling development. However, it remains largely unknown how histone-modifying enzymes interpose within the molecular framework of light signaling network. In this study, we show that AtHDA15 positively regulates photomorphogenesis by directly binding to COP1, a master regulator in the repression of photomorphogenesis. hda15 T-DNA knock-out and RNAi lines exhibited light hyposensitivity with reduced HY5 and PIF3 protein levels leading to long hypocotyl phenotypes in the dark while its overexpression leads to increased HY5 concentrations and short hypocotyl phenotypes. In vivo and in vitro binding assays show that HDA15 directly interacts with COP1 inside the nucleus modulating COP1’s repressive activities. As COP1 is established to act within the nucleus to regulate specific transcription factors associated with growth and development in skotomorphogenesis, the direct binding by HDA15 is predicted to abrogate activities of COP1 in the presence of light and modulate its repressive activities in the dark. Our results append the mounting evidence for the role of HDACs in post-translational regulation in addition to their well-known histone modifying functions.

Interactive Regulation of Formate Dehydrogenase during CO2 Fixation in Gas-Fermenting Bacteria.

Protein lysine acetylation, a prevalent posttranslational modification, regulates numerous crucial biological processes in cells. Nevertheless, how lysine acetylation interacts with other types of regulation to coordinate metabolism remains largely unknown owing to the complexity of the process. Here, using a representative gas-fermenting bacterium, Clostridium ljungdahlii, we revealed a novel regulatory mechanism that employs both the lysine acetylation and transcriptional regulation systems to interactively control CO2 fixation, a key biological process for utilizing this one-carbon gas. A dominant lysine acetyltransferase/deacetylase system, At2/Dat1, was identified and found to regulate FDH1 (formate dehydrogenase responsible for CO2 fixation) activity via a crucial acetylation site (lysine-29). Notably, the global transcription factor CcpA was also shown to be regulated by At2/Dat1; in turn, CcpA could directly control At2 expression, thus indicating an unreported interaction mode between the acetylation system and transcription factors. Moreover, CcpA was observed to negatively regulate FDH1 expression, which, when combined with At2/Dat1, leads to the collaborative regulation of this enzyme. Based on this concept, we reconstructed the regulatory network related to FDH1, realizing significantly increased CO2 utilization by C. ljungdahliiIMPORTANCE Microbial CO2 fixation and conversion constitute a potential solution to both utilization of greenhouse gas or industrial waste gases and sustainable production of bulk chemicals and fuels. Autotrophic gas-fermenting bacteria play central roles in this bioprocess. This study provides new insights regarding the metabolic regulatory mechanisms underlying CO2 reduction in Clostridium ljungdahlii, a representative gas-fermenting bacterium. A critical formate dehydrogenase (FDH1) responsible for fixing CO2 and a dominant reversible lysine acetylation system, At2/Dat1, were identified. Furthermore, FDH1 was found to be interactively regulated by both the At2/Dat1 system and the global transcriptional factor CcpA, and the two regulatory systems are mutually restricted. Reconstruction of this multilevel metabolic regulatory module led to improved CO2 metabolism by C. ljungdahlii These findings not only substantively expand our understanding but also provide a potentially useful metabolic engineering strategy for microbial carbon fixation.

Activation of HDAC4 and GR signaling contributes to stress-induced hyperalgesia in the medial prefrontal cortex of rats

“Stress-induced hyperalgesia (SIH)” is a phenomenon that stress can lead to an increase in pain sensitivity. Epigenetic mechanisms have been known to play fundamental roles in stress and pain. Histone acetylation is an epigenetic feature that is changed in numerous stress-related disease situations. However, epigenetic mechanism for SIH is not well known. We investigated the effect of histone acetylation on pain hypersensitivity using SPS (single-prolonged stress) + CFA (complete Freund’s adjuvant) model. We showed that the glucocorticoid receptor (GR)-pERK-pCREB-Fos signaling pathway was upregulated on stress-induced hyperalgesia and the paw withdrawal threshold in the SPS + CFA group dropped significantly compared with the SPS or CFA group. Histone deacetylases 4 (HDAC4)-expressing neurons in the medial prefrontal cortex (mPFC) were increased in the SPS + CFA-exposed group compared with CFA-exposed or SPS-exposed group. And we showed that the effects of stress-induced hyperalgesia were critically regulated via reversible acetylation (HDAC4) of the GR. Inhibiting HDAC4 by microinjection of sodium butyrate into the mPFC could disrupt glucocorticoid receptor (GR) signaling pathway, which lowered SPS + CFA-caused mechanical allodynia and alleviated anxiety-like behavior. Together, our studies suggest that HDAC inhibitors might involve in the process of stress-induced hyperalgesia.

Acetylation Stabilizes Phosphoglycerate Dehydrogenase by Disrupting the Interaction of E3 Ligase RNF5 to Promote Breast Tumorigenesis

Phosphoglycerate dehydrogenase (PHGDH) is the first enzyme in the serine synthesis pathway in which it is also the rate-limiting enzyme. It is significantly upregulated in many cancers, especially breast cancer. However, the posttranslational mechanism of PHGDH upregulation in breast cancer is unknown. In this study, we find that RNF5, an E3 ubiquitin ligase, is essential for the degradation of PHGDH protein. PHGDH is degraded by RNF5 to prevent the proliferation of breast cancer cells. The acetylation of PHGDH at K58 is able to disrupt the interaction of RNF5-PHGDH and promote the proliferation of breast cancer cells. Tip60 and SIRT2 regulate the reversible acetylation modification of PHGDH in response to glucose alteration. Moreover, PHGDH is significantly upregulated in samples of human breast cancer and is associated with decreased RNF5 expression. This implies a potential therapeutic target through the interference interaction of PHGDH-RNF5 to degrade PHGDH in breast cancer.

Regulation of poly(a)-specific ribonuclease activity by reversible lysine acetylation

Poly(A)-specific ribonuclease (PARN) is a 3'-exoribonuclease that plays an important role in regulating the stability and maturation of RNAs. Recently, PARN has been found to regulate the maturation of the human telomerase RNA component (hTR), a noncoding RNA required for telomere elongation. Specifically, PARN cleaves the 3'-end of immature, polyadenylated hTR to form the mature, nonpolyadenylated template. Despite PARN's critical role in mediating telomere maintenance, little is known about how PARN's function is regulated by post-translational modifications. In this study, using shRNA- and CRISPR/Cas9-mediated gene silencing and knockout approaches, along with 3'-exoribonuclease activity assays and additional biochemical methods, we examined whether PARN is post-translationally modified by acetylation and what effect acetylation has on PARN's activity. We found PARN is primarily acetylated by the acetyltransferase p300 at Lys-566 and deacetylated by sirtuin1 (SIRT1). We also revealed how acetylation of PARN can decrease its enzymatic activity both in vitro, using a synthetic RNA probe, and in vivo, by quantifying endogenous levels of adenylated hTR. Furthermore, we also found that SIRT1 can regulate levels of adenylated hTR through PARN. The findings of our study uncover a mechanism by which PARN acetylation and deacetylation regulate its enzymatic activity as well as levels of mature hTR. Thus, PARN's acetylation status may play a role in regulating telomere length.

1944-P: CREBZF Acetylation at Lys126 Couples Glucose to White Adipose Tissue Browning

Glucose uptake is highly induced during cold exposure or feeding in adipocytes, which is utilized as an important energy source for most cells. However, little is known about whether glucose regulates downstream targets that govern thermogenesis and metabolic homeostasis in adipose tissue. Here, we characterize CREB/ATF bZIP transcription factor CREBZF as a novel glucose sensor and regulates thermogenesis via acetylation in adipocytes. Proteomic analysis using LC-MS/MS identifies Lys126 as an evolutionally conserved residue that is acetylated in a glucose-dependent manner. Ectopic expression of CREBZF mutant, in which Lys126 is substituted by alanine, abolishes glucose-stimulated acetylation and protein stabilization of CREBZF. The effects of glucose on protein stabilization of CREBZF are regulated by reversible acetylation that is mediated by transacetylase CBP/p300 and deacetylase HDAC3. Interestingly, endogenous levels of CREBZF are induced by pharmacological inhibition of HDAC3 RGFP966 in SVF-differentiated primary adipocytes. Adipose specific CREBZF knockout (FKO) mice were cold insensitivity and showed enhanced browning and energy metabolism. In the inguinal white adipose tissue (iWAT) of mice in response to cold exposure or β3-adrenergic receptor agonist, the activity of CREBZF is increased, leading to decreased thermogenic gene expression, energy expenditure, and cold tolerance. These findings 1) characterize glucose as a chemical signal to regulate acetylation and stabilization of CREBZF in adipocytes; 2) reveal that Lys126 may play a key role in mediating glucose’s effects on the stimulation of CREBZF activity and inhibition of white adipose tissue browning; 3) uncover an unknown mechanism of glucose sensing in the adipocyte that contributes to homeostasis of energy metabolism. Disclosure A. Cui: None. W. Su: None. Y. Xue: None. Z. Liu: None. F. Ma: None. Y. Liu: None. Z. Hu: None. Y. Han: None. G. Cai: None. J. Gao: None. E. Chin: None. A. Xu: None. Y. Li: None. Funding National Key Research and Development Program of China (2019YFA0802502); National Natural Science Foundation of China (81925008); Chinese Academy of Sciences (XDA12030210); Shanghai Science and Technology Commission (19140903300)

GC-MS and Molecular Docking Studies of Tecoma Stans Methanolic Leaf Extract As Potent Anti-Alzheimer’s

The aim of this study was to explore the anti-alzhemier’s effect of phytocompounds identified from Tecoma stans using GC-MS analysis and molecular docking studies. Acetylcholinesterase antagonists are beneficial in the treatment of Alzheimer’s by improving the cholinergic deficit. The aim of the present study was to investigate the AchE antagonistic property of phytocompounds from Tecoma stans using an in silico approach. Molecular docking of Tecoma stans on human AchE protein was determined by Glide 5.6 (Schrodinger Inc) and compared with Donepezil, a known reversible acetyl cholinesterase inhibitor. Our present study reports the phytochemical analysis of the extract of the leaves of Tecoma stans. 25 compounds were revealed through GC-MS analysis and screened using Glide 5.6 (Schrodinger Inc) against AchE. Docking studies recommended that luteolin and quercetin, an existing phytochemical from the leaves of Tecoma stans had the highest fitness score of −14.95 kcal/mol, -14.58 kcal/mol and hence could be a potent antialzheimer’s drugs. Tecoma stans leaf extract and its compounds luteolin and quercetin have a significant antialzheimer’s against AchE. The molecular binding interaction of an in-silico data demonstrated that luteolin and quercetin has more specificity towards the AchE binding site and could be a potent antialzheimer’s compound.

Histone deacetylases as targets in autoimmune and autoinflammatory diseases.

Reversible lysine acetylation of histones is a key epigenetic regulatory process controlling gene expression. Reversible histone acetylation is mediated by two opposing enzyme families: histone acetyltransferases (HATs) and histone deacetylases (HDACs). Moreover, many non-histone targets of HATs and HDACs are known, suggesting a crucial role for lysine acetylation as a posttranslational modification on the cellular proteome and protein function far beyond chromatin-mediated gene regulation. The HDAC family consists of 18 members and pan-HDAC inhibitors (HDACi) are clinically used for the treatment of certain types of cancer. HDACi or individual HDAC member-deficient (cell lineage-specific) mice have also been tested in a large number of preclinical mouse models for several autoimmune and autoinflammatory diseases and in most cases HDACi treatment results in an attenuation of clinical disease severity. A reduction of disease severity has also been observed in mice lacking certain HDAC members. This indicates a high therapeutic potential of isoform-selective HDACi for immune-mediated diseases. Isoform-selective HDACi and thus targeted inactivation of HDAC isoforms might also overcome the adverse effects of current clinically approved pan-HDACi. This review provides a brief overview about the fundamental function of HDACs as epigenetic regulators, highlights the roles of HDACs beyond chromatin-mediated control of gene expression and summarizes the studies showing the impact of HDAC inhibitors and genetic deficiencies of HDAC members for the outcome of autoimmune and autoinflammatory diseases with a focus on rheumatoid arthritis, inflammatory bowel disease and experimental autoimmune encephalomyelitis (EAE) as an animal model of multiple sclerosis.

Acetylation Stabilizes Phosphoglycerate Dehydrogenase by Disrupting the Interaction of E3 Ligase RNF5 to Promote Breast Tumorigenesis

Phosphoglycerate dehydrogenase (PHGDH) is the first and the rate-limiting enzyme in the serine synthesis pathway, which is significantly upregulated in many cancers, especially in breast cancer. However, the posttranslational mechanism of upregulating PHGDH in breast cancer is unknown. In this study, we found that RNF5, an E3 ubiquitin ligase, was essential for the degradation of PHGDH protein. PHGDH was degraded by RNF5 to prevent the proliferation of breast cancer cells. Acetylated at K58 of PHGDH was able to disrupt the interaction of RNF5-PHGDH and promote breast cancer cell proliferation. Tip60 and SIRT2 regulate the reversible acetylation modification of PHGDH in response to glucose alteration. Interestingly, PHGDH was significantly upregulated in PR-negative breast cancer compared with other breast cancer subtypes, which implying a potential therapeutic target through interference acetylation to degrade PHGDH in PR-negative breast cancer.

New AMP-forming acid:CoA ligases from Streptomyces lividans, some of which are posttranslationally regulated by reversible lysine acetylation.

In nature, organic acids are a commonly used source of carbon and energy. Many bacteria use AMP-forming acid:CoA ligases to convert organic acids into their corresponding acyl-CoA derivatives, which can then enter metabolism. The soil environment contains a broad diversity of organic acids, so it is not surprising that bacteria such as Streptomyces lividans can activate many of the available organic acids. Our group has shown that the activity of many acid:CoA ligases is posttranslationally controlled by acylation of an active-site lysine. In some cases, the modification is reversed by deacylases of different types. We identified eight new acid:CoA ligases in S. lividans TK24. Here, we report the range of organic acids that each of these enzymes can activate, and determined that two of thenewly identified CoA ligases were under NAD+ -dependent sirtuin deacylase reversible lysine (de)acetylation control, four were not acetylated by two acetyltransferases used in this work, and two were acetylated but not deacetylated by sirtuin. This work provides insights into the broad organic-acid metabolic capabilities of S. lividans, and sheds light into the control of the activities of CoA ligases involved in the activation of organic acids in this bacterium.

Boundary maintenance in the ancestral metazoan Hydra depends on histone acetylation

Much of boundary formation during development remains to be understood, despite being a defining feature of many animal taxa. Axial patterning of Hydra, a member of the ancient phylum Cnidaria which diverged prior to the bilaterian radiation, involves a steady-state of production and loss of tissue, and is dependent on an organizer located in the upper part of the head. We show that the sharp boundary separating tissue in the body column from head and foot tissue depends on histone acetylation. Histone deacetylation disrupts the boundary by affecting numerous developmental genes including Wnt components and prevents stem cells from entering the position dependent differentiation program. Overall, our results suggest that reversible histone acetylation is an ancient regulatory mechanism for partitioning the body axis into domains with specific identity, which was present in the common ancestor of cnidarians and bilaterians, at least 600 million years ago.

DWARF WITH SLENDER LEAF1 Encoding a Histone Deacetylase Plays Diverse Roles in Rice Development.

In plants, reversible histone acetylation and deacetylation play a crucial role in various biological activities, including development and the response to environmental stress. Histone deacetylation, which is generally associated with gene silencing, is catalyzed by multiple histone deacetylases (HDACs). Our understanding of HDAC function in plant development has accumulated from molecular genetic studies in Arabidopsis thaliana. By contrast, how HDACs contribute to the development of rice (Oryza sativa) is poorly understood and no rice mutants of HDAC have been reported. Here we have characterized a new rice mutant showing semi-dwarfism, which we named dwarf with slender leaf1 (dsl1). The mutant showed pleiotropic defects in both vegetative and reproductive developments; e.g. dsl1 produced short and narrow leaves, accompanied by a reduction in the number and size of vascular bundles. The semi-dwarf phenotype was due to suppression of the elongation of some culm (stem) internodes. Interestingly, despite this suppression of the upper internodes, the elongation and generation of lower internodes were slightly enhanced. Inflorescence and spikelet development were also affected by the dsl1 mutation. Some of the observed morphological defects were related to a reduction in cell numbers, in addition to reduced cell division in leaf primordia revealed by in situ hybridization analysis, suggesting the possibility that DSL1 is involved in cell division control. Gene cloning revealed that DSL1 encodes an HDAC belonging to the reduced potassium dependence3/histone deacetylase1 family. Collectively, our study shows that the HDAC DSL1 plays diverse and important roles in development in rice.

Make the right measurement: Discovery of an allosteric inhibition site for p300-HAT.

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) catalyze the dynamic and reversible acetylation of proteins, an epigenetic regulatory mechanism associated with multiple cancers. Indeed, HDAC inhibitors are already approved in the clinic. The HAT paralogs p300 and CREB-binding protein (CBP) have been implicated in human pathological conditions including several hematological malignancies and androgen receptor-positive prostate cancer. Others have reported CoA-competitive inhibitors of p300 and CBP with cell-based activity. Here, we describe 2 compounds, CPI-076 and CPI-090, discovered through p300-HAT high throughput screening screening, which inhibit p300-HAT via binding at an allosteric site. We present the high resolution (1.7 and 2.3 Å) co-crystal structures of these molecules bound to a previously undescribed allosteric site of p300-HAT. Derivatization yielded actionable structure-activity relationships, but the full-length enzymatic assay demonstrated that this allosteric HAT inhibitor series was artifactual, inhibiting only the HAT domain of p300 with no effect on the full-length enzyme.

Enzymatic and nonenzymatic protein acetylations control glycolysis process in liver diseases.

Impaired glycolysis has pathologic effects on the occurrence and progression of liver diseases, and it appears that glycolysis is increased to different degrees in different liver diseases. As an important post-translational modification, reversible lysine acetylation regulates almost all cellular processes, including glycolysis. Lysine acetylation can occur enzymatically with acetyltransferases or nonenzymatically with acetyl-coenzyme A. Accompanied by the progression of liver diseases, there seems to be a temporal and spatial variation between enzymatic and nonenzymatic acetylations in the regulation of glycolysis. Here, we summarize the most recent findings on the functions and targets of acetylation in controlling glycolysis in the different stages of liver diseases. In addition, we discuss the differences and causes between enzymatic and nonenzymatic acetylations in regulating glycolysis throughout the progression of liver diseases. Then, we review these new discoveries to provide the potential implications of these findings for therapeutic interventions in liver diseases.-Li, J., Wang, T., Xia, J., Yao, W., Huang, F. Enzymatic and nonenzymatic protein acetylations control glycolysis process in liver diseases.

Lysine acetyltransferases and lysine deacetylases as targets for cardiovascular disease.

Lysine acetylation is a conserved, reversible, post-translational protein modification regulated by lysine acetyltransferases (KATs) and lysine deacetylases (KDACs; also known as histone deacetylases (HDACs)) that is involved in many cellular signalling pathways and diseases. Studies in animal models have revealed a regulatory role of reversible lysine acetylation in hypertension, vascular diseases, arrhythmia, heart failure and angiogenesis. Evidence from these studies indicates a therapeutic role of KDAC inhibitors (also known as HDAC inhibitors) in cardiovascular diseases. In this Review, we describe the diverse roles of KATs and KDACs in both the normal and the diseased heart. Among KDACs, class II and class III HDACs seem to have a protective role against both cardiac damage and vessel injury, whereas class I HDACs protect against vessel injury but have deleterious effects on the heart. These observations have important implications for the clinical utility of HDAC inhibitors as therapeutic agents for cardiovascular diseases. In addition, we summarize the latest data on nonacetylation acylations in the context of cardiovascular disease.

Systematic analysis of lysine acetylome reveals potential functions of lysine acetylation in Shewanella baltica, the specific spoilage organism of aquatic products

Protein lysine acetylation is a major post-translational modification and plays a critical regulatory role in almost every aspect in both eukaryotes and prokaryotes, yet there have been no data on Shewanella baltica, which is one of the specific spoilage organism (SSO) of aquatic products. Here, we performed the first global acetylproteome analysis of S. baltica. 2929 lysine acetylation sites were identified in 1103 proteins, accounting for 26.1% of the total proteins which participate in a wide variety of biological processes, especially in the constituent of ribosome, the biosynthesis of aminoacyl-tRNA, the amino acids and fatty acid metabolism. Besides, 14 conserved acetylation motifs were detected in S. baltica. Notably, various directly or indirectly spoilage-related proteins were prevalently acetylated, including enzymes involved in the unsaturated fatty acids biosynthesis closely related to the cold adaptability, cold shock proteins, pivotal enzymes involved in the putrescine biosynthesis, and a LuxR-type protein in quorum sensing system. The acetylome analysis in Shewanella can supplement the database and provide new insight into uncovering the spoilage mechanisms of S. baltica. The provided dataset illuminates the potential role of reversible acetylation in S. baltica, and serves as an important resource for exploring the physiological role of lysine acetylation in prokaryotes. SignificanceThe psychrotrophic nature and the ability of S. baltica to make good use of “habitat” nutrients explain its importance in spoilage of seafood stored at low temperatures. However, the underlying mechanism of spoilage potential from the perspective of protein post-translational modification was rarely studied. This work identifies the first comprehensive survey of a lysine acetylome in S. baltica and uncovers the involvement of lysine acetylation in the diverse biological processes, especially in the closely spoilage-related pathways. This study provides a resource for functional analysis of acetylated proteins and creates opportunities for in-depth elucidation of the physiological role of protein acetylation in Shewanella spp.

311-OR: CREBZF as a Novel Target of Glucose Sensing Signaling in the Control of Adaptive Thermogenesis in the Adipose Tissue

Although glucose is generally considered to be required for generating heat during cold-induced nonshivering thermogenesis in the adipose tissue, whether it engages nutrient sensing pathways in the adipose tissue to negatively regulate thermogenesis and impairs metabolic homeostasis remains largely unknown. Here we report CREB/ATF bZIP transcription factor CREBZF as a key target of adipocyte glucose sensing signaling that exerts a negative effect on the adaptive thermogenesis in the adipose tissue. We found that CREBZF was significantly induced in inguinal white adipose tissue (iWAT) in response to cold exposure or β3AR agonist treatment, which was associated with an induced expression of glucose transporter genes such as GLUT1 and GLUT4. To elucidate the function of CREBZF, we generated adipose-specific CREBZF knockout (CREBZF FKO) mice. Compared with WT mice, CREBZF FKO mice exhibited enhanced browning of iWAT and thermogenic capacity in response to acute and chronic cold exposure. Moreover, CREBZF FKO mice were less cold sensitive. In the adipocyte, CREBZF was induced by glucose treatment, which was associated with increased acetylation of CREBZF. Interestingly, the protein stability of CREBZF was dynamically regulated by reversible acetylation mediated by transacetylase CREB-binding protein (CBP) and deacetylase HDAC. Deletion of CBP ameliorated glucose-induced CREBZF. Proteomic analysis was performed to identify potential acetylation sites of CREBZF. Furthermore, CREBZF associated with PGC-1α and inhibited its transcription activity. Together, we propose that in addition to its role as a fuel source to promote thermogenesis, glucose may act as a chemical signal to stimulate CREBZF activity and cause impaired browning and thermogenesis in the adipose tissue. This study uncovers an unknown mechanism of glucose sensing in the adipocyte that contributes to homeostasis of energy metabolism. Disclosure A. Cui: None. Z. Liu: None. F. Ma: None. J. Bai: None. Y. Xue: None. Y. Liu: None. Z. Hu: None. Y. Han: None. F.F. Zhang: None. J. Gao: None. X. Gao: None. Y. Li: None. Funding National Key Research and Development Program of China (2017YFC0909601); National Natural Science Foundation of China (31471129, 31671224); Chinese Academy of Sciences (KJZD-EW-G20-02); K.C. Wong Education Foundation (to Y.L.)

Staphylococcus aureus modulates the activity of acetyl-Coenzyme A synthetase (Acs) by sirtuin-dependent reversible lysine acetylation.

Lysine acylation is a posttranslational modification used by cells of all domains of life to modulate cellular processes in response to metabolic stress. The paradigm for the role of lysine acylation in metabolism is the acetyl-coenzyme A synthetase (Acs) enzyme. In prokaryotic and eukaryotic cells alike, Acs activity is downregulated by acetylation and reactivated by deacetylation. Proteins belonging to the bacterial GCN5-related N-acetyltransferase (bGNAT) superfamily acetylate the epsilon amino group of an active site lysine, inactivating Acs. A deacetylase can remove the acetyl group, thereby restoring activity. Here we show the Acs from Staphylococcus aureus (SaAcs) activates acetate and weakly activates propionate, but does not activate >C3 organic acids or dicarboxylic acids (e.g. butyrate, malonate and succinate). SaAcs activity is regulated by AcuA (SaAcuA); a type-IV bGNAT. SaAcuA can acetylate or propionylate SaAcs reducing its activity by >90% and 95% respectively. SaAcuA also succinylated SaAcs, with this being the first documented case of a bacterial GNAT capable of succinylation. Inactive SaAcsAc was deacetylated (hence reactivated) by the NAD+ -dependent (class III) sirtuin protein deacetylase (hereafter SaCobB). In vivo and in vitro evidence show that SaAcuA and SaCobB modulate the level of SaAcs activity in S. aureus.

Molecular characterization of class I histone deacetylases and their expression in response to thermal and oxidative stresses in the red flour beetle, Tribolium castaneum.

Reversible acetylation of core histones plays an important role in the epigenetic regulation of gene transcription, and is controlled by the action of histone acetyltransferases (HATs) and histone deacetylases (HDACs). While HDACs have been well studied in Drosophila melanogaster, information from insect pests is still limited. In the current study, we cloned and characterized three class I enzymes, TcHDAC1, TcHDAC 3 and TcHDAC 8, in the red flour beetle, Tribolium castaneum. Expression profiling showed that T. castaneum HDAC genes are expressed in all developmental stages and tissues examined. A dramatic increase of mRNA expression level was observed from prepupae to 1-day-old pupae for all three T. castaneum HDAC genes. Both TcHDAC1 and TcHDAC3 exhibited the highest mRNA expression levels in thorax, whereas TcHDAC8 was highly expressed in fat body. Furthermore, T. castaneum HDAC genes were found to respond to heat, cold and oxidative stresses. While the heat-stress treatment decreased the mRNA expression levels of T. castaneum HDAC genes, their transcripts were induced by paraquat treatment. These results suggest a possible role for class I HDAC genes in the epigenetic regulation of T. castaneum development and stress responses.

HDAC2 Regulates Site-Specific Acetylation of MDM2 and Its Ubiquitination Signaling in Tumor Suppression

SummaryHistone deacetylases (HDACs) are promising targets for cancer therapy, although their individual actions remain incompletely understood. Here, we identify a role for HDAC2 in the regulation of MDM2 acetylation at previously uncharacterized lysines. Upon inactivation of HDAC2, this acetylation creates a structural signal in the lysine-rich domain of MDM2 to prevent the recognition and degradation of its downstream substrate, MCL-1 ubiquitin ligase E3 (MULE). This mechanism further reveals a therapeutic connection between the MULE ubiquitin ligase function and tumor suppression. Specifically, we show that HDAC inhibitor treatment promotes the accumulation of MULE, which diminishes the t(X; 18) translocation-associated synovial sarcomagenesis by directly targeting the fusion product SS18-SSX for degradation. These results uncover a new HDAC2-dependent pathway that integrates reversible acetylation signaling to the anticancer ubiquitin response.