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Project description:The DNA methyltransferase activity of DNMT1 is vital for genomic maintenance of DNA methylation. We report here that DNMT1 function is regulated by O-GlcNAcylation, a protein modification that is sensitive to glucose levels, and that elevated O-GlcNAcylation of DNMT1 from high glucose environment leads to alterations to the epigenome. Using mass spectrometry and complementary alanine mutation experiments, we identified S878 as the major residue that is O-GlcNAcylated on human DNMT1. Functional studies in human and mouse cells further revealed that O-GlcNAcylation of DNMT1-S878 results in an inhibition of methyltransferase activity, resulting in a general loss of DNA methylation that preferentially occurs at partially methylated domains (PMDs). This loss of methylation corresponds with an increase in DNA damage and apoptosis. These results establish O-GlcNAcylation of DNMT1 as a mechanism through which the epigenome is regulated by glucose metabolism and implicates a role for glycosylation of DNMT1 in metabolic diseases characterized by hyperglycemia.
| S-EPMC10390045 | biostudies-literature
Project description:The DNA methyltransferase activity of DNMT1 is vital for genomic maintenance of DNA methylation. We report here that DNMT1 function is regulated by O-GlcNAcylation, a protein modification that is sensitive to glucose levels, and that elevated O-GlcNAcylation of DNMT1 from high glucose environment leads to alterations to the epigenome. Using mass spectrometry and complementary alanine mutation experiments, we identified S878 as the major residue that is O-GlcNAcylated on DNMT1. Functional studies further revealed that O-GlcNAcylation of DNMT1-S878 results in an inhibition of methyltransferase activity, resulting in a general loss of DNA methylation that is preferentially at partially methylated domains (PMDs). This loss of methylation corresponds with an increase in DNA damage and apoptosis. These results establish O-GlcNAcylation of DNMT1 as a mechanism through which the epigenome is regulated by glucose metabolism and implicates a role for glycosylation of DNMT1 in metabolic diseases characterized by hyperglycemia.
2023-07-26 | PXD043031 | Pride
Project description:Inhibition of DNMT1 methyltransferase activity via glucose-regulated O-GlcNAcylation alters the epigenome
| PRJNA831845 | ENA
Project description:DNA methylation and histone acetylation/deacetylation are distinct biochemical processes that control gene expression. While DNA methylation is a common epigenetic signal that inhibits gene transcription, histone deacetylation similarly represses transcription but can be both an epigenetic and nonepigenetic phenomenon. Here we report that the histone deacetylase SIRT1 regulates the activities of DNMT1, a key enzyme responsible for DNA methylation. In mass spectrometry analysis, 12 new acetylated lysine sites were identified in DNMT1. SIRT1 physically associates with DNMT1 and can deacetylate acetylated DNMT1 in vitro and in vivo. Interestingly, deacetylation of different lysines on DNMT1 has different effects on the functions of DNMT1. For example, deacetylation of Lys1349 and Lys1415 in the catalytic domain of DNMT1 enhances DNMT1's methyltransferase activity, while deacetylation of lysine residues in the GK linker decreases DNMT1's methyltransferase-independent transcriptional repression function. Furthermore, deacetylation of all identified acetylated lysine sites in DNMT1 abrogates its binding to SIRT1 and impairs its capability to regulate cell cycle G(2)/M transition. Finally, inhibition of SIRT1 strengthens the silencing effects of DNMT1 on the expression of tumor suppressor genes ER-α and CDH1 in MDA-MB-231 breast cancer cells. Together, these results suggest that SIRT1-mediated deacetylation of DNMT1 is crucial for DNMT1's multiple effects in gene silencing.
| S-EPMC3232929 | biostudies-literature
Project description:The subcutaneous and systemic injection of serotonin reduces cutaneous and visceral pain thresholds and increases responses to noxious stimuli. Different subtypes of 5-hydroxytryptamine (5-HT) receptors are suggested to be associated with different types of pain responses. Here we show that serotonin also inhibits catechol O-methyltransferase (COMT), an enzyme that contributes to modultion the perception of pain, via non-competitive binding to the site bound by catechol substrates with a binding affinity comparable to the binding affinity of catechol itself (K(i)?=?44 ?M). Using computational modeling, biochemical tests and cellular assays we show that serotonin actively competes with the methyl donor S-adenosyl-L-methionine (SAM) within the catalytic site. Binding of serotonin to the catalytic site inhibits the access of SAM, thus preventing methylation of COMT substrates. The results of in vivo animal studies show that serotonin-induced pain hypersensitivity in mice is reduced by either SAM pretreatment or by the combined administration of selective antagonists for ?(2)- and ?(3)-adrenergic receptors, which have been previously shown to mediate COMT-dependent pain signaling. Our results suggest that inhibition of COMT via serotonin binding contributes to pain hypersensitivity, providing additional strategies for the treatment of clinical pain conditions.
| S-EPMC3495668 | biostudies-literature
Project description:ObjectiveThe intestine is an important organ for nutrient metabolism via absorption and endocrine systems. Nutrients regulate O-GlcNAcylation, a post-translational modification of various proteins by O-GlcNAc transferase (OGT). We have previously shown that general OGT knockout induced severe weight loss and hypoglycaemia in mice, but little is known about how O-GlcNAcylation in the intestine modulates nutrient metabolism, especially glucose metabolism, through absorption. We aimed to reveal the roles of O-GlcNAcylation in glucose absorption by the small intestine and elucidate the mechanism by which O-GlcNAcylation regulates sodium-glucose cotransporter 1 (SGLT1) expression.MethodsFirst, we fasted normal mice and examined the changes in glucose transporters and O-GlcNAcylation in the intestine. Then, we generated two lines of small intestine-specific OGT-deficient mice (congenital: Ogt-VKO, tamoxifen-inducible: Ogt-iVKO) and observed the changes in body weight and in glucose and lipid metabolism. Finally, we investigated Sglt1 gene regulation by O-GlcNAcylation using enteroendocrine STC-1 cells.ResultsFasting decreased O-GlcNAcylation in the intestinal epithelium of normal mice. The Ogt-VKO mice showed significantly lower non-fasted blood glucose levels and were underweight compared with litter matched controls. Glycaemic excursion in the Ogt-VKO mice was significantly lower during the oral glucose tolerance test but comparable during the intraperitoneal glucose tolerance test. Furthermore, the Ogt-VKO mice exhibited lower Sglt1 expression in the small intestine compared with the control mice. We obtained similar results using the Ogt-iVKO mice only after tamoxifen administration. The oral d-xylose administration test revealed that the intestinal sugar absorption was diminished in the Ogt-iVKO mice and that GLP-1 secretion did not sufficiently increase after glucose gavage in the Ogt-iVKO mice. When using STC-1 cells, O-GlcNAcylation increased Sglt1 mRNA via a PKA/CREB-dependent pathway.ConclusionCollectively, loss of O-GlcNAcylation in the intestine reduced glucose absorption via suppression of SGLT1 expression; this may lead to new treatments for malabsorption, obesity and diabetes.
| S-EPMC8902621 | biostudies-literature
Project description:Protein O-glycosylation by attachment of β-N-acetylglucosamine (GlcNAc) to the Ser or Thr residue is a major posttranslational glycosylation event and is often associated with protein folding, stability, and activity. The methylation of histone H3 at Lys-27 catalyzed by the methyltransferase EZH2 was known to suppress gene expression and cancer development, and we previously reported that the O-GlcNAcylation of EZH2 at S76 stabilized EZH2 and facilitated the formation of H3K27me3 to inhibit tumor suppression. In this study, we employed a fluorescence-based method of sugar labeling combined with mass spectrometry to investigate EZH2 glycosylation and identified five O-GlcNAcylation sites. We also find that mutation of one or more of the O-GlcNAcylation sites S73A, S76A, S84A, and T313A in the N-terminal region decreases the stability of EZH2, but does not affect its association with the PRC2 components SUZ12 and EED. Mutation of the C-terminal O-GlcNAcylation site (S729A) in the catalytic domain of EZH2 abolishes the di- and trimethylation activities, but not the monomethylation of H3K27, nor the integrity of the PRC2/EZH2 core complex. Our results show the effect of individual O-GlcNAcylation sites on the function of EZH2 and suggest an alternative approach to tumor suppression through selective inhibition of EZH2 O-GlcNAcylation.
| S-EPMC6048490 | biostudies-literature
Project description:CREB is a cAMP- and calcium-responsive transcriptional activator that is required for islet beta cell proliferation and survival. Glucose and incretin hormones elicit beta cell insulin secretion and promote synergistic CREB activity by inducing the nuclear relocalization of TORC2 (also known as Crtc2), a coactivator for CREB. In islet cells under basal conditions when CREB activity is low, TORC2 is phosphorylated and sequestered in the cytoplasm by 14-3-3 proteins. In response to feeding stimuli, TORC2 is dephosphorylated, enters the nucleus, and binds to CREB located at target gene promoters. The dephosphorylation of TORC2 at Ser-171 in response to cAMP is insufficient to account for the dynamics of TORC2 localization and CREB activity in islet cells. Here, we identify Ser-275 of TORC2 as a 14-3-3 binding site that is phosphorylated under low glucose conditions and which becomes dephosphorylated by calcineurin in response to glucose influx. Dephosphorylation of Ser-275 is essential for both glucose and cAMP-mediated activation of CREB in beta cells and islets. Using a cell-based screen of 180 human protein kinases, we identified MARK2, a member of the AMPK family of Ser/Thr kinases, as a Ser-275 kinase that blocks TORC2:CREB activity. Taken together, these data provide the mechanistic underpinning for how cAMP and glucose cooperatively promote a transcriptional program critical for islet cell survival, and identifies MARK2 as a potential target for diabetes treatment.
| S-EPMC2481316 | biostudies-literature
Project description:Epigenetic mechanisms are emerging key players for the regulation of brain function, synaptic activity, and the formation of neuronal engrams in health and disease. As one important epigenetic mechanism of transcriptional control, DNA methylation was reported to distinctively modulate synaptic activity in excitatory and inhibitory cortical neurons in mice. Since DNA methylation signatures are responsive to neuronal activity, DNA methylation seems to contribute to the neuron's capacity to adapt to and integrate changing activity patterns, being crucial for the plasticity and functionality of neuronal circuits. Since most studies addressing the role of DNA methylation in the regulation of synaptic function were conducted in mice or murine neurons, we here asked whether this functional implication applies to human neurons as well. To this end, we performed calcium imaging in human induced pluripotent stem cell (iPSC)-derived excitatory cortical neurons forming synaptic contacts and neuronal networks in vitro. Treatment with DNMT1 siRNA that diminishs the expression of the DNA (cytosine-5)-methyltransferase 1 (DNMT1) was conducted to investigate the functional relevance of DNMT1 as one of the main enzymes executing DNA methylations in the context of neuronal activity modulation. We observed a lowered proportion of actively firing neurons upon DNMT1-knockdown in these iPSC-derived excitatory neurons, pointing to a correlation of DNMT1-activity and synaptic transmission. Thus, our experiments suggest that DNMT1 decreases synaptic activity of human glutamatergic neurons and underline the relevance of epigenetic regulation of synaptic function also in human excitatory neurons.
| S-EPMC7922860 | biostudies-literature
Project description:Serine/threonine phosphorylation of the nonstructural protein 5 (NS5) is conserved feature of flaviviruses, but the kinase(s) responsible and function(s) remain unknown. Mass spectrometry was used to characterize phosphorylated residues of yellow fever virus (YFV) NS5 expressed in mammalian cells. Multiple different phosphopeptides were detected. Mutational and additional mass spectrometry data implicated serine 56 (S56), a conserved residue near the active site in the NS5 methyltransferase domain, as one of the phosphorylation sites. Methyltransferase activity is required to form a methylated RNA cap structure and for translation of the YFV polyprotein. We show the 2'-O methylation reaction requires the hydroxyl side chain of S56, and replacement with a negative charge inhibits enzymatic activity. Furthermore mutational alteration of S56, S56A or S56D, prevents amplification in a viral replicon system. Collectively our data suggest phosphorylation of NS5 S56 may act to shut down capping in the viral life cycle.
| S-EPMC2583469 | biostudies-literature