Aspartate Residues Far From the Active Site Drive O-GlcNAc Transferase Substrate Selection
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE132205 | GEO | 2019/07/24
REPOSITORIES: GEO
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Project description:Here we use protein microarray technology and proteome-wide glycosylation profiling to show that conserved aspartate residues in the tetratricopeptide repeat (TPR) lumen of OGT drive substrate selection. Changing these residues to alanines alters substrate selectivity and unexpectedly increases rates of protein glycosylation. Our findings support a model where sites of glycosylation for many OGT substrates are determined by TPR domain contacts to substrate side chains five to fifteen residues Cterminal to the glycosite. In addition to guiding design of inhibitors that target OGT’s TPR domain, this information will inform efforts to engineer substrates to explore biological functions.
2019-07-26 | PXD014731 | Pride
Project description:Abstract: The essential mammalian enzyme O-GlcNAc Transferase (OGT) is uniquely responsible for transferring N-acetylglucosamine to over a thousand nuclear and cytoplasmic proteins, yet there is no known consensus sequence and it remains unclear how OGT recognizes its substrates. To address this question, we have developed a protein microarray assay that chemoenzymatically labels de novo sites of glycosylation with biotin, allowing us to simultaneously as-sess OGT activity across >6000 human proteins. We used this assay to examine the contribution of a conserved asparagine ladder within the lumen of OGT’s superhelical tetratri-copeptide repeat (TPR) domain to substrate selection. When these residues were mutated, OGT retained full activity against short peptides, but showed low to no activity against most of the OGT substrates on the microarray. O-GlcNAcylation of protein substrates in cell extracts was also greatly attenuated. We conclude that OGT recognizes a majority of its substrates by binding them to the asparagine ladder in the TPR lumen proximal to the catalytic domain. This series contains microarray data both comparing the new chemoenzymatic method to antibody-based detection as well as comparing arrays treated with wild-type OGT, 5N5A mutant OGT, or controls not treated with enzyme. Note: all CTD-stained arrays or control array raw files are contained in GSE107911_RAW.tar
2018-02-26 | GSE107911 | GEO
Project description:Nucleocytoplasmic O-linked N-acetylglucosamine (O-GlcNAc) is an essential post-translational modification that is installed to thousands of protein substrates by O-GlcNAc transferase (OGT). Substrate selection by OGT and its isoforms is primarily mediated by the tetratricopeptide repeat (TPR) domain, yet the impact of truncations to the TPR domain on substrate and glycosite selection remains unresolved. Here, we report the effects of TPR truncations on the substrate and glycosite selection of OGT against the model protein GFP-JunB and the surrounding O-GlcNAc proteome in U2OS cells. Truncation of the TPR domain of OGT maintains glycosyltransferase activity but alters subcellular localization in cells. Examination of the glycoproteome across the TPR truncations revealed the broadest substrate activity from the canonical nucleocytoplasmic OGT, with the greatest changes in O-GlcNAc occurring on proteins associated with mRNA splicing processes. Glycosite analysis revealed alterations to the O-GlcNAc consensus sequence globally and differential glycosite selectivity on GFP-JunB as a function of the OGT TPR isoform. This dataset provides a foundation to analyze how perturbations to the TPR domain and expression of OGT isoforms affects the glycosylation of substrates, which will be critical for future protein engineering of OGT, the biology of OGT isoforms, and diseases associated with the TPR domain of OGT.
2021-11-01 | PXD028141 | Pride
Project description:The dynamic modification of specific serine and threonine residues of intracellular proteins by O-linked N-acetyl-β-D-glucosamine (O-GlcNAc) mitigates injury and promotes cytoprotection in a variety of stress models. The O-GlcNAc transferase (OGT) and the O-GlcNAcase (OGA) are the sole enzymes that add and remove O-GlcNAc, respectively, from thousands of substrates. It remains unclear how just two enzymes can be specifically controlled to affect glycosylation of target proteins and signaling pathways both basally and in response to stress. Several lines of evidence suggest that protein interactors regulate these responses by affecting OGT and OGA activity, localization and substrate specificity. To provide insight into the mechanisms by which OGT function is controlled, we have utilized quantitative proteomics to define OGT’s basal and stress-induced interactomes. OGT and its interaction partners were immunoprecipitated from OGT wild-type, null and hydrogen peroxide treated cell lysates that had been isotopically labeled with light, medium and heavy lysine and arginine (stable isotopic labeling of amino acids in cell culture [SILAC]). In total, more than 130 proteins were found to interact with OGT, many of which change their association upon hydrogen peroxide stress. These proteins include the major OGT cleavage and glycosylation substrate, host cell factor 1, which demonstrated a time-dependent dissociation following stress. To validate less-well characterized interactors, such as glyceraldehyde 3-phosphate dehydrogenase and histone deacetylase 1, we turned to parallel reaction monitoring, which recapitulated our discovery-based SILAC approach. Although the majority of proteins identified are novel OGT interactors, 64% of them are previously characterized glycosylation targets that contain varied domain architecture and function. Together these data demonstrate that OGT interacts with unique and specific interactors in a stress-responsive manner.
2021-04-05 | PXD021091 | panorama
Project description:Drosophila development is a complex and dynamic process regulated, in part, by members of the Polycomb (Pc), Trithorax (Trx) and Compass chromatin modifier complexes. O-GlcNAc Transferase (OGT/SXC) is essential for Pc repression suggesting that the O-GlcNAcylation of proteins plays a key role in regulating development. OGT transfers N-acetyl-D-glucosamine (GlcNAc) onto hydroxyl groups of serine or threonine residues of key transcriptional regulators using the nutrient-derived UDP-GlcNAc as a substrate, which is dynamically removed by O-GlcNAcase (OGA). We performed ChIP-chip and microarray analysis after OGT or OGA RNAi knockdown in Drosophila S2 cells and found that O-GlcNAc was elevated genome wide particularly at genes related to mitosis and cell cycle in OGA RNAi cells, but not at sites co-occupied by Pc member Pleiohomeotic (Pho), such as the Hox and NK homeobox gene clusters. Microarray analysis suggested that altered O-GlcNAc cycling perturbed the expression of genes associated with morphogenesis and cell cycle regulation. To examine the in vivo consequences of disturbed O-GlcNAc cycling in the whole animal, we produced a null allele of oga (ogadel.1) in Drosophila. Epigenetic activators including Trx group members Trithorax (Trx), Absent small or homeotic discs 1 (Ash1) and Compass member Set1 histone methyltransferases are O-GlcNAc modified in ogadel.1 mutants. ogadel.1 mutants displayed altered expression of a distinct set of cell cycle related genes in ovaries. Our results suggest that the loss of OGA could affect epigenetic machinery by accumulating O-GlcNAc on numerous chromatin factors including Trx, Ash1 and Set1 in Drosophila. We performed affymetrix tilingarray analysis after OGT or OGA RNAi knockdown in Drosophila S2 cells to find if that O-GlcNAc was elevated genome wide particularly at genes related to mitosis and cell cycle in OGA RNAi cells, but not at sites co-occupied by Pc member Pleiohomeotic (Pho), ------------------------------- This represents the gene expression component only
2016-07-21 | E-GEOD-74846 | biostudies-arrayexpress
Project description:O-GlcNAcylation occurs on thousands of proteins involved in various cellular events. O-GlcNAc transferase (OGT), one of the enzymes responsible for protein O-GlcNAcylation, is known to be auto-O-GlcNAcylated at multiple sites. However, the role of O-GlcNAcylation on OGT is still unknown. Here, we report the role of O-GlcNAcylation on short form OGT (sOGT). By LC-ETD-MS analysis and western blot, we show that sOGT was mainly O-GlcNAcylated in the tetratricopeptide repeat (TPR) motifs with T12 and S56 being two “key” sites. T12 was a predominant O-GlcNAcylation site and the absence of S56 O-GlcNAcylation enhanced sOGT O-GlcNAcylation level. We found that O-GlcNAcylation of sOGT did not affect the enzyme activity but increased its binding to substrate proteins. S56A bound to and hence glycosylated more proteins, while T12A associated with fewer substrates. Proteomic studies combined with cell proliferation/cell cycle analyses indicated that S56A substantially enhanced cell proliferation, while T12A reduced it, and T12A led to a G2/M cell cycle arrest, due to O-GlcNAcylation of diverse proteins. These findings demonstrate that the O-GlcNAc pattern on sOGT modulates its function in cells by targeting different proteins.
2019-09-16 | PXD010173 | Pride
Project description:O-GlcNAcylation occurs on thousands of proteins involved in various cellular events. O-GlcNAc transferase (OGT), one of the enzymes responsible for protein O-GlcNAcylation, is known to be auto-O-GlcNAcylated at multiple sites. However, the role of O-GlcNAcylation on OGT is still unknown. Here, we report the role of O-GlcNAcylation on short form OGT (sOGT). By LC-ETD-MS analysis and western blot, we show that sOGT was mainly O-GlcNAcylated in the tetratricopeptide repeat (TPR) motifs with T12 and S56 being two “key” sites. T12 was a predominant O-GlcNAcylation site and the absence of S56 O-GlcNAcylation enhanced sOGT O-GlcNAcylation level. We found that O-GlcNAcylation of sOGT did not affect the enzyme activity but increased its binding to substrate proteins. S56A bound to and hence glycosylated more proteins, while T12A associated with fewer substrates. Proteomic studies combined with cell proliferation/cell cycle analyses indicated that S56A substantially enhanced cell proliferation, while T12A reduced it, and T12A led to a G2/M cell cycle arrest, due to O-GlcNAcylation of diverse proteins. These findings demonstrate that the O-GlcNAc pattern on sOGT modulates its function in cells by targeting different proteins.
2019-09-16 | PXD009731 | Pride
Project description:OGT (O-GlcNAc transferase) is the distinctive enzyme responsible for catalyzing O-GlcNAc to the serine or threonine residues of thousands of cytoplasm and nuclear proteins that are involved in DNA damage, RNA splicing, and transcription preinitiation and initiation complex assembly. However, the molecular mechanism by OGT regulating gene transcription remains elusive. Using proximity labeling based mass spectrometry, we searched for functional partners of OGT and found that Dot1L, the conserved and unique histone methyltransferase mediated histone H3 lys79 methylation required for gene transcription, DNA damage repair, cell proliferation, and embryo development, interacts with OGT. Although this specific interaction does not regulate the enzymatic activity of Dot1L, it facilitates OGT-dependent histones O-GlcNAcylation. Moreover, OGT associates with Dot1L at transcription start sites, and depleting Dot1L decreased OGT associated with chromatin globally. Notably, downregulation of Dot1L reduces the levels of histone H2B S112 O-GlcNAcylation and histone H2B K120 ubiquitination in vivo, which are associated with gene transcription regulation. Taken together, these results reveal a Dot1L-dependent O-GlcNAcylation of chromatin.
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Project description:O-linked N-acetylglucosamine (O-GlcNAc ) transferase (OGT) activity is essential for embryonic stem (ES) cell viability and mouse development. OGT is present in both cytoplasm and nucleus of different cell types and mediates serine or threonine glycosylation. The Ogt gene locus resides on the X-chromosome and its activity is required for the viability of male ES cells. Using Ogt conditional knock out (KO) ES cells it was shown the failure of establishing stable KO ES clones further suggesting that Ogt activity is required for ES cell self-renewal and pluripotency. For understanding these changes, we performed global gene expression upon silencing of Ogt mediated by esiRNA in mouse Embryonic Stem Cells. Total RNA was extracted from E14 ES cells (derived from Ola129 mice) transiently transfected with Ogt specific and control esiRNA oligos 48 hrs. post-transfection.
2013-01-06 | E-GEOD-39321 | biostudies-arrayexpress
Project description:Tumorigenesis is characterised by changes in transcriptional regulation and the androgen receptor (AR) has been identified as a key driver in prostate cancer. In this study, we show that the hexosamine biosynthetic pathway (HBP) genes are overexpressed in clinical prostate cancer and androgen-regulated in cell-lines. HBP senses metabolic status of the cell and produces an essential substrate for O-GlcNAc transferase (OGT), which regulates target proteins via glycosylation. Using immunohistochemistry, we found that OGT is up-regulated in the protein level in prostate cancer (n=1987) and its expression correlates with high Gleason Score, pT and pN stages and biochemical recurrence (for all, p<0.0001). Both a small molecule inhibitor and siRNAs targeting OGT decreased prostate cancer cell growth. Microarray profiling revealed that the principal effects of the OGT inhibitor in prostate cancer cells are on cell cycle progression and DNA replication. We identified MYC as a candidate upstream regulator of these genes and found that OGT inhibitor caused a dose-dependent loss of c-MYC protein but not mRNA in cell lines. Finally, we observed a statistically significant co-expression between c-MYC and OGT in human prostate cancer samples (n=1306, p=0.0012). Total RNA was extracted and experiment has three biological replicates for each condition, conditions are: 12 hours ST045849, 24 hours ST045849, 12 hours vehicle, 24 hours vehicle, 12 hours siOGT, 24 hours siOGT, 12 hours scrambled, 24 hours scrambled
2013-05-30 | E-GEOD-44624 | biostudies-arrayexpress