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A neutral diphosphate mimic crosslinks the active site of human O-GlcNAc transferase.

ABSTRACT: Glycosyltransferases (Gtfs) catalyze the formation of a diverse array of glycoconjugates. Small-molecule inhibitors to manipulate Gtf activity in cells have long been sought as tools for understanding Gtf function. Success has been limited because of challenges in designing inhibitors that mimic the negatively charged diphosphate substrates. Here we report the mechanism of action of a small molecule that inhibits O-linked N-acetylglucosamine transferase (OGT), an essential human enzyme that modulates cell signaling pathways by catalyzing a unique intracellular post-translational modification, ?-O-GlcNAcylation. The molecule contains a five-heteroatom dicarbamate core that functions as a neutral diphosphate mimic. One dicarbamate carbonyl reacts with an essential active site lysine that anchors the diphosphate of the nucleotide-sugar substrate. A nearby cysteine then reacts with the lysine adduct to form a carbonyl crosslink in the OGT active site. Though this unprecedented double-displacement mechanism reflects the unique architecture of the OGT active site, related dicarbamate scaffolds may inhibit other enzymes that bind nucleotide-containing substrates.

SUBMITTER: Jiang J

PROVIDER: S-EPMC3241908 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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A neutral diphosphate mimic crosslinks the active site of human O-GlcNAc transferase.

Jiang Jiaoyang J Lazarus Michael B MB Pasquina Lincoln L Sliz Piotr P Walker Suzanne S

Nature chemical biology 20111113 1

Glycosyltransferases (Gtfs) catalyze the formation of a diverse array of glycoconjugates. Small-molecule inhibitors to manipulate Gtf activity in cells have long been sought as tools for understanding Gtf function. Success has been limited because of challenges in designing inhibitors that mimic the negatively charged diphosphate substrates. Here we report the mechanism of action of a small molecule that inhibits O-linked N-acetylglucosamine transferase (OGT), an essential human enzyme that modu ...[more]

PMID: 22082911

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Project description:BackgroundTranscription, metabolism and DNA damage response are tightly regulated to preserve the genomic integrity, and O-GlcNAc transferase (OGT) is positioned to connect the three. Prostate cancer is the most common cancer in men, and androgen-ablation therapy halts disease progression. However, a significant number of prostate cancer patients develop resistance against anti-androgens, and this incurable disease is termed castration-resistant prostate cancer (CRPC). We have shown that combined inhibition of OGT and the transcription elongation kinase CDK9 induce CRPC-selective anti-proliferative effects. Here, we explain the functional basis for these combinatorial effects.MethodsWe used comprehensive mass spectrometry profiling of short-term CDK9 inhibitor effects on O-GlcNAcylated proteins in an isogenic cell line system that models transition from PC to CRPC. In addition, we used both ChIP-seq and RNA-seq profiling, and pulldown experiments in multiple CRPC models. Finally, we validated our findings in prostate cancer patient samples.ResultsInhibition of CDK9 results in an OGT-dependent remodeling of the proteome in prostate cancer cells. More specifically, the activity of the DNA damage repair protein MRE11 is regulated in response to CDK9 inhibition in an OGT-dependent manner. MRE11 is enriched at the O-GlcNAc-marked loci. CDK9 inhibition does not decrease the expression of mRNAs whose genes are bound by both O-GlcNAc and MRE11. Combined inhibition of CDK9 and OGT or MRE11 further decreases RNA polymerase II activity, induces DNA damage signaling, and blocks the survival of prostate cancer cells. These effects are seen in CRPC cells but not in normal prostate cells. Mechanistically, OGT activity is required for MRE11 chromatin-loading in cells treated with CDK9 inhibitor. Finally, we show that MRE11 and O-GlcNAc are enriched at the prostate cancer-specific small nucleotide polymorphic sites, and the loss of MRE11 activity results in a hyper-mutator phenotype in patient tumors.ConclusionsBoth OGT and MRE11 are essential for the repair of CDK9 inhibitor-induced DNA damage. Our study raises the possibility of targeting CDK9 to elicit DNA damage in CRPC setting as an adjuvant to other treatments.

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A neutral diphosphate mimic crosslinks the active site of human O-GlcNAc transferase.

Publications

A neutral diphosphate mimic crosslinks the active site of human O-GlcNAc transferase.

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