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SummaryTET enzymes including TET1, 2 and 3 convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC)1 and regulate gene transcription2-5. However, this molecular mechanism by which TET family enzymes regulate gene transcription remains elusive5-6. Here, using protein affinity purification, we searched for functional partners of TET proteins, and found that TET2 and TET3 associate with OGT, an enzyme that by itself catalyzes O-GlcNAcylation in vivo7-8. TET2 directly interacts with OGT, which is important for the chromatin association of OGT in vivo. Although this specific interaction does not regulate the enzymatic activity of TET2, it facilitates OGT-dependent histone O-GlcNAcylation. Moreover, OGT associates with TET2 at transcription starting sites (TSS). Down-regulation of TET2 reduces the amount of H2B S112 GlcNAc marks in vivo, which are associated with gene transcription regulation. Taken together, these results reveal a TET2-dependent O-GlcNAcylation of chromatin. The double epigenetic modifications on both DNA and histones by TET2 and OGT coordinate together for the gene transcription regulation.

Chromatin reorganization is governed by multiple post-translational modifications of chromosomal proteins and DNA. These histone modifications are reversible, dynamic events that can regulate DNA-driven cellular processes. However, the molecular mechanisms that coordinate histone modification patterns remain largely unknown. In metazoans, reversible protein modification by O-linked N-acetylglucosamine (GlcNAc) is catalysed by two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). However, the significance of GlcNAcylation in chromatin reorganization remains elusive. Here we report that histone H2B is GlcNAcylated at residue S112 by OGT in vitro and in living cells. Histone GlcNAcylation fluctuated in response to extracellular glucose through the hexosamine biosynthesis pathway (HBP). H2B S112 GlcNAcylation promotes K120 monoubiquitination, in which the GlcNAc moiety can serve as an anchor for a histone H2B ubiquitin ligase. H2B S112 GlcNAc was localized to euchromatic areas on fly polytene chromosomes. In a genome-wide analysis, H2B S112 GlcNAcylation sites were observed widely distributed over chromosomes including transcribed gene loci, with some sites co-localizing with H2B K120 monoubiquitination. These findings suggest that H2B S112 GlcNAcylation is a histone modification that facilitates H2BK120 monoubiquitination, presumably for transcriptional activation.