TET2 promotes histone O-GlcNAcylation during gene transcription

Abstract

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.

O-GlcNAcylation regulates EZH2 protein stability and function

“…The functions of most histone O-GlcNAcylations are currently not clear, nor do we completely understand how OGT is recruited to chromatin, although some progress has been made. It is known that OGT can bind to corepressor mSin3A (21) and also associate with the DNA demethylase TET family proteins TET2 and TET3 and potentiate TET family protein-mediated gene activation (22)(23)(24)(25). Another critical mediator of OGT is the polycomb repressive complex 2 (PRC2).…”

“TET-on” pluripotency

“…Yu and colleagues used streptavidin-binding peptide (SBP)-tagged TET proteins as bait and identified OGT as an interaction partner of TET2 and TET3, but not TET1 in mESCs. The interactions were further confirmed in 293T cells [10]. Using a flag-tagged biotinylated form of OGT, Pasini's group found that TET1 and TET2 were stable partners of OGT in mESCs [11].…”

“…It has been shown that TET proteins associate with either various histone modifications including the methylation of H3K4 and H3K27 or epigenetic regulators such as PRC2 complex and SIN3A co-npg repressor complex [2], suggesting that TET proteins could employ multiple mechanisms to regulate chromatin contexts with respect to the control of gene expression. Notably, three groups recently demonstrated that TET proteins can physically interact with O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) [10][11][12]. OGT is a unique glycosyltransferase that modifies hundreds of proteins by transferring single O-GlcNAc onto serine/threonine residues, thus participates in signal transduction and transcriptional regulation [11].…”

“…Although controversial results were obtained, these studies suggest the following: (1) TET2 interacts with OGT in all three studies. The catalytic domain of TET2 and the tetratricopeptide repeat (TPR) 5 and 6 domains in OGT are essential for the interaction [10]; (2) The interaction between TET proteins and OGT does not affect their enzymatic activity [10]; (3) OGT-TET complex occupies CpG islands at transcriptional start sites (TSSs), where low levels of 5mC and 5hmC but high level of O-GlcNAcmodified histones exist [11,12]. These data suggest that TET proteins not only function as DNA hydroxylases, but also mediate the recruitment of OGT to genomic loci to modify histones and regulate gene expression [11]; (4) TET proteins recruit OGT and HCF1, an OGT-targeted protein that interacts with the H3K4 methyltransferase complex SET1/COMPASS.…”

L’interaction TET-OGT facilite la transcription en régulant la méthylation de l’histone H3

“…Cette activité accrue permet à son tour de glycosyler la sous-unité HCF1 (host cell factor-1) du complexe SET1/ COMPASS, ce qui stabilise le complexe sur la chromatine et promeut la triméthyla-tion de l'histone H3 ainsi que l'activation transcriptionnelle [5]. Ce lien physique et fonctionnel a été confirmé par d'autres laboratoires qui ont également montré que TET1 était capable d'interagir avec OGT dans des cellules embryonnaires murines, et que TET2 participe à la glycosylation d'H2B dépendante d'OGT [7,8]. Plusieurs articles ont également décrit que les trois protéines TET peuvent être à leur tour glycosylées par OGT, ce qui (1) la glycosylation du complexe SET1/COMPASS sur sa sous-unité HCF1, et (2) la glycosylation de l'histone H2B.…”