Evidence of the involvement of O-GlcNAc-modified human RNA polymerase II CTD in transcription in vitro and in vivo

Metabolism Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
Journal of Biological Chemistry (Impact Factor: 4.6). 05/2012; 287(28):23549-61. DOI: 10.1074/jbc.M111.330910
Source: PubMed

ABSTRACT The RNA polymerase II C-terminal domain (CTD), which serves as a scaffold to recruit machinery involved in transcription, is modified post-translationally. Although the O-GlcNAc modification of RNA polymerase II CTD was documented in 1993, its functional significance remained obscure. We show that O-GlcNAc transferase (OGT) modified CTD serine residues 5 and 7. Drug inhibition of OGT and OGA (N-acetylglucosaminidase) blocked transcription during preinitiation complex assembly. Polymerase II and OGT co-immunoprecipitated, and OGT is a component of the preinitiation complex. OGT shRNA experiments showed that reduction of OGT causes a reduction in transcription and RNA polymerase II occupancy at several B-cell promoters. These data suggest that the cycling of O-GlcNAc on and off of polymerase II occurs during assembly of the preinitiation complex. Our results define unexpected roles for both the CTD and O-GlcNAc in the regulation of transcription initiation in higher eukaryotes.

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    • "Only recently, at the formation of transcription preinitiation complex, glycosylated CTD on serine residues (Ser5/ Ser2-G) has been demonstrated. Since glycosylation and phosphorylation are mutually exclusive, these data suggest a functional role of Ser2/Ser5-G in preventing phosphorylation of CTD before its recruitment on promoters (Ranuncolo et al., 2012). As already mentioned, residues at position 7 of nonconsensus heptads are mainly arginines or lysines. "
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