O-GlcNAcylation is a posttranslational modification catalyzed by the O-Linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and reversed by O-GlcNAcase (OGA). Numerous transcriptional regulators, including chromatin modifying enzymes, transcription factors, and co-factors, are targeted by O-GlcNAcylation, indicating that this modification is central for chromatin-associated processes. Recently, OGT-mediated O-GlcNAcylation was reported to be a novel histone modification, suggesting a potential role in directly coordinating chromatin structure and function. In contrast, using multiple biochemical approaches, we report here that histone O-GlcNAcylation is undetectable in mammalian cells. Conversely, O-GlcNAcylation of the transcription regulators Host Cell Factor-1 (HCF-1) and Ten-Eleven Translocation protein 2 (TET2) could be readily observed. Our study raises questions on the occurrence and abundance of O-GlcNAcylation as a histone modification in mammalian cells and reveals technical complications regarding the detection of genuine protein O-GlcNAcylation. Therefore, the identification of the specific contexts in which histone O-GlcNAcylation might occur is still to be established.
Keywords: Chromatin; Epigenetics; H2B K120ub, Histone H2B lysine 120 monoubiquitination; H2B S112 O-GlcNAc, Histone H2B serine 112 O-GlcNAc; HCF-1; HCF-1, Host Cell Factor-1; Histone; O-GlcNAc; O-GlcNAc, O-Linked N-acetylglucosamine; O-GlcNAcylation; OGA, O-GlcNAcase; OGT; OGT, O-Linked N-acetylglucosamine transferase; PUGNAc, O-(2-acetamido-2-deoxyglucopyranosylidene) amino N-phenylcarbamate; Polycomb; TET2; TET2, Ten-Eleven Translocation protein 2; UDP-GlcNAc, Uridine Diphosphate N-Acetylglucosamine; WGA, Wheat Germ Agglutinin.; posttranslational modification.