Pluto Bioinformatics

GSE93539: Protein O-GlcNAcylation Silences Methylated Promoters in Mammalian Genomes

Bulk RNA sequencing

Methylated mammalian promoters are transcriptionally silenced even in the presence of all the factors required for their expression. Repression requires the assembly of a methylation-dependent silencing complex that contains the TRIM28 (also known as KAP1 and TIF1) protein. An internally controlled interaction screen identified O-linked -N-acetylglucosamine transferase (O-GlcNAc transferase or OGT) as a protein that was complexed with TRIM28 in wild type em-bryonic stem cells but not in Dnmt1-/- cells that had severely demethylated genomes. In the ab-sence of DNA methylation, multiple proteins associated with TRIM28 failed to undergo modifica-tion by N-Acetylglucosamine (GlcNAc). Mass spectrometry identified several of these proteins as known mediators of transcriptional silencing. The most active transposon in the mouse ge-nome is the IAP LTR retrotransposon, which have been previously shown to be repressed by DNA methylation. A Bacteroides O-GlcNAc hydrolase was fused to a catalytically inactive Cas9 and targeted to methylated IAP retrotransposon promoter sequences via IAP-specific guide RNAs; fulminating reactivation of IAP transcription was induced. These data revealed that Glc-NAcylation is directly involved in the transcriptional repression of methylated promoters. SOURCE: John,R.,Edwards (jredwards@wustl.edu) - Washington University School of Medicine