Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters

• Verfasst von: Boulard, Mathieu [VerfasserIn]
• Verfasst von: Rucli, Sofia [VerfasserIn]
• Verfasst von: Edwards, John R. [VerfasserIn]
• Verfasst von: Bestor, Timothy H. [VerfasserIn]
• Titel: Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
• Verf.angabe: Mathieu Boulard, Sofia Rucli, John R. Edwards, and Timothy H. Bestor
• E-Jahr: 2020
• Jahr: June 10, 2020
• Umfang: 7 S.
• Fussnoten: Gesehen am 14.08.2020
• Titel Quelle: Enthalten in: National Academy of Sciences (Washington, DC)Proceedings of the National Academy of Sciences of the United States of America
• Ort Quelle: Washington, DC : National Acad. of Sciences, 1915
• Jahr Quelle: 2020
• Band/Heft Quelle: 117(2020), 25, Seite 14292-14298
• ISSN Quelle: 1091-6490
• DOI: doi:10.1073/pnas.1912074117
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: complex
• Sach-SW: dna methylation
• Sach-SW: DNA methylation
• Sach-SW: endogenous retroviruses
• Sach-SW: expression
• Sach-SW: gene silencing
• Sach-SW: in-vitro
• Sach-SW: interacts
• Sach-SW: o-glcnac transferase
• Sach-SW: protein O-glycosylation
• Sach-SW: replication
• Sach-SW: sequence
• Sach-SW: transcription
• K10plus-PPN: 1727046242

Abstract

The mechanisms by which methylated mammalian promoters are transcriptionally silenced even in the presence of all of the factors required for their expression have long been a major unresolved issue in the field of epigenetics. Repression requires the assembly of a methylation-dependent silencing complex that contains the TRIM28 protein (also known as KAP1 and TIF1 beta), a scaffolding protein without intrinsic repressive or DNA-binding properties. The identity of the key effector within this complex that represses transcription is unknown. We developed a methylation-sensitized interaction screen which revealed that TRIM28 was complexed with O-linked beta-N-acetylglucosamine transferase (OGT) only in cells that had normal genomic methylation patterns. OGT is the only glycosyltransferase that modifies cytoplasmic and nuclear protein by transfer of N-acetylglucosamine (O-GlcNAc) to serine and threonine hydroxyls. Whole-genome analysis showed that O-glycosylated proteins and TRIM28 were specifically bound to promoters of active retrotransposons and to imprinting control regions, the two major regulatory sequences controlled by DNA methylation. Furthermore, genome-wide loss of DNA methylation caused a loss of O-GlcNAc from multiple transcriptional repressor proteins associated with TRIM28. A newly developed Cas9-based editing method for targeted removal of O-GlcNAc was directed against retrotransposon promoters. Local chromatin de-GlcNAcylation specifically reactivated the expression of the targeted retrotransposon family without loss of DNA methylation. These data revealed that O-linked glycosylation of chromatin factors is essential for the transcriptional repression of methylated retrotransposons.