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Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters

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 co...

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Autores principales: Boulard, Mathieu, Rucli, Sofia, Edwards, John R., Bestor, Timothy H.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: National Academy of Sciences 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322000/
https://www.ncbi.nlm.nih.gov/pubmed/32522876
http://dx.doi.org/10.1073/pnas.1912074117
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author Boulard, Mathieu
Rucli, Sofia
Edwards, John R.
Bestor, Timothy H.
author_facet Boulard, Mathieu
Rucli, Sofia
Edwards, John R.
Bestor, Timothy H.
author_sort Boulard, Mathieu
collection PubMed
description 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 TIF1β), 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 β-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.
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spelling pubmed-73220002020-07-01 Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters Boulard, Mathieu Rucli, Sofia Edwards, John R. Bestor, Timothy H. Proc Natl Acad Sci U S A Biological Sciences 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 TIF1β), 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 β-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. National Academy of Sciences 2020-06-23 2020-06-10 /pmc/articles/PMC7322000/ /pubmed/32522876 http://dx.doi.org/10.1073/pnas.1912074117 Text en Copyright © 2020 the Author(s). Published by PNAS. http://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY) (http://creativecommons.org/licenses/by/4.0/) .
spellingShingle Biological Sciences
Boulard, Mathieu
Rucli, Sofia
Edwards, John R.
Bestor, Timothy H.
Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title_full Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title_fullStr Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title_full_unstemmed Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title_short Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
title_sort methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
topic Biological Sciences
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322000/
https://www.ncbi.nlm.nih.gov/pubmed/32522876
http://dx.doi.org/10.1073/pnas.1912074117
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AT edwardsjohnr methylationdirectedglycosylationofchromatinfactorsrepressesretrotransposonpromoters
AT bestortimothyh methylationdirectedglycosylationofchromatinfactorsrepressesretrotransposonpromoters