1. Sirt1 suppresses RNA synthesis after UV irradiation in combined xeroderma pigmentosum group D/Cockayne syndrome (XP-D/CS) cells.
- Author
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Vélez-Cruz R, Zadorin AS, Coin F, and Egly JM
- Subjects
- Cells, Cultured, Cockayne Syndrome complications, DNA Repair, Heterochromatin genetics, Heterochromatin metabolism, Heterochromatin radiation effects, Humans, Mutation, RNA, Messenger genetics, RNA, Messenger metabolism, Sirtuin 1 antagonists & inhibitors, Sirtuin 1 genetics, Transcription Factor TFIIH chemistry, Transcription Factor TFIIH genetics, Transcription Factor TFIIH metabolism, Transcription, Genetic radiation effects, Ultraviolet Rays adverse effects, Xeroderma Pigmentosum complications, Xeroderma Pigmentosum Group D Protein chemistry, Cockayne Syndrome genetics, Cockayne Syndrome metabolism, RNA biosynthesis, Sirtuin 1 metabolism, Xeroderma Pigmentosum genetics, Xeroderma Pigmentosum metabolism, Xeroderma Pigmentosum Group D Protein genetics, Xeroderma Pigmentosum Group D Protein metabolism
- Abstract
Specific mutations in the XPD subunit of transcription factor IIH result in combined xeroderma pigmentosum (XP)/Cockayne syndrome (CS), a severe DNA repair disorder characterized at the cellular level by a transcriptional arrest following UV irradiation. This transcriptional arrest has always been thought to be the result of faulty transcription-coupled repair. In the present study, we showed that, following UV irradiation, XP-D/CS cells displayed a gross transcriptional dysregulation compared with "pure" XP-D cells or WT cells. Furthermore, global RNA-sequencing analysis showed that XP-D/CS cells repressed the majority of genes after UV, whereas pure XP-D cells did not. By using housekeeping genes as a model, we demonstrated that XP-D/CS cells were unable to reassemble these gene promoters and thus to restart transcription after UV irradiation. Furthermore, we found that the repression of these promoters in XP-D/CS cells was not a simple consequence of deficient repair but rather an active heterochromatinization process mediated by the histone deacetylase Sirt1. Indeed, RNA-sequencing analysis showed that inhibition of and/or silencing of Sirt1 changed the chromatin environment at these promoters and restored the transcription of a large portion of the repressed genes in XP-D/CS cells after UV irradiation. Our work demonstrates that a significant part of the transcriptional arrest displayed by XP-D/CS cells arises as a result of an active repression process and not simply as a result of a DNA repair deficiency. This dysregulation of Sirt1 function that results in transcriptional repression may be the cause of various severe clinical features in patients with XP-D/CS that cannot be explained by a DNA repair defect.
- Published
- 2013
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