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H2B ubiquitylation and the histone chaperone Asf1 cooperatively mediate the formation and maintenance of heterochromatin

Nucleic Acids Res. 2017 May 17. DOI: 10.1093/nar/gkx422
https://academic.oup.com/nar/article-lookup/doi/10.1093/nar/gkx422

Heterochromatin is a heritable form of gene repression, with critical roles in development and cell identity. Understanding how chromatin factors results in such repression is a fundamental question. Chromatin is assembled and disassembled during transcription, replication and repair by anti-silencing function 1 (Asf1), a highly conserved histone chaperone. Transcription and DNA replication are also affected by histone modifications that modify nucleosome dynamics, such as H2B ubiquitylation (H2Bub). We report here that H2Bub and Asf1 cooperatively promote transcriptional silencing at yeast telomeres and mating loci. Through real time monitoring of HML (Hidden MAT Left) locus silencing, we found that transcriptional repression was slowly initiated and never fully established in mutants lacking both Asf1 and H2Bub. These findings are consistent with impaired HML silencer-binding and spreading of repressor proteins, Sir2 and Sir3. In addition, mutants lacking H2Bub and Asf1 show  defects in both nucleosome assembly and higher-order heterochromatin organization at the HML locus. Our findings reveal a novel role for H2Bub and Asf1 in epigenetic silencing at mating loci. Thus, the interplay between H2Bub and Asf1 may fine-tune nucleosome dynamics and SIR protein recruitment, and represent an ongoing requirement for proper formation and maintenance of heterochromatin.

 


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115台北市南港區研究院路二段128號
Tel: 02-27899515
Fax: 02-27858059
icob@gate.sinica.edu.tw
Copyright © ICOB 2013. All rights reserved. 最佳瀏覽網頁方式請用最新版IE11或其他瀏覽器 /瀏覽人數:1002697--
 瀏覽人數:1002697