Publication Date:
2013-03-15
Description:
A hallmark of histone H3 lysine 9 (H3K9)-methylated heterochromatin, conserved from the fission yeast Schizosaccharomyces pombe to humans, is its ability to spread to adjacent genomic regions. Central to heterochromatin spread is heterochromatin protein 1 (HP1), which recognizes H3K9-methylated chromatin, oligomerizes and forms a versatile platform that participates in diverse nuclear functions, ranging from gene silencing to chromosome segregation. How HP1 proteins assemble on methylated nucleosomal templates and how the HP1-nucleosome complex achieves functional versatility remain poorly understood. Here we show that binding of the key S. pombe HP1 protein, Swi6, to methylated nucleosomes drives a switch from an auto-inhibited state to a spreading-competent state. In the auto-inhibited state, a histone-mimic sequence in one Swi6 monomer blocks methyl-mark recognition by the chromodomain of another monomer. Auto-inhibition is relieved by recognition of two template features, the H3K9 methyl mark and nucleosomal DNA. Cryo-electron-microscopy-based reconstruction of the Swi6-nucleosome complex provides the overall architecture of the spreading-competent state in which two unbound chromodomain sticky ends appear exposed. Disruption of the switch between the auto-inhibited and spreading-competent states disrupts heterochromatin assembly and gene silencing in vivo. These findings are reminiscent of other conditionally activated polymerization processes, such as actin nucleation, and open up a new class of regulatory mechanisms that operate on chromatin in vivo.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3907283/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3907283/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Canzio, Daniele -- Liao, Maofu -- Naber, Nariman -- Pate, Edward -- Larson, Adam -- Wu, Shenping -- Marina, Diana B -- Garcia, Jennifer F -- Madhani, Hiten D -- Cooke, Roger -- Schuck, Peter -- Cheng, Yifan -- Narlikar, Geeta J -- AR053720/AR/NIAMS NIH HHS/ -- R01 AR062279/AR/NIAMS NIH HHS/ -- R01 GM071801/GM/NIGMS NIH HHS/ -- R01GM071801/GM/NIGMS NIH HHS/ -- Intramural NIH HHS/ -- England -- Nature. 2013 Apr 18;496(7445):377-81. doi: 10.1038/nature12032. Epub 2013 Mar 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, University of California San Francisco, California 94158, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23485968" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Animals
;
*Chromatin Assembly and Disassembly
;
Chromosomal Proteins, Non-Histone/*antagonists &
;
inhibitors/*chemistry/*metabolism/ultrastructure
;
Cryoelectron Microscopy
;
Gene Silencing
;
Heterochromatin/chemistry/*metabolism/ultrastructure
;
Histones/chemistry/metabolism
;
Methylation
;
Models, Molecular
;
Molecular Sequence Data
;
Nucleosomes/chemistry/genetics/metabolism/ultrastructure
;
Protein Structure, Tertiary
;
Schizosaccharomyces/genetics/*metabolism
;
Schizosaccharomyces pombe Proteins/antagonists &
;
inhibitors/*chemistry/*metabolism/ultrastructure
;
Xenopus laevis
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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