title: Recombinational repair within heterochromatin requires ATP-dependent chromatin remodeling.
abstract: Heterochromatin plays a key role in protection of chromosome integrity by suppressing homologous recombination. In Saccharomyces cerevisiae, Sir2p, Sir3p, and Sir4p are structural components of heterochromatin found at telomeres and the silent mating-type loci. Here we have investigated whether incorporation of Sir proteins into minichromosomes regulates early steps of recombinational repair in vitro. We find that addition of Sir3p to a nucleosomal substrate is sufficient to eliminate yRad51p-catalyzed formation of joints, and that this repression is enhanced by Sir2p/Sir4p. Importantly, Sir-mediated repression requires histone residues that are critical for silencing in vivo. Moreover, we demonstrate that the SWI/SNF chromatin-remodeling enzyme facilitates joint formation by evicting Sir3p, thereby promoting subsequent Rad54p-dependent formation of a strand invasion product. These results suggest that recombinational repair in the context of heterochromatin presents additional constraints that can be overcome by ATP-dependent chromatin-remodeling enzymes.
authors.affiliation: University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Manisha
authors.initials: M
authors.lastname: Sinha
authors.forename: Shinya
authors.initials: S
authors.lastname: Watanabe
authors.forename: Aaron
authors.initials: A
authors.lastname: Johnson
authors.forename: Danesh
authors.initials: D
authors.lastname: Moazed
authors.forename: Craig L
authors.initials: CL
authors.lastname: Peterson
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004260:DNA Repair; D006570:Heterochromatin / Q000378:metabolism*; D006655:Histone Deacetylases / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism; D056565:Sirtuin 2; D037761:Sirtuins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; C445179:SWI-SNF-B chromatin-remodeling complex; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D014157:Transcription Factors; D000255:Adenosine Triphosphate; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases