title: Chromatin remodeling factors Isw2 and Ino80 regulate checkpoint activity and chromatin structure in S phase.
abstract: When cells undergo replication stress, proper checkpoint activation and deactivation are critical for genomic stability and cell survival and therefore must be highly regulated. Although mechanisms of checkpoint activation are well studied, mechanisms of checkpoint deactivation are far less understood. Previously, we reported that chromatin remodeling factors Isw2 and Ino80 attenuate the S-phase checkpoint activity in Saccharomyces cerevisiae, especially during recovery from hydroxyurea. In this study, we found that Isw2 and Ino80 have a more pronounced role in attenuating checkpoint activity during late S phase in the presence of methyl methanesulfonate (MMS). We therefore screened for checkpoint factors required for Isw2 and Ino80 checkpoint attenuation in the presence of MMS. Here we demonstrate that Isw2 and Ino80 antagonize checkpoint activators and attenuate checkpoint activity in S phase in MMS either through a currently unknown pathway or through RPA. Unexpectedly, we found that Isw2 and Ino80 increase chromatin accessibility around replicating regions in the presence of MMS through a novel mechanism. Furthermore, through growth assays, we provide additional evidence that Isw2 and Ino80 partially counteract checkpoint activators specifically in the presence of MMS. Based on these results, we propose that Isw2 and Ino80 attenuate S-phase checkpoint activity through a novel mechanism.
authors.affiliation: Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109 Molecular and Cellular Biology Program and Fred Hutchinson Cancer Research Center, University of Washington, Seattle, Washington 98195.
authors.forename: Laura
authors.initials: L
authors.lastname: Lee
authors.affiliation: Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109.
authors.forename: Jairo
authors.initials: J
authors.lastname: Rodriguez
authors.affiliation: Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109 ttsukiya@fhcrc.org.
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsukiyama
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D002843:Chromatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D059807:S Phase Cell Cycle Checkpoints; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; C483404:INO80 complex, S cerevisiae; C086468:ISWI protein; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000251:Adenosine Triphosphatases
keywords: Ino80; Isw2; S-phase checkpoint; chromatin accessibility