title: Swi1 and Swi3 are components of a replication fork protection complex in fission yeast.
abstract: Swi1 is required for programmed pausing of replication forks near the mat1 locus in the fission yeast Schizosaccharomyces pombe. This fork pausing is required to initiate a recombination event that switches mating type. Swi1 is also needed for the replication checkpoint that arrests division in response to fork arrest. How Swi1 accomplishes these tasks is unknown. Here we report that Swi1 copurifies with a 181-amino-acid protein encoded by swi3(+). The Swi1-Swi3 complex is required for survival of fork arrest and for activation of the replication checkpoint kinase Cds1. Association of Swi1 and Swi3 with chromatin during DNA replication correlated with movement of the replication fork. swi1Delta and swi3Delta mutants accumulated Rad22 (Rad52 homolog) DNA repair foci during replication. These foci correlated with the Rad22-dependent appearance of Holliday junction (HJ)-like structures in cells lacking Mus81-Eme1 HJ resolvase. Rhp51 and Rhp54 homologous recombination proteins were not required for viability in swi1Delta or swi3Delta cells, indicating that the HJ-like structures arise from single-strand DNA gaps or rearranged forks instead of broken forks. We propose that Swi1 and Swi3 define a fork protection complex that coordinates leading- and lagging-strand synthesis and stabilizes stalled replication forks.
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA. Eishi.Noguchi@drexel.edu
authors.forename: Eishi
authors.initials: E
authors.lastname: Noguchi
authors.forename: Chiaki
authors.initials: C
authors.lastname: Noguchi
authors.forename: W Hayes
authors.initials: WH
authors.lastname: McDonald
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D051135:Rad51 Recombinase; D016196:S Phase / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C084232:RHP51 protein, S pombe; C072981:SWI3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C085412:rad52 protein, S pombe; C513096:swi1 protein, S pombe; D051135:Rad51 Recombinase; D004259:DNA-Directed DNA Polymerase; D004720:Endonucleases; C411624:MUS81 protein, S cerevisiae; D004265:DNA Helicases; C099034:Rhp54 protein, S pombe