title: Critical functions of Rpa3/Ssb3 in S-phase DNA damage responses in fission yeast.
abstract: Replication Protein A (RPA) is a heterotrimeric, single-stranded DNA (ssDNA)-binding complex required for DNA replication and repair, homologous recombination, DNA damage checkpoint signaling, and telomere maintenance. Whilst the larger RPA subunits, Rpa1 and Rpa2, have essential interactions with ssDNA, the molecular functions of the smallest subunit Rpa3 are unknown. Here, we investigate the Rpa3 ortholog Ssb3 in Schizosaccharomyces pombe and find that it is dispensable for cell viability, checkpoint signaling, RPA foci formation, and meiosis. However, increased spontaneous Rad11Rpa1 and Rad22Rad52 nuclear foci in ssb3Δ cells indicate genome maintenance defects. Moreover, Ssb3 is required for resistance to genotoxins that disrupt DNA replication. Genetic interaction studies indicate that Ssb3 has a close functional relationship with the Mms1-Mms22 protein complex, which is required for survival after DNA damage in S-phase, and with the mitotic functions of Mus81-Eme1 Holliday junction resolvase that is required for recovery from replication fork collapse. From these studies we propose that Ssb3 plays a critical role in mediating RPA functions that are required for repair or tolerance of DNA lesions in S-phase. Rpa3 orthologs in humans and other species may have a similar function.
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America.
authors.forename: Santiago
authors.initials: S
authors.lastname: Cavero
authors.forename: Oliver
authors.initials: O
authors.lastname: Limbo
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004843:Epistasis, Genetic / Q000187:drug effects; D005800:Genes, Fungal / Q000235:genetics; D008540:Meiosis / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects; D009153:Mutagens / Q000633:toxicity; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D021381:Protein Transport / Q000187:drug effects; D016196:S Phase / Q000187:drug effects; D012568:Schizosaccharomyces / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D009153:Mutagens; C101144:SSB3 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins