title: Genetic Interaction Landscape Reveals Critical Requirements for Schizosaccharomyces pombe Brc1 in DNA Damage Response Mutants.
abstract: Brc1, which was first identified as a high-copy, allele-specific suppressor of a mutation impairing the Smc5-Smc6 holocomplex in Schizosaccharomyces pombe, protects genome integrity during normal DNA replication and when cells are exposed to toxic compounds that stall or collapse replication forks. The C-terminal tandem BRCT (BRCA1 C-terminus) domain of fission yeast Brc1 docks with phosphorylated histone H2A (γH2A)-marked chromatin formed by ATR/Rad3 checkpoint kinase at arrested and damaged replication forks; however, how Brc1 functions in relation to other genome protection modules remains unclear. Here, an epistatic mini-array profile reveals critical requirements for Brc1 in mutants that are defective in multiple DNA damage response pathways, including checkpoint signaling by Rad3-Rad26/ATR-ATRIP kinase, DNA repair by Smc5-Smc6 holocomplex, replication fork stabilization by Mrc1/claspin and Swi1-Swi3/Timeless-Tipin, and control of ubiquitin-regulated proteolysis by the COP9 signalosome (CSN). Exogenous genotoxins enhance these negative genetic interactions. Rad52 and RPA foci are increased in CSN-defective cells, and loss of γH2A increases genotoxin sensitivity, indicating a critical role for the γH2A-Brc1 module in stabilizing replication forks in CSN-defective cells. A negative genetic interaction with the Nse6 subunit of Smc5-Smc6 holocomplex indicates that the DNA repair functions of Brc1 and Smc5-Smc6 holocomplex are at least partially independent. Rtt107, the Brc1 homolog in Saccharomyces cerevisiae, has a very different pattern of genetic interactions, indicating evolutionary divergence of functions and DNA damage responses.
authors: Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037.
authors: Arancha
authors: http://orcid.org/0000-0003-1523-3694
authors: A
authors: Sánchez
authors: Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94158.
authors: Assen
authors: A
authors: Roguev
authors: Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94158.
authors: Nevan J
authors: NJ
authors: Krogan
authors: Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037 prussell@scripps.edu.
authors: Paul
authors: P
authors: Russell
mesh_terms: D004249:DNA Damage; D004843:Epistasis, Genetic / Q000187:drug effects; D015870:Gene Expression; D055786:Gene Knockout Techniques; D063990:Gene Ontology; D006657:Histones / Q000378:metabolism; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics / Q000378:metabolism; D051716:Replication Protein A / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D006657:Histones; D009153:Mutagens; D051721:Rad52 DNA Repair and Recombination Protein; D051716:Replication Protein A; D029702:Schizosaccharomyces pombe Proteins
keywords: Brc1; CSN/signalosome complex; DNA damage response; Schizosaccharomyces pombe