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G3 (Bethesda). 2015 Mar 19;5(5):953-62. doi: 10.1534/g3.115.017251.

Genetic Interaction Landscape Reveals Critical Requirements for Schizosaccharomyces pombe Brc1 in DNA Damage Response Mutants.

Author information

1
Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037.
2
Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94158.
3
Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037 prussell@scripps.edu.

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.

KEYWORDS:

Brc1; CSN/signalosome complex; DNA damage response; Schizosaccharomyces pombe

PMID:
25795664
PMCID:
PMC4426379
DOI:
10.1534/g3.115.017251
[Indexed for MEDLINE]
Free PMC Article

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