Rad18 is required for DNA repair and checkpoint responses in fission yeast.
To survive damage to the genome, cells must respond by activating both DNA repair and checkpoint responses. Using genetic screens in the fission yeast Schizosaccharomyces pombe, we recently isolated new genes required for DNA damage checkpoint control. We show here that one of these strains defines a new allele of the previously described rad18 gene, rad18-74. rad18 is an essential gene, even in the absence of extrinsic DNA damage. It encodes a conserved protein related to the structural maintenance of chromosomes proteins. Point mutations in rad18 lead to defective DNA repair pathways responding to both UV-induced lesions and, as we show here, double-stranded breaks. Furthermore, rad18p is required to maintain cell cycle arrest in the presence of DNA damage, and failure of this leads to highly aberrant mitoses. A gene encoding a BRCT-containing protein, brc1, was isolated as an allele-specific high-copy suppressor of rad18-74. brc1 is required for mitotic fidelity and for cellular viability in strains with rad18 mutations but is not essential for DNA damage responses. Mutations in rad18 and brc1 are synthetically lethal with a topoisomerase II mutant (top2-191), indicating that these proteins play a role in chromatin organization. These studies show a role for chromatin organization in the maintenance or activation of responses to DNA damage.
Verkade
H M
HM
Trescowthick Research Laboratories, Peter MacCallum Cancer Institute, Melbourne, Victoria 8006, Australia.
Bugg
S J
SJ
Lindsay
H D
HD
Carr
A M
AM
O'Connell
M J
MJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000483:Alleles; D001665:Binding Sites; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015825:Chromosomes, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016195:G2 Phase; D018628:Gene Dosage; D005800:Genes, Fungal; D008938:Mitosis; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic
D002843:Chromatin; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; C063607:RAD18 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D000071877:Checkpoint Kinase 1; D004250:DNA Topoisomerases, Type II