The ATM homologue MEC1 is required for phosphorylation of replication protein A in yeast.
Replication protein A (RPA) is a highly conserved single-stranded DNA-binding protein, required for cellular DNA replication, repair, and recombination. In human cells, RPA is phosphorylated during the S and G2 phases of the cell cycle and also in response to ionizing or ultraviolet radiation. Saccharomyces cerevisiae exhibits a similar pattern of cell cycle-regulated RPA phosphorylation, and our studies indicate that the radiation-induced reactions occur in yeast as well. We have examined yeast RPA phosphorylation during the normal cell cycle and in response to environmental insult, and have demonstrated that the checkpoint gene MEC1 is required for the reaction under all conditions tested. Through examination of several checkpoint mutants, we have placed RPA phosphorylation in a novel pathway of the DNA damage response. MEC1 is similar in sequence to human ATM, the gene mutated in patients with ataxia-telangiectasia (A-T). A-T cells are deficient in multiple checkpoint pathways and are hypersensitive to killing by ionizing radiation. Because A-T cells exhibit a delay in ionizing radiation-induced RPA phosphorylation, our results indicate a functional similarity between MEC1 and ATM, and suggest that RPA phosphorylation is involved in a conserved eukaryotic DNA damage-response pathway defective in A-T.
Brush
G S
GS
Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Morrow
D M
DM
Hieter
P
P
Kelly
T J
TJ
D001260:Ataxia Telangiectasia / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000528:radiation effects; D018797:Cell Cycle Proteins; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D005838:Genotype; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008954:Models, Biological; D010766:Phosphorylation; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics; D011839:Radiation, Ionizing; D051716:Replication Protein A; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism* / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases