RESUMO
RAD53 and MEC1 are essential genes required for the transcriptional and cell cycle responses to DNA damage and DNA replication blocks. We have examined the essential function of these genes and found that their lethality but not their checkpoint defects can be suppressed by increased expression of genes encoding ribonucleotide reductase. Analysis of viable null alleles revealed that Mec1 plays a greater role in response to inhibition of DNA synthesis than Rad53. The loss of survival in mec1 and rad53 null or point mutants in response to transient inhibition of DNA synthesis is not a result of inappropriate anaphase entry but primarily to an inability to complete chromosome replication. We propose that this checkpoint pathway plays an important role in the maintenance of DNA synthetic capabilities when DNA replication is stressed.
Assuntos
Proteínas de Ciclo Celular , Replicação do DNA , Proteínas Serina-Treonina Quinases , Fase S/fisiologia , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/metabolismo , Quinase do Ponto de Checagem 2 , Dano ao DNA , Replicação do DNA/genética , DNA Fúngico/biossíntese , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Deleção de Genes , Expressão Gênica , Genes Fúngicos , Hidroxiureia/toxicidade , Peptídeos e Proteínas de Sinalização Intracelular , Mitose/genética , Mitose/fisiologia , Mutação Puntual , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Ribonucleotídeo Redutases/genética , Ribonucleotídeo Redutases/metabolismo , Fase S/genética , Saccharomyces cerevisiae/genética , Transcrição GênicaRESUMO
Mutants of the Saccharomyces cerevisiae ataxia telangiectasia mutated (ATM) homolog MEC1/SAD3/ESR1 were identified that could live only if the RAD53/SAD1 checkpoint kinase was overproduced. MEC1 and a structurally related gene, TEL1, have overlapping functions in response to DNA damage and replication blocks that in mutants can be provided by overproduction of RAD53. Both MEC1 and TEL1 were found to control phosphorylation of Rad53p in response to DNA damage. These results indicate that RAD53 is a signal transducer in the DNA damage and replication checkpoint pathways and functions downstream of two members of the ATM lipid kinase family. Because several members of this pathway are conserved among eukaryotes, it is likely that a RAD53-related kinase will function downstream of the human ATM gene product and play an important role in the mammalian response to DNA damage.
