Functions of fission yeast orp2 in DNA replication and checkpoint control.
orp2 is an essential gene of the fission yeast Schizosaccharomyces pombe with 22% identity to budding yeast ORC2. We isolated temperature-sensitive alleles of orp2 using a novel plasmid shuffle based on selection against thymidine kinase. Cells bearing the temperature-sensitive allele orp2-2 fail to complete DNA replication at a restrictive temperature and undergo cell cycle arrest. Cell cycle arrest depends on the checkpoint genes rad1 and rad3. Even when checkpoint functions are wild type, the orp2-2 mutation causes high rates of chromosome and plasmid loss. These phenotypes support the idea that Orp2 is a replication initiation factor. Selective spore germination allowed analysis of orp2 deletion mutants. These experiments showed that in the absence of orp2 function, cells proceed into mitosis despite a lack of DNA replication. This suggests either that the Orp2 protein is a part of the checkpoint machinery or more likely that DNA replication initiation is required to induce the replication checkpoint signal.
Kiely
J
J
Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, New York 11794-5222, USA.
Haase
S B
SB
Russell
P
P
Leatherwood
J
J
D001483:Base Sequence; D002453:Cell Cycle / Q000502:physiology*; D017931:DNA Primers; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D020043:Genes, Essential; D016296:Mutagenesis; D051738:Origin Recognition Complex; D010957:Plasmids; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins; D013937:Thymidine Kinase / Q000235:genetics
D017931:DNA Primers; D004268:DNA-Binding Proteins; D051738:Origin Recognition Complex; D029702:Schizosaccharomyces pombe Proteins; C097704:orc2 protein, S pombe; D013937:Thymidine Kinase