title: A novel mutant allele of Schizosaccharomyces pombe rad26 defective in monitoring S-phase progression to prevent premature mitosis.
abstract: A semipermissive growth condition was defined for a Schizosaccharomyces pombe strain carrying a thermosensitive allele of DNA polymerase delta (pol delta ts03). Under this condition, DNA polymerase delta is semidisabled and causes a delay in S-phase progression. Using a genetic strategy, we have isolated a panel of mutants that enter premature mitosis when DNA replication is incomplete but which are not defective for arrest in G2/M following DNA damage. We characterized the aya14 mutant, which enters premature mitosis when S phase is arrested by genetic or chemical means. However, this mutant is sensitive to neither UV nor gamma irradiation. Two genomic clones, rad26+ and cds1+, were found to suppress the hydroxyurea sensitivity of the aya14 mutant. Genetic analysis indicates that aya14 is a novel allele of the cell cycle checkpoint gene rad26+, which we have named rad26.a14. cds1+ is a suppressor which suppresses the S-phase feedback control defect of rad26.a14 when S phase is inhibited by either hydroxyurea or cdc22, but it does not suppress the defect when S phase is arrested by a mutant DNA polymerase. Analyses of rad26.a14 in a variety of cdc mutant backgrounds indicate that strains containing rad26.a14 bypass S-phase arrest but not G1 or late S/G2 arrest. A model of how Rad26 monitors S-phase progression to maintain the dependency of cell cycle events and coordinates with other rad/hus checkpoint gene products in responding to radiation damage is proposed.
authors.affiliation: Department of Pathology, Stanford University School of Medicine, California 94305-5324, USA.
authors.forename: M
authors.initials: M
authors.lastname: Uchiyama
authors.forename: I
authors.initials: I
authors.lastname: Galli
authors.forename: D J
authors.initials: DJ
authors.lastname: Griffiths
authors.forename: T S
authors.initials: TS
authors.lastname: Wang
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000494:pharmacology; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004258:DNA Polymerase III; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000494:pharmacology; D006918:Hydroxyurea / Q000494:pharmacology; D008938:Mitosis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D016196:S Phase; D012568:Schizosaccharomyces; D029702:Schizosaccharomyces pombe Proteins
chemical_list: D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D029702:Schizosaccharomyces pombe Proteins; C080926:cdc22 protein, S pombe; C088086:rad26 protein, S pombe; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D006918:Hydroxyurea