Schizosaccharomyces pombe Hsk1p is a potential cds1p target required for genome integrity.
The fission yeast Hsk1p kinase is an essential activator of DNA replication. Here we report the isolation and characterization of a novel mutant allele of the gene. Consistent with its role in the initiation of DNA synthesis, hsk1(ts) genetically interacts with several S-phase mutants. At the restrictive temperature, hsk1(ts) cells suffer abnormal S phase and loss of nuclear integrity and are sensitive to both DNA-damaging agents and replication arrest. Interestingly, hsk1(ts) mutants released to the restrictive temperature after early S-phase arrest in hydroxyurea (HU) are able to complete bulk DNA synthesis but they nevertheless undergo an abnormal mitosis. These findings indicate a second role for hsk1 subsequent to HU arrest. Consistent with a later S-phase role, hsk1(ts) is synthetically lethal with Deltarqh1 (RecQ helicase) or rad21ts (cohesin) mutants and suppressed by Deltacds1 (RAD53 kinase) mutants. We demonstrate that Hsk1p undergoes Cds1p-dependent phosphorylation in response to HU and that it is a direct substrate of purified Cds1p kinase in vitro. These results indicate that the Hsk1p kinase is a potential target of Cds1p regulation and that its activity is required after replication initiation for normal mitosis.
Snaith
H A
HA
Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA.
Brown
G W
GW
Forsburg
S L
SL
D000483:Alleles; D000595:Amino Acid Sequence; D001761:Bleomycin / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D064447:Checkpoint Kinase 2; D004261:DNA Replication; D004307:Dose-Response Relationship, Radiation; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D016193:G1 Phase; D006918:Hydroxyurea / Q000494:pharmacology; D015151:Immunoblotting; D008938:Mitosis; D008969:Molecular Sequence Data; D010641:Phenotype; D010766:Phosphorylation; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D016196:S Phase / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D012568:Schizosaccharomyces / Q000737:chemistry*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D029702:Schizosaccharomyces pombe Proteins; D001761:Bleomycin; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; C094761:HSK1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D006918:Hydroxyurea