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Mol. Cell. Biol., Jun 1997, 3103-3115, Vol 17, No. 6
M Uchiyama, I Galli, DJ Griffiths and TS Wang
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.
Copyright © 1997, American Society for Microbiology
A novel mutant allele of Schizosaccharomyces pombe rad26 defective in monitoring S-phase progression to prevent premature mitosis
Department of Pathology, Stanford University School of Medicine, California 94305-5324, USA.
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