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Mol. Cell. Biol., 04 1996, 1356-1366, Vol 16, No. 4
JD Singer, BM Manning and T Formosa
We have developed a genetic screen of the yeast Saccharomyces cerevisiae to
identify genes that act to coordinate DNA replication so that each part of
the genome is copied exactly once per cell cycle. A mutant was recovered in
this screen that accumulates aberrantly high DNA contents but does not
complete a second round of synthesis. The mutation principally responsible
for this phenotype is in the DOA4 gene, which encodes a ubiquitin
hydrolase, one of several yeast genes that encode enzymes that can remove
the signalling polypeptide ubiquitin hydrolase, one of several yeast genes
that encode enzymes that can remove the signaling polypeptide ubiquitin
from its covalently linked conjugated forms. DOA4 is nonessential, and
deleting this gene causes uncoordinated replication. Overreplication does
not occur in cells with limiting amounts of Cdc7 protein kinase, suggesting
that entry into S phase is required for this phenotype. The DNA formed in
doa4 mutants is not highly unusual in the sense that mitotic recombination
rates are normal, implying that a high level of repair is not induced. The
temperature sensitivity of doa4 mutations is partially suppressed by extra
copies of the polyubiquitin gene UB14, but overreplication still occurs in
the presence of this suppressor. Mutations in DOA4 cause loss of the free
ubiquitin pool in cells under heat stress conditions, and extra copies of
UB14 restore this pool without restoring coordination of replication. We
conclude that a ubiquitin-mediated signaling event directly involving the
ubiquitin hydrolase encoded by DOA4 is needed in S. cerevisiae to prevent
uncoordinated DNA replication.
Copyright © 1996, American Society for Microbiology
Coordinating DNA replication to produce one copy of the genome requires genes that act in ubiquitin metabolism
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, 84132, USA.
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