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Molecular and Cellular Biology, September 2001, p. 5767-5777, Vol. 21, No. 17
Department of Molecular Genetics and
Microbiology, State University of New York, Stony Brook, New York
11794-5222
Received 28 March 2001/Accepted 7 May 2001
Cdc2 kinase is a master regulator of cell cycle progression in the
fission yeast Schizosaccharomyces pombe. Our data
indicate that Cdc2 phosphorylates replication factor Orp2, a subunit of the origin recognition complex (ORC). Cdc2 phosphorylation of Orp2
appears to be one of multiple mechanisms by which Cdc2 prevents DNA
rereplication in a single cell cycle. Cdc2 phosphorylation of Orp2 is
not required for Cdc2 to activate DNA replication initiation. Phosphorylation of Orp2 appears first in S phase and becomes maximal in
G2 and M when Cdc2 kinase activity is required to prevent
reinitiation of DNA replication. A mutant lacking Cdc2 phosphorylation
sites in Orp2 (orp2-T4A) allowed greater rereplication
of DNA than congenic orp2 wild-type strains when the
limiting replication initiation factor Cdc18 was deregulated. Thus,
Cdc2 phosphorylation of Orp2 may be redundant with regulation of Cdc18
for preventing reinitiation of DNA synthesis. Since Cdc2
phosphorylation sites are present in Orp2 (also known as Orc2)
from yeasts to metazoans, we propose that cell cycle-regulated
phosphorylation of the ORC provides a safety net to prevent DNA
rereplication and resulting genetic instability.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.17.5767-5777.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Control of DNA Rereplication via Cdc2
Phosphorylation Sites in the Origin Recognition Complex
*
Corresponding author. Mailing address: Department of
Molecular Genetics and Microbiology, State University of New York,
Stony Brook, NY 11794-5222. Phone: (631) 632-9644. Fax: (631) 632-9797. E-mail: janet.leatherwood{at}sunysb.edu.
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