Control of DNA rereplication via Cdc2 phosphorylation sites in the origin recognition complex.
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 G(2) 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.
Vas
A
A
Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, NY 11794-5222, USA.
Mok
W
W
Leatherwood
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002453:Cell Cycle; D016384:Consensus Sequence; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex; D010766:Phosphorylation; D011817:Rabbits; D018741:Replication Origin; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D051738:Origin Recognition Complex; D029702:Schizosaccharomyces pombe Proteins; C097704:orc2 protein, S pombe; D016203:CDC2 Protein Kinase