title: Loss of meiotic rereplication block in Saccharomyces cerevisiae cells defective in Cdc28p regulation.
abstract: Cdc28p is the major cyclin-dependent kinase in Saccharomyces cerevisiae. Its activity is required for blocking the reinitiation of DNA replication during mitosis. Here, we show that under conditions where Cdc28p activity is improperly regulated--either through the loss of function of the Schizosaccharomyces pombe wee1 ortholog Swe1p or through the expression of a dominant CDC28 allele, CDC28AF--diploid yeast cells are able to complete several rounds of premeiotic DNA replication within a single meiotic cell cycle. Moreover, a percentage of mutant cells exhibit a "multispore" phenotype, possessing the ability to package more than four spores within a single ascus. These multispored asci contain both even and odd numbers of viable spores. In order for meiotic rereplication and multispore formation to occur, cells must initiate homologous recombination and maintain proper chromosome cohesion during meiosis I. Rad9p- or Rad17p-dependent checkpoint mechanisms are not required for multispore formation and neither are the B-type cyclin Clb6p and the cyclin-dependent kinase inhibitor Sic1p. Finally, we present evidence of a possible role for a Cdc55p-dependent protein phosphatase 2A in initiating meiotic replication.
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, 245 North 15th St., NCB#11115, MS#497, Philadelphia, PA 19102, USA.
authors.forename: Lyndi M
authors.initials: LM
authors.lastname: Rice
authors.forename: Constantine
authors.initials: C
authors.lastname: Plakas
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Nickels
mesh_terms: D000483:Alleles; D015152:Blotting, Northern; D017489:CDC28 Protein Kinase, S cerevisiae / Q000235:genetics* / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002469:Cell Separation; D019926:Cyclin B / Q000378:metabolism; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004247:DNA / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D005434:Flow Cytometry; D015966:Gene Expression Regulation, Fungal; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008540:Meiosis; D008957:Models, Genetic; D009687:Nuclear Proteins; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D054648:Protein Phosphatase 2; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: C071246:CDC55 protein, S cerevisiae; C095227:CLB6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C501395:RAD17 protein, S cerevisiae; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C069930:rad9 protein; D049452:Green Fluorescent Proteins; D012313:RNA; D004247:DNA; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2