Mutations in SID2, a novel gene in Saccharomyces cerevisiae, cause synthetic lethality with sic1 deletion and may cause a defect during S phase.
SIC1 encodes a nonessential B-type cyclin/CDK inhibitor that functions at the G1/S transition and the exit from mitosis. To understand more completely the regulation of these transitions, mutations causing synthetic lethality with sic1 Delta were isolated. In this screen, we identified a novel gene, SID2, which encodes an essential protein ... that appears to be required for DNA replication or repair. sid2-1 sic1 Delta strains and sid2-21 temperature-sensitive strains arrest preanaphase as large-budded cells with a single nucleus, a short spindle, and an approximately 2C DNA content. RAD9, which is necessary for the DNA damage checkpoint, is required for the preanaphase arrest of sid2-1 sic1 Delta cells. Analysis of chromosomes in mutant sid2-21 cells by field inversion gel electrophoresis suggests the presence of replication forks and bubbles at the arrest. Deleting the two S phase cyclins, CLB5 and CLB6, substantially suppresses the sid2-1 sic1 Delta inviability, while stabilizing Clb5 protein exacerbates the defects of sid2-1 sic1 Delta cells. In synchronized sid2-1 mutant strains, the onset of replication appears normal, but completion of DNA synthesis is delayed. sid2-1 mutants are sensitive to hydroxyurea indicating that sid2-1 cells may suffer DNA damage that, when combined with additional insult, leads to a decrease in viability. Consistent with this hypothesis, sid2-1 rad9 cells are dead or very slow growing even when SIC1 is expressed.
Mesh Terms:
Alleles, Anaphase, Cell Cycle Proteins, Cell Nucleus, Cell Separation, Chromosomes, Cloning, Molecular, Cyclin-Dependent Kinase Inhibitor Proteins, Cytoplasm, DNA Damage, DNA Repair, DNA-Binding Proteins, Electrophoresis, Polyacrylamide Gel, Flow Cytometry, Fungal Proteins, Gene Deletion, Gene Library, Genetic Complementation Test, Hydroxyurea, Microscopy, Fluorescence, Models, Genetic, Mutagenesis, Site-Directed, Mutation, Phenotype, Plasmids, Precipitin Tests, Protein Binding, Protein Kinases, Recombinant Fusion Proteins, S Phase, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Staphylococcal Protein A, Temperature, Time Factors, Transcription Factors, Two-Hybrid System Techniques
Alleles, Anaphase, Cell Cycle Proteins, Cell Nucleus, Cell Separation, Chromosomes, Cloning, Molecular, Cyclin-Dependent Kinase Inhibitor Proteins, Cytoplasm, DNA Damage, DNA Repair, DNA-Binding Proteins, Electrophoresis, Polyacrylamide Gel, Flow Cytometry, Fungal Proteins, Gene Deletion, Gene Library, Genetic Complementation Test, Hydroxyurea, Microscopy, Fluorescence, Models, Genetic, Mutagenesis, Site-Directed, Mutation, Phenotype, Plasmids, Precipitin Tests, Protein Binding, Protein Kinases, Recombinant Fusion Proteins, S Phase, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Staphylococcal Protein A, Temperature, Time Factors, Transcription Factors, Two-Hybrid System Techniques
Genetics
Date: Sep. 01, 2001
PubMed ID: 11560884
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