title: Mutations in SID2, a novel gene in Saccharomyces cerevisiae, cause synthetic lethality with sic1 deletion and may cause a defect during S phase.
abstract: 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.
authors.affiliation: The Rockefeller University, New York, New York 10021, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Jacobson
authors.forename: C X
authors.initials: CX
authors.lastname: Muñoz
authors.forename: K S
authors.initials: KS
authors.lastname: Knox
authors.forename: B E
authors.initials: BE
authors.lastname: Williams
authors.forename: L L
authors.initials: LL
authors.lastname: Lu
authors.forename: F R
authors.initials: FR
authors.lastname: Cross
authors.forename: E A
authors.initials: EA
authors.lastname: Vallen
mesh_terms: D000483:Alleles; D000705:Anaphase; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D002875:Chromosomes / Q000378:metabolism; D003001:Cloning, Molecular; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D015723:Gene Library; D005816:Genetic Complementation Test; D006918:Hydroxyurea / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013205:Staphylococcal Protein A / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013205:Staphylococcal Protein A; C499592:TAH11 protein, S cerevisiae; D014157:Transcription Factors; D011494:Protein Kinases; D006918:Hydroxyurea