title: Budding yeast RSI1/APC2, a novel gene necessary for initiation of anaphase, encodes an APC subunit.
abstract: SIC1 is a non-essential gene encoding a CDK inhibitor of Cdc28-Clb kinase activity. Sic1p is involved in both mitotic exit and the timing of DNA synthesis. To identify other genes involved in controlling Clb-kinase activity, we have undertaken a genetic screen for mutations which render SIC1 essential. Here we describe a gene we have identified by this means, RSI1/APC2. Temperature-sensitive rsi1/apc2 mutants arrest in metaphase and are unable to degrade Clb2p, suggesting that Rsi1p/Apc2p is associated with the anaphase promoting complex (APC). This is an E3 ubiquitin-ligase that controls anaphase initiation through degradation of Pds1p and mitotic exit via degradation of Clb cyclins. Indeed, the anaphase block in rsi1/apc2 temperature-sensitive mutants is overcome by removal of PDS1, consistent with Rsi1p/Apc2p being part of the APC. In addition, like our rsi1/apc2 mutations, cdc23-1, encoding a known APC subunit, is also lethal with sic1Delta. Thus SIC1 clearly becomes essential when APC function is compromised. Finally, we find that Rsi1p/Apc2p co-immunoprecipitates with Cdc23p. Taken together, our results suggest that RSI1/APC2 is a subunit of APC.
authors.affiliation: Division of Yeast Genetics, National Institute for Medical Research, London, UK.
authors.forename: K M
authors.initials: KM
authors.lastname: Kramer
authors.forename: D
authors.initials: D
authors.lastname: Fesquet
authors.forename: A L
authors.initials: AL
authors.lastname: Johnson
authors.forename: L H
authors.initials: LH
authors.lastname: Johnston
mesh_terms: D000595:Amino Acid Sequence; D000705:Anaphase / Q000235:genetics*; D064173:Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; D018797:Cell Cycle Proteins / Q000235:genetics*; D019926:Cyclin B; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins / Q000172:deficiency / Q000378:metabolism / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D005800:Genes, Fungal; D005804:Genes, Lethal; D008025:Ligases / Q000235:genetics*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; D013696:Temperature; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases
chemical_list: D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; C577441:CDC23 protein, S cerevisiae; C093749:CLB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; D005656:Fungal Proteins; D009687:Nuclear Proteins; C578004:PDS1 protein, S cerevisiae; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; D043743:Ubiquitin-Protein Ligase Complexes; C577346:APC2 protein, S cerevisiae; D064173:Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D008025:Ligases