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Budding yeast RSI1/APC2, a novel gene necessary for initiation of anaphase, encodes an APC subunit.

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.

Pubmed ID: 9430641

Authors

  • Kramer KM
  • Fesquet D
  • Johnson AL
  • Johnston LH

Journal

The EMBO journal

Publication Data

January 15, 1998

Associated Grants

None

Mesh Terms

  • Amino Acid Sequence
  • Anaphase
  • Anaphase-Promoting Complex-Cyclosome
  • Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome
  • Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome
  • Cell Cycle Proteins
  • Cyclin B
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Cyclins
  • Fungal Proteins
  • Genes, Fungal
  • Genes, Lethal
  • Ligases
  • Molecular Sequence Data
  • Mutagenesis
  • Nuclear Proteins
  • Phenotype
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Securin
  • Temperature
  • Ubiquitin-Protein Ligase Complexes
  • Ubiquitin-Protein Ligases