A cyclin B homolog in S. cerevisiae: chronic activation of the Cdc28 protein kinase by cyclin prevents exit from mitosis

Cell. 1991 Apr 5;65(1):163-74. doi: 10.1016/0092-8674(91)90417-w.


A cyclin B homolog was identified in Saccharomyces cerevisiae using degenerate oligonucleotides and the polymerase chain reaction. The protein, designated Scb1, has a high degree of similarity with B-type cyclins from organisms ranging from fission yeast to human. Levels of SCB1 mRNA and protein were found to be periodic through the cell cycle, with maximum accumulation late, most likely in the G2 interval. Deletion of the gene was found not to be lethal, and subsequently other B-type cyclins have been found in yeast functionally redundant with Scb1. A mutant allele of SCB1 that removes an amino-terminal fragment of the encoded protein thought to be required for efficient degradation during mitosis confers a mitotic arrest phenotype. This arrest can be reversed by inactivation of the Cdc28 protein kinase, suggesting that cyclin-mediated arrest results from persistent protein kinase activation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Northern
  • Cell Cycle
  • Cyclin B
  • Cyclins / genetics*
  • DNA, Fungal
  • Enzyme Activation
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Genes, Fungal
  • Mitosis / physiology*
  • Molecular Sequence Data
  • Phenotype
  • Polymerase Chain Reaction
  • Protamine Kinase / metabolism
  • Protein Kinases / metabolism*
  • RNA, Fungal / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Nucleic Acid


  • CLB1 protein, S cerevisiae
  • Cyclin B
  • Cyclins
  • DNA, Fungal
  • Fungal Proteins
  • RNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • Protein Kinases
  • Protamine Kinase

Associated data

  • GENBANK/M62389