The C-terminal region of the meiosis-specific protein kinase Ime2 mediates protein instability and is required for normal spore formation in budding yeast

J Mol Biol. 2008 Apr 18;378(1):31-43. doi: 10.1016/j.jmb.2008.02.001. Epub 2008 Feb 12.


The cyclin-dependent kinase Cdk1 and the related kinase Ime2 act in concert to trigger progression of the meiotic cell cycle in the yeast Saccharomyces cerevisiae. These kinases share several functions and substrates during meiosis, but their regulation seems to be clearly different. In contrast to Cdk1, no cyclin seems to be involved in the regulation of Ime2 activity. Ime2 is a highly unstable protein, and we aimed to elucidate the relevance of Ime2 instability. We first determined the sequence elements required for Ime2 instability by constructing a set of deletions in the IME2 gene. None of the small deletions in Ime2 affected its instability, but deletion of a 241 amino acid C-terminal region resulted in a highly stabilized protein. Thus, the C-terminal domain of Ime2 is important for mediating protein instability. The stabilized, truncated Ime2 protein is highly active in vivo. Replacement of the IME2 gene with the truncated IME2DeltaC241 in diploid strains did not interfere with meiotic nuclear divisions, but caused abnormalities in spore formation, as manifested by the appearance of many asci with a reduced spore number such as triads and dyads. The truncated Ime2 caused a reduction of spore number in a dominant manner. We conclude that downregulation of Ime2 kinase activity mediated by the C-terminal domain is required for the efficient production of normal four-spore asci. Our data suggest a role for Ime2 in spore number control in S. cerevisiae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Division
  • DNA Mutational Analysis
  • Haploidy
  • Intracellular Signaling Peptides and Proteins
  • Meiosis* / genetics
  • Phosphorylation
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sequence Deletion
  • Spores, Fungal / enzymology
  • Spores, Fungal / genetics
  • Spores, Fungal / physiology*


  • Cell Cycle Proteins
  • Intracellular Signaling Peptides and Proteins
  • Saccharomyces cerevisiae Proteins
  • Protein Kinases
  • IME2 protein, S cerevisiae
  • Protein-Serine-Threonine Kinases