Cdc55p, the B-type regulatory subunit of protein phosphatase 2A, has multiple functions in mitosis and is required for the kinetochore/spindle checkpoint in Saccharomyces cerevisiae

Mol Cell Biol. 1997 Feb;17(2):620-6. doi: 10.1128/MCB.17.2.620.

Abstract

Saccharomyces cerevisiae, like most eucaryotic cells, can prevent the onset of anaphase until chromosomes are properly aligned on the mitotic spindle. We determined that Cdc55p (regulatory B subunit of protein phosphatase 2A [PP2A]) is required for the kinetochore/spindle checkpoint regulatory pathway in yeast. ctf13 cdc55 double mutants could not maintain a ctf13-induced mitotic delay, as determined by antitubulin staining and levels of histone H1 kinase activity. In addition, cdc55::LEU2 mutants and tpd3::LEU2 mutants (regulatory A subunit of PP2A) were nocodazole sensitive and exhibited the phenotypes of previously identified kinetochore/spindle checkpoint mutants. Inactivating CDC55 did not simply bypass the arrest that results from inhibiting ubiquitin-dependent proteolysis because cdc16-1 cdc55::LEU2 and cdc23-1 cdc55::LEU2 double mutants arrested normally at elevated temperatures. CDC55 is specific for the kinetochore/spindle checkpoint because cdc55 mutants showed normal sensitivity to gamma radiation and hydroxyurea. The conditional lethality and the abnormal cellular morphogenesis of cdc55::LEU2 were suppressed by cdc28F19, suggesting that the cdc55 phenotypes are dependent on the phosphorylation state of Cdc28p. In contrast, the nocodazole sensitivity of cdc55::LEU2 was not suppressed by cdc28F19. Therefore, the mitotic checkpoint activity of CDC55 (and TPD3) is independent of regulated phosphorylation of Cdc28p. Finally, cdc55::LEU2 suppresses the temperature sensitivity of cdc20-1, suggesting additional roles for CDC55 in mitosis.

Publication types

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

MeSH terms

  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • DNA Damage
  • DNA, Fungal / biosynthesis
  • Fungal Proteins / genetics
  • Gamma Rays
  • Genetic Complementation Test
  • Hydroxyurea / pharmacology
  • Kinetochores / physiology*
  • Microtubules / drug effects
  • Mitosis / physiology*
  • Mutation
  • Nocodazole / pharmacology
  • Nuclear Proteins / genetics
  • Nucleic Acid Synthesis Inhibitors / pharmacology
  • Phosphoprotein Phosphatases / genetics
  • Phosphoprotein Phosphatases / metabolism*
  • Phosphorylation
  • Protamine Kinase / metabolism
  • Protein Phosphatase 2
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / radiation effects
  • Saccharomyces cerevisiae Proteins*
  • Spindle Apparatus / physiology
  • Spores, Fungal
  • Suppression, Genetic
  • Temperature

Substances

  • CDC55 protein, S cerevisiae
  • CTF13 protein, S cerevisiae
  • Cell Cycle Proteins
  • DNA, Fungal
  • Fungal Proteins
  • Nuclear Proteins
  • Nucleic Acid Synthesis Inhibitors
  • Saccharomyces cerevisiae Proteins
  • Protamine Kinase
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2
  • Nocodazole
  • Hydroxyurea