Phosphoregulation of Spc105 by Mps1 and PP1 regulates Bub1 localization to kinetochores

Curr Biol. 2012 May 22;22(10):900-6. doi: 10.1016/j.cub.2012.03.052. Epub 2012 Apr 19.

Abstract

Kinetochores are the macromolecular complexes that interact with microtubules to mediate chromosome segregation. Accurate segregation requires that kinetochores make bioriented attachments to microtubules from opposite poles. Attachments between kinetochores and microtubules are monitored by the spindle checkpoint, a surveillance system that prevents anaphase until every pair of chromosomes makes proper bioriented attachments. Checkpoint activity is correlated with the recruitment of checkpoint proteins to the kinetochore. Mps1 is a conserved protein kinase that regulates segregation and the spindle checkpoint, but few of the targets that mediate its functions have been identified. Here, we show that Mps1 is the major kinase activity that copurifies with budding yeast kinetochore particles and identify the conserved Spc105/KNL-1/blinkin kinetochore protein as a substrate. Phosphorylation of conserved MELT motifs within Spc105 recruits the Bub1 protein to kinetochores, and this is reversed by protein phosphatase I (PP1). Spc105 mutants lacking Mps1 phosphorylation sites are defective in the spindle checkpoint and exhibit growth defects. Together, these data identify Spc105 as a key target of the Mps1 kinase and show that the opposing activities of Mps1 and PP1 regulate the kinetochore localization of the Bub1 protein.

Publication types

  • Research Support, American Recovery and Reinvestment Act
  • Research Support, N.I.H., Extramural

MeSH terms

  • Gene Expression Regulation, Fungal
  • Kinetochores / metabolism*
  • M Phase Cell Cycle Checkpoints / physiology*
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Phosphorylation / physiology
  • Protein Phosphatase 1 / genetics
  • Protein Phosphatase 1 / metabolism*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • Microtubule-Associated Proteins
  • Saccharomyces cerevisiae Proteins
  • Spc105 protein, S cerevisiae
  • Bub1 spindle checkpoint protein
  • Protein-Serine-Threonine Kinases
  • MPS1 protein, S cerevisiae
  • Protein Phosphatase 1