A Bub1-Mad1 interaction targets the Mad1-Mad2 complex to unattached kinetochores to initiate the spindle checkpoint

J Cell Biol. 2014 Mar 3;204(5):647-57. doi: 10.1083/jcb.201311015. Epub 2014 Feb 24.

Abstract

Recruitment of Mad1-Mad2 complexes to unattached kinetochores is a central event in spindle checkpoint signaling. Despite its importance, the mechanism that recruits Mad1-Mad2 to kinetochores is unclear. In this paper, we show that MAD-1 interacts with BUB-1 in Caenorhabditis elegans. Mutagenesis identified specific residues in a segment of the MAD-1 coiled coil that mediate the BUB-1 interaction. In addition to unattached kinetochores, MAD-1 localized between separating meiotic chromosomes and to the nuclear periphery. Mutations in the MAD-1 coiled coil that selectively disrupt interaction with BUB-1 eliminated MAD-1 localization to unattached kinetochores and between meiotic chromosomes, both of which require BUB-1, and abrogated checkpoint signaling. The identified MAD-1 coiled-coil segment interacted with a C-terminal region of BUB-1 that contains its kinase domain, and mutations in this region prevented MAD-1 kinetochore targeting independently of kinase activity. These results delineate an interaction between BUB-1 and MAD-1 that targets MAD-1-MAD-2 complexes to kinetochores and is essential for spindle checkpoint signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase / physiology
  • Animals
  • Binding Sites
  • Caenorhabditis elegans / cytology*
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Caenorhabditis elegans Proteins / physiology*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • Chromosomes / metabolism
  • Kinetochores / metabolism*
  • Kinetochores / physiology
  • M Phase Cell Cycle Checkpoints*
  • Mad2 Proteins / genetics
  • Mad2 Proteins / metabolism
  • Mad2 Proteins / physiology
  • Meiosis / physiology
  • Models, Biological
  • Mutagenesis
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • Protein Serine-Threonine Kinases / physiology
  • Protein Structure, Tertiary
  • Signal Transduction
  • Two-Hybrid System Techniques

Substances

  • Caenorhabditis elegans Proteins
  • Cell Cycle Proteins
  • MDF-1 protein, C elegans
  • Mad2 Proteins
  • Nuclear Proteins
  • Protein Serine-Threonine Kinases
  • bub-1 protein, C elegans