Mps1 Phosphorylates Its N-Terminal Extension to Relieve Autoinhibition and Activate the Spindle Assembly Checkpoint

Curr Biol. 2018 Mar 19;28(6):872-883.e5. doi: 10.1016/j.cub.2018.02.002. Epub 2018 Mar 1.

Abstract

Monopolar spindle 1 (Mps1) is a conserved apical kinase in the spindle assembly checkpoint (SAC) that ensures accurate segregation of chromosomes during mitosis. Mps1 undergoes extensive auto- and transphosphorylation, but the regulatory and functional consequences of these modifications remain unclear. Recent findings highlight the importance of intermolecular interactions between the N-terminal extension (NTE) of Mps1 and the Hec1 subunit of the NDC80 complex, which control Mps1 localization at kinetochores and activation of the SAC. Whether the NTE regulates other mitotic functions of Mps1 remains unknown. Here, we report that phosphorylation within the NTE contributes to Mps1 activation through relief of catalytic autoinhibition that is mediated by the NTE itself. Moreover, we find that this regulatory NTE function is independent of its role in Mps1 kinetochore recruitment. We demonstrate that the NTE autoinhibitory mechanism impinges most strongly on Mps1-dependent SAC functions and propose that Mps1 activation likely occurs sequentially through dimerization of a "prone-to-autophosphorylate" Mps1 conformer followed by autophosphorylation of the NTE prior to maximal kinase activation segment trans-autophosphorylation. Our observations underline the importance of autoregulated Mps1 activity in generation and maintenance of a robust SAC in human cells.

Keywords: Mps1; SAC; Spindle checkpoint; autoactivation; autoinhibition; kinase; kinetochore; mitosis.

Publication types

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

MeSH terms

  • Cell Cycle Proteins / metabolism*
  • Cell Cycle Proteins / physiology
  • Cytoskeletal Proteins
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Kinetochores / physiology
  • M Phase Cell Cycle Checkpoints / physiology*
  • Mitosis
  • Nuclear Proteins / metabolism
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism*
  • Protein-Serine-Threonine Kinases / physiology
  • Protein-Tyrosine Kinases / metabolism*
  • Protein-Tyrosine Kinases / physiology
  • Spindle Apparatus / metabolism

Substances

  • Cell Cycle Proteins
  • Cytoskeletal Proteins
  • NDC80 protein, human
  • Nuclear Proteins
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases
  • TTK protein, human