Role of Polo-like kinase 1 in the regulation of the action of p31comet in the disassembly of mitotic checkpoint complexes

Proc Natl Acad Sci U S A. 2019 Jun 11;116(24):11725-11730. doi: 10.1073/pnas.1902970116. Epub 2019 May 22.


The Mad2-binding protein p31comet has important roles in the inactivation of the mitotic checkpoint system, which delays anaphase until chromosomes attach correctly to the mitotic spindle. The activation of the checkpoint promotes the assembly of a Mitotic Checkpoint Complex (MCC), which inhibits the action of the ubiquitin ligase APC/C (Anaphase-Promoting Complex/Cyclosome) to degrade inhibitors of anaphase initiation. The inactivation of the mitotic checkpoint requires the disassembly of MCC. p31comet promotes the disassembly of mitotic checkpoint complexes by liberating their Mad2 component in a joint action with the ATPase TRIP13. Here, we investigated the regulation of p31comet action. The release of Mad2 from checkpoint complexes in extracts from nocodazole-arrested HeLa cells was inhibited by Polo-like kinase 1 (Plk1), as suggested by the effects of selective inhibitors of Plk1. Purified Plk1 bound to p31comet and phosphorylated it, resulting in the suppression of its activity (with TRIP13) to disassemble checkpoint complexes. Plk1 phosphorylated p31comet on S102, as suggested by the prevention of the phosphorylation of this residue in checkpoint extracts by the selective Plk1 inhibitor BI-2536 and by the phosphorylation of S102 with purified Plk1. An S102A mutant of p31comet had a greatly decreased sensitivity to inhibition by Plk1 of its action to disassemble mitotic checkpoint complexes. We propose that the phosphorylation of p31comet by Plk1 prevents a futile cycle of MCC assembly and disassembly during the active mitotic checkpoint.

Keywords: cell cycle; mitosis; protein degradation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Anaphase-Promoting Complex-Cyclosome / genetics
  • Cell Cycle Proteins / genetics*
  • Cell Line, Tumor
  • Chromatin Assembly and Disassembly / genetics
  • HeLa Cells
  • Humans
  • Mad2 Proteins / genetics
  • Mitosis / genetics*
  • Nuclear Proteins / genetics*
  • Phosphorylation / genetics
  • Protein Serine-Threonine Kinases / genetics*
  • Proto-Oncogene Proteins / genetics*
  • Spindle Apparatus / genetics


  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • MAD2L1BP protein, human
  • Mad2 Proteins
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • Anaphase-Promoting Complex-Cyclosome
  • Protein Serine-Threonine Kinases
  • polo-like kinase 1