Orderly inactivation of the key checkpoint protein mitotic arrest deficient 2 (MAD2) during mitotic progression

J Biol Chem. 2011 Apr 15;286(15):13052-9. doi: 10.1074/jbc.M110.201897. Epub 2011 Feb 18.

Abstract

Anaphase is promoted by the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C) only when all the chromosomes have achieved bipolar attachment to the mitotic spindles. Unattached kinetochores or the absence of tension between the paired kinetochores activates a surveillance mechanism termed the spindle-assembly checkpoint. A fundamental principle of the checkpoint is the activation of mitotic arrest deficient 2 (MAD2). MAD2 then forms a diffusible complex called mitotic checkpoint complex (designated as MAD2(MCC)) before it is recruited to APC/C (designated as MAD2(APC/C)). Large gaps in our knowledge remain on how MAD2 is inactivated after the checkpoint is satisfied. In this study, we have investigated the regulation of MAD2-containing complexes during mitotic progression. Using selective immunoprecipitation of checkpoint components and gel filtration chromatography, we found that MAD2(MCC) and MAD2(APC/C) were regulated very differently during mitotic exit. Temporally, MAD2(MCC) was broken down ahead of MAD2(APC/C). The inactivation of the two complexes also displayed different requirements of proteolysis; although APC/C and proteasome activities were dispensable for MAD2(MCC) inactivation, they are required for MAD2(APC/C) inactivation. In fact, the degradation of CDC20 is inextricably linked to the breakdown of MAD2(APC/C). These data extended our understanding of the checkpoint complexes during checkpoint silencing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase-Promoting Complex-Cyclosome
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Cdc20 Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Kinetochores / metabolism*
  • Mad2 Proteins
  • Mitosis / physiology*
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Spindle Apparatus / genetics
  • Spindle Apparatus / metabolism*
  • Ubiquitin-Protein Ligase Complexes / genetics
  • Ubiquitin-Protein Ligase Complexes / metabolism*

Substances

  • Calcium-Binding Proteins
  • Cdc20 Proteins
  • Cell Cycle Proteins
  • MAD2L1 protein, human
  • Mad2 Proteins
  • Repressor Proteins
  • CDC20 protein, human
  • Ubiquitin-Protein Ligase Complexes
  • Anaphase-Promoting Complex-Cyclosome
  • Proteasome Endopeptidase Complex