Chk1-Mad2 interaction: a crosslink between the DNA damage checkpoint and the mitotic spindle checkpoint

Cell Cycle. 2013 Apr 1;12(7):1083-90. doi: 10.4161/cc.24090. Epub 2013 Mar 1.


Chk1 is implicated in several checkpoints of the cell cycle acting as a key player in the signal transduction pathway activated in response to DNA damage and crucial for the maintenance of genomic stability. Chk1 also plays a role in the mitotic spindle checkpoint, which ensures the fidelity of mitotic segregation during mitosis, preventing chromosomal instability and aneuploidy. Mad2 is one of the main mitotic checkpoint components and also exerts a role in the cellular response to DNA damage. To investigate a possible crosslink existing between Chk1 and Mad2, we studied Mad2 protein levels after Chk1 inhibition either by specific siRNAs or by a specific and selective Chk1 inhibitor (PF-00477736), and we found that after Chk1 inhibition, Mad2 protein levels decrease only in tumor cells sensitive to Chk1 depletion. We then mapped six Chk1's phosphorylatable sites on Mad2 protein, and found that Chk1 is able to phosphorylate Mad2 in vitro on more than one site, while it is incapable of phoshorylating the Mad2 form mutated on all six phosphorylatable sites. Moreover our studies demonstrate that Chk1 co-localizes and physically associates with Mad2 in cells both under unstressed conditions and after DNA damage, thus providing new and interesting evidence on Chk1 and Mad2 crosstalk in the DNA damage checkpoint and in the mitotic spindle checkpoint.

Keywords: Chk1; DNA damage checkpoint; Mad2; mitotic spindle checkpoint.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Benzodiazepinones / pharmacology
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Checkpoint Kinase 1
  • DNA Damage*
  • Humans
  • M Phase Cell Cycle Checkpoints
  • Mad2 Proteins
  • Molecular Sequence Data
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinases / chemistry
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Pyrazoles / pharmacology
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*


  • Benzodiazepinones
  • Calcium-Binding Proteins
  • Cell Cycle Proteins
  • MAD2L1 protein, human
  • Mad2 Proteins
  • PF 00477736
  • Protein Kinase Inhibitors
  • Pyrazoles
  • RNA, Small Interfering
  • Repressor Proteins
  • Protein Kinases
  • CHEK1 protein, human
  • Checkpoint Kinase 1