Proteolysis of the mismatch repair protein MLH1 by caspase-3 promotes DNA damage-induced apoptosis

J Biol Chem. 2004 Jun 25;279(26):27542-8. doi: 10.1074/jbc.M400971200. Epub 2004 Apr 15.


Caspases are critical proapoptotic proteases that execute cell death signals by selectively cleaving proteins at Asp residues to alter their function. Caspases trigger apoptotic chromatin degradation by activating caspase-activated DNase and by inactivating a number of enzymes that sense or repair DNA damage. We have identified the mismatch repair protein MLH1 as a novel caspase-3 substrate by screening small pools of a human prostate adenocarcinoma cDNA library for cDNAs encoding caspase substrates. In this report, we demonstrate that human MLH1 is specifically cleaved by caspase-3 at Asp(418) in vitro. Furthermore, MLH1 is rapidly proteolyzed by caspase-3 in cancer cells induced to undergo apoptosis by treatment with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the topoisomerase II inhibitor etoposide, which damages DNA. Importantly, proteolysis of MLH1 by caspase-3 triggers its partial redistribution from the nucleus to the cytoplasm and generates a proapoptotic carboxyl-terminal product. In addition, we demonstrate that a caspase-3 cleavage-resistant D418E MLH1 mutant inhibits etoposide-induced apoptosis but has little effect on TRAIL-induced apoptosis. These results indicate that the proteolysis of MLH1 by caspase-3 plays a functionally important and previously unrecognized role in the execution of DNA damage-induced apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins
  • Aspartic Acid / metabolism
  • Base Pair Mismatch
  • Carrier Proteins
  • Caspase 3
  • Caspases / metabolism*
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • DNA Damage / drug effects
  • DNA Damage / physiology*
  • DNA Repair / physiology*
  • Etoposide / pharmacology
  • Female
  • Humans
  • Male
  • Membrane Glycoproteins / pharmacology
  • MutL Protein Homolog 1
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Neoplasm Proteins / physiology*
  • Nuclear Proteins
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • TNF-Related Apoptosis-Inducing Ligand
  • Tumor Necrosis Factor-alpha / pharmacology


  • Adaptor Proteins, Signal Transducing
  • Apoptosis Regulatory Proteins
  • Carrier Proteins
  • MLH1 protein, human
  • Membrane Glycoproteins
  • Neoplasm Proteins
  • Nuclear Proteins
  • Recombinant Proteins
  • TNF-Related Apoptosis-Inducing Ligand
  • TNFSF10 protein, human
  • Tumor Necrosis Factor-alpha
  • Aspartic Acid
  • Etoposide
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • MutL Protein Homolog 1