title: Proteolysis of the mismatch repair protein MLH1 by caspase-3 promotes DNA damage-induced apoptosis.
abstract: 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.
authors.affiliation: Cell Death Regulation Laboratory, Department of Medicine, Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Onur K
authors.initials: OK
authors.lastname: Arseven
authors.forename: Vincent L
authors.initials: VL
authors.lastname: Cryns
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001224:Aspartic Acid / Q000378:metabolism; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology*; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C501486:MLH1 protein, human; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D001224:Aspartic Acid; D005047:Etoposide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000070957:MutL Protein Homolog 1