title: Human mismatch-repair protein MutL homologue 1 (MLH1) interacts with Escherichia coli MutL and MutS in vivo and in vitro: a simple genetic system to assay MLH1 function.
abstract: A simple genetic system has been developed to test the effect of over-expression of wild-type or mutated human MutL homologue 1 (hMLH1) proteins on methyl-directed mismatch repair (MMR) in Escherichia coli. The system relies on detection of Lac(+) revertants using MMR-proficient or MMR-deficient E. coli strains carrying a lac +1 frameshift mutation expressing hMLH1 proteins. We report that expression of wild-type hMLH1 protein causes an approx. 19-fold increase in mutation rates. The mutator phenotype was due to the ability of hMLH1 protein to interact with bacterial MutL and MutS proteins, thereby interfering with the formation of complexes between MMR proteins and mismatched DNA. Conversely, expression of proteins encoded by alleles deriving from hereditary-non-polyposis-colon-cancer (HNPCC) families decreases mutation rates, depending on the specific amino acid substitutions. These effects parallel the MutL-and MutS-binding and ATP-binding/hydrolysis activities of the mutated proteins.
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica G. Salvatore, Università degli Studi di Catanzaro Magna Graecia, Via Tommaso Campanella 115, 88100 Catanzaro, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Quaresima
authors.forename: Pietro
authors.initials: P
authors.lastname: Alifano
authors.forename: Pierfrancesco
authors.initials: P
authors.lastname: Tassone
authors.forename: Enrico V
authors.initials: EV
authors.lastname: Avvedimento
authors.forename: Francesco S
authors.initials: FS
authors.lastname: Costanzo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Venuta
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000483:Alleles; D001426:Bacterial Proteins; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005821:Genetic Techniques; D006801:Humans; D006868:Hydrolysis; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C501486:MLH1 protein, human; C074770:MutL protein, E coli; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli