Identification of Lynch syndrome mutations in the MLH1-PMS2 interface that disturb dimerization and mismatch repair.
Missense alterations of the mismatch repair gene MLH1 have been identified in a significant proportion of individuals suspected of having Lynch syndrome, a hereditary syndrome that predisposes for cancer of colon and endometrium. The pathogenicity of many of these alterations, however, is unclear. A number of MLH1 alterations are located in the C-terminal domain (CTD) of MLH1, which is responsible for constitutive dimerization with PMS2. We analyzed which alterations may result in pathogenic effects due to interference with dimerization. We used a structural model of CTD of MLH1-PMS2 heterodimer to select 19 MLH1 alterations located inside and outside two candidate dimerization interfaces in the MLH1-CTD. Three alterations (p.Gln542Leu, p.Leu749Pro, p.Tyr750X) caused decreased coexpression of PMS2, which is unstable in the absence of interaction with MLH1, suggesting that these alterations interfere with dimerization. All three alterations are located within the dimerization interface suggested by our model. They also compromised mismatch repair, suggesting that defects in dimerization abrogate repair and confirming that all three alterations are pathogenic. Additionally, we provided biochemical evidence that four alterations with uncertain pathogenicity (p.Ala586Pro, p.Leu636Pro, p.Thr662Pro, and p.Arg755Trp) are deleterious because of poor expression or poor repair efficiency, and confirm the deleterious effect of eight further alterations.
Kosinski
Jan
J
Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland. Jan.Kosinski@uniroma1.it
Hinrichsen
Inga
I
Bujnicki
Janusz M
JM
Friedhoff
Peter
P
Plotz
Guido
G
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution / Q000235:genetics; D002460:Cell Line; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D053843:DNA Mismatch Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D000070976:Mismatch Repair Endonuclease PMS2; D008958:Models, Molecular; D000070957:MutL Protein Homolog 1; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055503:Protein Multimerization / Q000235:genetics*; D017434:Protein Structure, Tertiary
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D050505:Mutant Proteins; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes