Human MutL-complexes monitor homologous recombination independently of mismatch repair.
The role of mismatch repair proteins has been well studied in the context of DNA repair following DNA polymerase errors. Particularly in yeast, MSH2 and MSH6 have also been implicated in the regulation of genetic recombination, whereas MutL homologs appeared to be less important. So far, little is known about the role of the human MutL homolog hMLH1 in recombination, but recently described molecular interactions suggest an involvement. To identify activities of hMLH1 in this process, we applied an EGFP-based assay for the analysis of different mechanisms of DNA repair, initiated by a targeted double-stranded DNA break. We analysed 12 human cellular systems, differing in the hMLH1 and concomitantly in the hPMS1 and hPMS2 status via inducible protein expression, genetic reconstitution, or RNA interference. We demonstrate that hMLH1 and its complex partners hPMS1 and hPMS2 downregulate conservative homologous recombination (HR), particularly when involving DNA sequences with only short stretches of uninterrupted homology. Unexpectedly, hMSH2 is dispensable for this effect. Moreover, the damage-signaling kinase ATM and its substrates BLM and BACH1 are not strictly required, but the combined effect of ATM/ATR-signaling components may mediate the anti-recombinogenic effect. Our data indicate a protective role of hMutL-complexes in a process which may lead to detrimental genome rearrangements, in a manner which does not depend on mismatch repair.
Siehler
Simone Yasmin
SY
Universitatsfrauenklinik, Prittwitzstrasse 43, D-89075 Ulm, Germany.
Schrauder
Michael
M
Gerischer
Ulrike
U
Cantor
Sharon
S
Marra
Giancarlo
G
Wiesmüller
Lisa
L
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002877:Chromosomes, Human / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D053843:DNA Mismatch Repair; D045643:DNA Repair Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D051856:Fanconi Anemia Complementation Group Proteins / Q000378:metabolism; D006801:Humans; D000070976:Mismatch Repair Endonuclease PMS2; D046912:Multiprotein Complexes / Q000378:metabolism*; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D053484:RecQ Helicases / Q000378:metabolism; D011995:Recombination, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C102108:BACH1 protein, human; D050976:Basic-Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D051856:Fanconi Anemia Complementation Group Proteins; C501486:MLH1 protein, human; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C088996:PMS1 protein, human; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; C094934:PMS2 protein, human; C497172:MSH2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein; D053484:RecQ Helicases; D045643:DNA Repair Enzymes