Dissociation of mismatch recognition and ATPase activity by hMSH2-hMSH3.
MSH2-MSH3 directs the repair of insertion/deletion loops of up to 13 nucleotides in vivo and in vitro. To examine the biochemical basis of this repair specificity, we characterized the mispair binding and ATPase activity of hMSH2-hMSH3. The ATPase was found to be regulated by a mismatch-stimulated ADP --> ATP exchange, which induces a conformational transition by the protein complex. We demonstrated strong binding of hMSH2-hMSH3 to an insertion/deletion loop containing 24 nucleotides that is incapable of provoking ADP --> ATP exchange, suggesting that mismatch recognition appears to be necessary but not sufficient to induce the intrinsic ATPase. These studies support the idea that hMSH2-hMSH3 functions as an adenosine nucleotide-regulated molecular switch that must be activated by mismatched nucleotides for classical mismatch repair to occur.
Genetics and Molecular Biology Program, Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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Wilson
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Guerrette
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Fishel
D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D020137:Base Pair Mismatch; D001665:Binding Sites; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D007700:Kinetics; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; C078444:MSH3 protein, human; C497172:MSH2 protein, human; C421109:multidrug resistance-associated protein 1