The interacting domains of three MutL heterodimers in man: hMLH1 interacts with 36 homologous amino acid residues within hMLH3, hPMS1 and hPMS2.
In human cells, hMLH1, hMLH3, hPMS1 and hPMS2 are four recognised and distinctive homologues of MutL, an essential component of the bacterial DNA mismatch repair (MMR) system. The hMLH1 protein forms three different heterodimers with one of the other MutL homologues. As a first step towards functional analysis of these molecules, we determined the interacting domains of each heterodimer and tried to understand their common features. Using a yeast two-hybrid assay, we show that these MutL homologues can form heterodimers by interacting with the same amino acid residues of hMLH1, residues 492-742. In contrast, three hMLH1 partners, hMLH3, hPMS1 and hPMS2 contain the 36 homologous amino acid residues that interact strongly with hMLH1. Contrary to the previous studies, these homologous residues reside at the N-terminal regions of three subdomains conserved in MutL homologues in many species. Interestingly, these residues in hPMS2 and hMLH3 may form coiled-coil structures as predicted by the MULTICOIL program. Furthermore, we show that there is competition for the interacting domain in hMLH1 among the three other MutL homologues. Therefore, the quantitative balance of these three MutL heterodimers may be important in their functions.
Kondo
E
E
Department of Molecular Pathology, Tohoku University School of Medicine, Sendai, Miyagi, 980-8575, Japan.
Horii
A
A
Fukushige
S
S
D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins / Q000737:chemistry; D020137:Base Pair Mismatch; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins; D019281:Dimerization; D029968:Escherichia coli Proteins; D006801:Humans; D016350:Leucine Zippers; D000070976:Mismatch Repair Endonuclease PMS2; D008969:Molecular Sequence Data; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C501486:MLH1 protein, human; C403623:MLH3 protein, human; C074770:MutL protein, E coli; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C088996:PMS1 protein, human; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D045643:DNA Repair Enzymes