DNA binding by yeast Mlh1 and Pms1: implications for DNA mismatch repair.
The yeast Mlh1-Pms1 heterodimer required for mismatch repair (MMR) binds to DNA. Here we map DNA binding to N-terminal fragments of Mlh1 and Pms1. We demonstrate that Mlh1 and Pms1 N-terminal domains (NTDs) independently bind to double-stranded and single-stranded DNA, in the absence of dimerization and with different affinities. Full-length Mlh1p alone, which can homodimerize, also binds to DNA. Substituting conserved positively charged amino acids in Mlh1 produces mutator phenotypes in a haploid yeast strain characteristic of reduced MMR. These substitutions strongly reduce DNA binding by the Mlh1 NTD and, to a lesser extent, they also reduce DNA binding by full-length Mlh1 and the Mlh1-Pms1 heterodimer. Replacement of a homologous Pms1 residue has a much smaller effect on mutation rate and does not reduce DNA binding. The results demonstrate that NTDs of yeast Mlh1 and Pms1 contain independent DNA binding sites and they suggest that the C-terminal region of Mlh1p may also contribute to DNA binding. The differential mutator effects and binding properties observed here further suggest that Mlh1 and Pms1 differ in their interactions with DNA. Finally, the results are consistent with the hypothesis that DNA binding by Mlh1 is important for MMR.
Hall
Mark C
MC
Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Shcherbakova
Polina V
PV
Fortune
John M
JM
Borchers
Christoph H
CH
Dial
J Michael
JM
Tomer
Kenneth B
KB
Kunkel
Thomas A
TA
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D020137:Base Pair Mismatch / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D019281:Dimerization; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009690:Nucleic Acid Conformation; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D005656:Fungal Proteins; C088859:MLH1 protein, S cerevisiae; D010446:Peptide Fragments; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; D000070957:MutL Protein Homolog 1