title: Arabidopsis MutS homologs-AtMSH2, AtMSH3, AtMSH6, and a novel AtMSH7-form three distinct protein heterodimers with different specificities for mismatched DNA.
abstract: Arabidopsis mismatch repair genes predict MutS-like proteins remarkably similar to eukaryotic MutS homologs-MSH2, MSH3, and MSH6. A novel feature in Arabidopsis is the presence of two MSH6-like proteins, designated AtMSH6 and AtMSH7. Combinations of Arabidopsis AtMSH2 with AtMSH3, AtMSH6, or AtMSH7 proteins-products of in vitro transcription and translation-were analyzed for interactions by analytical gel filtration chromatography. The AtMSH2 protein formed heterodimers with AtMSH3, AtMSH6, and AtMSH7, but no single proteins formed homodimers. The abilities of the various heterodimers to bind to mismatched 51-mer duplexes were measured by electrophoretic mobility-shift assays. Similar to the behavior of the corresponding human proteins, AtMSH2*AtMSH3 heterodimers bound "insertion-deletion" DNA with three nucleotides (+AAG) or one nucleotide (+T) looped out much better than they bound DNA with a base/base mispair (T/G), whereas AtMSH2*AtMSH6 bound the (+T) substrate strongly, (T/G) well, and (+AAG) no better than it did a (T/A) homoduplex. However, AtMSH2*AtMSH7 showed a different specificity: moderate affinity for a (T/G) substrate and weak binding of (+T). Thus, AtMSH2*AtMSH7 may be specialized for lesions/base mispairs not tested or for (T/G) mispairs in special contexts.
authors.affiliation: Program in Molecular and Cellular Biology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Culligan
authors.forename: J B
authors.initials: JB
authors.lastname: Hays
mesh_terms: D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020137:Base Pair Mismatch; D002850:Chromatography, Gel; D018744:DNA, Plant / Q000378:metabolism; D004268:DNA-Binding Proteins; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D000251:Adenosine Triphosphatases; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D009692:Nucleic Acid Heteroduplexes; D010940:Plant Proteins; C121984:MSH3 protein, Arabidopsis; C121985:AT4G02070 protein, Arabidopsis; C499543:MSH7 protein, Arabidopsis; C108984:MSH2 protein, Arabidopsis; C497175:MutS protein, E coli