Mismatch-, MutS-, MutL-, and helicase II-dependent unwinding from the single-strand break of an incised heteroduplex.
Escherichia coli MutS, MutL, and DNA helicase II are sufficient to initiate mismatch-dependent unwinding of an incised heteroduplex (Yamaguchi, M., Dao, V., and Modrich, P. (1998) J. Biol. Chem., 273, 9197-9201). We have studied unwinding of 6.4-kilobase circular G-T heteroduplexes that contain a single-strand incision, 808 base pairs 5' to the mismatch or 1023 base pairs 3' to the mispair as viewed along the shorter path between the two DNA sites. Unwinding of both substrates in the presence of MutS, MutL, DNA helicase II, and single-stranded DNA binding protein was mismatch-dependent and initiated at the single-strand break. Although unwinding occurred in both directions from the strand break, it was biased toward the shorter path linking the strand break and the mispair. MutS and MutL are thus sufficient to coordinate mismatch recognition to the orientation-dependent activation of helicase II unwinding at a single-strand break located a kilobase from the mispair.
Dao
V
V
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
Modrich
P
P
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001482:Base Composition; D001483:Base Sequence; D004265:DNA Helicases / Q000378:metabolism*; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008958:Models, Molecular; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism; D015345:Oligonucleotide Probes
D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D009692:Nucleic Acid Heteroduplexes; D015345:Oligonucleotide Probes; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D004265:DNA Helicases