Interaction of Escherichia coli MutS and MutL at a DNA mismatch.
MutS and MutL are both required to activate downstream events in DNA mismatch repair. We examined the rate of dissociation of MutS from a mismatch using linear heteroduplex DNAs or heteroduplexes blocked at one or both ends by four-way DNA junctions in the presence and absence of MutL. In the presence of ATP, dissociation of MutS from linear heteroduplexes or heteroduplexes blocked at only one end occurs within 15 s. When both duplex ends are blocked, MutS remains associated with the DNA in complexes with half-lives of 30 min. DNase I footprinting of MutS complexes is consistent with migration of MutS throughout the DNA duplex region. When MutL is present, it associates with MutS and prevents ATP-dependent migration away from the mismatch in a manner that is dependent on the length of the heteroduplex. The rate and extent of mismatch-provoked cleavage at hemimethylated GATC sites by MutH in the presence of MutS, MutL, and ATP are the same whether the mismatch and GATC sites are in cis or in trans. These results suggest that a MutS-MutL complex in the vicinity of a mismatch is involved in activating MutH.
Schofield
M J
MJ
Genetics and Biochemistry Branch, NIDDKD, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nayak
S
S
Scott
T H
TH
Du
C
C
Hsieh
P
P
D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins / Q000378:metabolism*; D020137:Base Pair Mismatch; D001483:Base Sequence; D002875:Chromosomes / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; D009692:Nucleic Acid Heteroduplexes; D011485:Protein Binding; D021381:Protein Transport; D013997:Time Factors
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D009692:Nucleic Acid Heteroduplexes; D004247:DNA; D004706:Endodeoxyribonucleases; C059682:methyl-directed mismatch repair protein, E coli; D003850:Deoxyribonuclease I; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D045643:DNA Repair Enzymes