MutS and UvrD proteins stimulate exonuclease action: insights into exonuclease-mediated strand repair.
MutS and UvrD proteins individually stimulate Escherichia coli exonuclease VII activity on blunt-ended short duplex DNA substrates. Stimulation by both proteins is ATP-dependent but not mismatch-specific and is not accompanied by apparent strand separation. Under similar conditions, MutS and UvrD proteins in fact confer resistance to exonuclease VII action on ssDNA targets, thereby implying that a novel state of a double-stranded DNA intermediate, which we term a "destabilized duplex", is involved in exonuclease-mediated strand degradation. We find that DNA strands in such a destabilized duplex can be displaced by the challenge of a molar excess of homologous single- and double-stranded DNA targets, in trans. Such an action of the UvrD protein is ATP-dependent. We discuss these results in relation to the (i) directional excision repair of E. coli MMR, (ii) downregulation of repeat deletions by exonucleases during replication slippage, and (iii) the fork reversal function of UvrD at stalled replication forks.
Noothi
Sunil K
SK
Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India.
Minda
Renu
R
Rao
Basuthkar J
BJ
D020029:Base Pairing / Q000235:genetics; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics; D053843:DNA Mismatch Repair / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000235:genetics; D051719:MutS DNA Mismatch-Binding Protein / Q000737:chemistry* / Q000235:genetics; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D020080:Tandem Repeat Sequences / Q000235:genetics
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D009692:Nucleic Acid Heteroduplexes; D005090:Exodeoxyribonucleases; C026870:exodeoxyribonuclease VII; C506746:UvrD protein, E coli; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D004265:DNA Helicases