DNA strand invasion promoted by Escherichia coli RecT protein.
The RecT protein of Escherichia coli is a DNA-pairing protein required for the RecA-independent recombination events promoted by the RecE pathway. The RecT protein was found to bind to both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in the absence of Mg2+. In the presence of Mg2+, RecT binding to dsDNA was inhibited drastically, whereas binding to ssDNA was inhibited only to a small extent. RecT promoted the transfer of a single-stranded oligonucleotide into a supercoiled homologous duplex to form a D (displacement)-loop. D-loop formation occurred in the absence of Mg2+ and at 1 mM Mg2+ but was inhibited by increasing concentrations of Mg2+ and did not require a high energy cofactor. Strand transfer was mediated by a RecT-ssDNA nucleoprotein complex reacting with a naked duplex DNA and was prevented by the formation of RecT-dsDNA nucleoprotein complexes. Finally, RecT mediated the formation of joint molecules between a supercoiled DNA and a linear dsDNA substrate with homologous 3'-single-stranded tails. Together these results indicate that RecT is not a helix-destabilizing protein promoting a reannealing reaction but rather is a novel type of pairing protein capable of promoting recombination by a DNA strand invasion mechanism. These results are consistent with the observation that RecE (exonuclease VIII) and RecT can promote RecA-independent double-strand break repair in E. coli.
Noirot
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Division of Human Cancer Genetics, Dana Farber Cancer Institute, and the Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Kolodner
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D001426:Bacterial Proteins / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D011485:Protein Binding
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C084497:RecT protein, E coli