A switch in the formation of alternative DNA loops modulates lambda site-specific recombination.
The virally encoded Xis protein is one of the components in the site-specific recombination reactions of bacteriophage lambda. It is required for excisive recombination and inhibits integrative recombination. The mechanism of Xis inhibition of the integration reaction was investigated by methylation protection assays (footprinting analyses) in conjunction with recombination assays. Xis is shown to mediate the formation of a specific attP looped structure involving cooperative and competitive long-range interactions among integrase, integration host factor, and Xis proteins. This higher-order structure precludes supercoiled attP from engaging in the productive partner interactions that lead to execution of the first strand exchange in integrative recombination. In addition to its previously characterized role in excision, Xis-induced DNA bending is postulated to act as a regulatory switch (in an alternative loop mechanism) that converts the attP intasome from an integrative-competent complex to a nonreactive one.
Moitoso de Vargas
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Division of Biology and Medicine, Brown University, Providence, RI 02912.
Landy
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D001426:Bacterial Proteins / Q000378:metabolism; D010582:Bacteriophage lambda / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011995:Recombination, Genetic; D014764:Viral Proteins
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; D014764:Viral Proteins; C440502:integration host factor, E coli; D004254:DNA Nucleotidyltransferases; C063911:excisionase