LexA protein of Escherichia coli represses expression of the Tn5 transposase gene.
The LexA protein of Escherichia coli represses expression of a variety of genes that, by definition, constitute the SOS regulon. Genetic evidence suggests that Tn5 transposition is also regulated by the product of the lexA gene (C.-T. Kuan, S.-K. Liu, and I. Tessman, Genetics 128:45-57, 1991). We now show that the LexA protein represses expression of the tnp gene, located in the IS50R component of Tn5, which encodes a transposase, and that LexA does not repress expression of the IS50R inh gene, which encodes an inhibitor of transposition. Elimination of LexA resulted in increased expression of the tnp gene by a factor of 2.7 +/- 0.4, as indicated by the activity of a lacZ gene fused to the tnp gene. LexA protein retarded the electrophoretic movement of a 101-bp segment of IS50R DNA that contained a putative LexA protein-binding site in the tnp promoter; the interaction between the LexA repressor and the promoter region of the tnp gene appears to be relatively weak. These features show that the IS50R tnp gene is a member of the SOS regulon.
Kuan
C T
CT
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Tessman
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I
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013014:SOS Response, Genetics / Q000235:genetics; D012697:Serine Endopeptidases; D019895:Transposases; D001616:beta-Galactosidase / Q000235:genetics; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D009713:Nucleotidyltransferases; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D019895:Transposases; D001616:beta-Galactosidase; D000099160:LexA Repressor Protein