Inhibition of Escherichia coli RecA coprotease activities by DinI.
In Escherichia coli, the SOS response is induced upon DNA damage and results in the enhanced expression of a set of genes involved in DNA repair and other functions. The initial step, self-cleavage of the LexA repressor, is promoted by the RecA protein which is activated upon binding to single-stranded DNA. In this work, induction of the SOS response by the addition of mitomycin C was found to be prevented by overexpression of the dinI gene. dinI is an SOS gene which maps at 24.6 min of the E.coli chromosome and encodes a small protein of 81 amino acids. Immunoblotting analysis with anti-LexA antibodies revealed that LexA did not undergo cleavage in dinI-overexpressed cells after UV irradiation. In addition, the RecA-dependent conversion of UmuD to UmuD' (the active form for mutagenesis) was also inhibited in dinI-overexpressed cells. Conversely, a dinI-deficient mutant showed a slightly faster and more extensive processing of UmuD and hence higher mutability than the wild-type. Finally, we demonstrated, by using an in vitro reaction with purified proteins, that DinI directly inhibits the ability of RecA to mediate self-cleavage of UmuD.
Yasuda
T
T
Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
Morimatsu
K
K
Horii
T
T
Nagata
T
T
Ohmori
H
H
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016296:Mutagenesis; D011938:Rec A Recombinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D013014:SOS Response, Genetics / Q000235:genetics*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D004259:DNA-Directed DNA Polymerase; C055218:UmuD protein, E coli