Genetic evidence that the elevated levels of Escherichia coli helicase II antagonize recombinational DNA repair.
Some phages survive irradiation much better upon multiple than upon single infection, a phenomenon known as multiplicity reactivation (MR). Long ago MR of UV-irradiated lambda red phage in E. coli cells was shown to be a manifestation of recA-dependent recombinational DNA repair. We used this experimental model to assess the influence of helicase II on the type of recombinational repair responsible for MR. Since helicase II is encoded by the SOS-inducible uvrD gene, SOS-inducing treatments such as irradiating recA(+) or heating recA441 cells were used. We found: i) that MR was abolished by the SOS-inducing treatments; ii) that in uvrD background these treatments did not affect MR; and iii) that the presence of a high-copy plasmid vector carrying the uvrD(+) allele together with its natural promoter region was sufficient to block MR. From these results we infer that helicase II is able to antagonize the type of recA-dependent recombinational repair acting on multiple copies of UV-damaged lambda DNA and that its anti-recombinogenic activity is operative at elevated levels only.
Petranović
M
M
Department of Molecular Genetics, Ruder Bosković Institute, Bijenicka 54, P.O. Box 180, 10002 Zagreb, Croatia. dina@jouy.inra.fr
Zahradka
K
K
Zahradka
D
D
Petranović
D
D
Nagy
B
B
Salaj-Smic
E
E
Petranović
D
D
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics*; D010582:Bacteriophage lambda / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D004260:DNA Repair / Q000187:drug effects* / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D005786:Gene Expression Regulation; D011938:Rec A Recombinases / Q000494:pharmacology / Q000528:radiation effects; D011995:Recombination, Genetic / Q000187:drug effects; D013014:SOS Response, Genetics / Q000235:genetics*; D014157:Transcription Factors; D014466:Ultraviolet Rays / Q000009:adverse effects
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D014157:Transcription Factors; C419603:UvrY protein, E coli; D011938:Rec A Recombinases; D000251:Adenosine Triphosphatases; C506746:UvrD protein, E coli; D004265:DNA Helicases