Deoxyribonucleic Acid Damage by Monofunctional Mitomycins and Its Repair in Escherichia coli

Abstract

Exposure of Escherichia coli to the antibiotic mitomycin C (MTC) at a concentration of 0.5 ,ug/ml caused cross-linkage between complementary strands of deoxyribonucleic acid (DNA). Derivatives of mitomycin, 7-methoxymitosene (7-MMT) and decarbamoyl mitomycin C (DCMTC), at a level as high as 20 ,ug/ml formed no cross-links between DNA strands. Ultraviolet light-sensitive mutants of E. coli K-12 bearing uvrA, uvrB, uvrC, or recA mutations were more sensitive to the lethal action of 7-MMT and of DCMTC than was the wild-type strain. Treatment of wild-type cells with these antibiotics resulted in the production of single-strand breaks in DNA, which were repaired upon incubation in a growth medium. Such breaks in DNA were not produced in the uvrA and the uvrB mutants. In the uvrC mutant, single-strand breaks were produced by 7-MMT or by DCMTC, but these breaks were not repaired upon incubation. These results are discussed in connection with the mechanism for removal of pyrimidine dimers in ultraviolet-irradiated bacteria.

Isolation and Characterization of an Escherichia coli ruv Mutant Which Forms Nonseptate Filaments After Low Doses of Ultraviolet Light Irradiation

“…A 1-ml volume of the cells was removed at zero time, and the rest (1 ml) was incubated for 60 min in EM plus thymidine (20 ug/ml) medium. The cells were centrifuged, concentrated to 0.4 ml, and converted to spheroplasts, as described in a previous paper (18). Spheroplasts (10 lliters, about 107) were lysed in 0.2 ml of 0.5 N NaOH containing 0.1% sodium dodecyl sulfate in the surface layer on a 4.6-ml gradient of 5 to 20% (wt/vol) sucrose containing 10-3 M ethylenediaminetetraacetate (EDTA) and 0.9 M NaCl (adjusted to pH 12 with NaOH).…”

“…The Ion-, or fil+, mutant of Escherichia coli can be assumed to be typical of such conditional division mutants, since it forms multinucleate filaments and fails to divide after low doses of UV irradiation (1,2,7,12,(22)(23)(24). To isolate a similar mutant, we have used a conventional replica plating method with mitomycin C (MTC) as a selecting agent, which has effects very similar to those of UV (5,15,18,19). By this method, we isolated two additional UVsensitive mutants of E. coli, designated RuvAand RuvB-, which formed long nonseptate filaments after very low doses of UV irradiation.…”

THE ISOLATION AND PARTIAL CHARACTERIZATION OF UV SENSITIVE MUTANTS OF Synechococcus PCC7943 (Anacystis nidulans 602)

“…1). In E. coli, uvrand recstrains are both Uv ' and MTC' (Iyer and Sybalski, 1963;Boyce and Howard-Flanders, 1964;Otsuji and Muramaya, 1972). If analogous repair systems exist in Synechococcus, the isolation of MTC' mutants should facilitate the isolation of strains defective in either excision or recombination repair.…”

Biochemical Studies on the χ Mutation of Bacteriophage T4: Differential Inhibition of χ + and χ DNA Synthesis by Mitomycin C

“…This implies that the v gene product, T4 endonuclease V, does not function to repair MC-damaged DNA. It has been shown that E. coli uvr genes, whose function can be replaced by the v gene product (14,27), are involved in repair of MC-induced damage (19). It seems of interest to see whether the apparent difference is due to different specificities of T4 and E. coli repair enzymes.…”