Summary
Irradiation of Escherichia coli cells with UV or X-rays followed by incubation under conditions in which protein synthesis can occur results in a population of cells that is resistant to X-rays; however, this resistance develops only if the cells are recA + and lexA +, a fact that associates the phenomenon with induced (S.O.S.) repair. By observing separately the component of a culture that is resistant and the component that retains its normal growth, the fraction of induced and uninduced cells for a dose of UV or X-rays can be estimated. Such estimates show that the dose-response for UV induction of resistant cells agrees with that of the recA gene product. Thus induced radioresistance is considered to be due to the changes in the cell occasioned by the derepression of recA and lexA. These changes are expected to be involved with the synapsis of homologous genomes that is necessary for the use of a second genome to repair damage occurring in both strands of a duplex at the same base, as exemplified by a double-strand break or an interstrand crosslink. This consideration is additionally supported by the increased resistance of cells grown to contain multiple genomes in the same envelope, an increased resistance not found in recA - or lexA - cells. The condition of a completed chromosome is also resistant, again not in recA - or lexA - cells. We suggest that cell killing by X-rays is due to the double-strand breaks which are not repaired by molecular synapsis before the arrival of the replication polymerase at the break.
Similar content being viewed by others
References
Bockrath RC, Hanawalt PC (1980) Ultraviolet light induction of recA protein in a recB uvrB mutant of Escherichia coli. J Bacteriol 143:1025–1028
Braun A, Gluck D (1977) Effect of transient lambda prophage induction on ultraviolet light resistance and recombination in Escherichia coli. J Bacteriol 131:208–213
Bridges BA (1971) RecA +-dependent repair of gamma-ray damage to Escherichia coli does not require recombination between existing homologous chromosomes. J Bacteriol 108:944–945
Castellazzi M, George J, Buttin G (1972) Prophage induction and cell division in E. coli. Further characterization of the thermosensitive mutation tif-1 whose expression mimics the effect of UV irradiation. Mol Gen Genet 119:153–174
Cooper S, Helmstetter CE (1967) Chromosome replication and the division cycle of Escherichia coli B/r. J Mol Biol 31:519–540
Krasin F, Hutchinson F (1977) Repair of DNA double-strand breaks in Escherichia coli which requires recA function and the presence of a duplicate genome. J Mol Biol 116:81–98
Krasin F, Hutchinson F (1981) Repair of DNA double-strand breaks in Escherichia coli cells requires synthesis of proteins which can be induced by ultraviolet light. Proc Natl Acad Sci USA (in press)
Kubitschek HE, Freedman HL (1971) Chromosome replication and the division cycle of Escherichia coli B/r. J Bacteriol 107:95–99
Lydersen BK, Pettijohn DE (1977) Interactions stabilizing DNA tertiary structure in the Escherichia coli chromosome investigated with ionizing radiation. Chromosoma 62:199–215
Mount DW, Low KB, Edmiston SJ (1972) Dominant mutations (lex) in Escherichia coli K12 which affect radiation sensitivity and frequency of ultraviolet light-induced mutations. J Bacteriol 112:886–893
Mount DW, Walker A, Kosel C (1973) Suppression of lex mutation affecting DNA repair in Escherichia coli K12 by closely linked thermosensitive mutations. J Bacteriol 116:850–956
Munson RA, Bridges BA (1966) Site of lethal damage by ionizing radiation in Escherichia coli B/r growing exponentially in minimal medium. Nature 210:922–925
Oishi M, Smith CL (1978) Inactivation of phage repressor in a permeable cell system: Role of recBC DNase in induction. Proc Natl Acad Sci USA 75:3569–3573
Pollard EC, Achey PM (1975) Induction of radioresistance in Escherichia coli. Biophys J 15:1141–1154
Pollard EC, Fluke DJ, Kazanis D (1981) Comparative induction studies. In: Cohn W (ed) Nucleic acids, vol 26. Academic Press, New York, pp 315–322
Pollard EC, Fugate JK Jr (1978) Relative rates of repair of single-strand breaks and postirradiation DNA degradation in normal and induced cells of Escherichia coli. Biophys J 24:429–437
Pollard EC, Person S, Rader M, Fluke DJ (1977) Relation of ultraviolet light mutagenesis to a radiation-damage inducible system in Escherichia coli. Radiat Res 72:519–532
Pollard EC, Randall EP (1973) Srudies on the inducible inhibitor of radiation induced DNA degradation of Escherichia coli. Radiat Res 55:265–279
Pollard EC, Tilberg A (1972) Action of ionizing radiation on sensitive strains of Escherichia coli B. Biophys J 12:133–156
Smith KC, Martignoni KD (1976) Protection of Escherichia coli cells against the lethal effect of UV and X-irradiation by prior X-irradiation. Photochem Photobiol 24:515–523
Trogovčevié Z, Rupp WD (1974) Interaction of bacterial and lambda phage recombination systems in the X-ray sensitivity of Escherichia coli K12. Proc Natl Acad Sci USA 71:503–506
Weinstock GM, McEntee K, Lehman IR (1979) ATP-dependent renaturation of DNA catalyzed by the recA protein of Escherichia coli. Proc Natl Acad Sci USA 76:126–130
Author information
Authors and Affiliations
Additional information
Communicated by B. A. Bridges
Rights and permissions
About this article
Cite this article
Pollard, E.C., Fluke, D.J. & Kazanis, D. Induced radioresistance: An aspect of induced repair. Mol Gen Genet 184, 421–429 (1981). https://doi.org/10.1007/BF00352516
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00352516