Repair of near-ultraviolet (365 nm)-induced strand breaks in Escherichia coli DNA. The role of the polA and recA gene products
The action of near-ultraviolet (UV-365 nm) radiation in cellular inactivation (biological measurements) and induction and repair of DNA strand breaks (physical measurements) were studied in a repair-proficient strain and in polA-, recA-, uvrA-, and polA uvrA-deficient strains of Escherichia coli K-12. The induction of breaks in the polA and polA uvrA strains was linear with dose (4.0 and 3.7 X 10(-5) breaks/2.5 X 10(9) daltons/Jm-2, respectively). However, in the recA-, uvrA-, and repair-proficient strains, there was an initial lag in break induction at low doses and then a linear induction of breaks at higher doses with rates of 4.6, 2.8, and 3.2 X 10(-5) breaks/2.5 X 10(9) daltons/Jm-2, respectively. We interpret these strain differences as indicating simultaneous induction and repair of breaks in polymerase 1 (polA)-proficient strains under the 0 degrees C, M9 buffer irradiation conditions that, for maximum efficiency, require both the polA and recA gene products. Strand-break rejoining also occurred at 30 degrees C in complete growth medium. We propose that at least three (and possibly four) distinct types of pathways can act to reduce the levels of 365-nm radiation-induced strand breaks. A quantitative comparison of the number of breaks remaining with the number of lethal events remaining after repair in complete medium at 30 degrees C showed that between one and three breaks remain per lethal event in the wild-type and recA strains, whereas in the polA strain one order of magnitude more breaks were induced.
- Research Organization:
- Universidade Federal do Rio de Janeiro, Brazil
- OSTI ID:
- 5676589
- Journal Information:
- Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 2; ISSN BIOJA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIOLOGICAL PATHWAYS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
DNA POLYMERASES
DNA REPAIR
ELECTROMAGNETIC RADIATION
ENZYMES
ESCHERICHIA COLI
MICROORGANISMS
NEAR ULTRAVIOLET RADIATION
NUCLEOTIDYLTRANSFERASES
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
RADIATIONS
RECOVERY
REPAIR
STRAND BREAKS
TRANSFERASES
ULTRAVIOLET RADIATION