Open AccessEnzymatic induction of DNA double-strand breaks in gamma-irradiated Escherichia coli K-12.
Author(s) -
Thomas Bonura,
Kendric C. Smith,
Henry S. Kaplan
Publication year - 1975
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.72.11.4265
Subject(s) - dna , ionizing radiation , strain (injury) , escherichia coli , yield (engineering) , dna damage , irradiation , incubation , microbiology and biotechnology , double strand , dna repair , chemistry , biology , biochemistry , biophysics , materials science , gene , physics , anatomy , nuclear physics , metallurgy
The polA1 mutation increases the sensitivity of E. coli K-12 by killing by gamma-irradiation in air by a factor of 2.9 and increases the yield of DNA double-strand breaks by a factor of 2.5. These additional DNA double-strand breaks appear to be due to the action of nucleases in the polA1 strain rather than to the rejoining of radiation-induced double-strand breaks in the pol+ strain. This conclusion is based upon the observation that gamma-irradiation at 3 degrees did not affect the yield of DNA double-strand breaks in the pol+ strain, but decreased the yield in the polA1 strain by a factor of 2.2. Irradiation of the polA1 strain at 3 degrees followed by incubation at 3 degrees for 20 min before plating resulted in approximately a 1.5-fold increase in the D0. The yield of DNA double-strand breaks was reduced by a factor of 1.5. The pol+ strain, however, did not show the protective effect of the low temperature incubation upon either survival or DNA double-strand breakage. We suggest that the increased yield of DNA double-strand breaks in the polA1 strain may be the result of the unsuccessful exision repair of ionizing radiation-induced DNA base damage.