期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：11
页码：4265-4269
DOI：10.1073/pnas.72.11.4265
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
