The repair of double-strand breaks in the nuclear DNA of Saccharomyces cerevisiae and its genetic control |
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Authors: | Michael A Resnick and Patricia Martin |
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Institution: | (1) Department of Radiation Biology and Biophysics, School of Medicine and Dentistry, University of Rochester, 14642 Rochester, New York, U.S.A.;(2) Present address: National Institute for Medical Research, Mill Hill, NW7 1AA London, England |
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Abstract: | Summary With the use of neutral sucrose sedimentation techniques, the size of unirradiated nuclear DNA and the repair of double-strand breaks induced in it by ionizing radiation have been determined in both wild-type and homozygous rad52 diploids of the yeast Saccharomyces cerevisiae. The number average molecular weight of unirradiated DNA in these experiments is 3.0×108±0.3 Daltons. Double-strand breaks are induced with a frequency of 0.58×10-10 per Daltonkrad in the range of 25 to 100 krad. Since repair at low doses is observed in wild-type but not homozygous rad52 strains, the corresponding rad52 gene product is concluded to have a role in the repair process. Cycloheximide was also observed to inhibit repair to a limited extent indicating a requirement for protein synthesis. Based on the sensitivity of various mutants and the induction frequency of double-strand breaks, it is concluded that there are 1 to 2 double-strand breaks per lethal event in diploid cells incapable of repairing these breaks. |
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