In Vitro Repair of X-Irradiated DNA Extracted from Bacillus subtilis Deficient in Polymerase I

In Vitro Repair of X-Irradiated DNA Extracted from Bacillus subtilis Deficient in Polymerase I

Philip J. Laipis* and
A. T. Ganesan†,‡

^*Department of Biochemical Sciences, Princeton University, Princeton, New Jersey 08540
^†Department of Genetics, Lt. Joseph P. Kennedy, Jr. Laboratories for Molecular Medicine, Stanford School of Medicine, Stanford, California 94035

Abstract

DNA extracted from x-irradiated cells of a mutant of Bacillus subtilis deficient in DNA polymerase I has greatly reduced biological activity. This DNA, which has many single-strand nicks, can be repaired in vitro with purified DNA polymerase I and DNA ligase or with lysates of wild-type B. subtilis cells, which restore biological activity and increase the single-strand molecular weight. Lysates of polymerase I-deficient B. subtilis cells cannot repair such irradiated DNA until purified DNA polymerase I or lysate from wild-type cells is added to the deficient lysate.