Replication and repair of DNA in cells of Escherichia coli treated with toluene

Abstract

DNA synthesis has been studied in Escherichia coli cells made permeable to nucleotides by treatment with toluene. Replicative synthesis, as distinguished from repair synthesis, occurs at a rate comparable to that observed in vivo; it is dependent on the presence of all four deoxyribonucleoside triphosphates, but does not require exogenous DNA; and it is stimulated by ATP. Furthermore, replicative synthesis can be abolished at the restrictive temperature in DNA temperature-sensitive mutants. N-ethylmaleimide completely inhibits this type of synthesis, whereas it does not inhibit repair synthesis. Repair synthesis further differs from replicative synthesis in the following points: it does not require ATP; it persists at the restrictive temperature in DNA temperature-sensitive mutants; it can be induced by endogenous or exogenous nuclease activity; and its demonstration requires a Pol(+) strain.