The molecular action of ultraviolet and visible light. II: Dark repair. Mechanisms of mutation induction

Abstract

At the end of Chapter 10, two related phenomena in UV-mutagenesis of bacteria have been described: mutation frequency decline (MFD) and mutation fixation (MF). It will be recalled that MFD is the irreversible loss of potential mutations to prototrophy by inhibition of protein synthesis and that MF is the event, presumably DNA synthesis, that terminates the period during which MFD can occur. In 1961 (1) Witkin and, independently, Lieb (2) suggested that MFD might be due to an enzymatic repair process that did not require visible light. This was the first suggestion that there might be dark repair of UV damage. At present, several dark repair systems are known in a variety of organisms, prokaryotes as well as eukaryotes, and their study forms a major area of research on radiation damage (see Bibliography: Radiation Res. Suppl. 1966; Cold Spring Harbor Symp. 1968; Witkin, 1969).