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Mutation Research, 62 (1979) 311--323

© Elsevier/North-Holland Biomedical Press

DNA EXCISION-REPAIR PROCESSES IN HUMAN CELLS CAN ELIMINATE THE CYTOTOXIC AND MUTAGENIC CONSEQUENCES OF ULTRAVIOLET IRRADIATION

V E R O N I C A M. M A H E R , DELIA J. D O R N E Y , A L A N L. M E N D R A L A , B E A T E K O N Z E - T H O M A S and J. JUSTIN M c C O R M I C K

Department of Microbiology and Department of Biochemistry, Carcinogenesis Laboratory, Fee Hail, Michigan State University, East Lansing, M148824 (U.S.A.)

(Received 17 May 1978) (Revision received 10 April 1979) (Accepted 23 April 1979)

Summary The ability of DNA excision-repair processes in diploid human flbroblasts to eliminate potentially cytotoxic and mutagenic lesions induced by UV radiation (254 nm) was demonstrated in two ways: (1) Cells with normal rates of excision were compared with cells with an intermediate rate of excision (XP2BE) and cells with an excision rate ~ nr

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Fig. 1. Compa1~ng the cytotoxic and mutagenic effect of UV radiation in human flbroblasts with different rates of excision repair. Cells from exponentially-growing cultures were plated into culture dishes at appropriate densities, allowed ~ 1 2 h to attach, irradiated, and allowed to develop into colonies. Selection in sltu with 20 ~M AG was begun after 5--8 days of expi~eseion (>S population doublings). See Materials and Methods section for experimental details.

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mutations). In contrast, the XP2BE cells are not fast enough to reach 100% survival but can remove a large number of the potentially cytotoxic damage and at least some of potentially mutagenic lesions. If this is so, then if one were able to lengthen the time before the "critical event" in some way, cells which possess at least some excision capacity should be able to eliminate all the potentially cytotoxic and mutagenic lesions.

Evidence of recovery from potentially cytotoxic and mutagenic DNA damage in cells capable of excision repair. To test this prediction, we investigated whether cells irradiated in confluence (Go state), and prevented from entering the cell cycle but allowed to excise,

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