Mechanisms of the ultraviolet light response in mammalian cells.

Environmental stresses produce physical and/or chemical damage in cells. Commonly, we accept that an affected cell may either die or repair the damage. Over the past few years a much more elaborate type of response to environmental stress has been elucidated. A common feature of the new type of response is the synthesis of new macromolecules and the subsequent change in behavior that could at least in part be defined as 'response modification'. Transiently, the cells maintain memory of the particular stress factor and will react differently upon a second encounter with the same or a related factor. Examples are the synthesis of heat-shock proteins and the concomittantly acquired heat resistance (Johnston and Kucey, 1988; Riabowohl et al. 1988); reduced metal toxicity by cadmium-induced metal binding proteins (Beach and Palmiter, 1981; Karin et al. 1983; for earlier evidence, see Kagi and Nordberg, 1979) and the 'u.v. response' (Schorpp et al. 1984; Kaina et al. 1989a,fe).