Bacteria react to irradiation with short wave length UV (UVC) by mount
ing a rescuing response which involves the synthesis of proteins engag
ed in DNA repair, replication and mutagenesis. We analyse here an anal
ogous response shown by mammalian cells in culture and present experim
ental evidence for the chain of events induced by UV irradiation that
leads to enhanced gene expression. Available results suggest that the
UV induced signal cascade depends on damage to DNA and also involves c
omponents located at the plasma membrane, such as src, ras and raf. Th
ese components, upon activation by UV, signal into the cell's nucleus,
thereby activating transcription factors which control the activity o
f UV responsive genes.