UV-enhanced expression of a reporter gene is induced at lower UV fluences in transcription-coupled repair deficient compared to normal human fibroblasts, and is absent in SV40-transformed counterparts

UV irradiation enhances transcription of a number of cellular and viral gen es, We have compared dose responses for alterations in expression from repo rter constructs driven by the human and murine cytomegalovirus (CMV) immedi ate early (IE) promoters in cells from patients with deficiencies in nucleo tide excision repair (complementation groups of xeroderma pigmentosum and C ockayne syndrome) following UV exposure, or infection with W-damaged recomb inant vectors. Results suggest that unrepaired damage in active genes trigg ers increased reporter activity from constructs driven by the CMV promoters in human fibroblasts. Similar to human fibroblasts, HeLa cells and cells f rom Li-Fraumeni syndrome patients (characterized by an inherited mutation i n the p53 gene) also displayed an increase in reporter activity following U V exposure; however, this response was absent in all simian virus 40 (SV40) -transformed cell lines examined. This suggests that a pathway affected by SV40-transformation (other than p53) plays an essential role in UV-enhanced expression from the CMV IE promoter.