Heat-shock enhanced reactivation of a UV-damaged reporter gene in human cells involves the transcription coupled DNA repair pathway
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abstract
A recombinant nonreplicating human adenovirus type 5, Ad5HCMVsp1lacZ, expressing the lacZ gene under control of the human cytomegalovirus immediate early promoter, was used to assess the effect of heat-shock (HS) on DNA repair of a UV-damaged reporter gene. Host cell reactivation (HCR) of beta-galactosidase (beta-gal) activity for UV-irradiated Ad5HCMVsp1lacZ was used as an indicator of DNA repair in the transcribed strand of an active gene. Repair was examined in heat-shock (HS) pretreated and mock-treated normal fibroblasts, normal lung epithelial cells, xeroderma pigmentosum group A, C, D and G fibroblasts (XP-A, XP-C, XP-D and XP-G), Cockayne's syndrome group A fibroblasts (CS-A), SV40-transformed normal fibroblasts (GM637f) and 5 tumour cell lines (SKOV-3, HeLa, HT29, SCC-25 and U20S). HS enhanced reactivation (HSER) of the reporter gene was detected in normal cells, HT29 tumour cells and XP-C fibroblasts. HSER was reduced or absent in all other XP, CS and tumour cell lines tested. HSER in normal and XP-C cell lines, but not CS-A, XP-A, XP-D or XP-G cells, suggests that HS treatment can enhance the repair of UV-damaged DNA through an enhancement of transcription coupled repair (TCR) or a mechanism which involves the TCR pathway. Since this response was absent in the SV40-transformed fibroblast cell line and 4 of 5 tumour cell lines examined, HSER of beta-gal activity for UV-irradiated Ad5HCMVsp1lacZ also requires some cellular function(s) affected by transformation.
