Capacity of UV-lrradiated Human Fibroblasts to Support Adenovirus DNA Synthesis Correlates with Transcription-Coupled Repair and is Reduced in SV40-Transformed Cells and Cells Expressing Mutant p53
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We have examined the capacity of UV-irradiated human diploid fibroblasts to support adenovirus (Ad) DNA synthesis in order to assess repair of UV-damaged DNA. The capacity of UV-irradiated xeroderma pigmentosum group C (XP-C) fibroblasts to support Ad DNA synthesis was similar to that of UV-irradiated normal diploid fibroblasts, following UV exposures of greater than 9 J/m2. In contrast, XP-A, Cockayne syndrome groups A and B (CS-A and CS-B) fibroblasts were reduced in their capacity to support Ad DNA synthesis compared to normal diploid fibroblasts following a similar UV treatment. These results demonstrate that the capacity of UV-irradiated fibroblasts to support Ad DNA synthesis correlates with their ability to remove UV-induced DNA damage from active genes by transcription-coupled repair (TCR). We also demonstrate that simian virus 40 (SV40)-transformed human fibroblasts, Li-Fraumeni syndrome (LFS) fibroblasts, heterozygous for mutations in one allele of the p53 gene and immortalized LFS cell lines expressing only mutant p53 are reduced in their capacity to support Ad DNA replication following similar UV treatments. These results suggest that the capacity of UV-irradiated cells to support viral DNA synthesis involves TCR of UV-damaged DNA and is disrupted by SV40 transformation and expression of mutant p53. We propose a model in which p53-dependent TCR regulates p53 stability in response to UV.
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