The human p53 gene is repaired in UV (254 nm)-irradiated xeroderma pigmentosum group C (XP-C) cells as part of a large genomic region that is about twice the size of the gene. Surrounding genomic regions are not repaired. Through DNA cloning and measurements of DNA repair, we mapped the location of the repair domain, including the terminal regions, relative to the topological features of the gene. The domain includes only the DNA strand that is transcribed and extends in both 3′ and 5′ directions beyond the promoter and transcription termination sites. No transcriptional activity other than that associated with the p53 gene was detected. The results suggest that nontranscribed regions adjacent to the p53 transcribed regions are efficiently repaired in XP-C cells. This means that factors associated with transcription other than RNA polymerase II and the associated transcription repair coupling factor must also play a role in the selective repair process in XP-C cells. We also found that a DNA fragment that contains the p53 promoters is nearly twice as sensitive to cyclobutane pyrimidine dimer induction by UV irradiation than are the surrounding fragments, which have the expected sensitivity.


This research was supported by USPHS Grant CA49411 from the National Cancer Institute, NIH, and by the Biological Sciences Department and the Biomedical Sciences Ph.D. program, Wright State University.

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