Expression of wild-type p53 is required for efficient global genomic nucleotide excision repair in UV-irradiated human fibroblasts.
We have shown previously that Li-Fraumeni syndrome fibroblasts homozygous for p53 mutations are deficient in the removal of UV-induced cyclobutane pyrimidine dimers from genomic DNA, but still proficient in the transcription-coupled repair pathway (Ford, J. M., and Hanawalt, P. C. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 8876-8880). We have now utilized monoclonal antibodies specific for cyclobutane pyrimidine dimers or 6-4 photoproducts, respectively, to measure their repair in UV-irradiated human fibroblasts. Cells homozygous for p53 mutations were deficient in the repair of both photoproducts, whereas cells heterozygous for mutant p53 exhibited normal repair of 6-4 photoproducts, but decreased initial rates of removal of cyclobutane pyrimidine dimers, compared with normal cells. The specificity of the effect of wild-type p53 on nucleotide excision repair was demonstrated in a p53 homozygous mutant cell line containing a tetracycline-regulated wild-type p53 gene. Wild-type p53 expression and activity were suppressed in the presence of tetracycline, whereas withdrawal of tetracycline resulted in the induction of p53 expression, cell cycle checkpoint activation, and DNA damage-induced apoptosis. The regulated expression of wild-type p53 resulted in the recovery of normal levels of repair of both cyclobutane pyrimidine dimers and 6-4 photoproducts in genomic DNA, but did not alter the transcription-coupled repair of cyclobutane pyrimidine dimers. Therefore, the wild-type p53 gene product is an important determinant of nucleotide excision repair activity in human cells.
Ford
J M
JM
Department of Biological Sciences, Stanford University, Stanford, California 94305, USA. jmf@leland.stanford.edu
Hanawalt
P C
PC
D002478:Cells, Cultured; D004260:DNA Repair; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D015870:Gene Expression; D015894:Genome, Human; D006720:Homozygote; D006801:Humans; D009154:Mutation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism; D014466:Ultraviolet Rays
D016159:Tumor Suppressor Protein p53