Journal Article

Modulation of the DNA damage response in UV-exposed human lymphoblastoid cells through genetic-versus functional-inactivation of the p53 tumor suppressor

Caroline Léger and Elliot A. Drobetsky

in Carcinogenesis

Volume 23, issue 10, pages 1631-1640
Published in print October 2002 | ISSN: 0143-3334
Published online October 2002 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/23.10.1631
Modulation of the DNA damage response in UV-exposed human lymphoblastoid cells through genetic-versus functional-inactivation of the p53 tumor suppressor

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The global cellular response to UV-induced DNA damage has been analyzed in the p53-proficient human lymphoblastoid strain TK6 versus two isogenic derivatives wherein p53 activity was abrogated by diverse experimental approaches: (i) NH32, carrying a homozygous genetic knockout of p53; and (ii) TK6-5E, expressing the human papillomavirus E6 oncoprotein which binds and functionally inactivates p53 protein. Although widely employed as such, the extent to which intracellular E6 expression faithfully models the p53 deficient state still remains uncertain. Following irradiation with UV (either monochromatic 254 nm UV or broad-spectrum simulated sunlight), relative to wild-type TK6, p53-null NH32 exhibited virtually identical clonogenic survival and kinetics of G1–S progression but was nonetheless profoundly resistant to apoptosis. In addition, there were significant qualitative and quantitative differences between NH32 and TK6 with respect to UV mutagenesis at the endogenous hypoxanthine phosphoribosyltransferase (hprt) locus. However, important disparities were observed between genetically p53-deficient NH32 and E6-expressing TK6-5E regarding the manner in which they responded to UV-induced genotoxic stress in relation to wild-type TK6. Indeed, although NH32 and TK6-5E behaved similarly with respect to UV mutagenesis at the hprt locus, there were significant differences between these strains in clonogenic survival, apoptosis, and G1–S progression. Using a well-defined isogenic system, our data clearly reveal the influence of p53 inactivation on the global response of human cells to UV-induced DNA damage, and highlight an important caveat in the field of p53 biology by directly demonstrating that this influence varies substantially depending upon whether p53 function is abrogated genetically, or through E6 oncoprotein expression.

Keywords: CPD, cyclobutane pyrimidine dimers; GNER, global nucleotide excision repair; IR, ionizing radiation; NER, nucleotide excision repair; PI, propidium iodide; SSL, simulated sunlight; 6-tg, 6-thioguanine.

Journal Article.  8344 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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