Abstract
The survival of UV-irradiated mammalian cells is not necessarily correlated with their overall capacity to carry out DNA repair. Human cells typically remove 80% of the pyrimidine dimers produced by a UV dose of 5 J/m2 within 24 hr. In contrast, a Chinese hamster ovary (CHO) cell line survives UV irradiation equally well while removing only 15% of the dimers. Using a newly developed technique to measure dimer frequencies in single-copy specific sequences, we find that the CHO cells remove 70% of the dimers from the essential dihydrofolate reductase (DHFR) gene but only 20% from sequences located 30 kilobases or more upstream from the 5' end of the gene in a 24-hr period. Repair-deficient human cells from xeroderma pigmentosum complementation group C (XPC) are similar to the CHO cells in overall repair levels, but they are extremely sensitive to killing by UV irradiation. In the XPC cells, we find little or no repair in the DHFR gene; in contrast, in normal human fibroblasts and epidermal keratinocytes, greater than 80% of the dimers induced in the gene by 20 J/m2 are removed in 24 hr. Since the CHO and normal human cells exhibit similar UV resistance, much higher than that of XPC cells, our findings suggest a correlation between efficient repair of essential genes and resistance to DNA-damaging agents such as UV light.
Full text
PDF



Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Andrews A. D., Barrett S. F., Robbins J. H. Xeroderma pigmentosum neurological abnormalities correlate with colony-forming ability after ultraviolet radiation. Proc Natl Acad Sci U S A. 1978 Apr;75(4):1984–1988. doi: 10.1073/pnas.75.4.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bohr V. A., Smith C. A., Okumoto D. S., Hanawalt P. C. DNA repair in an active gene: removal of pyrimidine dimers from the DHFR gene of CHO cells is much more efficient than in the genome overall. Cell. 1985 Feb;40(2):359–369. doi: 10.1016/0092-8674(85)90150-3. [DOI] [PubMed] [Google Scholar]
- Chen M. J., Shimada T., Moulton A. D., Cline A., Humphries R. K., Maizel J., Nienhuis A. W. The functional human dihydrofolate reductase gene. J Biol Chem. 1984 Mar 25;259(6):3933–3943. [PubMed] [Google Scholar]
- Hanawalt P. C., Cooper P. K., Ganesan A. K., Smith C. A. DNA repair in bacteria and mammalian cells. Annu Rev Biochem. 1979;48:783–836. doi: 10.1146/annurev.bi.48.070179.004031. [DOI] [PubMed] [Google Scholar]
- Kleijer W. J., de Weerd-Kastelein E. A., Sluyter M. L., Keijzer W., de Wit J., Bootsma D. UV-induced DNA repair synthesis in cells of patients with different forms of xeroderma pigmentosum and of heterozygotes. Mutat Res. 1973 Dec;20(3):417–428. doi: 10.1016/0027-5107(73)90062-6. [DOI] [PubMed] [Google Scholar]
- Liu S. C., Parsons C. S., Hanawalt P. C. DNA repair response in human epidermal keratinocytes from donors of different age. J Invest Dermatol. 1982 Nov;79(5):330–335. doi: 10.1111/1523-1747.ep12500087. [DOI] [PubMed] [Google Scholar]
- Mullenders L. H., van Kesteren A. C., Bussmann C. J., van Zeeland A. A., Natarajan A. T. Preferential repair of nuclear matrix associated DNA in xeroderma pigmentosum complementation group C. Mutat Res. 1984 Oct;141(2):75–82. doi: 10.1016/0165-7992(84)90014-9. [DOI] [PubMed] [Google Scholar]
- Urlaub G., Käs E., Carothers A. M., Chasin L. A. Deletion of the diploid dihydrofolate reductase locus from cultured mammalian cells. Cell. 1983 Jun;33(2):405–412. doi: 10.1016/0092-8674(83)90422-1. [DOI] [PubMed] [Google Scholar]
- van Zeeland A. A., Smith C. A., Hanawalt P. C. Sensitive determination of pyrimidine dimers in DNA of UV-irradiated mammalian cells. Introduction of T4 endonuclease V into frozen and thawed cells. Mutat Res. 1981 Jun;82(1):173–189. doi: 10.1016/0027-5107(81)90148-2. [DOI] [PubMed] [Google Scholar]