Damage-recognition proteins as a potential indicator of DNA-damage-mediated sensitivity or resistance of human cells to ultraviolet radiation

We have previously identified damage-recognition proteins that bind to cisplatin[cis-diamminedichloroplatinum(II), a DNA cross-linking agent]- or u.v.-modified DNA in HeLa cells [Chao, Huang, Huang & Lin-Chao (1991) Mol. Cell. Biol. 11, 2075-2080; Chao, Huang, Lee & Lin-Chao (1991) Biochem. J. 277, 875-878]. In the present study we compared damage-recognition proteins in cells expressing different sensitivities to DNA damage. An increase in damage-recognition proteins and an enhancement of plasmid re-activation were detected in HeLa cells resistant to cisplatin and u.v. However, repair-defective cells derived from xeroderma-pigmentosum (a rare skin disease) patients did not express less cisplatin damage-recognition proteins than repair-competent cells, suggesting that damage-recognition-protein expression may not be related to DNA repair. By contrast, cells resistant to DNA damage consistently expressed high levels of u.v.-modified-DNA damage-recognition proteins. The results support the notion that u.v. damage-recognition proteins are different from those that bind to cisplatin. These findings also suggest that the damage-recognition proteins identified could be used as potential indicators of the sensitivity or resistance of cells to u.v.