INDUCTION OF UV-DAMAGE RECOGNITION PROTEIN BY CISPLATIN TREATMENT

The biological functions of DNA damage recognition proteins are not we ll understood. Using the band shift assay, we detected in nuclear extr acts from human carcinoma cell lines damage recognition protein which bound selectively to W-damaged double-stranded DNA. No consistent corr elation was found between steady-state levels of the UV-damage recogni tion protein and either cisplatin cytotoxicity or DNA repair activity; However, cisplatin treatment caused accumulation of the UV-damage rec ognition protein. The cisplatin-responsive induction of UV-damage reco gnition protein in the nucleus was higher in cisplatin-resistant cell lines than in their parental counterparts. These results imply that th e level of inducibility in response to treatment, but not the constitu tive binding activity, of UV-damage recognition protein correlates wit h cisplatin resistance. Inhibition of UV-damage recognition protein ex pression by actinomycin and cycloheximide suggests that induction of U V-damage recognition protein requires de novo RNA and protein synthesi s, rather than post-translational modification of pre-existing protein . The increased level of UV-damage recognition protein after cisplatin treatment could be a direct response to adduct formation, since it co rrelated with the number of Pt-DNA adducts. However, it could also be a secondary effect of DNA replication inhibition following DNA damage, since inhibition of DNA synthesis by aphidicolin and hydroxyurea caus ed the same induction of UV-damage recognition protein. Inducibility o f UV-damage recognition protein binding activity by Pt drug treatment suggests involvement of this protein in drug resistance, although a di rect link between its function and DNA repair or damage tolerance has not been demonstrated.