EFFECT OF 5-BROMODEOXYURIDINE ON DEOXYRIBONUCLEIC ACID-PROTEIN ADDUCTS INDUCED BY ULTRAVIOLET-LIGHT ON CHROMATIN CELLS

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 38  (1) , 58-66
Abstract
The formation of DNA-protein adducts induced by UV irradiation (254 nm) was analyzed by cesium chloride equilibrium sedimentation. The formation of UV-induced DNA-protein adducts was increased in 5-bromodeoxyuridine[5-BUdR]-substituted chromatin. Cross-linking was dependent in part upon the extent of 5-BUdR substitution and was detectable either in chromatin irradiated in vitro or in chromatin from cells irradiated in vivo prior to the isolation of chromatin. As much as 80% of the DNA was cross-linked to proteins by UV irradiation of 5-BUdR-substituted chromatin at a fluence of 2928 Jm-2. In unsubstituted chromatin 11,712 Jm-2 were required to obtain the same effect. Under the same conditions of 5-BUdR replacement and UV irradiation only 10% of the total chromosomal proteins were cross-linked to DNA, whether in vivo or in vitro. Approximately 2/3 of the cross-linked proteins chromatographed as nonhistone proteins, the remaining 1/3 as histones. [Baby hamster kidney AF8 cells were studied.].