Damaged DNA-binding proteins: recognition of N-acetoxy-acetylaminofluorene-induced DNA adducts.

Abstract

Proteins which bind to the DNA damaged by genotoxic agents can be detected in all living organisms. Damage-recognition proteins are thought to be generally involved in DNA repair mechanisms. On the other hand, the relevance to DNA repair of some other proteins which show elevated affinity to damaged DNA (e.g. HMG-box containing proteins or histone H1) has not been established. Using the electrophoretic mobility-shift assay we have investigated damage-recognition proteins in nuclei from rat hepatocytes. We detected two different protein complexes which preferentially bound the DNA damaged by N-acetoxy-acetylaminofluorene. One of them also recognized the DNA damaged by benzo(a)pyrene diol epoxide (yet with much lower efficiency). The proteins which bind to damaged DNA are permanently present in rat cells and their level does not change after treatment of animals with the carcinogens. Differences in the affinity of the detected damage-recognition proteins to DNA lesion evoked by either carcinogen did not correlate with more efficient removal from hepatic DNA of 2-acetylaminofluorene-induced adducts than benzo(a)pyrene-induced ones.