Analysis of DNA–protein complexes induced by chemical carcinogens

DNA–protein complexes induced in intact cells by chromate have been isolated and compared with those formed by other agents such as cis‐platinum. Actin has been identified as one of the major proteins that is complexed to the DNA by chromate based upon a number of criteria including, a molecular weight and isoelectric point identical to actin, positive reaction with actin polyclonal antibody, and proteolytic mapping. Chromate and cis‐platinum both complex proteins of very similar molecular weight and isoelectric points and these complexes can be disrupted by exposure to chelating or reducing agents. These results suggest that the metal itself is participating in rather than catalyzing the formation of a DNA–protein complex. An antiserum which was raised to chromate‐induced DNA–protein complexes reacted primarily with a 97,000 protein that could not be detected by silver staining. Western blots and slot blots were utilized to detect p97 DNA–protein complexes formed by cis‐platinum, UV, formaldehyde, and chromate. Other work in this area, involving studying whether DNA–protein complexes are formed in actively transcribed DNA compared with genetically inactive DNA, is discussed. Methods to detect DNA–protein complexes, the stability and repair of these lesions, and characterization of DNA–protein complexes are reviewed. Nuclear matrix proteins have been identified as a major substrate for the formation of DNA–protein complexes and these findings are also reviewed.