We have initiated a study of the role of the initial step of DNA repair in human carcinogenesis. This research program utilizes recombinant DNA technology and DNA repair genes from E. coli. Having successfully amplified E. coli uvr-genes to high levels, we are producing antibodies to uvr-proteins for detection of cross-reacting antigens in human cells. In addition, we have developed a method to genetically identify DNA repair gene products by inactivation mapping and specific labeling of plasmid encoded gene products.