The DNA protein complex is a lesion produced by a wide variety of chemical agents. The nature of this lesion and its biological significance are poorly understood. Potassium chromate-induced DNA-protein complex formation will be studied in normal intact cultured Chinese hamster embryo cells. The DNA protein complex will be isolated based upon the ultracentrifugation sedimentation properties of DNA and the stability of the components of the crosslink t SDS. Proteins complexed to the DNA will be analyzed by SDS polyacrylamide gel electrophoresis. The nature of the complex will be examined by studying the stability of the 51 Cr, protein and DNA to various reagents that disrupt specific chemical bonds. Formation of DNA-protein complexes will be examined both in vitro and in intact cells with a variety of carcinogenic and noncarcinogenic metal ions using a recently developed rapid and simple nitrocellulose microfiltration assay. These studies will facilitate the identification of other interesting complex forming metal ions that could be selected in future years for more detailed studies. Preliminary evidence suggests that there is considerable specificity in the complexing of proteins to DNA by chromate. Proteins involved in this complex will be purified and reacted in vitro with chromate and DNA in order to understand whether this specificity is also observed in vitro. Antibodies to complexed proteins will be utilized to purify these proteins. These antibodies will also be utilized to study by immunofluorescence the changes in antigen following chromate treatment. This may also help explain the protein specificity observed in the complexing reaction. Finally, to begin to understand the significance of the chromate-induced DNA-protein complex, the replication of a known sequence of DNA containing a chromate-crosslinked protein will be studied.
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