Type C RNA virus proteins: lack of binding specificity to host cell chromosomal DNA in vitro

Through the use of two different DNA-protein reconstitution methods, we examined the potential role of type C RNA tumor virus proteins as putative regulatory agents in the control of virus expression. Rauscher murine leukemia virus, purified from chronically infected rat cell cultures, was iodinated in vitro with [125I], and dissociated in a nondetergent high-ionic-strength urea-containing buffer. The chemically separated [125I]-labeled viral polypetides were reconstituted with purified DNA by affinity column chromatography and by gradient dialysis renaturation. In both instances, no detectable amount of radioactivity specifically bound to double-stranded DNA of any origin. This observation was in contrast to the binding behavior of identically prepared and radiolabeled, nonhistone chromosomal proteins purified from rat cell nuclei. This finding may rule out, in eukaryotic cells, a well-described prokarytoic regulatory mechanism for the control of integrated viral gene expression.