Endogenous viral genes of the White Leghorn chicken: common site of residence and sites associated with specific phenotypes of viral gene expression.

The DNAs from greater than 150 individual White Leghorn chickens were digested with restriction endonucleases BamHI, EcoRI, HindIII, and Sst I, fractionated by gel electrophoresis, denatured, and transferred to nitrocellulose filters. Fragments containing the endogenous viral genes were detected by hybridization with 70S Rous associated virus type 2[32P]RNA. Embryos of several different phenotypes with respect to production of the endogenous virus and expression of viral group-specific antigen and viral envelope protein were analyzed. DNA from birds of each phenotype produced a distinctive pattern of fragments containing viral genetic information. Individual fragments were seen to segregate as genetic loci in mating experiments. From the fragment patterns and the segregation data, the following conclusions were drawn with respect to the sites of residence in the chicken chromosome of the endogenous viral genes: (i) the DNA of all chickens contains viral genetic information in at least one site, and this site of residence appears to be the same in all chickens analyzed; (ii) four other sites have been identified, and the presence of viral information at each of these sites is always accompanied by a specific phenotype of endogenous viral gene expression; (iii) in addition to the above-mentioned five sites, a small number of other sites have been identified which are not associated with a known phenotype.