Use of DNA-DNA annealing to detect new virus-specific DNA sequences in chicken embryo fibroblasts after infection by avian sarcoma virus.

Labeled, virus-specific DNA synthesized in vitro by the virion-associated polymerase of avian sarcoma virus (ASV) was used to measure virus-specific sequences in cell DNA in three ways: (i) by determining the effect of cell DNA upon the reassociation rate of double-stranded polymerase products; (ii) by measuring the kinetics of annealing of single-stranded polymerase product (cDNA) to cell DNA; or (iii) by measuring the amount of cDNA which anneals to a large excess of cell DNA. With these three assays and modifications of them, we show that fewer than five copies of ASV-specific DNA sequences are present per diploid cell in uninfected chicken embryos; that a two- to several-fold increase in copy number of viral DNA follows infection by ASV; that infection introduces to the cell viral sequences not present before infection; and that DNAs from uninfected Pekin duck and Japanese quail embryos show no homology with DNA synthesized by the ASV polymerase. Some of these results differ from data in a previous report from this laboratory (H. E. Varmus, R. A. Weiss, R. R. Friis, W. Levinson, and J. M. Bishop, 1972) and, in general, reconcile our observations with those from other laboratories.