Restriction endonuclease mapping of the DNA of Rous-Associated virus 0 reveals extensive homology in structure and sequence with avian sarcoma virus DNA

Abstract

We have prepared a physical map of the DNA of Rous-associated virus O (RAV-O), an endogenous virus released by certain chicken lines, in order to examine the relationship between the genome of this virus and closely related proviruses endogenous to chickens. Nineteen recognition sties for 11 restriction endonucleases have been mapped on the unintegrated linear and circular forms of RAV-O DNA isolated from acutely infected quail cells. PvuI is the only enzyme tested which does not cleave RAV-O DNA. Most of the sites (18 of 19) occur at similar or identical positions in the DNA of avian sarcoma virus (ASV). Significant differences between the maps of corrseponding regions of RAV-O and ASV DNA are observed only with those endonucleases which recognize sites encoded near the 3′ terminus of ASV RNA ( PvuI and EcoRI). Both ends of RAV-O linear DNA contain sequences copied from both the 3′ and the 5′ ends of viral RNA. Two species of closed circular DNA were found: one the same size as the terminally redundant linear DNA (5.0 × 10 6 M r and the other lacking ca. 0.35 kb from an end of linear DNA. Thus the unintegrated forms of RAV-O DNA appear structurally similar to those of ASV DNA[ Shank, P. R., et al. (1978b) . Cell 15, 1383–1395; Hsu, W., et al. (1978) . J. Virol. 28, 810–818]; presumably one copy of a ca. 0.35-kb terminal repeat unit is lost during formation of the smaller circle from linear DNA. The following paper illustrates the utility of the physical map for differentiating between endogenous proviruses which might or might not have sequence identity with the RAV-O genome.