DELETION MUTANT OF THE BRATISLAVA-77 STRAIN OF ROUS-SARCOMA VIRUS CONTAINING A FUSION OF THE GROUP-SPECIFIC ANTIGEN AND ENVELOPE GENES

The genetic compositions of 2 independently derived preparations of the Bratislava-77 strain (B77) of Rous sarcoma virus were analyzed after each was passaged 7 or more times in duck embryo fibroblasts. RNase T1-resistant oligonucleotide fingerprint analysis of virion RNA from both preparations of duck-passaged B77 revealed the presence of 2 large noncontiguous deletions. Approximately 75% of the RNA contained a deletion which spans oligonucleotides 304 to 4 on the viral genome (about 3500 nucleotides) and encompasses all of the B77 polymerase gene. More than 90% of the RNA also contained a deletion which spans src-specific oligonucleotides 6 and 5 (about 2200 nucleotides) and is identical to the deletion observed in transformation-defective B77. Virion RNA from duck-passaged B77 also contained 2 oligonucleotides (D1 and D2) not observed in the RNA of B77 virus grown on chicken embryo fibroblasts. Analysis of the virion RNA of duck-passaged B77 by denaturing agarose gel electrophoresis revealed 4 major subunits with MW of 3.40 .times. 106, 2.65 .times. 106, 2.25 .times. 106 and 1.55 .times. 106. Whereas the 3.40 and 2.65 megadalton (Mdal) RNA species comigrated with the nondefective and transformation-defective RNA of B77 propagated on chicken embryo fibroblasts, no counterparts to the 2.25 and 1.55 Mdal RNA were observed in the RNA of B77 grown on chicken embryo fibroblasts. Oligonucleotide fingerprint analysis of these RNA species revealed that the 2.65 Mdal RNA contains the src-specific deletion and that 2.25 Mdal RNA contains the polymerase region deletion; both of these deletions were observed in the 1.55 Mdal RNA, which was the major RNA subunit species detected in duck-passaged B77. The new oligonucleotides (D1 and D2) observed in the duck-passaged virus were present in the 2.25 and 1.55 Mdal RNA species, but not in the 2.65 Mdal RNA. The 1.55 Mdal RNA can function as an mRNA in vitro and in vivo and directs the synthesis of a 130,000 dalton protein (p130). p130 contains antigenic determinants specific for p27 (gag gene) and gp85 (env gene) but does not contain sequences which cross-react with antisera directed against the .alpha..beta. form of RNa-dependent DNA polymerase (pol gene). This RNA is generated by a fusion of the gag and env genes of Rous sarcoma virus B77.