The genomic RNA of avian reticuloendotheliosis virus REV

Purified virus obtained from a subline of chicken bone marrow cells transformed by avian reticuloendotheliosis virus (REV) was found to contain the RNA of REV in excess over the RNA of its associated helper virus REV-A. Electrophoretic and sedimentation analyses resolved these RNAs into a 28 S and a 34 S component, respectively. Comparison of these RNA species with the RNA obtained from plaque-purified preparations of REV-A confirmed that the 28 S RNA represents the genome of transforming REV. The small size of 28 S REV RNA suggests that the defectiveness of REV is due to a deletion of replicative sequences. Hybridization experiments indicated that about 25–30% of REV RNA sequences are unrelated to REV-A. These may include the putative transforming sequences of REV. REV shared 12–15 of 42 identifiable large RNase T₁-resistant oligonucleotides with REV-A. The 28 S REV RNA did not contain the transformation-specific oligonucleotides which are largely conserved among avian acute leukemia viruses MC29, MH2, and CMII or the src-specific oligonucleotides of avian sarcoma viruses. It is concluded that the sequences which are unique for REV contain a new class of avian tumor virus transforming genes.