30S MOLONEY SARCOMA-VIRUS RNA CONTAINS LEUKEMIA-VIRUS NUCLEOTIDE-SEQUENCES

The 50S-70S RNA of a Moloney sarcoma-leukemia virus [Mo-MSV(MLV)] complex produced by a particular mouse [thymus-bone marrow TB] cell line was shown by gel electrophoresis to contain a major (.simeq. 97%) 30S sarcoma-specific subunit species and a minor (.simeq. 3%) 38S leukemia virus-specific subunit. From its sedimentation coefficient and known complexity, the 30S Mo-MSV RNA was estimated to be a unique RNA molecule of about 6000 nucleotides. Hybridization experiments using viral RNA and DNA complementary to viral RNA (cDNA) made by viral DNA polymerase indicated that the 30S Mo-MSV RNA shared 70% of its sequences with Mo-MLV, 30% with another MLV derived from Mo-MLV and 30% with Kirsten sarcoma-xenotropic leukemia virus. The 30S Mo-MSV RNA sequences shared with these viruses were not additive. The Tm [melting temperature] of a Mo-MSV RNA.cntdot.MLV cDNA hybrid was 83.degree. C, indicating that large contiguous nucleotide sequences were shared between the 2 nucleic acids. Mo-MSV RNA and Mo-MLV RNA shared possibly 7 of 20-30 RNase T1-resistant oligonucleotides, while Mo-MSV RNA contained 3, and Mo-MLV RNA contained at least 5 specific oligonucleotides. Apparently, the 30S Mo-MSV RNA molecule consists of about 70% (about 4200 nucleotides) Mo-MLV-specific sequences and of 30% (1800 nucleotides) Mo-MSV-specific sequences covalently linked, indicating that 30S Mo-MSV RNA was generated by recombination between Mo-MLV and other genetic elements. The question whether all or only the MSV-specific sequences of the 30S Mo-MSV RNA function as sarcoma genes is discussed. Mo-MLV cDNA was hybridized about 45% by unfractionated Mo-MSV (MLV) RNA at RNA/DNA ratios of up to 10, about 50% by electrophoretically purified 30S Mo-MSV RNA at RNA/DNA ratios up to 500, but close to 100% by unfractionated Mo-MSV(MLV) RNA at RNA/DNA ratios over 900. This indicated that unfractionated RNA of this Mo-MSV(MLV) contained a complete complement of Mo-MLV, albeit at a low ratio.