Dino Dina

The 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 cell line was shown by gel electrophoresis to contain a major (97%) 30S sarcoma-specific subunit species and a minor (3%) 38S leukemia virus-specific subunit. On the basis of 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 of a Mo-MSV RNA-MLV cDNA hybrid was 83 degrees C, indicating that large contiguous nucleotide sequences were shared between the two nucleic acids. Mo-MSV RNA and Mo-MLV RNA shared possibly seven of 20-30 RNAase T1-resistant oligonucleotides, while Mo-MSV RNA contained three, and Mo-MLV RNA contained at least five specific oligonucleotides. We conclude that the 30S Mo-MSV RNA molecule consists of approximately 70% (about 4200 nucleotides) Mo-MLV-specific sequences and of 30% (1800 nucleotides) Mo-MSV-specific sequences covalently linked. Our results favor the hypothesis that 30S Mo-MSV RNA was generated by recombination between Mo-MLV and other genetic elements. We discuss whether all or only the MSV-specific sequences of the 30S Mo-MSV RNA function as sarcoma genes. 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 our Mo-MSV(MLV) contained a complete complement of Mo-MLV, albeit at a low ratio.

Murine sarcoma viruses: the helper-independence reported for a Moloney variant is unconfirmed; distinct strains differ in the size of their RNAs.

Abstract A variant of Moloney murine sarcoma virus (Mo-MSV) reported to behave like a nondefective sarcoma virus was subjected to biological and biochemical analyses to determine whether its alleged helper-independence could be confirmed. When plated at low multiplicity the virus was shown to readily generate (four out of six) transformed clones which failed to produce virus unless superinfected with helper leukemia virus. The RNA of the parental virus stock was compared electrophoretically to that from clones which produced virus after the initial infection (producer clones) or after superinfection with Mo-murine leukemia virus (MLV) (nonproducer clones). All clones contained a MSV-specific 30 S RNA species. In addition, virus from one producer clone also contained 38 S MLV RNA at a high relative concentration, indicating that the original Mo-MSV stock must have contained such an RNA species. However, the original virus stock as well as virus from another producer clone contained 38 S MLV RNA at a low, uncertain relative concentration. A hypothesis consistent with these and previous data suggests that the Mo-MSV variant investigated here is defective and contains helper leukemia virus at a low concentration. This explains (i) the ready generation of nonproducer clones by infection at low multiplicity, (ii) the difficulty in detecting helper leukemia virus 38 S RNA in the original virus stock, and (iii) the low complexity (approximately 1.9 × 10 6 daltons) of the MSV-specific 30 S RNA. These results are compatible with the properties reported for a defective MSV genome, but incompatible with those of a nondefective MSV genome. The MSV-specific RNA components of different clonal isolates of Mo-MSV differed from each other in size, ranging between 2.1 and 1.6 × 10 6 . The Harvey sarcoma virus-specific RNA was 1.9 × 10 6 , that of Kirsten sarcoma virus was 2.5 × 10 6 , and the spleen focus forming component of Friend virus was 2.0 × 10 6 . The sarcoma- or transformation-specific RNA components of all transforming viruses tested here were smaller than the 38 S RNA of helper leukemia viruses of 3.1 × 10 6 .