title: DNA sequence of the Bryan high-titer strain of Rous sarcoma virus: extent of env deletion and possible genealogical relationship with other viral strains.
abstract: The genetic structure of the Bryan high-titer strain of Rous sarcoma virus (BH-RSV) was analyzed by using a molecular clone obtained from proviral DNA. DNA sequencing of the pol-src junction of BH-RSV revealed that the env sequence was almost entirely absent; only six base pairs following the pol termination codon remained. Beginning at nucleotide 7 (relative to the end of pol), a 91-base pair sequence identical to the 91 base pairs immediately upstream from src in other strains of RSV was found. The helper virus-related sequence of about 100 base pairs, which is present as a direct repeat in the 5' and 3' regions flanking src in other RSVs, was present only on the 3' side of src in BH-RSV. The 3' end of BH-RSV, from the last 16 base pairs of src through the U3 region, was virtually identical to a region downstream of env through U3 in the nontransforming helper virus Rous-associated virus-2, suggesting that BH-RSV may have been derived by recombination between Rous-associated virus-2 and cellular src DNA. The possibility that the original RSV may have been a defective transforming virus and a precursor of the nondefective RSV strains is discussed.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004279:DNA, Viral / Q000235:genetics*; D005814:Genes, Viral; D051381:Rats; D013045:Species Specificity; D014764:Viral Proteins / Q000235:genetics
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D004262:DNA Restriction Enzymes