title: Isolation and characterization of recombinant DNA clones of avian retroviruses: size heterogeneity and instability of the direct repeat.
abstract: Unintegrated proviral DNA of Schmidt-Ruppin B Rous sarcoma virus was cloned in the bacteriophage lambda vector Charon 21A. A total of 12 independent recombinant lambda SRBtd clones which were derived from the transformation-defective component in the viral preparation were analyzed with restriction endonucleases and molecular hybridization techniques. Three classes of clones were observed. Type I clones contained a 5.0-megadalton insert of viral DNA, type II clones contained phage with two size classes of inserts (5.0 and 5.2 megadaltons), and one type III clone contained only a 5.2-megadalton insert. The smaller insert present in type II clones appeared to be derived by deletion of one copy of a directly repeated sequence which was present in the larger insert. Mapping data indicated that the deletion includes all or part of the terminal repeat found in linear double-stranded proviral DNA. Similar results were obtained from lambda RAV2 recombinant clones derived from Rous-associated virus type 2. Analysis of DNA from type II and type III clones of lambda SRBtd and lambda RAV2 revealed limited heterogeneity in the size of the direct repeat.
mesh_terms: D001354:Avian Leukosis Virus / Q000235:genetics*; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis / Q000235:genetics*; D005814:Genes, Viral
chemical_list: D004274:DNA, Recombinant; D004279:DNA, Viral; D004262:DNA Restriction Enzymes