A novel sequence segment and other nncleotide structural features in the long terminal repeat of a BALB/c mouse genomic leukemia virus-related DNA clone

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Abstract
A recombinant DNA clone, named AL10, that contains murine leukemia virus (MuLV) related sequences was isolated from BALB/c mouse chromosomal DNA and examined in detail. Restriction endonuclease mapping revealed that the 10.5 kbp EcoRI insert consists of a 3.6 kbp left flanking cellular DNA region and a 6.9 kbp MuLV-related region that has a typical proviral LTR-gag-pol-env structure up to the EcoRI site in the env gene region. Comparison of the AL10 map with ecotropic and xenotropic virus isolates revealed many common restriction sites in the LTR and pol gene regions, but much fewer in the leader and gag regions. A stretch of 1,700 nucleotides containing the cell-provirus junctional region was sequenced and revealed transcriptional consensus signals and other structural features characteristic of MuLV LTRs, as well as two distinctive features: (a) a sequence of ∑170 bp with direct and inverted terminal repeats not seen in infectious MuLV LTRs was identified in the U3 region between the “enhancer” region and the “CAT” box. This novel segment or its homologous sequences appear to be present in most of the endogenous MuLV-related LTRs and in other chromosomal locations of the mouse (b) The tRNA primer binding site is not complementary to proline tRNA, the primer for all known MuLVs, but is a 17/18 match with rat glutamine tRNA. The integration site of AL10 provirus was in a unique DNA region but contained an “Alu”-like short interdispersed repeat in the 5' adjacent cellular region. The AL10 proviral integration found in BALB/c was also apparent in RFM, AKR and SENCAR mouse cells but not in cells of NFS/N, C3H, HRS/J, SC-1, and a California Lake Casitas wild mouse.