An MuLV transmission vector system designed to permit recovery in E. coli of proviral and cellular flanking sequences.

We have introduced a bacterial suppressor gene (supF) into the long terminal repeat of a molecular clone of the murine leukemia virus (MuLV) SL3-3. A panel of replication competent virus was derived that replicates to high titers in NIH3T3 cells in culture. The tRNA gene is stably carried in the provirus. The supF and viral sequences are present in equimolar amounts in the RNA genome of the expressed recombinant virus. The proviral sequences containing supF can be recovered by cloning into a lambda vector carrying amber mutations. The DNA sequences in the recovered lambda recombinants show a high degree of stability. The presented system should facilitate the study of the interaction between proviral and cellular sequences flanking the integration site.