EFFECT OF INTERNAL GENOMIC SEQUENCES OF T HE MOLONEY MURINE LEUKEMIA-VIRUS ON REPLICATION

Construction and using of retrovirus vectors derived from the Moloney murine leukemia virus (MoMuLV) are described. These vectors, designate d minimal vectors, contain the left and right long terminal repeats (L TRs), a binding site for proline tRNA, a polypurine tract (PPT), and a dominant marker for selective introduction of vectors into a packagin g cell line, but lack the internal sequences of the virus genome. The experiments showed that the minimal vectors can be replicated and that their titer was approximately 1500-fold lower than that of wild-type vectors. The minimal vectors were shown to contain all the cis-acting sequences necessary for correct reverse transcription. One infectious virion, like wild-type viruses, produced only one provirus. Unlike the avian reticuloendotheliosis virus (REV), psi(+) and psi(-) -genomes o f MoMuLV did not compete for virion proteins in the psi 2 packaging ce ll line. When an insert was introduced into a central part of the LTR U5 region, the titer of the minimal vector remained the same, while th e titer of the wild-type vector decreased approximately 40-fold.