[Effect of internal sequences in the Moloney murine leukemia virus genome on replication].

Construction and using of retrovirus vectors derived from the Moloney murine leukemia virus (MoMuLV) are described. These vectors, designated minimal vectors, contain the left and right long terminal repeats (LTRs), a binding site for proline tRNA, a polypurine tract (PPT), and a dominant marker for selective introduction of vectors into a packaging 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 of MoMuLV did not compete for virion proteins in the psi2 packaging cell 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 the titer of the wild-type vector decreased approximately 40-fold.