Study of the 78A1 isolate of Moloney murine sarcoma virus. I. Molecular cloning and characterization.

The 78A1 isolate of Moloney murine sarcoma virus (78A1 Mo-MuSV) was cloned from a genomic library obtained from virus producer rat cells, in the lambda vector L47. Among the recombinants hybridizing with a probe specific for the v-mos sequences, we recovered a recombinant which contained leukaemia virus (MuLV) sequences and was able to transform both mouse and rat cells in transfection experiments. The cloned provirus could be rescued by both Mo-MuLV ecotropic and amphotropic viruses in mouse cells, but only with the amphotropic helper virus in rat cells. Comparative restriction mapping indicates that the 78A1 provirus is 200 bp longer than the HT1 provirus. The difference lies in the gag-pol junction region of Mo-MuSV. Other minor differences were found in the gag region, whereas the restriction patterns of the 3' parts of the proviruses were identical.