Cloning of integrated Moloney sarcoma proviral DNA sequences in bacteriophage λ

The authors identified integrated proviral DNA sequences of ml and HT-1 isolates of Moloney sarcoma virus (MuSV) in EcoRI digests of transformed mink cell genomic DNA and have cloned these fragments in bacteriophage λ. Both the λ-HT1 phage recombinant, containing a 12.3-kilobase MuSV pair (kb) fragment, and the λ-ml phage recombinant, containing a 7.0-kb fragment, possess full copies of the sarcoma viruses along with 5' and 3' host flanking sequences. The MuSV proviral DNA sequences, 6.7 kb for HT-1 and 5.2 kb for ml, are colinear by heteroduplex microscopy with the 1.5-kb difference in size accounted for by two ~0.8-kb deleted regions in ml. Both integrated viral genomes are terminally redundant and have integrated at the same site in the provirus but at different sites on the host chromosome. The host sequences flanking integrated HT-1 MuSV have been identified as a single EcoRI restriction fragment of 5.6 kb in normal mink cells.