Frequent site-specific deletion of coliphage λ murine sarcoma virus recombinants and its use in the identification of a retrovirus integration site

Stocks of hybrid λ phages carrying the complete integrated provirus of either ml or HT1 Moloney murine sarcoma virus, as well as flanking host sequences, frequently contain significant numbers of phages carrying a specific deletion. This deletion arises from a recombination event between the terminally repeated sequences in the provirus that deletes the unique Moloney murine sarcoma virus sequences bracketed by the terminally repeated sequences. Physical mapping had shown that the deletion phage retains one complete copy of the terminally repeated sequence and the flanking mink host sequences. One such deletion, λHT1r⁺, was used to characterize a mink genomic DNA sequence that contains an HT1 Moloney murine sarcoma virus integration site. This integration site sequence from normal mink cells was also cloned into phage λ. An analysis of the heteroduplexes between the integration site and the λHT1r⁺ deletion indicated that no major rearrangement of host sequences occurred upon integration of the Moloney murine sarcoma provirus.