Restriction endonuclease mapping of ecotropic murine leukemia viral DNAs: Size and sequence heterogeneity of the long terminal repeat

Abstract

A physical map for 12 restriction endonucleases has been derived for the unintegrated linear viral DNA of 11B3 murine leukemia virus (MuLV), which is the endogenous ecotropic XC plaque-forming virus released from the cell line from which integrated MuLV molecular clones 614 and 623 were isolated. This virus had originally been isolated from a mouse carrying the Akv-1 locus. The 11B3 MuLV DNA map was compared with the maps derived for the DNAs of several other endogenous ecotropic MuLVs isolated from inbred mouse strains and from the Asian feral mouse Mus musculus molossinus. In general, their maps were highly related, indicating a common origin for most of their sequences. However, 11B3 MuLV DNA differed from the other MuLV DNAs in that its long terminal repeat (LTR) was about 50 by longer than that of the other MuLVs and it lacked a HindIII site which was located 3 kbp from the 5′ end in the other MuLVs. These two differences in 11B3 MuLV probably arose after virus activation in the mouse, perhaps by recombination with other endogenous MuLV sequences. In the endogenous ecotropic MuL V DNAs (including 11B3 MuLV), the U3 region of the LTR differed from this region in Moloney MuLV for each of the five restriction endonaclease sites which were tested. We conclude that the LTR of murine C-type viruses may contain size and sequence heterogeneity.