FIG. 3.

Mammary tumors of MMTV(HeJ)-infected C3H/HeJ mice contain a recombinant MMTV. (A) Map of endogenous (endo) proviruses present in C3H/He and BALB/c mice. Also shown are the maps of exogenous (exo) MMTV(C3H) and HP. The presence of the 2.3- or 2.3- and 1.5-kb fragments is characteristic of newly integrated copies of HP or MMTV(C3H), respectively. Abbreviations: E, EcoRI; P, PstI; B, BglII; P∗, PstI site present in Mtv9 provirus inherited by BALB/c but not C3H/He mice. Filled bars, two probes used for hybridization. (B) Mammary tumors of C3H/HeJ mice are not induced by wild-type exogenous MMTV(C3H). Top panel, high-molecular-weight DNAs from mammary gland tumors of MMTV(HeJ)-infected C3H/HeJ mice and from the spleen of a C3H/HeJ mouse were digested with PstI and BglII and subjected to Southern blot analysis with the hybridization gag-pol probe depicted in panel A. DNAs isolated from mammary tumors induced by MMTV(C3H) in C3H/HeN MMTV⁺ mice are shown for comparison (MGT C3H/HeN MMTV⁺). Bottom panel, the same DNA samples were digested with EcoRI endonuclease and hybridized with the env probe depicted in panel A. The 6.7-, 5.8-, and 4.3-kb fragments correspond to endogenous Mtv proviruses present in C3H/He mice. Arrows show newly integrated exogenous MMTVs. SP, splenic DNA of a C3H/HeJ mouse.