Identification of ecotropic proviral sequences in high- and low-ecotropic-virus-producing mouse strains.

The arrangement of endogenous ecotropic retroviruses in selected high- and low-ecotropic-virus-producing mouse strains was examined by Southern blot hybridization analysis, using an ecotropic retrovirus-specific DNA probe. High-ecotropic-virus-producing mouse strains of the AKR family displayed heterogeneity with respect to the number of copies and the sites of insertion of endogenous ecotropic specific DNA. This diversity was seen even among individuals of the same AKR subline. Contrastingly, individuals within the same low-ecotropic-retrovirus-producing mouse strain showed no evidence of variability in their endogenous ecotropic proviral sequences. These results favored the hypothesis that germ line proviral reinsertion was responsible for the proviral sequence heterogeneity observed in high-ecotropic-virus-producing mouse strains.