Isolation of the mouse mammary tumor virus sequences not transmitted as germinal provirus in the C3H and RIII mouse strains

Abstract

Radioactive 60-70S RNA from the mouse mammary tumor virus (MMTV) produced by the C3H mouse mammary tumor cell line (Mm5mt) hybridized to a greater extent, and at a lower C0t1/2 [half maximal value of the product of the initial nucleotide concentration and time] value, to the DNA of C3H mammary tumor cells than to the DNA of C3H liver cells. The 125I-labeled MMTV(C3H) 60-70S RNA was annealed to a vast excess of DNA from C3H livers, and single-stranded RNA was eluted from hydroxylapatite and recovered. This recycled RNA did not hybridize to the DNA of the apparently normal organs tested from normal or from mammary tumor-bearing C3H mice, but hybridized extensively to the DNA from the C3H mammary tumor cell line and the DNA from spontaneous C3H mammary tumors. This hybridization could be competed out by the addition of unlabeled MMTV 60-70S RNA but was unaffected by the addition of unlabeled 60-70S RNA of C3H type C virus. Similar experiments were conducted with the RIII mouse strain. The isolation of the sequences of the RNA genomes of the MMTV from C3H and RIII mice that are transmitted by some mechanism other than via the germ line is reported. These studies further define the differences, via molecular hybridization, between the MMTV-S [early tumor virus] and the MMTV-L [late tumor virus] in both C3H and RIII mice.