Changes in genome composition of the Friend virus complex in erythroleukemia cells during the course of differentiation induced by dimethyl sulfoxide.

The Friend spleen focus-forming virus (SFFV) complex released by Friend virus-transformed erythroid cells has been analyzed with respect to changes in the genome composition that may occur during induction of erythropoiesis with dimethyl sulfoxide. It is shown that: (a) There are three types of virus particles, one with buoyant density 1.20 g/ml, one with density 1.17 g/ml (the density of the cloned lymphatic leukemia virus helper component of the complex), and a major fraction that has a density of 1.14 g/ml. (b) Three RNA subunits-35S, 32S, and 30S-have previously been shown to be detectable in the Friend virus complex. The 1.20-g/ml particles contain only 30S RNA, whilst the 1.14- to 1.17-g/ml particles contain a mixture consisting of predominantly 30S and 32S RNA and about 5-10% 35S RNA. (c) Induction of differentiation results in an increase in the 1.14-g/ml particles and 32S RNA. The amount of 30S RNA does not change. (d) Hybridization of the different genomic viral RNAs with full-length virus cDNA shows that the 30S RNA (of induced and uninduced Friend virus) is more closely related to the 32S RNA of the induced Friend virus than to the 32S RNA of the constitutively released Friend virus. (e) The 30S RNA contains SFFV-specific sequences. (f) A hypothesis is presented in which the induction of the new 32S RNA species is related to the increase of SFFV activity and to a specific function of the SFFV during induction of erythropoiesis.