Induction of intracisternal A-type particles during Friend cell differentiation

Abstract

A number of Friend cell lines have been characterized in order to examine the relationship between C-type virus production, A-type particle formation and dimethylsulfoxide (Me 2SO) induced differentiation. Cell lines can be classified as either low virus producers (V − and V (+)) or high virus producers (V ++). V ++ cells usually have a low number of intracisternal A-type particles (V ++, A+) and mutate spontaneously to give low virus-producing A-type particle negative (V −, A−) cell clones. The simultaneous loss of virus release and A-type particle expression suggests coordinate regulation of the two entities. One can isolate thymidine kinase deficient (TK−) cells (V (+), A++) from V ++ clone F4. These clones show spontaneous mutation either to the V −, A− or to the V ++, A+ state. Me 2SO induction of V (+) A++ cells leads to increased levels of A-type particles. V ++ cell lines which are inducible with Me 2SO for the endogenous spleen focus-forming virus complex show only a marginal increase of A-type particle formation. However, if these cells are treated with Me 2SO together with an inhibitor of C-type virus production, such as azidothymidine or interferon, they show a marked increase in A-type particle formation. The A-type particle negative cell clones (V −, A−) are not inducible for A-type particle formation during erythroid differentiation. They show a marginal increase in Friend C-type viral RNA levels in the cytoplasm. A-type particle positive cell lines (V (+), A++) which show an increase in the number of A-type particles during differentiation also show a distinct increase in Friend virus related RNA. The evidence favors the hypothesis that intracisternal A-type particles in Friend cells are related to Friend virus and that the increase in expression of this component is linked but is not conditional for erythropoietic differentiation of Friend cells.