[Hormone-dependent process of the maturation of the major structural proteins of the mouse mammary tumor virus].

: The following findings were obtained by the radio-immunoprecipitation method with antisera to gp52 and p27. When the cells were cultivated in a hormone-free medium, they contained precursors of proteins of gene gag (Pr 73gag) and gene evn (gPr 70env). No mature structural MTV proteins were found. The addition of insulin to the growth medium had no effect on maturation of protein precursors. When dexamethazone was added to the medium, gPr 70env "maturated" to gp52 of the main envelope glycoprotein of virion coat whereas Pr 73gag was not cleaved into final products. When the cells were cultivated in the presence of insulin and dexamethazone, there was a marked stimulation of Pr 73gag (although its maturation did not occur), g Pr 70env, and, especially, gp 52. Extracellular particles were found to contain p27 which was precipitated by homologous monospecific antiserum, that is, in the system of clone F2 cells processing of Pr 73gag occurred mainly in extracellular particles. Thus, expression of all three known genes (gag, pol, and env) occurred in the cells of cloned F2 culture.