Enhanced expression of viral polypeptides and messenger RNA in dimethyl sulfoxide and bromodeoxyuridine-treated Friend erythroleukemic cells

Abstract

The intracellular virus-specific macromolecular changes induced by dimethyl sulfoxide (Me 2SO) and/or bromodeoxyuridine (BUdR) have been analysed in the Friend erythroleukemic cell clone 745 A 19 (FLC). These cells, which were transformed in vivo by the Friend virus, are arrested in an undifferentiated state but can be induced to differentiate in vitro by Me 2SO. We have shown that treatment of FLC with 2% Me 2SO for 4 days enhances the extracellular virus production and, concomitantly, increases by about 4-fold the intracellular virus-specific polyribosomal RNA. The simultaneous addition to FLC of Me 2SO and BUdR (the latter is known to inhibit the Me 2SO-induced differentiation) brings about an even greater increase in both viral polypeptides and viral messenger RNA (mRNA). As a consequence of treatment with both drugs, new viral nucleotide sequences are expressed, as revealed by nucleic acid hybridization studies. Moreover, it appears that two p30-like virus-specific intracellular polypeptides, instead of one single p30, are expressed in FLC treated with Me 2SO and BUdR. These data also support the idea that gene sequences different from those present in the original Friend virus are expressed as a consequence of the combined treatment. It is concluded that the main site of action of both drugs in this cell system, is at the level of transcription of viral RNA and it is suggested that the drugs may act upon cell differentiation by modulating differently the expression of integrated viral genomes.