Dimethyl-10,12-benz(a)acridine; evidence for differential effects on the synthesis of RNA of mammalian or avian fibroblasts and some RNA viruses.

We have studied the differential effect of dimethyl-10,12-benz(a)acridine (DBMAcr) on the synthesis of RNA of chicken or mouse fibroblasts in culture and that of some RNA-containing viruses such as Rous sarcoma virus and Mengovirus. DMBAcr at low concentrations blocks the cell multiplication of both normal and Rous sarcoma virus-transformed chicken fibroblasts in culture; it affects transformed cells more than normal ones. The cell growth inhibiting effect of DMBAcr is reversible after short periods of incubation. DMBAcr depresses the synthesis of cellular DNA and RNA in parallel. Concurrently the synthesis of protein proceedes at a relatively high rate in DMBAcr-treated cultures. Its inhibitory effect on cellular RNA synthesis is mostly due to a block in the formation of 28 S and 18 S ribosomal RNA species; in contrast, the synthesis of 45 S ribosomal RNA precursor is proceeding at almost control rate. Also, the synthesis of heterogeneous nuclear RNA is not blocked by DMBAcr. The production of Rous sarcoma virus in transformed fibroblasts is not affected by DMBAcr. Since this is correlated with persisting high rates of protein and heterogenous nuclear RNA synthesis, the effects of DMBAcr suggest that the synthesis of Rous sarcoma virus-RNA shares the specificity of messenger and heterogeneous nuclear RNA. DMBAcr inhibits the synthesis of viral RNA of Mengovirus under conditions where the synthesis of total cellular RNA is not appreciably depressed, suggesting its differential effect on the DNA-directed and the RNA-directed RNA synthesis.