Gene expression in differentiated cells

This communication is concerned with the dynamics of gene control over specific biochemical functions in a differentiated cell. Direct experimental access to the intracellular link between gene action and the target cell characters has become feasible with the accumulation of evidence demonstrating that the synthesis of specific RNA's on the genomic DNA template is the actual primary mechanism of gene function in the cell and with the development of the highly effective inhibitor of that synthetic reaction, actinomycin D. In the experiments to be presented, this agent was used to block nuclear RNA synthesis in a cultured mammalian cell type which has retained in vitro a differentiated cellular activity. The effect of actinomycin treatment on this cell function and on a specific mitochondrial enzyme activity was then followed. Actinomycin treatment was found to inhibit the specific cell function immediately, while, in contrast, the mitochondrial enzyme activity appeared to remain impervious to the effects of this agent for long periods.