Translational efficiency of heat-induced messages in Drosophila melanogaster cells

When Drosophila cells are exposed to elevated temperatures, pre-existing polysomes are depleted and normal cellular protein synthesis is greatly reduced. Polysomes rapidly reform on newly synthesized messenger RNA as the so-called heat shock proteins become the major products of protein synthesis in the cell. These circumstances afford the opportunity to calculate rates of initiation and elongation of protein synthesis directly from measurements of the quantity of actively translated messenger RNA and the quantity of protein produced over a given period. Ribosomes were found to initiate on heat-induced messages in Drosophila with a frequency of between 9 and 14 initiations per minute at 37 °C. This rate is close to that reported for other eukaryotic systems at similar temperatures. Thus, although heat treatment causes a profound change in the patterns of protein synthesis, it does not deleteriously affect the capacity of cells to synthesize protein.