FIGURE 4.

Cordycepin inhibits protein synthesis. A, protein synthesis rates of NIH3T3 cells as measured by ³⁵S incorporation into protein, corrected for total protein concentration. The effects of treatment with 200 μm cordycepin or adenosine or with 10 μg/ml actinomycin D (AcD) are shown. B, polyribosome profiles of control cells and cells treated with cordycepin (200 μm) for 2 h. 40S and 60S indicate the dissociated free ribosomal subunit peaks, polysomes indicates ribosomes translating mRNA. The inset shows the RNA isolated from a control gradient, proving the identification of the 40 S peak. C, dose response of the effect of cordycepin on protein synthesis rates in NIH3T3 cells treated for 2 h. D, time course of the response of protein synthesis rates to three doses of cordycepin. E, dose response of the effect of cordycepin on protein synthesis rates in HeLa cells treated for 2 h. F, incorporation of radioactive methionine into protein in vitro in reticulocyte lysate supplemented with cordycepin, adenosine, cordycepin triphosphate (cordyTP), ATP, or cap analogue (m7GpppG) (all at 200 μm).