Figure 1.

Hypoxia inhibits mRNA translation. HeLa cells were exposed to 0.0% O₂ for 0–16 h and cell lysates were separated on a sucrose gradient. (A) The optical density (OD) at 254 nm is shown as a function of gradient depth for each time point. Actively translated mRNA is associated with high-molecular-weight polysomes deep in the gradient. (B) Translation efficiency in HeLa cells as a function of time in 0.0% O₂. As a measure of overall translation efficiency, the relative amount of rRNA participating in polysomes was estimated. This fraction is proportional to the integrated area under the curve containing polysomes, as marked in (A). (C) The average number of ribosomes per mRNA in the polysomes as a function of time in 0.0% O₂. This was calculated by differential integration of the profiles in (A).