Elongation factor-1 alpha mRNA is selectively translated following mitogenic stimulation.

Stimulation of quiescent Swiss 3T3 cells to proliferate leads to a selective 6-fold increase in the rate of translation of protein synthesis elongation factor eEF-1 alpha. Northern blot and solution hybridization protection studies show that levels of eEF-1 alpha mRNA remain constant following serum stimulation, demonstrating that eEF-1 alpha transcripts are not degraded following mitogenic stimulation and that the increase in eEF-1 alpha synthesis is accounted for by pre-existing mRNA. Localization of these transcripts in resting cells shows that they are largely distributed equally between stored mRNA protein particles and monosomes/disomes. Following serum addition, eEF-1 alpha transcripts present in mRNA protein particles redistribute to large polysomes rather than to monosomes and disomes as would be expected. The same is true for those transcripts present in monosomes and disomes. Salt-shift and translational runoff studies indicate that eEF-1 alpha transcripts sedimenting with monosomes and disomes in quiescent cells are associated with actively translating ribosomes. The results suggest that a specific transcript can move within polysome profile as a function of the affinity of translational apparatus for that transcript.