Direct measurement of tubulin and bulk message distributions on polysomes of growing, starved and deciliatedTetrahymenausing RNA gel blots of sucrose gradients containing acrylamide

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Abstract
A method was developed using sucrose gradients containing acrylamide which greatly simplifies the measurement of the polysomal distribution of messages. After centrifugation, the acrylamide was polymerized, forming a "polysome gel". RNA gel blots of polysome gels were used to determine the polysomal distributions of .alpha.-tubulin and total polyadenylated mRNA in growing, starved (nongrowing) and starved-deciliated Tetrahymena and the number of messages loaded onto polysomes was calculated. These measurements indicated that the translational efficiencies of .alpha.-tubulin mRNA and total polyadenylated mRNA are largely unaffected when the rates of tubulin and total protein synthesis vary dramatically. Thus, differential regulation of .alpha.-tubulin mRNA translation initiation does not contribute to the > 100-fold induction of tubulin synthesis observed during cilia regeneration and in growing cells. The major translation-level process regulating tubulin synthesis in Tetrahymena appears to be a change in message loading mediated by a non-specific message recruitment or unmasking factor.