A heat shock-induced, polymerase III-transcribed RNA selectively associates with polysomal ribosomes in Tetrahymena thermophila.

Tetrahymena thermophila cells, subjected to a heat shock-inducing temperature, manifest a number of translationally regulated changes during the course of a continuous heat shock treatment. One particular change, the resumption of translation of mRNAs coding for normal cellular proteins, was found to correlate with a polysomal ribosome association not found prior to heat shock. A low molecular weight RNA (ca. 270 nucleotides), whose rapid accumulation was induced by heat shock, became quantitatively associated with polysomal ribosomes during that time when normal cell protein synthesis became reestablished. We estimated that there were one or two of these RNAs per ribosome uniformly distributed throughout the polysomal ribosome population. The gene (or genes) coding for this RNA were found to be transcribed by polymerase III.