Heat shock proteins in sea urchin embryos. Transcriptional and post-transcriptional regulation.

The production of heat-shock proteins in sea urchin embryos is accompanied by the appearance at the polysomal
level of their relative mRNAs, as shown by their translation in a cell-free system; thus suggesting that the
regulation of their production occurs at a transcriptional level. The mechanism for the inhibition of the bulk
protein synthesis and for its reversal on the other hand should be looked for at a posttranscriptional level, since
both these phenomena occur also in the presence of actinomycin D. The heat-shock proteins produced as early as
at the mesenchyme blastula stage persist within the embryo at least till the pluteus stage.