ACTIVATION BY HEAT-SHOCK OF HSP70 GENE-TRANSCRIPTION IN SEA-URCHIN EMBRYOS

We had previously shown that P. lividus embryos subjected to heat shoc k are unable to synthesize proteins of the hsp70 family at a detectabl e level before the hatching blastula stage. We show here that this is not due to the inability to synthesize the hsp70 mRNAs, which are dete ctable following heat shock also in early stages, although in much low er amounts per embryo than in later stages. These mRNAs are also trans lated, as judged by the facts that they are present in the polysomal p ellet, and that they are translatable in a cell free system. As to the question of the amount of hsp70 RNAs per nucleus, we conclude that th is is also higher in later than in earlier stages. The presence of hsp 70 mRNAs is already detectable after heating at 4 centigrades above 20 and their amount increases with the increase of temperature in the ra nge between 24 degrees C and 28 degrees C. (C) 1995 Academic Press, In c.