Sea urchin HSF activity in vitro and in transgenic embryos.

Abstract Evidence is provided for the presence at the physiological temperature of 20°C of a heat shock transcriptor factor, HSF, in the nuclei of P.lividus embryos. This HSF is able to specifically bind in vitro the heat shock element, HSE, of the promoter of the hsp70 gene IV, as suggested by DNA–protein binding reactions and DNAse I protection assays. Upon heat-shock, at the temperature of 31°C, its ability to bind the HSE units becomes much higher. The HSF activated by heat-shock drives in vivo the transcription of the β-galactosidase reporter gene in transgenic sea urchin gastrulae. An ATF-like transcription factor, widely described in other organisms but not at all in sea urchins, is also present in the nuclear extracts and is able to bind the consensus individuated in the hsp70 IV gene promoter.