We reported previously that a tilapia (Oreochromis mossambicus) heat shock protein 70 (HSP70) promoter is able to confer heat shock response on a reporter gene after transient expression both in cell culture and in microinjected zebrafish embryos. Here we present the first functional analysis of a fish HSP70 promoter, the tiHSP70 promoter. Using transient expression experiments in carp EPC (epithelioma papulosum cyprini) cells and in microinjected zebrafish embryos, we show that a distal heat shock response element (HSE1) at approx. −800 is predominantly responsible for the heat shock response of the tiHSP70 promoter. This element specifically binds an inducible transcription factor, most probably heat shock factor, and a constitutive factor. The constitutive complex is not observed with the non-functional, proximal HSE3 sequence, suggesting that both factors are required for the heat shock response mediated by HSE1.
Abbreviations used: EMSA, electrophoretic mobility-shift assay; EPC, epithelioma papulosum cyprini; GFP, green fluorescent protein; HSE, heat shock element; HSF, heat shock factor; HSP70, heat shock protein 70; Luc, luciferase; tiHSP70, tilapia HSP70; TK or tk, thymidine kinase.