Heat shock regulatory elements function as an inducible enhancer in the Xenopus hsp70 gene and when linked to a heterologous promoter.

The Xenopus hsp70 promoter contains three copies of the consensus heat shock element (HSE) between positions -260 and -100. When the gene is transfected into mammalian cells, maximal heat-induced expression requires two HSEs in addition to a CCAAT box located next to the TATA box. The HSE-containing region can be separated from the CCAAT/TATA region without affecting expression of the gene, and it can enhance transcription of a linked beta-globin gene upon heat shock. It thus has the properties of a heat-inducible enhancer. Such an enhancer can also be generated by duplication of HSE sequences from the Drosophila hsp70 promoter, which were previously identified as an upstream promoter element and are known to bind a purified heat shock transcription factor in vitro.