The Saccharomyces and Drosophila heat shock transcription factors are identical in size and DNA binding properties.

The heat shock transcription factor (HSTF) has been purified to apparent homogeneity from S. cerevisiae and D. melanogaster by sequence-specific DNA-affinity chromatography. A synthetic oligonucleotide containing an hsp83-like heat shock element (HSE) was prepared and ligated into concatamers and covalently coupled to Sepharose. This DNA-affinity resin allowed the rapid isolation of a yeast and a Drosophila protein with the same apparent molecular weight (70 kd). The yeast HSTF will bind to both its own and the Drosophila HSEs. Similarly, the Drosophila HSTF will bind to both its own and the yeast HSEs. The yeast and Drosophila HSTFs were subjected to preparative SDS gel electrophoresis, and the 70 kd polypeptides were eluted, renatured, and observed to generate the identical footprint pattern as the native HSTFs. Affinity-purified Drosophila HSTF was further shown to stimulate specific HSE-dependent transcription from a Drosophila hsp70 gene in vitro.