Structural features are as important as sequence homologies in Drosophila heat shock gene upstream regions

Pelham has shown that the Drosophila hsp 70 gene is not transcribed under heat shock conditions unless a given upstream region is present. Davidson et al. have recently compiled a list of sequences homologous to this region in other Drosophila heat shock genes. They proposed that a set of unlinked genes, such as the heat shock genes, could be coordinately induced through an interaction in cis with a common regulatory molecule. That this interaction involves structural elements is suggested by the fact that these upstream regions share inverted repeats as well as areas of Z-DNA potential. Furthermore, using the Calladine-Dickerson rules for local helical parameters, we show that these regions share structural homology. This is significant because the presence of regions homologous to a derived consensus sequence does not necessarily imply structural similarity. Therefore, we suggest that these structural features are at least as important as the sequence homologies in enabling the heat shock response.