Association of an S1 nuclease-sensitive structure with short direct repeats 5' of Drosophila heat shock genes.

The potential for a DNA molecule to assume different tertiary structures has been suggested as a possible determinant of transcriptional regulation in eukaryotes. Such forms include cruciforms transitions from B to Z DNA in the same molecule and short unpaired stretches of DNA in an alternating copolymer. All such structures contain regions which are preferentially sensitive to S1 nuclease. We report here an additional class of S1 nuclease sensitive sites associated with short direct repeats of DNA found in the 5' flanking regions of certain Drosophila melanogaster heat shock genes.