Different conformations of the circular DNA domains containing the intergenic region of the Saccharomyces cerevisiae GAL1-GAL10 divergent genes (914 base pairs) were modified by in vitro ligation in various conditions. The effect of increasing torsional stress on the conformation of the composing elements was determined by analysis of the sensitivity to the single strand-specific S1 endonuclease and it was observed that the sites of conformational alterations correspond to the positions relevant for promoter function (upstream activator sequence, TATA sequence, and RNA initiation site).