S1 nuclease was used to probe the architectural characteristics of the maize alcohol dehydrogenase-1 gene promoter. Three sites were identified as hypersensitive to S1 digestion in supercoiled, but not linear plasmids containing the Adh1 gene. The sites mapped to areas located 65, 330 and 800 base pairs 5′ to the start of transcription. In each case, the strand specific nicking pattern was determined with nucleotide level precision. The −65 site was found to be a homopurine/homopyrimidine tract. The −330 site mapped to the boundaries of a region of high Z-DNA potential and the −800 site mapped to a non-descript sequence. The possible biological significance of these sites is discussed.
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