Negatively supercoiled simian virus 40 DNA contains Z-DNA segments within transcriptional enhancer sequences

Abstract
Three 8-base pair (bp) segments of alternating purine-pyrimidine from the simian virus 40 enhancer region form Z-DNA on negative supercoiling; minichromosome DNase I-hypersensitive sites determined by others bracket these three segments. A survey of transcriptional enhancer sequences reveals a pattern of potential Z-DNA-forming regions which occur in pairs 50–80 bp apart. This may influence local chromatin structure and may be related to transcriptional activation.