Evidence that Snf-Swi controls chromatin structure over both the TATA and UAS regions of the SUC2 promoter in Saccharomyces cerevisiae.

The Snf-Swi complex of the yeast Saccharomyces cerevisiae has been shown to control gene expression by controlling chromatin structure. We have analyzed the promoter of the SUC2 gene, a gene strongly controlled by Snf-Swi, by a high resolution analysis of micrococcal nuclease digests. This analysis suggests that there are at least four nucleosomes positioned over the SUC2 TATA and UAS regions under conditions repressing SUC2 transcription. Under derepressing conditions this entire promoter region is much more sensitive to MNase digestion. Analysis of an snf2 Delta mutant demonstrates that even under derepressing conditions the SUC2 promoter is resistant to MNase digestion. Thus, the Snf-Swi complex appears to control chromatin structure over both the SUC2 TATA and UAS regions. The presence of nucleosomes over both promoter regions may explain the strong requirement of SUC2 for Snf-Swi function.