DNase I hypersensitive sites in the 5'-region of the maize Shrunken gene in nuclei from different organs.

The chromatin structure of the 5'-upstream region of the Shrunken (Sh) gene in Zea mays has been examined. We have identified a region of DNase I hypersensitivity extending at least from the 3'-end of exon 1 for 2 kb into the 5'-flanking region. This region is composed of a set of closely spaced hypersensitive sites separated by small regions that are less accessible to DNase I. The most sensitive sites are located within 300 bp upstream of the transcription start site. Hypersensitive sites are found essentially at the same positions in kernels, roots and leaves, although the latter display different relative intensities. No changes are found in roots within the tested region upon anaerobic induction. Testing protein-free plasmid DNA containing the 5' upstream region of the Sh gene, we found a site sensitive to the single strand specific nuclease S1 located very close to a DNase I hypersensitive site identified in chromatin. Several hypersensitive sites are flanking in vitro binding sites of nuclear proteins as determined by Werr et al. (1988; accompanying paper).