We are interested in the chromatin structure of the 5' region of the Adh1 gene in corn. Areas of chromatin which are less condensed in the nucleosome array have been associated with gene regulation. These "open" regions have been characterized by their hypersensitivity to DNase I and are especially prevalent in promoter regions of the animal systems studied thus far (Wu, Nature 309:229, 1984).
We examined the 5' region of Adh1 defined by the BamHI site at -1103 and the HindIII site at +210 by in situ digestion of Dekalb XL80 nuclei. Within this region we found seven sites of DNase I hypersensitivity, ranging from a site at -40 to one at -740. These are illustrated in the figure as crosshatched bars under their respective sites. The width of the bar reflects the actual width of the band generated on the autoradiograph. The width of the band, in turn, reflects both the intensity and distribution of cuts introduced by DNase I. The data are the pooled results of several experiments.
In all cases, these sites were mapped using two distinct probes, one 5' and one 3' to the hypersensitive region, in order to confirm the presence and position of the hypersensitive sites (Wu, Nature 286:854, 1980).
These sites were found in all tissues examined (roots, shoots and leaves) regardless of the transcriptional state of the gene. While the Adh1 promoters in different tissues showed differences in their general sensitivity to DNase I, a suitable concentration of DNase I was found for each tissue to generate the hypersensitive sites.
Anna-Lisa Paul and Robert J. Ferl
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