THE USE OF DNASE-I HYPERSENSITIVITY SITE MAPPING TO IDENTIFY REGULATORY REGIONS OF THE HUMAN CHOLINERGIC GENE LOCUS

The DNase I hypersensitive sites of the human cholinergic gene locus, where both the choline acetyltransferase gene and the vesicular acetyl choline transporter gene are located, were analyzed to detect potentia l regulatory elements involved in cholinergic-specific transcriptional activation. From this analysis, seven cholinergic cell line-specific DNase I hypersensitive sites were found. The majority of these sites c orrespond to active promoter regions of the gene, including the promot er region of the vesicular acetylcholine transporter gene and the R, N , and M exons of the choline acetyltransferase gene. Two DNase I hyper sensitive sites were identified in two noncholinergic cell lines, HeLa and MCF-7. One corresponds to a previously observed non-cell-specific enhancer, whereas the other corresponds to a previously described neu ronal restrictive silencer element, NRSE. The NRSE has been shown to r epress expression of various neuron-specific genes, not restricted to cholinergic specific genes, in nonneuronal cells. This element can acc ount for repression of the cholinergic gene locus in nonneuronal cells but does not account for repression in noncholinergic neurons. In add ition, the chromatin boundary domain of the cholinergic gene locus, wh ich possibly corresponds to the end of the transcription unit, was ide ntified.