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 acetyl-transferase gene and the vesicular acetylcholine transporter gene are located, were analyzed to detect potential 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 correspond to active promoter regions of the gene, including the promoter region of the vesicular acetylcholine transporter gene and the R, N, and M exons of the choline acetyltransferase gene. Two DNase I hypersensitive 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 neuronal restrictive silencer element, NRSE. The NRSE has been shown to repress expression of various neuron- specific genes, not restricted to cholinergic-specific genes, in nonneuronal cells. This element can account for repression of the cholinergic gene locus in nonneuronal cells but does not account for repression in noncholinergic neurons. In addition, the chromatin boundary domain of the cholinergic gene locus, which possibly corresponds to the end of the transcription unit, was identified.