CHOLINERGIC NEURON-SPECIFIC EXPRESSION OF THE HUMAN CHOLINE-ACETYLTRANSFERASE GENE IS CONTROLLED BY SILENCER ELEMENTS

Choline acetyltransferase (ChAT) is specifically expressed in choliner gic neurons. To identify control mechanisms regulating the cell-specif ic expression of the gene encoding ChAT, transient expression of the l uciferase gene driven by human ChAT gene 5' flanking sequences was com pared in cholinergic and noncholinergic cell lines. Analysis of the ge ne indicated the presence of two regulatory elements with selective si lencing activity. These elements, located between nucleotides -2043 to -3347 and nucleotides -3347 to -6550, act cooperatively to repress pr omoter activity >10-fold in a human adrenergic neuroblastoma cell line , SHSY5Y, and a human osteosarcoma cell line, 143 TK-, while exhibitin g less than a two-fold effect in cholinergic cell lines. Deletion of e ither nucleotides -2043 to -3347 or nucleotides -3348 to -6550 reduced cell-specific repression by approximately half. Such differential rep ression appears to be responsible for the selective expression of the ChAT component of the cholinergic phenotype.