A cell type-specific silencer in the human choline acetyltransferase gene requiring two distinct and interactive E boxes

We have previously reported that cholinergic neuron-specific expression of the human choline acetyltransferase gene is mediated by two co-operative silencers. We have now localized the proximal silencer to the region from nucleotide -2195 to -2409, which contains two distinct E boxes (CACCTG and CATGTG). Deletion or mutation of either of these E boxes results in a loss of silencer activity. There are specific nuclear proteins in adrenergic cells which bind to each of the two E boxes. However, nuclear proteins from cholinergic cells only bind the 5′ E box not the 3′ E box. It is this interaction which appears to be the cause of the inactivity of this silencer in these cells.