Transcriptional Repression by a Conserved Intronic Sequence in the Nicotinic Receptor α3 Subunit Gene*
- Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, the University of Massachusetts Medical School, Worcester, Massachusetts 01604
- 1 To whom correspondence should be addressed: Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, 303 Belmont St., Worcester, MA 01604. Tel.: 508-856-4035; Fax: 508-856-4130; E-mail: paul.gardner{at}umassmed.edu.
Abstract
The genes encoding the nicotinic acetylcholine receptor α3, α5, and β4 subunits are genomically clustered. These genes are co-expressed in a variety of cells in the peripheral and central nervous systems. Their gene products assemble in a number of stoichiometries to generate several nicotinic receptor subtypes that have distinct pharmacological and physiological properties. Signaling through these receptors is critical for a variety of fundamental biological processes. Despite their importance, the transcriptional mechanisms underlying their coordinated expression remain to be completely elucidated. By using a bioinformatics approach, we identified a highly conserved intronic sequence within the fifth intron of the α3 subunit gene. Reporter gene analysis demonstrated that this sequence, termed “α3 intron 5,” inhibits the transcriptional activities of the α3 and β4 subunit gene promoters. This repressive activity is position- and orientation-independent. Importantly, repression occurs in a cell type-specific manner, being present in cells that do not express the receptor genes or expresses them at very low levels. Electrophoretic mobility shift assays demonstrate that nuclear proteins specifically interact with α3 intron 5 at two distinct sites. We propose that this intronic repressor element is important for the restricted expression patterns of the nicotinic receptor α3 and β4 subunit genes.
Footnotes
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↵2 The abbreviations used are: nACh, nicotinic ACh; NGF, nerve growth factor; RT-PCR, reverse transcription; EMSA, electrophoretic mobility shift assay.
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↵* This work was supported in part by National Institutes of Health Grant NS30243, Philip Morris USA Inc., and Philip Morris International. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement”in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Received March 19, 2007.
- Revision received May 1, 2007.
