SP1 AND SP3 REGULATE EXPRESSION OF THE NEURONAL NICOTINIC ACETYLCHOLINE-RECEPTOR BETA-4 SUBUNIT GENE

Neuronal nicotinic acetylcholine receptors play important roles in sig nal transduction within the nervous system. The receptors exist in a v ariety of functionally distinct subtypes that are determined by their subunit structures. The subunits are encoded by 11 genes, alpha 2-alph a 9 and beta 2-beta 4. Three of the genes, alpha 3, alpha 5, and beta 4, are tightly clustered, and their encoded proteins make up the predo minant receptor subtype in the peripheral nervous system. The tight li nkage of the genes suggests there may be a common regulatory mechanism underlying their expression. However, although their expression patte rns significantly overlap, they are not identical, indicating that ind ependent regulatory mechanisms must also exist. Our studies have focus ed upon the gene encoding the beta 4 subunit for which we have identif ied several transcriptional regulatory elements. One of these elements , E2, specifically interacts with the general transcription factor Sp1 . Here we show that another member of the Sp family of factors, Sp3, c an specifically interact with E2 whereas two other members, Sp2 and Sp 4, cannot. Co-transfection experiments indicate that Sp3 can transacti vate a beta 4 promoter/reporter gene construct and, furthermore, that Sp1 and Sp3 can transactivate the beta 4 reporter construct synergisti cally. The transactivation is dependent upon an intact E2 and may invo lve direct interactions between Sp1 and Sp3.