Positive- and negative-acting promoter sequences regulate cell type-specific expression of the rat synapsin I gene

Abstract

The phosphoprotein synapsin I is expressed exclusively in neuronal cells. We interested in elucidating the promoter sequences involved in cell type-specific expression of the synapsin I gene. The PC12 cell line expresses the 3.4 kb and 4.5 kb synapsin I mRNAs and is used to analyze cell typespecific gene expression. A series of deletion fragments of the rat synapsin I gene promoter were fused to the promoterless reporter gene encoding bacterial chloramphenicol acetyltransferase (CAT) for transfection analysis in PC12 cells and in HeLa cells, which do not express the gene. A −349 bp to +110 bp rat synapsin I promoter fragment contains a positive regulator, shown to be 33-times more active in PC12 cells than HeLa cells. Transfection of reporter plasmids containing up to 4.4. kb of rat synapsin I gene promoter sequences exhibit significantly reduced CAT activity in PC12 cells. The reduction in CAT expression was attributed to a negative regulator located between −349 bp and −1341 bp in the rat synapsin I promoter. Our results suggest that both positive and negative-acting sequence elements regulate cell type-specific expression of the rat synapsin I gene.