GLIAL CELL-SPECIFIC EXPRESSION OF THE SEROTONIN-2 RECEPTOR GENE - SELECTIVE REACTIVATION OF A REPRESSED PROMOTER

The 5' flanking region of the 5-HT2 receptor gene has been cloned, seq uenced and its transcriptional regulatory functions analyzed. The prom oter lacks an identifiable TATA motif, and utilizes at least 11 cluste red start sites. Promoter function was analyzed by transient assays in rat C6 glioma cells, which were shown to express the endogenous 5-HT2 receptor gene, as well as in rat CREF and human HeLa cells which do n ot express the endogenous gene. The basal promoter functioned equally well in all three cell lines; and a repression domain, located upstrea m of the basal promoter, inhibited activity of the promoter in all thr ee cell lines. A far upstream cell specific activator domain restored promoter activity in C6 glioma cells, but did not reactivate the silen ced promoter in CREF or HeLa cells. The upstream activator domain, rep ressor domain and basal promoter functioned in concert to achieve cell type specific expression. The activator domain did not direct C6 glio ma cell specific expression in the absence of the repressor domain or in constructs carrying a heterologous basal promoter. These results in dicate that glial cell expression of the 5-HT2 receptor gene is achiev ed through a cell type specific reactivation of a repressed promoter.