Identification and Characterization of the Human Serotonin-4 Receptor Gene Promoter☆

Abstract The human serotonin-4 (5-HT 4 ) receptor gene expression is highly regulated in various tissues. We isolated the human 5-HT 4 receptor gene containing the 5′-flanking region and characterized its promoter. By 5′-RACE (5′-rapid amplification of the cDNA ends) and inverse PCR, multiple transcription initiation sites were identified. The most 5′ one (assigned to +1) was 5135 bp upstream to the translation start site. The 500-bp 5′-flanking region contained potential binding sites for transcription factor Sp-1, AP-2, AP-4, and GATA. However, this region lacked TATA- and CAAT-boxes. Transient transfection analyses in human choriocarcinoma T3M-3 (5-HT 4 receptor-positive) and HepG2 (5-HT 4 receptor-negative) cells revealed that the region (−210 to −105) is necessary for the basic and cell-type specific 5-HT 4 receptor gene expression. In addition, untranslated exon 1 contained negative (+112 to +182) as well as positive (+1 to +111) modulators, indicating that exon 1 plays a regulatory role in the 5-HT 4 receptor gene expression.