Characterization of transcriptional activity of taurine transporter using luciferase reporter constructs

Although taurine transporter (TAUT) activity has been known to be regulated by diverse intracellular and extracellular factors involved in the signal transduction pathway, such as protein kinase C, intracellular Ca concentration, and glucocorticoids, little is known concerning the underlying mechanisms. Evidence suggests that such stimulation-mediated changes in TAUT activity in mammalian cells are partly achieved through the modulation of TAUT transcription activity. In order to better understand the regulation of TAUT transcription activity and subsequently the role of taurine in the signal transduction pathway, we have cloned and sequenced the 5' flanking region of the human TAUT gene, and characterized the TAUT promoter region in human cells. For these reasons, the TAUT luciferase reporter vector was constructed using the 5' flanking region of the TAUT gene (1800 bp). The TAUT luciferase reporter vector was then transfected into SiHa cells, and luciferase activity was measured. The construct containing its own promoter of TAUT (pGL3 b TAU31) showed a 10 fold higher luciferase activity compared to the value found in the empty vector (pGL3 b). This implies a functional transcription of the homologous TAUT promoter. Similar results were obtained with the exon deleted construct [pGL3 b TAU31(-e)]. We also constructed the TAUT luciferase reporter gene (pGL3 pro TAU13) using a heterologous promoter. About 2.5 fold higher luciferase activity was observed in cells transfected with this construct containing the heterologous promoter compared to the value found in the control vector (PGL3 pro).