Functional promoter and polyadenylation site mapping of the human serotonin (5-HT) transporter gene

We have isolated and characterized the 5′-flanking region and the proximal polyadenylation site of the human 5-HT transporter gene. The major gene transcript is 2,793 bp in length and it contains 208 bp of 5′-untranslated region (5′-UTR) and 694 bases of 3′-UTR. While only a single mRNA species occurs in rats and mice, the most proximal signal for polyadenylation in the human gene appears to be highly degenerate in comparison to the rat and murine motif. This polyadenylation signal-like motif may lead to alternate usage of additional polyadenylation sites resulting in multiple mRNA species in humans. A TATA-like motif and several potential binding sites for transcription factors including AP1, AP2, SP1, and a cAMP response element (CRE)-like motif are present in the 5′-flanking region. A ∼1.7 kb fragment beginning 217 bp downstream from the transcription start site, which had been ligated into a luciferase reporter vector and transiently expressed in JAR human placental choriocarcinoma cells, displayed both constitutive and forskolin/cholera toxin-induced promoter activity. Functional promoter mapping revealed that there are negative attenuating elements between bp −1,428 and −1,185 and positive elements between bp −1,184 and −78 from the transcription initiation site. Studies with deletional mutants also indicated that core promoter sequences are contained within 78 bp of the transcription start site and that regulation of cAMP-inducible promoter activity depends on multiplecis-acting elements including two AP1 binding sites and a single CRE-like element located at bp −99. Our findings suggest that (1) the 5-HT transporter gene promoter is active in human JAR cells, but inactive in 5-HT transporter-deficient human SK-N-SH neuroblastoma and HeLa cells, (2) the information contained within 1.4kb of 5′-flanking sequence is sufficient to confer its cell-specific expression, (3) the promoter responds to cAMP induction, and (4) the expression of the 5-HT transporter gene is regulated by a combination of positive and negativecis-acting elements operating through a basal promoter unit defined by a TATA-like motif.

[1]  V. Ganapathy,et al.  Expression and cyclic AMP-dependent regulation of a high affinity serotonin transporter in the human placental choriocarcinoma cell line (JAR). , 1991, The Journal of biological chemistry.

[2]  P. Riederer,et al.  Organization of the human serotonin transporter gene , 2005, Journal of Neural Transmission / General Section JNT.

[3]  K. Lesch,et al.  Systematic screening for mutations in the coding region of the human serotonin transporter (5-HTT) gene using PCR and DGGE. , 1996, American journal of medical genetics.

[4]  R. Blakely,et al.  Antidepressant- and cocaine-sensitive human serotonin transporter: molecular cloning, expression, and chromosomal localization. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[5]  M. Wickens How the messenger got its tail: addition of poly(A) in the nucleus. , 1990, Trends in biochemical sciences.

[6]  R. Blakely,et al.  Expression of Serotonin Transporter Messenger RNA in the Human Brain , 1994, Journal of neurochemistry.

[7]  R. Blakely,et al.  Regulation of the human serotonin transporter. Cholera toxin-induced stimulation of serotonin uptake in human placental choriocarcinoma cells is accompanied by increased serotonin transporter mRNA levels and serotonin transporter-specific ligand binding. , 1993, The Journal of biological chemistry.

[8]  D. Murphy,et al.  Isolation of a cDNA encoding the human brain serotonin transporter , 2005, Journal of Neural Transmission / General Section JNT.

[9]  D. Murphy,et al.  Primary structure of the serotonin transporter in unipolar depression and bipolar disorder , 1995, Biological Psychiatry.

[10]  K. Lesch,et al.  Neurotransmitter Reuptake Mechanisms , 1995 .