Characterization of 5'-proximal sequence of mouse GABA transporter gene (GAT-1)

GABA transporter 1 transcriptional starting site exhibiting tissue specific difference

GABA transporter 1(GAT1) takes important roles in multiple physiological processes through the uptake and release of GABA, but the regulation of GAT1 gene expression in different tissues is rarely known. To address the question, first, 5' Rapid amplification of cDNA end (RACE) was used to determine GAT1 transcriptional starting sites in neonatal mouse cerebral cortex and intestine, adult mouse brain and adult rat testis. The products of 5'RACE were confirmed by DNA sequencing. We found that the transcript of GAT1 in neonatal mouse cerebral cortex and adult mouse brain starts at the same site (inside of exon 1), while in mouse intestine, GAT1 starts transcription in intron 1, and in rat testis, the transcript of GAT1 has an additional untranslation exon to the 5' direction.

Analysis of the 5' flanking sequence of the human norepinephrine transporter gene

The human norepinephrine transporter (NET) gene was cloned and structurally analyzed. The far 5' fragment containing exon 1 (a non-coding exon) and exon 2 was sequenced. The transcription start site of the gene in human brain stem tissue was determined by primer extension analysis. It was found that the gene could be transcribed from multiple starting points. The 5' flanking sequence contains a proximal G-C rich region, one possible GSG element and several SP1 sites. However it does not contain TATA box and CAAT box motifs. Gel shift analysis with nuclear extracts from different tissues of mouse shows that the G-C rich region may be involved in tissue specific expression of the gene.