Transcriptional control of human organic anion transporting polypeptide 2B1 gene.

Organic anion transporting polypeptides (OATPs) are a group of transmembrane carriers with a wide spectrum of amphipathic substrates. In particular, OATP2B1 (previously called OATP-B) can transport steroid hormone conjugates and is expressed in organs with steroidogenic activity, such as placenta, brain and skin. In this work, we have analyzed the transcription of the OATP2B1 gene (SLCO2B1) in 14 different human tissues by means of 5'-RACE analysis. Five promoters (only two of which were present in GenBank), associated with distinct first exons, were found to drive OATP2B1 expression, giving rise to transcripts with unique 5'-untranslated termini. Exon 1b is widely expressed and was found here in 10 tissues. It is partially coding, while the other four different first exons are untranslated. All exons are spliced to a common exon 2 that contains a putative ATG in frame with the following coding region. Sequence analysis of the 5'-flanking region of each first exon revealed a lack of TATA box, thus accounting for the use of multiple transcriptional start sites in nearly all first exons.