Characterization of the genomic structure and tissue-specific promoter of the human nuclear receptor NR5A2 (hB1F) gene

The human homologue of the Drosophila melanogaster orphan nuclear receptor fushi tarazu factor 1 (Ftz-F1),NR5A2(hB1F), was initially identified as a r egulatory factor that binds and activates enhancer II of hepatitis B virus. NR5A2 (hB1F) is expressed specifically in pancreas and liver, playing impo rtant roles in the regulation of several liver-specific genes. A detailed a nalysis on the genomic structure and promoter activity will greatly promote future studies on the function of the NR5A2 (hB1F) gene. In this report, a bacterial artificial chromosome clone and several phage clones covering th e NR5A2 (hB1F) Gene were isolated and the complete genomic sequence was obt ained. Alignment of different cDNAs of the NR5A2 (hB1F) gene with the genom ic sequence facilitated the delineation of its structural organization, whi ch spans over 150 kb and consists of ei-ht exons interrupted by seven intro ns. RT-PCR and 3 ' -RACE revealed that utilization of two polyadenylation s ignals results in the 3.8 and 5.2 kb transcripts that were observed previou sly. The transcription start site of the NR5A2 (hB1F) gene was mapped downs tream of a canonical TATA box. An upstream fragment containing binding site s for several liver-specific and ubiquitous transcription factors exhibits hepatocyte-specific promoter activity. Transient transfections indicated th at hepatocyte nuclear factors HNF1 and HNF3 beta could activate NR5A2 (hB1F ) promoter. (C) 2001 Elsevier Science B.V. All rights reserved.