Organisation and promoter activity of the retinoic-acid-induced-heparin-binding (RIHB) gene.

The heparin-binding protein, RIHB, is encoded by a gene that is expressed temporarily during the early period of chicken embryogenesis. We have now isolated genomic clones of the chicken RIHB gene, determined its transcription initiation sites, characterized its promoter region and established the functional activity of the RIHB gene promoter. The 5' flanking region and the beginning of the first exon revealed a structural organisation characteristic of housekeeping and growth-control-related genes. It lacked canonical TATA or CAAT boxes but contained several GC boxes. The structure of the RIHB gene is compared with those of the human and mouse midgestation kidney (MK) genes. In the coding exons, the similarities between the three genes are striking. In contrast, the structure and location of the first non-coding exon is different. Analysis of the promoter activity suggests an indirect regulation of transcription by retinoic acid and demonstrates a high degree of complexity of the regulation of the RIHB gene.