Interphotoreceptor retinoid-binding protein (IRBP) is an abundant glycolipoprotein that is expressed in the retina and pineal gland. IRBP mRNA is synthesized by the photoreceptor cells of the retina. We are characterizing the cis-elements regulating IRBP expression using a transient transfection assay and transgenic mice. There are two conserved areas of sequence in the 5'-flanking regions of the bovine, human, and mouse IRBP genes, one from -1 to -350 and another at -1200 to -1410. The 5'-flanking region is necessary for expression of IRBP in transient transfection assays in Y79 retinoblastoma cell cultures. In transgenic mice, the same region also shows promoter activity in the retina and pineal, demonstrating that tissue specificity is engendered within the tested 5'-flanking regions of the gene.
