Immediate upstream sequence of arrestin directs rod-specific expression inXenopus

Arrestins are a family of proteins that modulate G protein-coupled receptor responses with distinct arrestin genes expressed in rods and cones. To und erstand the regulatory mechanisms controlling rod-specific expression, the abundant Xenopus rod arrestin cDNA and a partial genomic clone, containing the immediate upstream region and amino terminus of the polypeptide, have b een characterized. The deduced polypeptide has similar to 69% identity to o ther vertebrate rod arrestins. Southern blot analysis and polymerase chain reaction of intronic sequences demonstrated multiple alleles for rod arrest in. DNase I footprinting with retinal proteins revealed four major DNA bind ing sites in the proximal promoter, coinciding with consensus sequences rep orted in mammalian promoters. Purified bovine Crx homeodomain and mouse Nrl proteins protected a number of these sites. A dual approach of transient e mbryo transfections and transgenesis was used to locate transcriptional con trol sequences essential for rod-specific expression in Xenopus. Constructs containing -1287/+113 of 5' upstream sequence with or without intron 1 dir ected high level expression, specifically in rods. A construct containing o nly -287/+113 directed expression of green fluorescent protein solely in ro d cells. These results suggest that the Crx and Nrl binding sites in the pr oximal promoter are the primary cis-acting sequences regulating arrestin ge ne expression in rods.