A novel, evolutionarily conserved enhancer of cone photoreceptor-specific expression

Abstract

The α subunit of cone transducin (TαC) is expressed exclusively in cone photoreceptors of the eye and pineal. TαC is a key phototransduction protein, and inherited mutations in TαC cause total color blindness in humans. We use transgenic zebrafish to identify and characterize cone photoreceptor regulatory element 1 (CPRE-1) a novel 20-bp enhancer element in the TαC promoter (TαCP). CPRE-1 is located ∼2.5 kb upstream of the translation start site and is necessary for strong cone photoreceptor-specific expression in vivo. CPRE-1 comprises of a modular arrangement of two 10-bp elements that have separate, but co-dependent transcriptional activities. In vitro, CPRE-1 specifically binds nuclear factors that are enriched in ocular tissue. Bioinformatic alignments reveal that CPRE-1 sites are evolutionarily conserved in the promoter regions of fish, rodent, and mammalian TαC orthologues and identify a 5′-CTGGAGTG(A/T)TGGA(G/A) GCAGGG(G/C)T-3′ consensus sequence. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.