Characterization of the chicken rhodopsin promoter: identification of retina-specific and glass-like protein binding domains.

The rhodopsin promoter was analyzed as a prototype for cis-acting DNA elements involved in photoreceptor-specific gene regulation. We report the isolation and sequence of 1.8 kb of 5' flanking sequence of the chicken rhodopsin gene and analysis of DNA-binding proteins to promoter fragments by gel retardation assay. These analyses identified retina- and brain-specific protein binding to several regions of the rhodopsin promoter both proximal and distal to the transcription start site. The tissue-specific protein binding patterns were consistent with that proposed previously based on the expression pattern of rhodopsin promoter-lacZ constructs in transgenic mice (1, 2). The data also confirm the presence of the chicken homolog to a rat retina-specific binding site in the proximal promoter described previously. The Drosophila glass gene, which encodes a site-specific DNA-binding zinc-finger protein, is known to be required for the normal development of all photoreceptors in this species (3). In this paper we identify a glass-like sequence motif in chick, which shows homology to the Drosophila Rh1 27-bp glass-binding sequence, and find that the chick glass-like element exhibits tissue-specific protein binding properties which parallel those observed with Drosophila glass.