Retina-specific cis-elements and binding nuclear proteins of carp rhodopsin gene

The upstream cis-elements controlling the retina-specific expression of carp rhodopsin gene were fully characterized in vivo. Transgenic studies demonstrated that both carp neural retina leucine zipper response-like element (cNRE, within nucleotides (nt) -63 to -75) and carp-specific element (CSE, nt -46 to -52) were crucial to reporter gene expression in medaka retinae. The retina-specific expression rates of embryos injected with nt -1 to -641 and longer fragments were much higher than those of embryos injected with nt -1 to -138 and shorter fragments, indicating that an enhancer is located in the nt -138 to -641 region. Retinal extracts and the probe BAT-1 (nt -90 to -120) formed two DNA-protein complexes, B1 and B2. Retinal extracts and the probes cNRE and CSE formed the complexes N1 and C1, respectively. The protein factors in B1 and C1 were mammal-like cone-rod homeobox proteins.