title: Evolutionarily conserved and divergent regulatory sequences in the fish rod opsin promoter.
abstract: Fish have multiple types and subtypes of opsin genes that are expressed in a highly regulated manner in retinal photoreceptor cells. In the rod opsin proximal promoter region (RPPR) of zebrafish (Danio rerio), the BAT 1 regulatory region contains highly conserved OTX (GATTA) and OTX-like (TATTA) sequences that can be recognized by the mammalian cone-rod homeobox (CRX) protein. However, binding of zebrafish crx to the OTX sequence has remained elusive. In contrast to the BAT 1 region, the Ret 1 region, located approximately 20 bp upstream of the BAT 1 region in mammals, is not conserved in zebrafish. In the Ret 1 region, even the core OTX-like sequence (AATTA sequence in mammals) is destructed. We show in this study that a region between Ret 1 and BAT 1 (denoted IRB, Inter-Ret 1-BAT 1) is highly conserved among fish species. Using electrophoretic mobility shift assay (EMSA), we show that zebrafish crx binds to the conserved OTX sequence and that the fish-specific IRB region specifically binds elements present in both retinal and brain nuclear extracts of zebrafish. These results imply that the regulatory mechanisms of opsin gene expression consist not only of evolutionarily conserved but also of divergent machinery among different animal taxa.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8652, Japan. kawamura@k.u-tokyo.ac.jp
authors.forename: Shoji
authors.initials: S
authors.lastname: Kawamura
authors.forename: Kumiko
authors.initials: K
authors.lastname: Takeshita
authors.forename: Taro
authors.initials: T
authors.lastname: Tsujimura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kasagi
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Matsumoto
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D051857:Otx Transcription Factors; D011401:Promoter Regions, Genetic; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry / Q000378:metabolism; D017299:Rod Opsins / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish
chemical_list: D018398:Homeodomain Proteins; D051857:Otx Transcription Factors; D017299:Rod Opsins; D015534:Trans-Activators; C109288:cone rod homeobox protein