The long-term objectives of this application are to elucidate the molecular events that control transcription and translation of the genes encoding rod- and cone-specific cyclic GMP phosphodiesterases (PDEs), enzymes that are fundamental for integrity and normal function of photoreceptors, and to identify the genes encoding regulatory proteins essential for expression of PDEs. Specifically, the investigators will focus on the isolation and characterization of protein(s) (YP) interacting with a cis-element (Y element) adjacent to the transcription start site of the rod beta-PDE gene (mutations in this element abolish transcription) and RNA-binding proteins (UBPs) which may regulate translational efficiency of rod and cone PDE subunits. The genes encoding YP and UBP will constitute new candidates to screen for mutations in the DNA of patients affected with different types of inherited retinal degenerations. They will characterize the Y element and also examine if a Y-like sequence in the cone alpha-PDE gene plays a similar role in transcription of this gene. Deletion and substitution mutational analyses using transfections and gel mobility shift assays will be employed. To obtain YP, the one-hybrid system will be used to clone the YP cDNA followed by expression of YP. Alternatively, they will use classical column and affinity chromatography methods. Recombinant YP will be characterized and tested for its ability to activate beta-PDE transcription. To study the role of rod and cone PDE mRNA structures in translational regulation, constructs containing the 5'- and/or 3'-untranslated regions or both will be analyzed for their effect on protein synthesis using in vitro translation assays or by expressing them in the appropriate cell lines. UBP will be obtained using affinity chromatography and its cDNA will be cloned and expressed. They will then clone, determine the structure, and map them o their corresponding human chromosomes the YP and UBP genes. The DNA of patients with different retinal degenerations will be screened for potential disease-causing mutations in the YP and UBP genes using haplotype/exon screening and single strand conformational polymorphism electrophoresis (SSCP). Overall, these studies are designed to increase our knowledge of the etiology and possibly the pathogenesis of certain hereditary retinal degenerations and open new avenues for future therapeutic modalities.
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