Regulatory Sequences in the 3 ' Untranslated Region of the Human cGMP-Phosphodiesterase beta-Subunit Gene

PURPOSE. Rod cGMP-phosphodiesterase, a key enzyme in visual transduction, is important for retinal integrity and function. Mutations in the gene encoding the phosphodiesterase beta-subunit (PDE beta) cause retinal degeneration in animals and humans. Here the authors tested the hypothesis that elements in the 3' untranslated region (3' UTR) of the PDE beta gene are involved in the regulation of PDE beta expression. METHODS. Involvement of the 3' UTR of PDE beta mRNA in the regulation of PDE beta expression was assessed by Y-79 retinoblastoma cells or the heads of Xenopus laevis tadpoles with constructs containing the SV40 or PDE beta promoter, the luciferase cDNA, and either the SV40 or the PDE beta 3' UTR (or fragments of its sequence). RESULTS. Compared with the SV40 3' UTR (used as control), the entire PDE beta 3' UTR decreased reporter gene expression in Y-79 retinoblastoma cells as well as in SY5Y neuroblastoma and 293 human embryonic kidney cell lines. However, the authors observed that two 100-nucleotide fragments from the PDE beta 3' UTR increased while its noncanonical poly-adenylation signal abolished reporter gene expression in Y-79 retinoblastoma cells and in ex vivo experiments using Xenopus tadpole heads. In particular, an 11-nucleotide element (EURE) in one of the 100-nucleotide fragments was responsible for the upregulation of luciferase expression. CONCLUSIONS. These studies indicate that the 3' UTR of the PDE beta mRNA is involved in the complex regulation of this gene's expression in the retina. Moreover, the results show that the PDE beta poly-A signal has a dominant inhibitory effect over two other regions in the 3' UTR that stimulate gene expression. (Invest Ophthalmol Vis Sci. 2009; 50: 2591-2598) DOI:10.1167/iovs.08-2010