Global ETD Search

11	Transcript-Specific Cytoplasmic Degradation of YRA1 Pre-mRNA Mediated by the Yeast EDC3 Protein: A Dissertation Dong, Shuyun 17 December 2007 (has links) mRNA degradation is a fundamental process that controls both the level and the fidelity of gene expression. Using a combination of bioinformatic, genomic, genetic, and molecular biology approaches, we have shown that Edc3p, a yeast mRNA decay factor, controls the stability of the intron-containing YRA1 pre-mRNA. We found that Edc3p-mediated degradation of YRA1 pre-mRNA: 1) is a component of a negative feedback loop involved in the autoregulation of YRA1, 2) takes place in the cytoplasm, 3) is independent of translation, 4) occurs through a deadenylation-independent decapping and 5΄ to 3΄ exonucleotic decay mechanism, and 5) is controlled by specific cis-acting elements and trans-regulatory factors. Cis-regulation of YRA1 pre-mRNA degradation is complicated and precise. Sequences in exon1 inhibit YRA1 pre-mRNA splicing and/or promote pre-mRNA export in a size-dependent but sequence-independent manner. Sequences in the intron dictate the substrate specificity for Edc3p-mediated decay. Five structurally different but functionally interdependent modules were identified in the YRA1 intron. Two modules, designated Edc3p-responsive elements (EREs), are required for triggering an Edc3p-response. Three other modules, designated translational repression elements (TREs), are required for repressing translation of YRA1 pre-mRNA. TREs enhance the efficiency of the response of the EREs to Edc3p by inhibiting translation-dependent nonsense-mediated mRNA decay (NMD). Trans-regulation of YRA1 pre-mRNA is governed by Yra1p, which inhibits YRA1 pre-mRNA splicing and commits the pre-mRNA to nuclear export, and the RNP export factors, Mex67p and Crm1p, which jointly promote YRA1 pre-mRNA export. Mex67p also appears to interact with sequences in the YRA1 intron to promote translational repression and to enhance the Edc3p response of YRA1 pre-mRNA. These results illustrate how common steps in the nuclear processing, export, and degradation of a transcript can be uniquely combined to control the expression of a specific gene and suggest that Edc3p-mediated decay may have additional regulatory functions in eukaryotic cells. Gene Expression Cell Nucleus Feedback Biochemical Nuclear Proteins RNA Stability RNA Precursors RNA-Binding Proteins Saccharomyces cerevisiae Amino Acids, Peptides, and Proteins Biochemistry Bioinformatics Cells Computational Biology Fungi Genetic Phenomena Genetics Genetics and Genomics Genomics Molecular Biology Molecular Genetics
12	Stoichiometric imbalance in the receptor complex contributes to dysfunctional BMPR-II mediated signalling in pulmonary arterial hypertension Nasim, Md. Talat, Ghouri, A., Patel, B., James, V., Rudarakanchana, N., Morrell, N.W., Trembath, R.C. January 2008 (has links) No / Heterozygous germline defects in a gene encoding a type II receptor for bone morphogenetic proteins (BMPR-II) underlie the majority of inherited cases of the vascular disorder known as pulmonary arterial hypertension (PAH). However, the precise molecular consequences of PAH causing mutations on the function of the receptor complex remain unclear. We employed novel enzymatic and fluorescence activity based techniques to assess the impact of PAH mutations on pre-mRNA splicing, nonsense-mediated decay (NMD) and receptor complex interactions. We demonstrate that nonsense and frameshift mutations trigger NMD, providing further evidence that haplo-insufficiency is a major molecular consequence of disease-related BMPR2 mutations. We identified heterogeneous functional defects in BMPR-II activity, including impaired type I receptor phosphorylation, receptor interactions and altered receptor complex stoichiometry leading to perturbation of downstream signalling pathways. Importantly, these studies demonstrate that the intracellular domain of BMPR-II is both necessary and sufficient for receptor complex interaction. Finally and to address the potential for resolution of stoichiometric balance, we investigated an agent that promotes translational readthrough of a BMPR2 nonsense reporter construct without interfering with the NMD pathway. We propose that stoichiometric imbalance, due to either haplo-insufficiency or loss of optimal receptor-receptor interactions impairs BMPR-II mediated signalling in PAH. Taken together, these studies have identified an important target for early therapeutic intervention in familial PAH. Aminoglycosides Pharmacology Bone morphogenetic protein receptors Type I Metabolism Bone morphogenetic protein receptors Type II Genetics Codon Nonsense Exons Genes Reporter Humans Hypertension Pulmonary Enzymology Introns Phosphorylation Protein biosynthesis RNA precursors RNA splicing RNA stability RNA messenger Signal transduction Transcription Drug effects REF 2014

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Transcript-Specific Cytoplasmic Degradation of YRA1 Pre-mRNA Mediated by the Yeast EDC3 Protein: A Dissertation

Stoichiometric imbalance in the receptor complex contributes to dysfunctional BMPR-II mediated signalling in pulmonary arterial hypertension