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Download or read book Identification and Characterization of New and Distinct Functional Roles of Posttranscriptional Control Elements in Cytoplasmic Expression of Retroviral Rna written by Stacey Lynn Hull and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The central focus of this dissertation is the identification and characterization of retroviral posttranscriptional control elements that affect protein production from unspliced viral RNA. We identify and characterize a new posttranscriptional control element in the Mason-Pfizer monkey virus 52 long terminal repeat (LTR) that modulates translational efficiency by augmentation of translational initiation. MPMV RU5 is necessary for cytoplasmic expression of HIV-1 gag-pol reporter RNA and also enhances cytoplasmic expression of intronless luc RNA by stimulation of ribosome loading. MPMV RU5 functions independently of any viral proteins and instead directs functional interaction with cellular posttranscriptional modulators to facilitate translational enhancement. This research has illuminated an essential step in viral gene expression and provides a new paradigm for understanding cellular control of the translation process. Secondly, we tested the hypothesis that combination of the MPMV constitutive transport element (CTE) and the MPMV or spleen necrosis virus (SNV) RU5 translational enhancer on a single RNA synergistically augments posttranscriptional gene expression. MPMV CTE functions compatibly with MPMV and SNV RU5 to increase cytoplasmic expression of HIV-1 gag-pol reporter RNA in monkey COS, but not 293 cells. The CTE-interactive cellular proteins, Tap and NXT1, are necessary and sufficient to rescue increased cytoplasmic expression of HIV-1 gag-pol reporter RNA in 293 cells. This work produced the realization that differences in cellular posttranscriptional modulators dramatically affect retroviral protein production. Thirdly, we evaluated the role of SNV RU5 on metabolism of homologous SNV RNA. SNV RU5 increases SNV Gag-GFP fusion protein production from unspliced genomic RNA. The increase in protein is attributable, at least in part, to increased cytoplasmic accumulation of the unspliced SNV transcript. RU5 exerts a distinct effect on the spliced env transcript. Deletion of RU5 has no effect on cytoplasmic accumulation of env RNA, but increases splicing efficiency. Therefore, SNV RU5 modulates metabolism of both unspliced and spliced SNV transcripts and is speculated to contain a RNA splicing suppressor. In summary, this dissertation has identified and characterized a new posttranscriptional control element in MPMV and synergistic interactions among functionally distinct retroviral posttranscriptional control elements and their cellular protein partners. This work also demonstrated an important role for SNV RU5 in SNV genomic RNA.