In collaboration with Projects 1, 2, 5 and Cores A and B, Project 3 has elucidated a new translationregulatory axis by comparative studies of retroviral genomes. Our results of proteomic, genetic andbiochemical analysis have identified a novel role for RNA helicase A (RHA) in both retroviral and cellulargenes. We have shown that RHA specifically recognizes a unique 5' terminal post-transcriptional controlelement (PCE) and neutralizes structural features of the 5' untranslated region (UTR) to facilitate efficientcap-dependent translation initiation. Our results of biochemical analyses and genome-wide translationprofiling have identified a subset of biologically-related genes that require RHA for their efficient translation.Many of these PCE candidates are proto-oncogenes encoding a complex 5' UTR, which require RHA/PCEinteraction to promote efficient translation. Our identification of the fundamental role of RHA in cellulartranslational control provides a platform to understand the observation that RHA dysregulation is a tumorbiomarker. Our collaborative studies have identified PCE activity in six divergent retroviruses, includingHTLV-1; that interaction with RHA is necessary; and this virus-host interaction is essential for efficient HTLV-1 translation. Our additional identification of PCE activity in cellular junD provided proof-of-concept thatretroviruses have adopted a host cell mechanism to achieve efficient RNA expression. We have applied thePCE/host interaction to stimulate protein output in retroviral vectors; this innovation is applicable to a widearray of gene expression systems. Our fundamental insights implicate RHA as an integrative effector in thecontinuum of gene expression from transcription to translation and in coordinating viral and cellular geneexpression. The outcomes of the initial funding period are inextricably linked to the common PPG goal tounderstand virus-host interactions and mechanisms of gene regulation. A primary focus of this highlyinteractive Continuation is to understand the scope and regulation of the RHA/PCE translational control axisin retroviral and host genes. Specifically, we postulate the RHA regulon is an inducible translational controlmechanism of selected genes, whose dvsregulation contributes to alterations of the cellularmicroenvironment leading to transformation and paraneoolastic disease. Our three interrelated Aims are:
Aim 1. To characterize essential features of RHA gene expression and cytoplasmic localization during cellcycle progression;
Aim 2. To examine role of RHA translational activity in osteoclast activity and Tax tumormodel;
Aim 3. To assess the essential features structure/function of junD PCE in relation to the retrovirusPCE database. Long-term objectives are application of knowledge of the RHA post-transcriptional regulon todevelop vectors and small molecules to selectively modulate RHA responsive genes involved in neoplastictransformation, paraneoplastic disease and retrovirus infection.
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