Diss Abstr Int (Sci); 47(3):883 1986. Unique Identifier : AIDSLINE ICDB/87638185 Broome SA; Harvard Univ., MA
Abstract:
The expression of proviruses is determined by complex interactions between cellular and viral components. Previously, provirus transcription was thought to reflect only the capacity of host cell transcription factors to recognize the LTR-promoter of a virus, with chromosomal position effects influencing the response at a given locus. In this thesis, I show that a typical retrovirus, Rous sarcoma virus (RSV), specifies polypeptide products that stimulate transcription from the LTR as well as from other promoters in transient expression assays. This activity was first detected in a control transformation in which RSV and rat preproinsulin gene plasmids were introduced simultaneously into cells by the calcium phosphate transformation procedure. Cotransfection had not been used previously as an assay for trans-activation, although it was known that multiple markers could be introduced into transformed cells. These experiments were presented at a conference on eukaryotic viral vectors held at Cold Spring Harbor Laboratory in 1981 (Chapter 2). Using activation in cotransfections as an assay, I determined that the product of an alternate reading frame in the p19-p10 region of the RSV gag gene increases transient expression of the rat insulin-II gene. A mRNA whose spliced structure would direct translation of this reading frame from the Pr76 gag initiator methionine is found in infected cells (Chapter 3, Broome and Gilbert, Cell 40, 537-546, 1985). Insulin gene activation in cotransfected cells is not effected by a specific increase in LTR-initiated transcription that secondarily results in increased insulin gene transcription. All induced RNA species appear to have counterparts in cells transfected with insulin gene plasmids alone (Chapter 3). In fact, LTR-initiated transcription is not stimulated by the alternate reading frame gag gene product. Instead, another gag protein is responsible for the LTR trans-activation seen in RSV cotransfection experiments (Chapter 4). It is suggested that other retroviral transcriptional activators, including the RSV alternate reading frame product and trans-activators recently mapped on the genomes of HTLV-I and II, BLV, LAV/HTLV-III and visna virus, might be derived from this gag function.
Keywords: Cell Transformation, Viral Sarcoma Viruses, Avian/*GENETICS *Transcription, Genetic *Translation, Genetic Viral Proteins/*GENETICS THESIS
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