Functional Map -- HIV Tat Second Exon in Cytokine Regulation

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Infection with HIV and AIDS are devastating worldwide health problems. Although progress has been outstanding in discovering the relationship between HIV and AIDS and this has resulted in dramatically improved treatment in the developed world, we are still far from effective prevention or treatment that can be implemented worldwide. Thus the burden on science to better understand the pathogenic relationship between virus and host remains. Indeed, there are some HFV-1 associated pathologies, including HIV-1 associated dementia (HIVD), that simply are not well explained by the level of viral replication and may not disappear simply with effective control of replication. The HIV-1 Tat protein, well-studied for its role in viral transcription, represents a conspicuous candidate viral component that mediates a range of HIV pathologies, including HIVD and Kaposi's sarcoma. The molecular mechanisms and amino acid requirements of Tat for these non-LTR activities remain unclear. Further the full-length Tat101 protein has been understudied relative to the single exon Tat72 form, particularly for its role in HIV-1 pathogenesis through regulation of host gene expression. This proposal seeks to fill that gap. The central hypothesis is that there is a unique, definable domain within the Tat second exon, that in the context of the full length protein, is responsible for full regulation of host genes. Our specific aims will address this hypothesis by defining the cytokine genes that respond in the most clearly differential manner to the two physiologically relevant forms of Tat (Tat72 and Tat101) in aim 1. This will be followed up in aim 2 by a rationally targeted deletion mutagenesis approach to grossly map the amino acid region in the second exon that provides the added function to the full length protein in regulation of cytokine genes. Finally, in aim 3, the functional region identified by the deletion analysis will be fine mapped by introduction of logically designed individual amino acid substitutions to test the effect on cytokine gene regulation. At the conclusion of this study, we will have significantly advance the field in understanding the molecular requirements of the second exon of Tat to fully mediate host gene regulation. We will be in an opportune position to continue to investigate the pathways by which Tat contributes to HFV-1 pathogenesis because we will have a unique set of tools with which to probe the cellular protein partners that contact the functional element within the Tat second exon. It is our long range goal to use these tools to investigate the biological role and significance of the Tat protein on HIV-1 associated pathologies, particularly HIVD.