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Impact of sustained RNAi-mediated suppression of cellular cofactor Tat-SF1 on HIV-1 replication in CD4+ T cells.

ABSTRACT: BACKGROUND: Conventional anti-HIV drug regimens targeting viral enzymes are plagued by the emergence of drug resistance. There is interest in targeting HIV-dependency factors (HDFs), host proteins that the virus requires for replication, as drugs targeting their function may prove protective. Reporter cell lines provide a rapid and convenient method of identifying putative HDFs, but this approach may lead to misleading results and a failure to detect subtle detrimental effects on cells that result from HDF suppression. Thus, alternative methods for HDF validation are required. Cellular Tat-SF1 has long been ascribed a cofactor role in Tat-dependent transactivation of viral transcription elongation. Here we employ sustained RNAi-mediated suppression of Tat-SF1 to validate its requirement for HIV-1 replication in a CD4+ T cell-derived line and its potential as a therapeutic target. RESULTS: shRNA-mediated suppression of Tat-SF1 reduced HIV-1 replication and infectious particle production from TZM-bl reporter cells. This effect was not a result of increased apoptosis, loss of cell viability or an immune response. To validate its requirement for HIV-1 replication in a more relevant cell line, CD4+ SupT1 cell populations were generated that stably expressed shRNAs. HIV-1 replication was significantly reduced for two weeks (~65%) in cells with depleted Tat-SF1, although the inhibition of viral replication was moderate when compared to SupT1 cells expressing a shRNA targeting the integration cofactor LEDGF/p75. Tat-SF1 suppression was attenuated over time, resulting from decreased shRNA guide strand expression, suggesting that there is a selective pressure to restore Tat-SF1 levels. CONCLUSIONS: This study validates Tat-SF1 as an HDF in CD4+ T cell-derived SupT1 cells. However, our findings also suggest that Tat-SF1 is not a critical cofactor required for virus replication and its suppression may affect cell growth. Therefore, this study demonstrates the importance of examining HIV-1 replication kinetics and cytotoxicity in cells with sustained HDF suppression to validate their therapeutic potential as targets.

SUBMITTER: Green VA

PROVIDER: S-EPMC3511259 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Impact of sustained RNAi-mediated suppression of cellular cofactor Tat-SF1 on HIV-1 replication in CD4+ T cells.

Green Victoria A VA Arbuthnot Patrick P Weinberg Marc S MS

Virology journal 20121115

<h4>Background</h4>Conventional anti-HIV drug regimens targeting viral enzymes are plagued by the emergence of drug resistance. There is interest in targeting HIV-dependency factors (HDFs), host proteins that the virus requires for replication, as drugs targeting their function may prove protective. Reporter cell lines provide a rapid and convenient method of identifying putative HDFs, but this approach may lead to misleading results and a failure to detect subtle detrimental effects on cells th ...[more]

PMID: 23153325

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Project description:Our previous work demonstrated that HIV-1 infection progressively reduces TCR/CD3 expression due to a defect in CD3g gene transcripts. We further found that knocking down expression of the viral tat and/or nef genes was correlated with CD3g transcript and TCR/CD3 surface receptor levels on HIV-1 infected cells. This study was undertaken to investigate the direct effect of HIV-1 Tat expression on the TCR/CD3 machinery. Progressive downregulation from TCR/CD3hi to TCR/CD3lo to TCR/CD3â was observed on Tat expressing cells in a manner that emulated HIV-1 infection, with a lack of CD3g transcripts again responsible for the defect. When Tat cell cultures containing a mixture of TCR/CD3 surface densities were separated into TCR/CD3hi and TCR/CD3lo/â populations, they quickly reverted to a mixed CD3 phenotype. Thus, the progression TCR/CD3hi to TCR/CD3lo to TCR/CD3â is an active, reversible process with receptor levels fluctuating in response to intracellular dynamics. Examination of tat mutants found that the regions involved in Tat-mediated transactivation and TAR binding are required for TCR/CD3 downregulation while the lysine at position 28 and Tat exon 2 are dispensable. Global gene expression, assessed in association with TCR/CD3 downregulation in HIV-1 infected and Tat expressing cells, detected broad suppression of TCR/CD3 signaling, co-stimulation and negative regulatory genes along with target transcription factors, ligands and receptors. A significant subset of the genes altered in HIV-1 infected cells was specifically targeted by Tat in association with TCR/CD3 loss. Our finding that Tat negatively regulates many facets of the TCR/CD3 machinery has important implications for disease pathogenesis. We used microarrays to investigate changes in CD4+ T cell gene expression induced by expression of the HIV-1 Tat protein. Examine changes in gene expression in HIV-1 Tat transduced cells compared with cells transduced with an antisense Tat sequence used as a control.

Project description:Our previous work demonstrated that HIV-1 infection progressively reduces TCR/CD3 expression due to a defect in CD3g gene transcripts. We further found that knocking down expression of the viral tat and/or nef genes was correlated with CD3g transcript and TCR/CD3 surface receptor levels on HIV-1 infected cells. This study was undertaken to investigate the direct effect of HIV-1 Tat expression on the TCR/CD3 machinery. Progressive downregulation from TCR/CD3hi to TCR/CD3lo to TCR/CD3â was observed on Tat expressing cells in a manner that emulated HIV-1 infection, with a lack of CD3g transcripts again responsible for the defect. When Tat cell cultures containing a mixture of TCR/CD3 surface densities were separated into TCR/CD3hi and TCR/CD3lo/â populations, they quickly reverted to a mixed CD3 phenotype. Thus, the progression TCR/CD3hi to TCR/CD3lo to TCR/CD3â is an active, reversible process with receptor levels fluctuating in response to intracellular dynamics. Examination of tat mutants found that the regions involved in Tat-mediated transactivation and TAR binding are required for TCR/CD3 downregulation while the lysine at position 28 and Tat exon 2 are dispensable. Global gene expression, assessed in association with TCR/CD3 downregulation in HIV-1 infected and Tat expressing cells, detected broad suppression of TCR/CD3 signaling, co-stimulation and negative regulatory genes along with target transcription factors, ligands and receptors. A significant subset of the genes altered in HIV-1 infected cells was specifically targeted by Tat in association with TCR/CD3 loss. Our finding that Tat negatively regulates many facets of the TCR/CD3 machinery has important implications for disease pathogenesis. We used microarrays to investigate changes in CD4+ T cell gene expression induced by HIV-1 infection for comparison with the Tat expressing cells. Examine changes in gene expression in TCR/CD3 negative HIV-1 infected cells compared to TCR/CD3 positive uninfected controls.

Dataset Information

Impact of sustained RNAi-mediated suppression of cellular cofactor Tat-SF1 on HIV-1 replication in CD4+ T cells.

Publications

Impact of sustained RNAi-mediated suppression of cellular cofactor Tat-SF1 on HIV-1 replication in CD4+ T cells.

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