Unknown,Transcriptomics,Genomics,Proteomics

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Tat controls RNA Polymerase II and the epigenetic landscape to precisely rewire cellular transcriptional programs (RNA-Seq)

ABSTRACT: Transcription factors mediate precise regulation of gene expression programs to modulate key biological processes. In addition to controlling HIV transcription, Tat appears to modulate cellular transcription to alter the biology of target immune cells and generate a permissive state for HIV infection. However, the molecular mechanisms of transcriptional control have remained elusive. Here, we identified the direct target genes of Tat using genomics and defined mechanisms by which Tat selectively rewires cellular transcriptional programs. Interestingly, Tat functions as both transcriptional activator and repressor of a defined set of genes sharing functional annotations and regulated by master transcriptional regulators such as T-cell identity factors. Tat is recruited to precise genomic domains (promoters and intragenic enhancers) through interaction with master transcriptional regulators to control both the transcription initiation and elongation steps. Tat mediates transcription initiation by modulating Pol II recruitment to promoters and intragenic enhancers and fine-tuning chromatin looping. Tat stimulates or blocks RNA Polymerase (Pol) II recruitment or promoter-proximal pause release thereby promoting gene activation or repression, respectively. Global analysis of chromatin signatures revealed correlation of transcription activity marks with Pol II recruitment or pause release status at gene promoters and enhancers, and transcription elongation at coding units. We propose that Tat has evolved these unique properties to hijack precise genomic domains to control cellular transcription using unexpected regulatory mechanisms, which showed marked differences to the regulation of the HIV genome. Our studies also reveal that Tat can be used as a molecular probe to decode general principles of transcriptional regulation. Tat vs. GFP

ORGANISM(S): Homo sapiens

SUBMITTER: Ivan D'Orso

PROVIDER: E-GEOD-65688 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

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Tat controls RNA Polymerase II and the epigenetic landscape to precisely rewire cellular transcriptional programs (RNA-Seq)

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