Article

Sustained Induction of NF-κB Is Required for Efficient Expression of Latent Human Immunodeficiency Virus Type 1

Gladstone Institute of Virology and Immunology, University of California San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA.
Journal of Virology (Impact Factor: 4.65). 07/2007; 81(11):6043-56. DOI: 10.1128/JVI.02074-06
Source: PubMed

ABSTRACT Cells harboring infectious, but transcriptionally latent, human immunodeficiency virus type 1 (HIV-1) proviruses currently pose an insurmountable barrier to viral eradication in infected patients. To better understand the molecular basis for HIV-1 latency, we used the J-Lat model of postintegration HIV-1 latency to assess the kinetic relationship between the induction of NF-kappaB and the activation of latent HIV-1 gene expression. Chromatin immunoprecipitation analyses revealed an oscillating pattern of RelA recruitment to the HIV-1 long terminal repeat (LTR) during continuous tumor necrosis factor alpha (TNF-alpha) stimulation. RNA polymerase II (Pol II) recruitment to the HIV-1 LTR closely mirrored RelA binding. Transient stimulation of cells with TNF-alpha for 15 min induced only a single round of RelA and RNA Pol II binding and failed to induce robust expression of latent HIV-1. Efficient formation of elongated HIV-1 transcripts required sustained induction by NF-kappaB, which promoted de novo synthesis of Tat. Cyclin-dependent kinase 9 (CDK9) and serine-2-phosphorylated RNA Pol II were rapidly recruited to the HIV-1 LTR after NF-kappaB induction; however, these elongating polymerase complexes were progressively dephosphorylated in the absence of Tat. Okadaic acid promoted sustained serine-2 phosphorylation of the C-terminal domain of RNA Pol II and stimulated efficient transcriptional elongation and HIV-1 expression in the absence of Tat. These findings underscore important differences between NF-kappaB and Tat stimulation of RNA Pol II elongation. While NF-kappaB binding to the HIV-1 LTR induces serial waves of efficient RNA Pol II initiation, elongation is impaired by the action of an okadaic acid-sensitive phosphatase that dephosphorylates the C-terminal domain of RNA Pol II. Conversely, the action of this phosphatase is overcome in the presence of Tat, promoting very efficient RNA Pol II elongation.

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    • "These results suggest that the mere presence of activated NFκB in the nucleus could not be sufficient to trigger HIV-1 promoter activity in monocytes/macrophages. Previous studies in T cells have suggested that time and level of NFκB activation could be determinants of this response.[44], and the kinetics of NFκB activation appears to be critical in controlling the magnitude of TLR-mediated cytokine production.[45] "
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    Cellular Immunology 03/2011; 269(1):38-45. DOI:10.1016/j.cellimm.2011.03.008 · 1.87 Impact Factor
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    • "The NF-κB p50-RelA heterodimers interact with HATs such as p300 (Gerritsen et al. 1997; Perkins et al. 1997), which are necessary for full Tat activity (Kaehlcke et al. 2003; Kiernan et al. 1999), as well as P-TEFb recruitment (Barboric et al. 2001). P-TEFb phosphorylates and aids in the function of RNA polymerase II, which will in turn produce fully elongated, productive transcripts (Kim et al. 2006; Williams et al. 2007). "
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    Journal of Neuroimmune Pharmacology 04/2010; 5(3):278-93. DOI:10.1007/s11481-010-9207-x · 3.17 Impact Factor
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    • "HIV-1 regulatory and accessory proteins, such as Tat, Vpr and Nef, also participate in the regulation of NF-κB activity (Hiscott et al., 2001; Mogensen and Paludan, 2001). Induction of the NF-κB pathway aids in HIV replication as it results in transactivation of the HIV long terminal repeat (LTR) that leads to enhanced viral transcription (Hiscott et al., 2001; Williams et al., 2007). Here we report that bovine foamy virus (BFV) is able to activate the NF-κB pathway through the action of its transactivator, BTas. "
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    ABSTRACT: Multiple families of viruses have evolved sophisticated strategies to regulate nuclear factor-kappaB (NF-kappaB) signaling, which plays a pivotal role in diverse cellular events, including virus-host interactions. In this study, we report that bovine foamy virus (BFV) is able to activate the NF-kappaB pathway through the action of its transactivator, BTas. Both cellular IKKbeta and IkappaBalpha also participate in this activation. In addition, we demonstrate that BTas induces the processing of p100, which implies that BTas can activate NF-kappaB through a noncanonical pathway as well. Co-immunoprecipitation analysis shows that BTas interacts with IKK catalytic subunits (IKKalpha and IKKbeta), which may be responsible for regulation of IKK kinase activity and persistent NF-kappaB activation. Furthermore, our results indicate that the level of BTas-mediated LTR transcription correlates with the activity of cellular NF-kappaB. Together, this study suggests that BFV activates the NF-kappaB pathway through BTas to enhance viral transcription.
    Virology 02/2010; 400(2):215-23. DOI:10.1016/j.virol.2010.01.035 · 3.28 Impact Factor
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