The CDK Inhibitor p21Cip1/WAF1 Is Induced by Fc R Activation and Restricts the Replication of Human Immunodeficiency Virus Type 1 and Related Primate Lentiviruses in Human Macrophages

Institut Pasteur, Unité de Régulation des Infections Rétrovirales, Paris, France.
Journal of Virology (Impact Factor: 4.44). 09/2009; 83(23):12253-65. DOI: 10.1128/JVI.01395-09
Source: PubMed


Macrophages are major targets of human immunodeficiency virus type 1 (HIV-1). We have previously shown that aggregation of activating immunoglobulin G Fc receptors (FcgammaR) by immune complexes inhibits reverse transcript accumulation and integration of HIV-1 and related lentiviruses in monocyte-derived macrophages. Here, we show that FcgammaR-mediated restriction of HIV-1 is not due to enhanced degradation of incoming viral proteins or cDNA and is associated to the induction of the cyclin-dependent kinase inhibitor p21(Cip1/WAF1) (p21). Small interfering RNA-mediated p21 knockdown rescued viral replication in FcgammaR-activated macrophages and enhanced HIV-1 infection in unstimulated macrophages by increasing reverse transcript and integrated DNA levels. p21 induction by other stimuli, such as phorbol myristate acetate and the histone deacetylase inhibitor MS-275, was also associated with preintegrative blocks of HIV-1 replication in macrophages. Binding of p21 to reverse transcription/preintegration complex-associated HIV-1 proteins was not detected in yeast two-hybrid, pulldown, or coimmunoprecipitation assays, suggesting that p21 may affect viral replication independently of a specific interaction with an HIV-1 component. Consistently, p21 silencing rescued viral replication from the FcgammaR-mediated restriction also in simian immunodeficiency virus SIV(mac)- and HIV-2-infected macrophages. Our results point to a role of p21 as an inhibitory factor of lentiviral infection in macrophages and to its implication in FcgammaR-mediated restriction.

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Available from: Anna Bergamaschi
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    • "In primary macrophages, dendritic cells and resting CD4+ T cells SAMHD1 degrades dNTPs which are required for efficient reverse transcription [2-4]. Two other factors p21 and PAF1 act at an early stage however their mechanism of action is not yet understood [5,6]. Once reverse transcription is complete the pre-integration complex (PIC) containing the double stranded (ds)DNA is then formed and integrated into the genome of the host cell. "
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    ABSTRACT: The discovery of novel anti-viral restriction factors illuminates unknown aspects of innate sensing and immunity. We identified RNA-associated Early-stage Anti-viral Factor (REAF) using a whole genome siRNA screen for restriction factors to human immunodeficiency virus (HIV) that act in the early phase of viral replication. We observed more than 50 fold rescue of HIV-1 infection, using a focus forming unit (FFU) assay, following knockdown of REAF by specific siRNA. Quantitative PCR was used to show that REAF knockdown results in an increase of early and late reverse transcripts which impacts the level of integration. REAF thus appears to act at an early stage of the viral life cycle during reverse transcription. Conversely when REAF is over-expressed in target cells less infected cells are detectable and fewer reverse transcripts are produced. Human REAF can also inhibit HIV-2 and simian immunodeficiency virus (SIV) infection. REAF associates with viral nucleic acids and may act to prevent reverse transcription. This report firmly places REAF alongside APOBECs and SAMHD1 as a potent inhibitor of HIV replication acting early in the replication cycle, just after cell entry. We propose that REAF is part of an anti-viral surveillance system destroying incoming retroviruses. This novel mechanism could apply to invasion of cells by any intracellular pathogen.
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    • "The status of HIV permissiveness in a given cell subset is dependent in part on virus ability to counteract intrinsic cellular defenses mechanisms [7] mediated by several restriction factors including APOBEC3G [8-10], TRIM5α [11,12], Tetherin/CD317 [13] and most recently discovered, SAMHD1 [14,15]. In addition to restriction factors that directly target the virus, p21/CDKN1A, a potent inhibitor of cyclin dependent kinases, was demonstrated to limit HIV replication in macrophages [16] and CD4+ T-cells from HIV elite controllers [17,18], likely by an indirect mechanism. On the other hand, HIV uses the host-cell machinery for its successful replication. "
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    • "Furthermore , differentiation of cells to an HIV-1-resistant phenotype is associated with a loss of CDK1 expression [89,90]. Interestingly, Cribier et al. demonstrated a decrease in T592 phosphorylation in cells treated with IFN-α, thus implying a link between type 1 IFN signaling and SAMHD1 activation [82] that may involve p21 Waf1/Cip1 , a cell-cycle-regulated inhibitor of HIV-1 replication [91], and CDK1, a cell-cycle-regulated kinase activity that is induced by IFN-α [92] [93]. "
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