A new class of capsid-targeting inhibitors that specifically block HIV-1 nuclear import.

HIV-1 capsids cross nuclear pore complexes (NPCs) by engaging with the nuclear import machinery. To identify compounds that inhibit HIV-1 nuclear import, we screened drugs in silico on a three-dimensional model of a CA hexamer bound by Transportin-1 (TRN-1). Among hits, compound H27 inhibited HIV-1 with a low micromolar IC.

Internal RNA 2'-O-methylation on the HIV-1 genome impairs reverse transcription.

Viral RNA genomes are modified by epitranscriptomic marks, including 2'-O-methylation that is added by cellular or viral methyltransferases. 2'-O-Methylation modulates RNA structure, function and discrimination between self- and non-self-RNA by innate immune sensors such as RIG-I-like receptors. This is illustrated by human immunodeficiency virus type-1 (HIV-1) that decorates its RNA genome through hijacking the cellular FTSJ3 2'-O-methyltransferase, thereby limiting immune sensing and interferon production.

Internal RNA 2'O-methylation in the HIV-1 genome counteracts ISG20 nuclease-mediated antiviral effect.

RNA 2'O-methylation is a 'self' epitranscriptomic modification allowing discrimination between host and pathogen. Indeed, human immunodeficiency virus 1 (HIV-1) induces 2'O-methylation of its genome by recruiting the cellular FTSJ3 methyltransferase, thereby impairing detection by RIG-like receptors. Here, we show that RNA 2'O-methylations interfere with the antiviral activity of interferon-stimulated gene 20-kDa protein (ISG20).

Regulation of Viral Restriction by Post-Translational Modifications.

Intrinsic immunity is orchestrated by a wide range of host cellular proteins called restriction factors. They have the capacity to interfere with viral replication, and most of them are tightly regulated by interferons (IFNs). In addition, their regulation through post-translational modifications (PTMs) constitutes a major mechanism to shape their action positively or negatively.

Alarmin S100A9 restricts retroviral infection by limiting reverse transcription in human dendritic cells.

Dendritic cells (DC) subsets, like Langerhans cells (LC), are immune cells involved in pathogen sensing. They express specific antimicrobial cellular factors that are able to restrict infection and limit further pathogen transmission. Here, we identify the alarmin S100A9 as a novel intracellular antiretroviral factor expressed in human monocyte-derived and skin-derived LC.

TRIM8 is required for virus-induced IFN response in human plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (pDCs) play a crucial role in antiviral innate immunity through their unique capacity to produce large amounts of type I interferons (IFNs) upon viral detection. Tripartite motif (TRIM) proteins have recently come forth as important modulators of innate signaling, but their involvement in pDCs has not been investigated. Here, we performed a rationally streamlined small interfering RNA (siRNA)-based screen of TRIM proteins in human primary pDCs to identify those that are critical for the IFN response.

Transportin-1 binds to the HIV-1 capsid via a nuclear localization signal and triggers uncoating.

The initial steps of HIV replication in host cells prime the virus for passage through the nuclear pore and drive the establishment of a productive and irreparable infection. The timely release of the viral genome from the capsid-referred to as uncoating-is emerging as a critical parameter for nuclear import, but the triggers and mechanisms that orchestrate these steps are unknown. Here, we identify β-karyopherin Transportin-1 (TRN-1) as a cellular co-factor of HIV-1 infection, which binds to incoming capsids, triggers their uncoating and promotes viral nuclear import.

Nanoscale organization of tetraspanins during HIV-1 budding by correlative dSTORM/AFM.

Membrane partition and remodeling play a key role in numerous cell mechanisms, especially in viral replication cycles where viruses subvert the plasma membrane to enter and escape from the host cell. Specifically assembly and release of HIV-1 particles require specific cellular components, which are recruited to the egress site by the viral protein Gag. We previously demonstrated that HIV-1 assembly alters both partitioning and dynamics of the tetraspanins CD9 and CD81, which are key players in many infectious processes, forming enriched areas where the virus buds.

Sensing of HIV-1 Entry Triggers a Type I Interferon Response in Human Primary Macrophages.

Along with CD4 T lymphocytes, macrophages are a major cellular source of HIV-1 replication and a potential viral reservoir. Following entry and reverse transcription in macrophages, cloaking of the viral cDNA by the HIV-1 capsid limits its cytosolic detection, enabling efficient replication. However, whether incoming HIV-1 particles are sensed by macrophages prior to reverse transcription remains unclear.

From Cells to Virus Particles: Quantitative Methods to Monitor RNA Packaging.

In cells, positive strand RNA viruses, such as Retroviridae, must selectively recognize their full-length RNA genome among abundant cellular RNAs to assemble and release particles. How viruses coordinate the intracellular trafficking of both RNA and protein components to the assembly sites of infectious particles at the cell surface remains a long-standing question. The mechanisms ensuring packaging of genomic RNA are essential for viral infectivity.

Imaging HIV-1 RNA dimerization in cells by multicolor super-resolution and fluctuation microscopies.

Dimerization is a unique and vital characteristic of retroviral genomes. It is commonly accepted that genomic RNA (gRNA) must be dimeric at the plasma membrane of the infected cells to be packaged during virus assembly. However, where, when and how HIV-1 gRNA find each other and dimerize in the cell are long-standing questions that cannot be answered using conventional approaches.

Requirements for nucleocapsid-mediated regulation of reverse transcription during the late steps of HIV-1 assembly.

HIV-1 is a retrovirus replicating within cells by reverse transcribing its genomic RNA (gRNA) into DNA. Within cells, virus assembly requires the structural Gag proteins with few accessory proteins, notably the viral infectivity factor (Vif) and two copies of gRNA as well as cellular factors to converge to the plasma membrane. In this process, the nucleocapsid (NC) domain of Gag binds to the packaging signal of gRNA which consists of a series of stem-loops (SL1-SL3) ensuring gRNA selection and packaging into virions.

HIV-1 nucleocapsid and ESCRT-component Tsg101 interplay prevents HIV from turning into a DNA-containing virus.

HIV-1, the agent of the AIDS pandemic, is an RNA virus that reverse transcribes its RNA genome (gRNA) into DNA, shortly after its entry into cells. Within cells, retroviral assembly requires thousands of structural Gag proteins and two copies of gRNA as well as cellular factors, which converge to the plasma membrane in a finely regulated timeline. In this process, the nucleocapsid domain of Gag (GagNC) ensures gRNA selection and packaging into virions.

MoMuLV and HIV-1 nucleocapsid proteins have a common role in genomic RNA packaging but different in late reverse transcription.

Retroviral nucleocapsid proteins harbor nucleic acid chaperoning activities that mostly rely on the N-terminal basic residues and the CCHC zinc finger motif. Such chaperoning is essential for virus replication, notably for genomic RNA selection and packaging in virions, and for reverse transcription of genomic RNA into DNA. Recent data revealed that HIV-1 nucleocapsid restricts reverse transcription during virus assembly--a process called late reverse transcription--suggesting a regulation between RNA packaging and late reverse transcription.

The interaction between the measles virus nucleoprotein and the Interferon Regulator Factor 3 relies on a specific cellular environment.

Background: The genome of measles virus consists of a non-segmented single-stranded RNA molecule of negative polarity, which is encapsidated by the viral nucleoprotein (N) within a helical nucleocapsid. The N protein possesses an intrinsically disordered C-terminal domain (aa 401-525, N(TAIL)) that is exposed at the surface of the viral nucleopcapsid. Thanks to its flexible nature, N(TAIL) interacts with several viral and cellular partners.