ABSTRACT
Detection of viruses by innate immune sensors induces protective antiviral immunity. The viral DNA sensor cyclic GMP-AMP synthase (cGAS) is necessary for detection of HIV by human dendritic cells and macrophages. However, synthesis of HIV DNA during infection is not sufficient for immune activation. The capsid protein, which associates with viral DNA, has a pivotal role in enabling cGAS-mediated immune activation. We now find that NONO is an essential sensor of the HIV capsid in the nucleus. NONO protein directly binds capsid with higher affinity for weakly pathogenic HIV-2 than highly pathogenic HIV-1. Upon infection, NONO is essential for cGAS activation by HIV and cGAS association with HIV DNA in the nucleus. NONO recognizes a conserved region in HIV capsid with limited tolerance for escape mutations. Detection of nuclear viral capsid by NONO to promote DNA sensing by cGAS reveals an innate strategy to achieve distinction of viruses from self in the nucleus.
Subject(s)
Capsid Proteins/immunology , Nuclear Matrix-Associated Proteins/immunology , Nuclear Matrix-Associated Proteins/physiology , Octamer Transcription Factors/immunology , Octamer Transcription Factors/physiology , RNA-Binding Proteins/immunology , RNA-Binding Proteins/physiology , Capsid/metabolism , Capsid Proteins/metabolism , Capsid Proteins/physiology , Cell Nucleus/metabolism , DNA, Viral/genetics , DNA, Viral/immunology , DNA-Binding Proteins , Dendritic Cells/immunology , HIV Infections/immunology , HIV-1/genetics , HIV-1/immunology , HIV-2/genetics , HIV-2/immunology , Host-Pathogen Interactions , Humans , Immunity, Innate/immunology , Macrophages/immunology , Membrane Proteins/metabolism , Nuclear Matrix-Associated Proteins/metabolism , Nucleotidyltransferases/metabolism , Nucleotidyltransferases/physiology , RNA-Binding Proteins/metabolism , Signal Transduction/immunologyABSTRACT
The DNA-mediated innate immune response underpins anti-microbial defenses and certain autoimmune diseases. Here we used immunoprecipitation, mass spectrometry, and RNA sequencing to identify a ribonuclear complex built around HEXIM1 and the long non-coding RNA NEAT1 that we dubbed the HEXIM1-DNA-PK-paraspeckle components-ribonucleoprotein complex (HDP-RNP). The HDP-RNP contains DNA-PK subunits (DNAPKc, Ku70, and Ku80) and paraspeckle proteins (SFPQ, NONO, PSPC1, RBM14, and MATRIN3). We show that binding of HEXIM1 to NEAT1 is required for its assembly. We further demonstrate that the HDP-RNP is required for the innate immune response to foreign DNA, through the cGAS-STING-IRF3 pathway. The HDP-RNP interacts with cGAS and its partner PQBP1, and their interaction is remodeled by foreign DNA. Remodeling leads to the release of paraspeckle proteins, recruitment of STING, and activation of DNAPKc and IRF3. Our study establishes the HDP-RNP as a key nuclear regulator of DNA-mediated activation of innate immune response through the cGAS-STING pathway.
