151
|
Molenberghs F, Bogers JJ, De Vos WH. Confined no more: Viral mechanisms of nuclear entry and egress. Int J Biochem Cell Biol 2020; 129:105875. [PMID: 33157236 DOI: 10.1016/j.biocel.2020.105875] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 10/27/2020] [Accepted: 10/29/2020] [Indexed: 12/14/2022]
Abstract
Viruses are obligatory intracellular parasites. For their efficient replication, many require access to the nuclear interior. Yet, only few viral particles are small enough to passively diffuse through the nuclear pore complexes, calling for alternative strategies to bypass the nuclear envelope barrier. Some viruses will await mitotic nuclear envelope breakdown to gain access, whereas others will exploit more active means, for instance by hijacking nuclear pore transport or by directly targeting constituents of the nuclear envelope so as to remodel and temporarily perturb its integrity. After replication, newly produced viral DNA complexes need to cross the same barrier to exit the nucleus and enter the cytoplasm, where the final stages of virion maturation take place. There are also different flavours to the feat of nuclear egress that vary in delicacy and intensity. In this review, we define the major entry and egress strategies that are exploited by different viruses and describe the molecular details thereof. Ultimately, a deeper understanding of these pathways may help identifying molecular targets for blocking viral reproduction or spreading.
Collapse
Affiliation(s)
- Freya Molenberghs
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences/Medicine and Health Sciences, University of Antwerp, Belgium
| | - Johannes J Bogers
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences/Medicine and Health Sciences, University of Antwerp, Belgium
| | - Winnok H De Vos
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences/Medicine and Health Sciences, University of Antwerp, Belgium.
| |
Collapse
|
152
|
Wu Y, Li S. Role of Post-Translational Modifications of cGAS in Innate Immunity. Int J Mol Sci 2020; 21:ijms21217842. [PMID: 33105828 PMCID: PMC7660100 DOI: 10.3390/ijms21217842] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/18/2020] [Accepted: 10/20/2020] [Indexed: 12/23/2022] Open
Abstract
Cyclic GMP–AMP synthase (cGAS) is the synthase that generates the second messenger cyclic GMP–AMP (cGAMP) upon DNA binding. cGAS was first discovered as the cytosolic DNA sensor that detects DNA exposed in the cytoplasm either from pathogens or cellular damage. Activated cGAS instigates the signaling cascades to activate type I interferon (IFN) expression, critical for host defense and autoimmune diseases. In addition, cGAS plays a role in senescence, DNA repair, apoptosis, and tumorigenesis. Recently, various post-translational modifications (PTMs) of cGAS have been reported, such as phosphorylation, ubiquitination, acetylation, glutamylation, and sumoylation. These PTMs profoundly affect cGAS functions. Thus, here we review the recent reported PTMs of cGAS and how these PTMs regulate cGAS enzymatic activity, DNA binding, and protein stability, and discuss the potential future directions.
Collapse
Affiliation(s)
| | - Shitao Li
- Correspondence: ; Tel.: +1-504-988-2203
| |
Collapse
|
153
|
Structural basis for nucleosome-mediated inhibition of cGAS activity. Cell Res 2020; 30:1088-1097. [PMID: 33051594 DOI: 10.1038/s41422-020-00422-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 09/24/2020] [Indexed: 12/11/2022] Open
Abstract
Activation of cyclic GMP-AMP synthase (cGAS) through sensing cytosolic double stranded DNA (dsDNA) plays a pivotal role in innate immunity against exogenous infection as well as cellular regulation under stress. Aberrant activation of cGAS induced by self-DNA is related to autoimmune diseases. cGAS accumulates at chromosomes during mitosis or spontaneously in the nucleus. Binding of cGAS to the nucleosome competitively attenuates the dsDNA-mediated cGAS activation, but the molecular mechanism of the attenuation is still poorly understood. Here, we report two cryo-electron microscopy structures of cGAS-nucleosome complexes. The structures reveal that cGAS interacts with the nucleosome as a monomer, forming 1:1 and 2:2 complexes, respectively. cGAS contacts the nucleosomal acidic patch formed by the H2A-H2B heterodimer through the dsDNA-binding site B in both complexes, and could interact with the DNA from the other symmetrically placed nucleosome via the dsDNA-binding site C in the 2:2 complex. The bound nucleosome inhibits the activation of cGAS through blocking the interaction of cGAS with ligand dsDNA and disrupting cGAS dimerization. R236A or R255A mutation of cGAS impairs the binding between cGAS and the nucleosome, and largely relieves the nucleosome-mediated inhibition of cGAS activity. Our study provides structural insights into the inhibition of cGAS activity by the nucleosome, and advances the understanding of the mechanism by which hosts avoid the autoimmune attack caused by cGAS.
Collapse
|
154
|
Abstract
The nuclear envelope is often depicted as a static barrier that regulates access between the nucleus and the cytosol. However, recent research has identified many conditions in cultured cells and in vivo in which nuclear membrane ruptures cause the loss of nuclear compartmentalization. These conditions include some that are commonly associated with human disease, such as migration of cancer cells through small spaces and expression of nuclear lamin disease mutations in both cultured cells and tissues undergoing nuclear migration. Nuclear membrane ruptures are rapidly repaired in the nucleus but persist in nuclear compartments that form around missegregated chromosomes called micronuclei. This review summarizes what is known about the mechanisms of nuclear membrane rupture and repair in both the main nucleus and micronuclei, and highlights recent work connecting the loss of nuclear integrity to genome instability and innate immune signaling. These connections link nuclear membrane rupture to complex chromosome alterations, tumorigenesis, and laminopathy etiologies.
Collapse
Affiliation(s)
- John Maciejowski
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA;
| | - Emily M Hatch
- Division of Basic Sciences and Human Biology, The Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA;
| |
Collapse
|
155
|
Chen H, Chen H, Zhang J, Wang Y, Simoneau A, Yang H, Levine AS, Zou L, Chen Z, Lan L. cGAS suppresses genomic instability as a decelerator of replication forks. SCIENCE ADVANCES 2020; 6:6/42/eabb8941. [PMID: 33055160 PMCID: PMC7556829 DOI: 10.1126/sciadv.abb8941] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 08/28/2020] [Indexed: 05/09/2023]
Abstract
The cyclic GMP-AMP synthase (cGAS), a sensor of cytosolic DNA, is critical for the innate immune response. Here, we show that loss of cGAS in untransformed and cancer cells results in uncontrolled DNA replication, hyperproliferation, and genomic instability. While the majority of cGAS is cytoplasmic, a fraction of cGAS associates with chromatin. cGAS interacts with replication fork proteins in a DNA binding-dependent manner, suggesting that cGAS encounters replication forks in DNA. Independent of cGAMP and STING, cGAS slows replication forks by binding to DNA in the nucleus. In the absence of cGAS, replication forks are accelerated, but fork stability is compromised. Consequently, cGAS-deficient cells are exposed to replication stress and become increasingly sensitive to radiation and chemotherapy. Thus, by acting as a decelerator of DNA replication forks, cGAS controls replication dynamics and suppresses replication-associated DNA damage, suggesting that cGAS is an attractive target for exploiting the genomic instability of cancer cells.
Collapse
Affiliation(s)
- Hao Chen
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA
- Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Hao Chen
- UPMC Hillman Cancer Center, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
| | - Jiamin Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA
| | - Yumin Wang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA
- Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Antoine Simoneau
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA
- Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Hui Yang
- Department of Molecular Biology, Center for Inflammation Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA
| | - Arthur S Levine
- UPMC Hillman Cancer Center, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA
- Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Zhijian Chen
- Department of Molecular Biology, Center for Inflammation Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA
| | - Li Lan
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02129, USA.
- Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| |
Collapse
|
156
|
Reisländer T, Groelly FJ, Tarsounas M. DNA Damage and Cancer Immunotherapy: A STING in the Tale. Mol Cell 2020; 80:21-28. [PMID: 32810436 DOI: 10.1016/j.molcel.2020.07.026] [Citation(s) in RCA: 162] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/08/2020] [Accepted: 07/28/2020] [Indexed: 12/19/2022]
Abstract
Cancer immunotherapies enhance anti-tumor immune responses using checkpoint inhibitors, such as PD-1 or PD-L1 inhibitors. Recent studies, however, have extended the scope of immunotherapeutics by unveiling DNA damage-induced innate immunity as a novel target for cancer treatment. Elucidating the interplay among the DNA damage response (DDR), cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation, and anti-tumoral immunity is critical for the development of effective cancer immunotherapies. Here, we discuss the current understanding of the mechanisms by which DNA damage activates immune responses that target and eradicate cancer cells. Yet, understanding how cancer cells can escape this immune surveillance and promote tumor progression represents an outstanding challenge. We highlight the most recent clinical advances, in particular how pharmacological fine-tuning of innate/adaptive immunity and its combination with DDR inhibitors, ionizing radiation (IR), and chemotherapy can be exploited to improve cancer treatment.
Collapse
Affiliation(s)
- Timo Reisländer
- Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Florian J Groelly
- Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Madalena Tarsounas
- Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| |
Collapse
|
157
|
Zhang Y, Ma Z, Wang Y, Boyer J, Ni G, Cheng L, Su S, Zhang Z, Zhu Z, Qian J, Su L, Zhang Q, Damania B, Liu P. Streptavidin Promotes DNA Binding and Activation of cGAS to Enhance Innate Immunity. iScience 2020; 23:101463. [PMID: 32861998 PMCID: PMC7476851 DOI: 10.1016/j.isci.2020.101463] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 06/15/2020] [Accepted: 08/12/2020] [Indexed: 12/13/2022] Open
Abstract
cGAS/STING signaling plays an essential role in sensing cytosolic DNA. cGAS activity is regulated by posttranslational modifications and binding partners. cGAS interactome largely includes mammalian or viral proteins. Whether and how bacterial proteins bind cGAS to modulate innate immunity remain elusive. Here, we found streptavidin, a secreted bacterial protein, selectively bound cGAS to promote DNA-induced cGAS activation and interferon-β production. Mechanistically, streptavidin enhanced DNA binding and cGAS phase separation, therefore facilitating cGAS activation. Using an HSV-1-infected mouse model, we found streptavidin nanoparticles facilitated HSV-1 clearance through improving innate immunity. Considering the clinical usage of streptavidin as an immune stimulant and drug delivery vehicle and its biotechnological usage for biotin-labeled protein purification and detection, our studies not only provide an example for a bacterial protein regulating cGAS activity but also suggest caution needs to be taken when using streptavidin in various applications given to its ability to induce innate immunity.
Collapse
Affiliation(s)
- Yanqiong Zhang
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Zhe Ma
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ying Wang
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Joshua Boyer
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Guoxin Ni
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Liang Cheng
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Siyuan Su
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Zhigang Zhang
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Zhichuan Zhu
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jiayi Qian
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Lishan Su
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Qi Zhang
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Blossom Damania
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- University of North Carolina Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Pengda Liu
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| |
Collapse
|
158
|
Guey B, Wischnewski M, Decout A, Makasheva K, Kaynak M, Sakar MS, Fierz B, Ablasser A. BAF restricts cGAS on nuclear DNA to prevent innate immune activation. Science 2020; 369:823-828. [PMID: 32792394 DOI: 10.1126/science.aaw6421] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 11/18/2019] [Accepted: 06/12/2020] [Indexed: 12/28/2022]
Abstract
The appearance of DNA in the cytosol is perceived as a danger signal that stimulates potent immune responses through cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS). How cells regulate the activity of cGAS toward self-DNA and guard against potentially damaging autoinflammatory responses is a fundamental biological question. Here, we identify barrier-to-autointegration factor 1 (BAF) as a natural opponent of cGAS activity on genomic self-DNA. We show that BAF dynamically outcompetes cGAS for DNA binding, hence prohibiting the formation of DNA-cGAS complexes that are essential for enzymatic activity. Upon acute loss of nuclear membrane integrity, BAF is necessary to restrict cGAS activity on exposed DNA. Our observations reveal a safeguard mechanism, distinct from physical separation, by which cells protect themselves against aberrant immune responses toward genomic DNA.
Collapse
Affiliation(s)
- Baptiste Guey
- Global Health Institute, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
| | - Marilena Wischnewski
- Global Health Institute, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
| | - Alexiane Decout
- Global Health Institute, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
| | | | - Murat Kaynak
- Institute of Mechanical Engineering, EPFL, Switzerland
| | | | - Beat Fierz
- Institute of Chemical Sciences and Engineering, EPFL, Switzerland
| | - Andrea Ablasser
- Global Health Institute, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland.
| |
Collapse
|
159
|
Kujirai T, Zierhut C, Takizawa Y, Kim R, Negishi L, Uruma N, Hirai S, Funabiki H, Kurumizaka H. Structural basis for the inhibition of cGAS by nucleosomes. Science 2020; 370:455-458. [PMID: 32912999 DOI: 10.1126/science.abd0237] [Citation(s) in RCA: 140] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/28/2020] [Indexed: 12/19/2022]
Abstract
The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) senses invasion of pathogenic DNA and stimulates inflammatory signaling, autophagy, and apoptosis. Organization of host DNA into nucleosomes was proposed to limit cGAS autoinduction, but the underlying mechanism was unknown. Here, we report the structural basis for this inhibition. In the cryo-electron microscopy structure of the human cGAS-nucleosome core particle (NCP) complex, two cGAS monomers bridge two NCPs by binding the acidic patch of the histone H2A-H2B dimer and nucleosomal DNA. In this configuration, all three known cGAS DNA binding sites, required for cGAS activation, are repurposed or become inaccessible, and cGAS dimerization, another prerequisite for activation, is inhibited. Mutating key residues linking cGAS and the acidic patch alleviates nucleosomal inhibition. This study establishes a structural framework for why cGAS is silenced on chromatinized self-DNA.
Collapse
Affiliation(s)
- Tomoya Kujirai
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Christian Zierhut
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA
| | - Yoshimasa Takizawa
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ryan Kim
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA
| | - Lumi Negishi
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Nobuki Uruma
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Seiya Hirai
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Hironori Funabiki
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA.
| | - Hitoshi Kurumizaka
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan. .,Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| |
Collapse
|
160
|
Michalski S, de Oliveira Mann CC, Stafford CA, Witte G, Bartho J, Lammens K, Hornung V, Hopfner KP. Structural basis for sequestration and autoinhibition of cGAS by chromatin. Nature 2020; 587:678-682. [PMID: 32911480 DOI: 10.1038/s41586-020-2748-0] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/24/2020] [Indexed: 01/14/2023]
Abstract
Cyclic GMP-AMP synthase (cGAS) is an innate immune sensor for cytosolic microbial DNA1. After binding DNA, cGAS synthesizes the messenger 2'3'-cyclic GMP-AMP (cGAMP)2-4, which triggers cell-autonomous defence and the production of type I interferons and pro-inflammatory cytokines via the activation of STING5. In addition to responding to cytosolic microbial DNA, cGAS also recognizes mislocalized cytosolic self-DNA and has been implicated in autoimmunity and sterile inflammation6,7. Specificity towards pathogen- or damage-associated DNA was thought to be caused by cytosolic confinement. However, recent findings place cGAS robustly in the nucleus8-10, where tight tethering of chromatin is important to prevent autoreactivity to self-DNA8. Here we show how cGAS is sequestered and inhibited by chromatin. We provide a cryo-electron microscopy structure of the cGAS catalytic domain bound to a nucleosome, which shows that cGAS does not interact with the nucleosomal DNA, but instead interacts with histone 2A-histone 2B, and is tightly anchored to the 'acidic patch'. The interaction buries the cGAS DNA-binding site B, and blocks the formation of active cGAS dimers. The acidic patch robustly outcompetes agonistic DNA for binding to cGAS, which suggests that nucleosome sequestration can efficiently inhibit cGAS, even when accessible DNA is nearby, such as in actively transcribed genomic regions. Our results show how nuclear cGAS is sequestered by chromatin and provides a mechanism for preventing autoreactivity to nuclear self-DNA.
Collapse
Affiliation(s)
- Sebastian Michalski
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Carina C de Oliveira Mann
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Che A Stafford
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Gregor Witte
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Joseph Bartho
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Katja Lammens
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Veit Hornung
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany
| | - Karl-Peter Hopfner
- Gene Center, Ludwig-Maximilians-Universität, Munich, Germany. .,Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany.
| |
Collapse
|
161
|
Boyer JA, Spangler CJ, Strauss JD, Cesmat AP, Liu P, McGinty RK, Zhang Q. Structural basis of nucleosome-dependent cGAS inhibition. Science 2020; 370:450-454. [PMID: 32913000 DOI: 10.1126/science.abd0609] [Citation(s) in RCA: 134] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/28/2020] [Indexed: 12/14/2022]
Abstract
Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) recognizes cytosolic foreign or damaged DNA to activate the innate immune response to infection, inflammatory diseases, and cancer. By contrast, cGAS reactivity against self-DNA in the nucleus is suppressed by chromatin tethering. We report a 3.3-angstrom-resolution cryo-electron microscopy structure of cGAS in complex with the nucleosome core particle. The structure reveals that cGAS uses two conserved arginines to anchor to the nucleosome acidic patch. The nucleosome-binding interface exclusively occupies the strong double-stranded DNA (dsDNA)-binding surface on cGAS and sterically prevents cGAS from oligomerizing into the functionally active 2:2 cGAS-dsDNA state. These findings provide a structural basis for how cGAS maintains an inhibited state in the nucleus and further exemplify the role of the nucleosome in regulating diverse nuclear protein functions.
Collapse
Affiliation(s)
- Joshua A Boyer
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Cathy J Spangler
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Joshua D Strauss
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Andrew P Cesmat
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Pengda Liu
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Robert K McGinty
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. .,Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Qi Zhang
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. .,Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| |
Collapse
|
162
|
Structural mechanism of cGAS inhibition by the nucleosome. Nature 2020; 587:668-672. [PMID: 32911482 DOI: 10.1038/s41586-020-2750-6] [Citation(s) in RCA: 151] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 07/22/2020] [Indexed: 12/17/2022]
Abstract
The DNA sensor cyclic GMP-AMP synthase (cGAS) initiates innate immune responses following microbial infection, cellular stress and cancer1. Upon activation by double-stranded DNA, cytosolic cGAS produces 2'3' cGMP-AMP, which triggers the induction of inflammatory cytokines and type I interferons 2-7. cGAS is also present inside the cell nucleus, which is replete with genomic DNA8, where chromatin has been implicated in restricting its enzymatic activity9. However, the structural basis for inhibition of cGAS by chromatin remains unknown. Here we present the cryo-electron microscopy structure of human cGAS bound to nucleosomes. cGAS makes extensive contacts with both the acidic patch of the histone H2A-H2B heterodimer and nucleosomal DNA. The structural and complementary biochemical analysis also find cGAS engaged to a second nucleosome in trans. Mechanistically, binding of the nucleosome locks cGAS into a monomeric state, in which steric hindrance suppresses spurious activation by genomic DNA. We find that mutations to the cGAS-acidic patch interface are sufficient to abolish the inhibitory effect of nucleosomes in vitro and to unleash the activity of cGAS on genomic DNA in living cells. Our work uncovers the structural basis of the interaction between cGAS and chromatin and details a mechanism that permits self-non-self discrimination of genomic DNA by cGAS.
Collapse
|
163
|
The molecular basis of tight nuclear tethering and inactivation of cGAS. Nature 2020; 587:673-677. [PMID: 32911481 PMCID: PMC7704945 DOI: 10.1038/s41586-020-2749-z] [Citation(s) in RCA: 144] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/12/2020] [Indexed: 12/31/2022]
Abstract
Pathogen-derived nucleic acids induce potent innate immune responses1-6. Cyclic GMP-AMP synthase (cGAS) is a dsDNA sensor that catalyzes the synthesis of a cyclic dinucleotide cGAMP, which mediates the induction of type I interferons through the STING-TBK1-IRF3 signaling axis7-11. It was widely accepted that cGAS is not reactive to self-DNA due to its cytosolic localization2,12,13. However, recent studies revealed that cGAS is mostly localized in the nucleus and tight nuclear tethering keeps cGAS inactive14-18. Here we show that cGAS binds to nucleosomes with nanomolar affinity and nucleosome binding potently inhibits the catalytic activity of cGAS. To elucidate the molecular basis of cGAS inactivation by nuclear tethering, we have determined the structure of mouse cGAS bound to human nucleosome by cryo-EM. The structure shows that cGAS binds to a negatively charged acidic patch formed by histone H2A and H2B via its second DNA binding site19. High affinity nucleosome binding blocks dsDNA binding and keeps cGAS in an inactive conformation. Mutations of cGAS that disrupt nucleosome binding dramatically affect cGAS mediated signaling in cells.
Collapse
|
164
|
Uhlorn BL, Gamez ER, Li S, Campos SK. Attenuation of cGAS/STING activity during mitosis. Life Sci Alliance 2020; 3:e201900636. [PMID: 32661021 PMCID: PMC7368095 DOI: 10.26508/lsa.201900636] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 07/08/2020] [Accepted: 07/08/2020] [Indexed: 12/14/2022] Open
Abstract
The innate immune system recognizes cytosolic DNA associated with microbial infections and cellular stress via the cGAS/STING pathway, leading to activation of phospho-IRF3 and downstream IFN-I and senescence responses. To prevent hyperactivation, cGAS/STING is presumed to be nonresponsive to chromosomal self-DNA during open mitosis, although specific regulatory mechanisms are lacking. Given a role for the Golgi in STING activation, we investigated the state of the cGAS/STING pathway in interphase cells with artificially vesiculated Golgi and in cells arrested in mitosis. We find that whereas cGAS activity is impaired through interaction with mitotic chromosomes, Golgi integrity has little effect on the enzyme's production of cGAMP. In contrast, STING activation in response to either foreign DNA (cGAS-dependent) or exogenous cGAMP is impaired by a vesiculated Golgi. Overall, our data suggest a secondary means for cells to limit potentially harmful cGAS/STING responses during open mitosis via natural Golgi vesiculation.
Collapse
Affiliation(s)
- Brittany L Uhlorn
- Cancer Biology Graduate Interdisciplinary Program, The University of Arizona, Tucson, AZ, USA
| | - Eduardo R Gamez
- Department of Physiology, The University of Arizona, Tucson, AZ, USA
| | - Shuaizhi Li
- Department of Immunobiology, The University of Arizona, Tucson, AZ, USA
| | - Samuel K Campos
- Cancer Biology Graduate Interdisciplinary Program, The University of Arizona, Tucson, AZ, USA
- Department of Immunobiology, The University of Arizona, Tucson, AZ, USA
- BIO5 Institute, The University of Arizona, Tucson, AZ, USA
- Department of Molecular and Cellular Biology, The University of Arizona, Tucson, AZ, USA
| |
Collapse
|
165
|
Ma R, Ortiz Serrano TP, Davis J, Prigge AD, Ridge KM. The cGAS-STING pathway: The role of self-DNA sensing in inflammatory lung disease. FASEB J 2020; 34:13156-13170. [PMID: 32860267 PMCID: PMC8121456 DOI: 10.1096/fj.202001607r] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/31/2020] [Accepted: 08/05/2020] [Indexed: 12/15/2022]
Abstract
The presence of DNA in the cytosol is usually a sign of microbial infections, which alerts the host innate immune system to mount a defense response. Cyclic GMP-AMP synthase (cGAS) is a critical cytosolic DNA sensor that elicits robust innate immune responses through the production of the second messenger, cyclic GMP-AMP (cGAMP), which binds and activates stimulator of interferon genes (STING). However, cGAS binds to DNA irrespective of DNA sequence, therefore, self-DNA leaked from the nucleus or mitochondria can also serve as a cGAS ligand to activate this pathway and trigger extensive inflammatory responses. Dysregulation of the cGAS-STING pathway is responsible for a broad array of inflammatory and autoimmune diseases. Recently, evidence has shown that self-DNA release and cGAS-STING pathway over-activation can drive lung disease, making this pathway a promising therapeutic target for inflammatory lung disease. Here, we review recent advances on the cGAS-STING pathway governing self-DNA sensing, highlighting its role in pulmonary disease.
Collapse
Affiliation(s)
- Ruihua Ma
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Tatiana P Ortiz Serrano
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Jennifer Davis
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Andrew D Prigge
- Division of Critical Care Medicine, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA
| | - Karen M Ridge
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| |
Collapse
|
166
|
Pollock AJ, Zaver SA, Woodward JJ. A STING-based biosensor affords broad cyclic dinucleotide detection within single living eukaryotic cells. Nat Commun 2020; 11:3533. [PMID: 32669552 PMCID: PMC7363834 DOI: 10.1038/s41467-020-17228-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 06/11/2020] [Indexed: 01/08/2023] Open
Abstract
Cyclic dinucleotides (CDNs) are second messengers conserved across all three domains of life. Within eukaryotes they mediate protective roles in innate immunity against malignant, viral, and bacterial disease, and exert pathological effects in autoimmune disorders. Despite their ubiquitous role in diverse biological contexts, CDN detection methods are limited. Here, using structure guided design of the murine STING CDN binding domain, we engineer a Förster resonance energy transfer (FRET) based biosensor deemed BioSTING. Recombinant BioSTING affords real-time detection of CDN synthase activity and inhibition. Expression of BioSTING in live human cells allows quantification of localized bacterial and eukaryotic CDN levels in single cells with low nanomolar sensitivity. These findings establish BioSTING as a powerful kinetic in vitro platform amenable to high throughput screens and as a broadly applicable cellular tool to interrogate the temporal and spatial dynamics of CDN signaling in a variety of infectious, malignant, and autoimmune contexts.
Collapse
Affiliation(s)
- Alex J Pollock
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Shivam A Zaver
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA
| | - Joshua J Woodward
- Department of Microbiology, University of Washington, Seattle, WA, 98195, USA.
| |
Collapse
|
167
|
Zhang X, Bai XC, Chen ZJ. Structures and Mechanisms in the cGAS-STING Innate Immunity Pathway. Immunity 2020; 53:43-53. [PMID: 32668227 DOI: 10.1016/j.immuni.2020.05.013] [Citation(s) in RCA: 317] [Impact Index Per Article: 79.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 05/19/2020] [Accepted: 05/26/2020] [Indexed: 01/29/2023]
Abstract
Besides its role as the blueprint of life, DNA can also alert the cell to the presence of microbial pathogens as well as damaged or malignant cells. A major sensor of DNA that triggers the innate immune response is cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS), which produces the second messenger cGAMP. cGAMP activates stimulator of interferon genes (STING), which activates a signaling cascade leading to the production of type I interferons and other immune mediators. Recent research has demonstrated an expanding role of the cGAS-cGAMP-STING pathway in many physiological and pathological processes, including host defense against microbial infections, anti-tumor immunity, cellular senescence, autophagy, and autoimmune and inflammatory diseases. Biochemical and structural studies have elucidated the mechanism of signal transduction in the cGAS pathway at the atomic resolution. This review focuses on the structural and mechanistic insights into the roles of cGAS and STING in immunity and diseases revealed by these recent studies.
Collapse
Affiliation(s)
- Xuewu Zhang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Xiao-Chen Bai
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Zhijian J Chen
- Department of Molecular biology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Center for Inflammation Research, University of Texas Southwestern Medical Center, Dallas, TX, USA; Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| |
Collapse
|
168
|
Bartok E, Hartmann G. Immune Sensing Mechanisms that Discriminate Self from Altered Self and Foreign Nucleic Acids. Immunity 2020; 53:54-77. [PMID: 32668228 PMCID: PMC7359798 DOI: 10.1016/j.immuni.2020.06.014] [Citation(s) in RCA: 99] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 12/19/2022]
Abstract
All lifeforms have developed highly sophisticated systems equipped to detect altered self and non-self nucleic acids (NA). In vertebrates, NA-sensing receptors safeguard the integrity of the organism by detecting pathogens, dyshomeostasis and damage, and inducing appropriate responses to eliminate pathogens and reconstitute homeostasis. Effector mechanisms include i) immune signaling, ii) restriction of NA functions such as inhibition of mRNA translation, and iii) cell death pathways. An appropriate effector response is necessary for host defense, but dysregulated NA-sensing can lead to devastating autoimmune and autoinflammatory disease. Their inherent biochemical similarity renders the reliable distinction between self NA under homeostatic conditions and altered or exogenous NA particularly challenging. In this review, we provide an overview of recent progress in our understanding of the closely coordinated and regulated network of innate immune receptors, restriction factors, and nucleases to effectively respond to pathogens and maintain host integrity.
Collapse
Affiliation(s)
- Eva Bartok
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Gunther Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany.
| |
Collapse
|
169
|
Piras F, Kajaste-Rudnitski A. Antiviral immunity and nucleic acid sensing in haematopoietic stem cell gene engineering. Gene Ther 2020; 28:16-28. [PMID: 32661282 PMCID: PMC7357672 DOI: 10.1038/s41434-020-0175-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 07/06/2020] [Indexed: 02/06/2023]
Abstract
The low gene manipulation efficiency of human hematopoietic stem and progenitor cells (HSPC) remains a major hurdle for sustainable and broad clinical application of innovative therapies for a wide range of disorders. Given that all current and emerging gene transfer and editing technologies are bound to expose HSPC to exogenous nucleic acids and most often also to viral vectors, we reason that host antiviral factors and nucleic acid sensors play a pivotal role in the efficacy of HSPC genetic manipulation. Here, we review recent progress in our understanding of vector–host interactions and innate immunity in HSPC upon gene engineering and discuss how dissecting this crosstalk can guide the development of more stealth and efficient gene therapy approaches in the future.
Collapse
Affiliation(s)
- Francesco Piras
- San Raffaele Telethon Institute for Gene Therapy, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Anna Kajaste-Rudnitski
- San Raffaele Telethon Institute for Gene Therapy, IRCCS San Raffaele Scientific Institute, Milan, Italy.
| |
Collapse
|
170
|
Song B, Greco TM, Lum KK, Taber CE, Cristea IM. The DNA Sensor cGAS is Decorated by Acetylation and Phosphorylation Modifications in the Context of Immune Signaling. Mol Cell Proteomics 2020; 19:1193-1208. [PMID: 32345711 PMCID: PMC7338091 DOI: 10.1074/mcp.ra120.001981] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/23/2020] [Indexed: 12/25/2022] Open
Abstract
The cyclic GMP-AMP synthase (cGAS) protein is a pattern-recognition receptor of the mammalian innate immune system that is recognized as a main cytosolic sensor of pathogenic or damaged DNA. cGAS DNA binding initiates catalytic production of the second messenger, cyclic GMP-AMP, which activates the STING-TBK1-IRF3 signaling axis to induce cytokine expression. Post-translational modification (PTM) has started to be recognized as a critical component of cGAS regulation, yet the extent of these modifications remains unclear. Here, we report the identification and functional analysis of cGAS phosphorylations and acetylations in several cell types under basal and immune-stimulated conditions. cGAS was enriched by immunoaffinity purification from human primary fibroblasts prior to and after infection with herpes simplex virus type 1 (HSV-1), as well as from immune-stimulated STING-HEK293T cells. Six phosphorylations and eight acetylations were detected, of which eight PTMs were not previously documented. PTMs were validated by parallel reaction monitoring (PRM) mass spectrometry in fibroblasts, HEK293T cells, and THP-1 macrophage-like cells. Primary sequence and structural analysis of cGAS highlighted a subset of PTM sites with elevated surface accessibility and high evolutionary sequence conservation. To assess the functional relevance of each PTM, we generated a series of single-point cGAS mutations. Stable cell lines were constructed to express cGAS with amino acid substitutions that prevented phosphorylation (Ser-to-Ala) and acetylation (Lys-to-Arg) or that mimicked the modification state (Ser-to-Asp and Lys-to-Gln). cGAS-dependent apoptotic and immune signaling activities were then assessed for each mutation. Our results show that acetyl-mimic mutations at Lys384 and Lys414 inhibit the ability of cGAS to induce apoptosis. In contrast, the Lys198 acetyl-mimic mutation increased cGAS-dependent interferon signaling when compared with the unmodified charge-mimic. Moreover, targeted PRM quantification showed that Lys198 acetylation is decreased upon infections with two herpesviruses-HSV-1 and human cytomegalovirus (HCMV), highlighting this residue as a regulatory point during virus infection.
Collapse
Affiliation(s)
- Bokai Song
- Department of Molecular Biology, Princeton University, Princeton, New Jersey
| | - Todd M Greco
- Department of Molecular Biology, Princeton University, Princeton, New Jersey
| | - Krystal K Lum
- Department of Molecular Biology, Princeton University, Princeton, New Jersey
| | - Caroline E Taber
- Department of Molecular Biology, Princeton University, Princeton, New Jersey
| | - Ileana M Cristea
- Department of Molecular Biology, Princeton University, Princeton, New Jersey.
| |
Collapse
|
171
|
Cyclic GMP-AMP synthase promotes the inflammatory and autophagy responses in Huntington disease. Proc Natl Acad Sci U S A 2020; 117:15989-15999. [PMID: 32581130 PMCID: PMC7354937 DOI: 10.1073/pnas.2002144117] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Huntington disease (HD) is a genetic disorder caused by glutamine-expansion in the huntingtin (mHTT) protein, which affects motor, psychiatric, and cognitive function, but the mechanisms remain unclear. mHTT is known to induce DNA damage and affect autophagy, both associated with inflammatory responses, but what mediates all these were unknown. Here we report that cGAS, a DNA damage sensor, is highly upregulated in the striatum of a mouse model and HD human patient’s tissue. We found ribosomes, which make proteins, are robustly accumulated on the cGAS mRNA in HD cells. cGAS depletion decreases—and cGAS expression increases—both inflammatory and autophagy responses in HD striatal cells. Thus, cGAS is a therapeutic target for HD. Blocking cGAS will prevent/slow down HD symptoms. Huntington disease (HD) is caused by an expansion mutation of the N-terminal polyglutamine of huntingtin (mHTT). mHTT is ubiquitously present, but it induces noticeable damage to the brain’s striatum, thereby affecting motor, psychiatric, and cognitive functions. The striatal damage and progression of HD are associated with the inflammatory response; however, the underlying molecular mechanisms remain unclear. Here, we report that cGMP-AMP synthase (cGAS), a DNA sensor, is a critical regulator of inflammatory and autophagy responses in HD. Ribosome profiling revealed that the cGAS mRNA has high ribosome occupancy at exon 1 and codon-specific pauses at positions 171 (CCG) and 172 (CGT) in HD striatal cells. Moreover, the protein levels and activity of cGAS (based on the phosphorylated STING and phosphorylated TBK1 levels), and the expression and ribosome occupancy of cGAS-dependent inflammatory genes (Ccl5 and Cxcl10) are increased in HD striatum. Depletion of cGAS diminishes cGAS activity and decreases the expression of inflammatory genes while suppressing the up-regulation of autophagy in HD cells. In contrast, reinstating cGAS in cGAS-depleted HD cells activates cGAS activity and promotes inflammatory and autophagy responses. Ribosome profiling also revealed that LC3A and LC3B, the two major autophagy initiators, show altered ribosome occupancy in HD cells. We also detected the presence of numerous micronuclei, which are known to induce cGAS, in the cytoplasm of neurons derived from human HD embryonic stem cells. Collectively, our results indicate that cGAS is up-regulated in HD and mediates inflammatory and autophagy responses. Thus, targeting the cGAS pathway may offer therapeutic benefits in HD.
Collapse
|
172
|
Regulation and Consequences of cGAS Activation by Self-DNA. Trends Cell Biol 2020; 30:594-605. [PMID: 32546434 DOI: 10.1016/j.tcb.2020.05.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 02/07/2023]
Abstract
Cyclic GMP-AMP (cGAMP) synthase (cGAS) is a major responder to the pathogenic DNA of viruses and bacteria. Upon DNA binding, cGAS becomes enzymatically active to generate the second messenger cGAMP, leading to activation of inflammatory genes, type I interferon production, autophagy, and cell death. Following genotoxic stress, cGAS can also respond to endogenous DNA, deriving from mitochondria, endogenous retroelements, and chromosomes to affect cellular signaling, secretion, and cell fate decisions. However, under unperturbed conditions, signaling from self-DNA is largely, but not completely, inhibited. Here we review how endogenous DNA is exposed to cGAS, how signaling is attenuated but activated under pathological conditions, and how low-level signaling under unperturbed conditions might prime antipathogenic responses.
Collapse
|
173
|
Hopfner KP, Hornung V. Molecular mechanisms and cellular functions of cGAS-STING signalling. Nat Rev Mol Cell Biol 2020; 21:501-521. [PMID: 32424334 DOI: 10.1038/s41580-020-0244-x] [Citation(s) in RCA: 834] [Impact Index Per Article: 208.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2020] [Indexed: 02/07/2023]
Abstract
The cGAS-STING signalling axis, comprising the synthase for the second messenger cyclic GMP-AMP (cGAS) and the cyclic GMP-AMP receptor stimulator of interferon genes (STING), detects pathogenic DNA to trigger an innate immune reaction involving a strong type I interferon response against microbial infections. Notably however, besides sensing microbial DNA, the DNA sensor cGAS can also be activated by endogenous DNA, including extranuclear chromatin resulting from genotoxic stress and DNA released from mitochondria, placing cGAS-STING as an important axis in autoimmunity, sterile inflammatory responses and cellular senescence. Initial models assumed that co-localization of cGAS and DNA in the cytosol defines the specificity of the pathway for non-self, but recent work revealed that cGAS is also present in the nucleus and at the plasma membrane, and such subcellular compartmentalization was linked to signalling specificity of cGAS. Further confounding the simple view of cGAS-STING signalling as a response mechanism to infectious agents, both cGAS and STING were shown to have additional functions, independent of interferon response. These involve non-catalytic roles of cGAS in regulating DNA repair and signalling via STING to NF-κB and MAPK as well as STING-mediated induction of autophagy and lysosome-dependent cell death. We have also learnt that cGAS dimers can multimerize and undergo liquid-liquid phase separation to form biomolecular condensates that could importantly regulate cGAS activation. Here, we review the molecular mechanisms and cellular functions underlying cGAS-STING activation and signalling, particularly highlighting the newly emerging diversity of this signalling pathway and discussing how the specificity towards normal, damage-induced and infection-associated DNA could be achieved.
Collapse
Affiliation(s)
- Karl-Peter Hopfner
- Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany. .,Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.
| | - Veit Hornung
- Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany. .,Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.
| |
Collapse
|
174
|
Zhong L, Hu MM, Bian LJ, Liu Y, Chen Q, Shu HB. Phosphorylation of cGAS by CDK1 impairs self-DNA sensing in mitosis. Cell Discov 2020; 6:26. [PMID: 32351706 PMCID: PMC7186227 DOI: 10.1038/s41421-020-0162-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 03/12/2020] [Indexed: 12/17/2022] Open
Abstract
The cyclic GMP-AMP synthase (cGAS) is a widely used DNA sensor, which detects cytosolic DNA species without a preference of self or non-self microbial DNA in interphase to initiate innate immune response. How cGAS is regulated to avoid self-DNA sensing upon nuclear envelope breakdown (NEBD) during mitosis remains enigmatic. Here we show that cGAS is mostly localized in the cytoplasm in interphase and rapidly translocated to chromosomes upon NEBD in mitosis. The major mitotic kinase CDK1-cyclin B complex phosphorylates human cGAS at S305 or mouse cGAS at S291, which inhibits its ability to synthesize cGAMP upon mitotic entry. The type 1 phosphatase PP1 dephosphorylates cGAS upon mitotic exit to enable its DNA sensing ability. Our findings reveal a mechanism on how the DNA sensor cGAS is post-translationally regulated by cell cycle-dependent enzymes to ensure its proper activation for host defense of cytosolic DNA in interphase and inert to self-DNA in mitosis.
Collapse
Affiliation(s)
- Li Zhong
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| | - Ming-Ming Hu
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| | - Li-Jun Bian
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| | - Ying Liu
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| | - Qiang Chen
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| | - Hong-Bing Shu
- Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Frontier Science Center for Immunology and Metabolism Medical Research Institute, Wuhan University, Wuhan, 430071 China
| |
Collapse
|
175
|
Brooks W. An Epigenetics-Based Hypothesis of Autoantigen Development in Systemic Lupus Erythematosus. EPIGENOMES 2020; 4:epigenomes4020006. [PMID: 34968240 PMCID: PMC8594704 DOI: 10.3390/epigenomes4020006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 04/20/2020] [Indexed: 11/16/2022] Open
Abstract
Currently, we have a limited understanding of mechanisms leading to systemic lupus erythematosus, but we know that genetics, environmental factors, and epigenetics contribute to the disease. One common aspect of the various environmental triggers is that they can cause cellular stress. When extraordinary stress occurs, such as viral activation, a cell's response can include increased nucleolar volume and activity to produce more machinery (e.g., ribosomes) to help the cell recover. However, nucleolar expansion can disrupt the epigenetic control in neighboring heterochromatin that comprises the nucleolar shell. This disruption can open underlying vulnerabilities that provoke an autoimmune reaction. Here, we review the "X chromosome-nucleolus nexus" hypothesis, which explains how nucleolar stress can disrupt epigenetically silenced chromatin, especially the neighboring inactive X chromosome (aka the nucleolar satellite). Chromatin disruption can lead to the expression of sequestered DNA, such as Alu elements and fully functional LINE-1 reverse transcriptase genes. In addition, Alu transcripts can disrupt the nucleolar structural integrity, leading to nucleolar disintegration. Such disintegration can leave nucleolar components and products in autoantigenic forms, such as abnormal conformations or incomplete macromolecular assemblies. Recent research on DNA sensing pathways can now be incorporated into the hypothesis to provide further details explaining how autoantibodies to endogenous nucleic acids arise.
Collapse
Affiliation(s)
- Wesley Brooks
- Department of Chemistry, University of South Florida, Tampa, FL 33620, USA
| |
Collapse
|
176
|
Riley JS, Tait SW. Mitochondrial DNA in inflammation and immunity. EMBO Rep 2020; 21:e49799. [PMID: 32202065 PMCID: PMC7132203 DOI: 10.15252/embr.201949799] [Citation(s) in RCA: 420] [Impact Index Per Article: 105.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 01/31/2020] [Accepted: 03/03/2020] [Indexed: 12/14/2022] Open
Abstract
Mitochondria are cellular organelles that orchestrate a vast range of biological processes, from energy production and metabolism to cell death and inflammation. Despite this seemingly symbiotic relationship, mitochondria harbour within them a potent agonist of innate immunity: their own genome. Release of mitochondrial DNA into the cytoplasm and out into the extracellular milieu activates a plethora of different pattern recognition receptors and innate immune responses, including cGAS‐STING, TLR9 and inflammasome formation leading to, among others, robust type I interferon responses. In this Review, we discuss how mtDNA can be released from the mitochondria, the various inflammatory pathways triggered by mtDNA release and its myriad biological consequences for health and disease.
Collapse
Affiliation(s)
- Joel S Riley
- Cancer Research UK Beatson Institute, Glasgow, UK.,Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Stephen Wg Tait
- Cancer Research UK Beatson Institute, Glasgow, UK.,Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| |
Collapse
|
177
|
Ma H, Qian W, Bambouskova M, Collins PL, Porter SI, Byrum AK, Zhang R, Artyomov M, Oltz EM, Mosammaparast N, Miner JJ, Diamond MS. Barrier-to-Autointegration Factor 1 Protects against a Basal cGAS-STING Response. mBio 2020; 11:e00136-20. [PMID: 32156810 PMCID: PMC7064753 DOI: 10.1128/mbio.00136-20] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 02/03/2020] [Indexed: 12/26/2022] Open
Abstract
Although the pathogen recognition receptor pathways that activate cell-intrinsic antiviral responses are well delineated, less is known about how the host regulates this response to prevent sustained signaling and possible immune-mediated damage. Using a genome-wide CRISPR-Cas9 screening approach to identify host factors that modulate interferon-stimulated gene (ISG) expression, we identified the DNA binding protein Barrier-to-autointegration factor 1 (Banf1), a previously described inhibitor of retrovirus integration, as a modulator of basal cell-intrinsic immunity. Ablation of Banf1 by gene editing resulted in chromatin activation near host defense genes with associated increased expression of ISGs, including Oas2, Rsad2 (viperin), Ifit1, and ISG15 The phenotype in Banf1-deficient cells occurred through a cGAS-, STING-, and IRF3-dependent signaling axis, was associated with reduced infection of RNA and DNA viruses, and was reversed in Banf1 complemented cells. Confocal microscopy and biochemical studies revealed that a loss of Banf1 expression resulted in higher level of cytosolic double-stranded DNA at baseline. Our study identifies an undescribed role for Banf1 in regulating the levels of cytoplasmic DNA and cGAS-dependent ISG homeostasis and suggests possible therapeutic directions for promoting or inhibiting cell-intrinsic innate immune responses.IMPORTANCE Although the interferon (IFN) signaling pathway is a key host mechanism to restrict infection of a diverse range of viral pathogens, its unrestrained activity either at baseline or in the context of an immune response can result in host cell damage and injury. Here, we used a genome-wide CRISPR-Cas9 screen and identified the DNA binding protein Barrier-to-autointegration factor 1 (Banf1) as a modulator of basal cell-intrinsic immunity. A loss of Banf1 expression resulted in higher level of cytosolic double-stranded DNA at baseline, which triggered IFN-stimulated gene expression via a cGAS-STING-IRF3 axis that did not require type I IFN or STAT1 signaling. Our experiments define a regulatory network in which Banf1 limits basal inflammation by preventing self DNA accumulation in the cytosol.
Collapse
Affiliation(s)
- Hongming Ma
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Wei Qian
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Monika Bambouskova
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Patrick L Collins
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
| | - Sofia I Porter
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
| | - Andrea K Byrum
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Rong Zhang
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Maxim Artyomov
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Eugene M Oltz
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
| | - Nima Mosammaparast
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Jonathan J Miner
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
- Andrew M. and Jane M. Bursky Center for Human Immunology and Immunotherapy Programs, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael S Diamond
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
- Andrew M. and Jane M. Bursky Center for Human Immunology and Immunotherapy Programs, Washington University School of Medicine, St. Louis, Missouri, USA
| |
Collapse
|