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de Reuver R, Maelfait J. Novel insights into double-stranded RNA-mediated immunopathology. Nat Rev Immunol 2024; 24:235-249. [PMID: 37752355 DOI: 10.1038/s41577-023-00940-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2023] [Indexed: 09/28/2023]
Abstract
Recent progress in human and mouse genetics has transformed our understanding of the molecular mechanisms by which recognition of self double-stranded RNA (self-dsRNA) causes immunopathology. Novel mouse models recapitulate loss-of-function mutations in the RNA editing enzyme ADAR1 that are found in patients with Aicardi-Goutières syndrome (AGS) - a monogenic inflammatory disease associated with increased levels of type I interferon. Extensive analyses of the genotype-phenotype relationships in these mice have now firmly established a causal relationship between increased intracellular concentrations of endogenous immunostimulatory dsRNA and type I interferon-driven immunopathology. Activation of the dsRNA-specific immune sensor MDA5 perpetuates the overproduction of type I interferons, and chronic engagement of the interferon-inducible innate immune receptors PKR and ZBP1 by dsRNA drives immunopathology by activating an integrated stress response or by inducing excessive cell death. Biochemical and genetic data support a role for the p150 isoform of ADAR1 in the cytosol in suppressing the spontaneous, pathological response to self-dsRNA.
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Affiliation(s)
- Richard de Reuver
- VIB-UGent Center for Inflammation Research, Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Jonathan Maelfait
- VIB-UGent Center for Inflammation Research, Ghent, Belgium.
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
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2
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Nichols PJ, Welty R, Krall JB, Henen MA, Vicens Q, Vögeli B. Zα Domain of ADAR1 Binds to an A-Form-like Nucleic Acid Duplex with Low Micromolar Affinity. Biochemistry 2024; 63:777-787. [PMID: 38437710 DOI: 10.1021/acs.biochem.3c00636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2024]
Abstract
The left-handed Z-conformation of nucleic acids can be adopted by both DNA and RNA when bound by Zα domains found within a variety of viral and innate immune response proteins. While Z-form adoption is preferred by certain sequences, such as the commonly studied (CpG)n repeats, Zα has been reported to bind to a wide range of sequence contexts. Studying how Zα interacts with B-/A-form helices prior to their conversion to the Z-conformation is challenging as binding coincides with Z-form adoption. Here, we studied the binding of Zα fromHomo sapiens ADAR1 to a locked "A-type" version of the (CpG)3 construct (LNA (CpG)3) where the sugar pucker is locked into the C3'-endo/C2'-exo conformation, which prevents the duplex from adopting the alternating C2'/C3'-endo sugar puckers found in the Z-conformation. Using NMR and other biophysical techniques, we find that ZαADAR1 binds to the LNA (CpG)3 using a similar interface as for Z-form binding, with a dissociation constant (KD) of ∼4 μM. In contrast to Z-DNA/Z-RNA, where two ZαADAR1 bind to every 6 bp stretch, our data suggests that ZαADAR1 binds to multiple LNA molecules, indicating a completely different binding mode. Because ZαADAR1 binds relatively tightly to a non-Z-form model, its binding to B/A-form helices may need to be considered when experiments are carried out which attempt to identify the Z-form targets of Zα domains. The use of LNA constructs may be beneficial in experiments where negative controls for Z-form adoption are needed.
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Affiliation(s)
- Parker J Nichols
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Robb Welty
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Jeffrey B Krall
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Morkos A Henen
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
- Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - Quentin Vicens
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
- RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
- Department of Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, Texas 77204, United States
| | - Beat Vögeli
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
- RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, United States
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Luan X, Wang L, Song G, Zhou W. Innate immune responses to RNA: sensing and signaling. Front Immunol 2024; 15:1287940. [PMID: 38343534 PMCID: PMC10854198 DOI: 10.3389/fimmu.2024.1287940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 01/11/2024] [Indexed: 02/15/2024] Open
Abstract
Nucleic acids are among the most essential PAMPs (pathogen-associated molecular patterns). Animals have evolved numerous sensors to recognize nucleic acids and trigger immune signaling against pathogen replication, cellular stress and cancer. Many sensor proteins (e.g., cGAS, AIM2, and TLR9) recognize the molecular signature of infection or stress and are responsible for the innate immune response to DNA. Remarkably, recent evidence demonstrates that cGAS-like receptors acquire the ability to sense RNA in some forms of life. Compared with the nucleic-acid sensing by cGAS, innate immune responses to RNA are based on various RNA sensors, including RIG-I, MDA5, ADAR1, TLR3/7/8, OAS1, PKR, NLRP1/6, and ZBP1, via a broad-spectrum signaling axis. Importantly, new advances have brought to light the potential clinical application of targeting these signaling pathways. Here, we highlight the latest discoveries in the field. We also summarize the activation and regulatory mechanisms of RNA-sensing signaling. In addition, we discuss how RNA sensing is tightly controlled in cells and why the disruption of immune homeostasis is linked to disease.
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Affiliation(s)
- Xiaohan Luan
- Shenzhen Key Laboratory of Biomolecular Assembling and Regulation, Southern University of Science and Technology, Shenzhen, Guangdong, China
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Lei Wang
- Department of Systems Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Guangji Song
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Wen Zhou
- Shenzhen Key Laboratory of Biomolecular Assembling and Regulation, Southern University of Science and Technology, Shenzhen, Guangdong, China
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
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Nichols PJ, Krall JB, Henen MA, Welty R, Macfadden A, Vicens Q, Vögeli B. Z-Form Adoption of Nucleic Acid is a Multi-Step Process Which Proceeds through a Melted Intermediate. J Am Chem Soc 2024; 146:677-694. [PMID: 38131335 DOI: 10.1021/jacs.3c10406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
The left-handed Z-conformation of nucleic acids can be adopted by both DNA and RNA when bound by Zα domains found within a variety of innate immune response proteins. Zα domains stabilize this higher-energy conformation by making specific interactions with the unique geometry of Z-DNA/Z-RNA. However, the mechanism by which a right-handed helix contorts to become left-handed in the presence of proteins, including the intermediate steps involved, is poorly understood. Through a combination of nuclear magnetic resonance (NMR) and other biophysical measurements, we have determined that in the absence of Zα, under low salt conditions at room temperature, d(CpG) and r(CpG) constructs show no observable evidence of transient Z-conformations greater than 0.5% on either the intermediate or slow NMR time scales. At higher temperatures, we observed a transient unfolded intermediate. The ease of melting a nucleic acid duplex correlates with Z-form adoption rates in the presence of Zα. The largest contributing factor to the activation energies of Z-form adoption as calculated by Arrhenius plots is the ease of flipping the sugar pucker, as required for Z-DNA and Z-RNA. Together, these data validate the previously proposed "zipper model" for Z-form adoption in the presence of Zα. Overall, Z-conformations are more likely to be adopted by double-stranded DNA and RNA regions flanked by less stable regions and by RNAs experiencing torsional/mechanical stress.
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Affiliation(s)
- Parker J Nichols
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
| | - Jeffrey B Krall
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
| | - Morkos A Henen
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
- Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - Robb Welty
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
| | - Andrea Macfadden
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
| | - Quentin Vicens
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
- RNA Bioscience Initiative, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
| | - Beat Vögeli
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, United States
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Escobar CA, Petersen RJ, Tonelli M, Fan L, Henzler-Wildman KA, Butcher SE. Solution Structure of Poly(UG) RNA. J Mol Biol 2023; 435:168340. [PMID: 37924862 PMCID: PMC10841838 DOI: 10.1016/j.jmb.2023.168340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/27/2023] [Accepted: 10/29/2023] [Indexed: 11/06/2023]
Abstract
Poly(UG) or "pUG" RNAs are UG or GU dinucleotide repeat sequences which are highly abundant in eukaryotes. Post-transcriptional addition of pUGs to RNA 3' ends marks mRNAs as vectors for gene silencing in C. elegans. We previously determined the crystal structure of pUG RNA bound to the ligand N-methyl mesoporphyrin IX (NMM), but the structure of free pUG RNA is unknown. Here we report the solution structure of the free pUG RNA (GU)12, as determined by nuclear magnetic resonance spectroscopy and small and wide-angle x-ray scattering (NMR-SAXS-WAXS). The low complexity sequence and 4-fold symmetry of the structure result in overlapped NMR signals that complicate chemical shift assignment. We therefore utilized single site-specific deoxyribose modifications which did not perturb the structure and introduced well-resolved methylene signals that are easily identified in NMR spectra. The solution structure ensemble has a root mean squared deviation (RMSD) of 0.62 Å and is a compact, left-handed quadruplex with a Z-form backbone, or "pUG fold." Overall, the structure agrees with the crystal structure of (GU)12 bound to NMM, indicating the pUG fold is unaltered by docking of the NMM ligand. The solution structure reveals conformational details that could not be resolved by x-ray crystallography, which explain how the pUG fold can form within longer RNAs.
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Affiliation(s)
- Cristian A Escobar
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Riley J Petersen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Marco Tonelli
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA; National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI, USA
| | - Lixin Fan
- Basic Science Program, Frederick National Laboratory for Cancer Research, SAXS Core Facility of National Cancer Institute, Frederick, MD, USA
| | - Katherine A Henzler-Wildman
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA; National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA; National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI, USA.
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Maelfait J, Rehwinkel J. The Z-nucleic acid sensor ZBP1 in health and disease. J Exp Med 2023; 220:e20221156. [PMID: 37450010 PMCID: PMC10347765 DOI: 10.1084/jem.20221156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 06/28/2023] [Accepted: 07/05/2023] [Indexed: 07/18/2023] Open
Abstract
Nucleic acid sensing is a central process in the immune system, with far-reaching roles in antiviral defense, autoinflammation, and cancer. Z-DNA binding protein 1 (ZBP1) is a sensor for double-stranded DNA and RNA helices in the unusual left-handed Z conformation termed Z-DNA and Z-RNA. Recent research established ZBP1 as a key upstream regulator of cell death and proinflammatory signaling. Recognition of Z-DNA/RNA by ZBP1 promotes host resistance to viral infection but can also drive detrimental autoinflammation. Additionally, ZBP1 has interesting roles in cancer and other disease settings and is emerging as an attractive target for therapy.
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Affiliation(s)
- Jonathan Maelfait
- VIB-UGent Center for Inflammation Research, Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Jan Rehwinkel
- Medical Research Council Human Immunology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
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DeAntoneo C, Herbert A, Balachandran S. Z-form nucleic acid-binding protein 1 (ZBP1) as a sensor of viral and cellular Z-RNAs: walking the razor's edge. Curr Opin Immunol 2023; 83:102347. [PMID: 37276820 PMCID: PMC10526625 DOI: 10.1016/j.coi.2023.102347] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/01/2023] [Accepted: 05/02/2023] [Indexed: 06/07/2023]
Abstract
Z-form nucleic acid-binding protein 1 (ZBP1) detects viral Z-form RNAs (Z-RNAs), activates receptor-interacting protein kinase 3, and triggers cell death during both RNA and DNA virus infections. Such cell death promotes virus clearance by eliminating infected cells and galvanizing antiviral immunity, and is thus often targeted for evasion by virus-encoded suppressors. Recent evidence demonstrates that ZBP1 can also be activated by cellular Z-RNAs transcribed from endogenous retroelements within mammalian genomes. These cellular Z-RNAs, if not edited and neutralized by adenosine deaminase RNA-specific 1, trigger ZBP1-dependent cell death and inflammation, which may drive disease in Aicardi-Goutière's syndrome and related interferonopathies. Thus, while well-controlled activation of ZBP1 by viral Z-RNAs during infections is beneficial, the same pathway can have harmful consequences when inappropriately triggered by cellular Z-RNAs in other disease settings.
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Affiliation(s)
- Carly DeAntoneo
- Drexel University College of Medicine, 2900 W. Queen Lane, Philadelphia, PA 19129, USA; Center for Immunology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Alan Herbert
- InsideOutBio, 42 8th Street, Charlestown, MA, USA
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Bartas M, Slychko K, Červeň J, Pečinka P, Arndt-Jovin DJ, Jovin TM. Extensive Bioinformatics Analyses Reveal a Phylogenetically Conserved Winged Helix (WH) Domain (Zτ) of Topoisomerase IIα, Elucidating Its Very High Affinity for Left-Handed Z-DNA and Suggesting Novel Putative Functions. Int J Mol Sci 2023; 24:10740. [PMID: 37445918 DOI: 10.3390/ijms241310740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 06/13/2023] [Accepted: 06/22/2023] [Indexed: 07/15/2023] Open
Abstract
The dynamic processes operating on genomic DNA, such as gene expression and cellular division, lead inexorably to topological challenges in the form of entanglements, catenanes, knots, "bubbles", R-loops, and other outcomes of supercoiling and helical disruption. The resolution of toxic topological stress is the function attributed to DNA topoisomerases. A prominent example is the negative supercoiling (nsc) trailing processive enzymes such as DNA and RNA polymerases. The multiple equilibrium states that nscDNA can adopt by redistribution of helical twist and writhe include the left-handed double-helical conformation known as Z-DNA. Thirty years ago, one of our labs isolated a protein from Drosophila cells and embryos with a 100-fold greater affinity for Z-DNA than for B-DNA, and identified it as topoisomerase II (gene Top2, orthologous to the human UniProt proteins TOP2A and TOP2B). GTP increased the affinity and selectivity for Z-DNA even further and also led to inhibition of the isomerase enzymatic activity. An allosteric mechanism was proposed, in which topoII acts as a Z-DNA-binding protein (ZBP) to stabilize given states of topological (sub)domains and associated multiprotein complexes. We have now explored this possibility by comprehensive bioinformatic analyses of the available protein sequences of topoII representing organisms covering the whole tree of life. Multiple alignment of these sequences revealed an extremely high level of evolutionary conservation, including a winged-helix protein segment, here denoted as Zτ, constituting the putative structural homolog of Zα, the canonical Z-DNA/Z-RNA binding domain previously identified in the interferon-inducible RNA Adenosine-to-Inosine-editing deaminase, ADAR1p150. In contrast to Zα, which is separate from the protein segment responsible for catalysis, Zτ encompasses the active site tyrosine of topoII; a GTP-binding site and a GxxG sequence motif are in close proximity. Quantitative Zτ-Zα similarity comparisons and molecular docking with interaction scoring further supported the "B-Z-topoII hypothesis" and has led to an expanded mechanism for topoII function incorporating the recognition of Z-DNA segments ("Z-flipons") as an inherent and essential element. We further propose that the two Zτ domains of the topoII homodimer exhibit a single-turnover "conformase" activity on given G(ate) B-DNA segments ("Z-flipins"), inducing their transition to the left-handed Z-conformation. Inasmuch as the topoII-Z-DNA complexes are isomerase inactive, we infer that they fulfill important structural roles in key processes such as mitosis. Topoisomerases are preeminent targets of anti-cancer drug discovery, and we anticipate that detailed elucidation of their structural-functional interactions with Z-DNA and GTP will facilitate the design of novel, more potent and selective anti-cancer chemotherapeutic agents.
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Affiliation(s)
- Martin Bartas
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Kristyna Slychko
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Jiří Červeň
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Petr Pečinka
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Donna J Arndt-Jovin
- Emeritus Laboratory of Cellular Dynamics, Max Planck Institute for Multidisciplinary Sciences, 37077 Göttingen, Germany
| | - Thomas M Jovin
- Emeritus Laboratory of Cellular Dynamics, Max Planck Institute for Multidisciplinary Sciences, 37077 Göttingen, Germany
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