1
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Villanueva Valencia JR, Li D, Casjens SR, Evilevitch A. 'SAXS-osmometer' method provides measurement of DNA pressure in viral capsids and delivers an empirical equation of state. Nucleic Acids Res 2023; 51:11415-11427. [PMID: 37889048 PMCID: PMC10681747 DOI: 10.1093/nar/gkad852] [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] [Received: 05/16/2023] [Revised: 09/21/2023] [Accepted: 09/30/2023] [Indexed: 10/28/2023] Open
Abstract
We present a novel method that provides a measurement of DNA pressure in viral capsids using small angle X-ray scattering (SAXS). This method, unlike our previous assay, does not require triggering genome release with a viral receptor. Thus, it can be used to determine the existence of a pressurized genome state in a wide range of virus systems, even if the receptor is not known, leading to a better understanding of the processes of viral genome uncoating and encapsidation in the course of infection. Furthermore, by measuring DNA pressure for a collection of bacteriophages with varying DNA packing densities, we derived an empirical equation of state (EOS) that accurately predicts the relation between the capsid pressure and the packaged DNA density and includes the contribution of both DNA-DNA interaction energy and DNA bending stress to the total DNA pressure. We believe that our SAXS-osmometer method and the EOS, combined, provide the necessary tools to investigate physico-chemical properties of confined DNA condensates and mechanisms of infection, and may also provide essential data for the design of viral vectors in gene therapy applications and development of antivirals that target the pressurized genome state.
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Affiliation(s)
| | - Dong Li
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Sherwood R Casjens
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Alex Evilevitch
- Department of Experimental Medical Science and NanoLund, Lund University, Box 124, Lund, Sweden
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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2
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Villanueva Valencia JR, Tsimtsirakis E, Krueger S, Evilevitch A. Temperature-induced DNA density transition in phage λ capsid revealed with contrast-matching SANS. Proc Natl Acad Sci U S A 2023; 120:e2220518120. [PMID: 37903276 PMCID: PMC10636372 DOI: 10.1073/pnas.2220518120] [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: 12/04/2022] [Accepted: 09/25/2023] [Indexed: 11/01/2023] Open
Abstract
Structural details of a genome packaged in a viral capsid are essential for understanding how the structural arrangement of a viral genome in a capsid controls its release dynamics during infection, which critically affects viral replication. We previously found a temperature-induced, solid-like to fluid-like mechanical transition of packaged λ-genome that leads to rapid DNA ejection. However, an understanding of the structural origin of this transition was lacking. Here, we use small-angle neutron scattering (SANS) to reveal the scattering form factor of dsDNA packaged in phage λ capsid by contrast matching the scattering signal from the viral capsid with deuterated buffer. We used small-angle X-ray scattering and cryoelectron microscopy reconstructions to determine the initial structural input parameters for intracapsid DNA, which allows accurate modeling of our SANS data. As result, we show a temperature-dependent density transition of intracapsid DNA occurring between two coexisting phases-a hexagonally ordered high-density DNA phase in the capsid periphery and a low-density, less-ordered DNA phase in the core. As the temperature is increased from 20 °C to 40 °C, we found that the core-DNA phase undergoes a density and volume transition close to the physiological temperature of infection (~37 °C). The transition yields a lower energy state of DNA in the capsid core due to lower density and reduced packing defects. This increases DNA mobility, which is required to initiate rapid genome ejection from the virus capsid into a host cell, causing infection. These data reconcile our earlier findings of mechanical DNA transition in phage.
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Affiliation(s)
| | - Efthymios Tsimtsirakis
- Department of Experimental Medical Science and NanoLund, Lund University, Lund22184, Sweden
| | - Susan Krueger
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD20899-6102
| | - Alex Evilevitch
- Department of Experimental Medical Science and NanoLund, Lund University, Lund22184, Sweden
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3
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Abstract
Biomolecular condensates formed by phase separation are widespread and play critical roles in many physiological and pathological processes. cGAS-STING signaling functions to detect aberrant DNA signals to initiate anti-infection defense and antitumor immunity. At the same time, cGAS-STING signaling must be carefully regulated to maintain immune homeostasis. Interestingly, exciting recent studies have reported that biomolecular phase separation exists and plays important roles in different steps of cGAS-STING signaling, including cGAS condensates, STING condensates, and IRF3 condensates. In addition, several intracellular and extracellular factors have been proposed to modulate the condensates in cGAS-STING signaling. These studies reveal novel activation and regulation mechanisms of cGAS-STING signaling and provide new opportunities for drug discovery. Here, we summarize recent advances in the phase separation of cGAS-STING signaling and the development of potential drugs targeting these innate immune condensates.
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Affiliation(s)
- Quanjin Li
- CAS Key Laboratory of Infection and Immunity, National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Pu Gao
- CAS Key Laboratory of Infection and Immunity, National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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4
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Bong S, Park CB, Cho SG, Bae J, Hapsari N, Jin X, Heo S, Lee JE, Hashiya K, Bando T, Sugiyama H, Jung KH, Sung B, Jo K. AT-specific DNA visualization revisits the directionality of bacteriophage λ DNA ejection. Nucleic Acids Res 2023; 51:5634-5646. [PMID: 37158237 PMCID: PMC10287942 DOI: 10.1093/nar/gkad340] [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] [Received: 10/18/2022] [Revised: 03/14/2023] [Accepted: 04/21/2023] [Indexed: 05/10/2023] Open
Abstract
In this study, we specifically visualized DNA molecules at their AT base pairs after in vitro phage ejection. Our AT-specific visualization revealed that either end of the DNA molecule could be ejected first with a nearly 50% probability. This observation challenges the generally accepted theory of Last In First Out (LIFO), which states that the end of the phage λ DNA that enters the capsid last during phage packaging is the first to be ejected, and that both ends of the DNA are unable to move within the extremely condensed phage capsid. To support our observations, we conducted computer simulations that revealed that both ends of the DNA molecule are randomized, resulting in the observed near 50% probability. Additionally, we found that the length of the ejected DNA by LIFO was consistently longer than that by First In First Out (FIFO) during in vitro phage ejection. Our simulations attributed this difference in length to the stiffness difference of the remaining DNA within the phage capsid. In conclusion, this study demonstrates that a DNA molecule within an extremely dense phage capsid exhibits a degree of mobility, allowing it to switch ends during ejection.
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Affiliation(s)
- Serang Bong
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Shin-Gyu Cho
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Jaeyoung Bae
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Natalia Diyah Hapsari
- Department of Chemistry, Sogang University, Seoul 04107, Korea
- Chemistry Education Program, Department of Mathematics and Science Education, Sanata Dharma University, Yogyakarta 55282, Indonesia
| | - Xuelin Jin
- Department of Chemistry, Sogang University, Seoul 04107, Korea
- College of Agriculture, Yanbian University, Yanji133000, China
| | - Sujung Heo
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Ji-eun Lee
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Kaori Hashiya
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Toshikazu Bando
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-Ku, Kyoto606-8502, Japan
| | - Kwang-Hwan Jung
- Department of Life Science, Sogang University, Seoul 04107, Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Korea
| | - Kyubong Jo
- Department of Chemistry, Sogang University, Seoul 04107, Korea
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5
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Wang L, Li S, Wang K, Wang N, Liu Q, Sun Z, Wang L, Wang L, Liu Q, Song C, Yang Q. Spermine enhances antiviral and anticancer responses by stabilizing DNA binding with the DNA sensor cGAS. Immunity 2023; 56:272-288.e7. [PMID: 36724787 DOI: 10.1016/j.immuni.2023.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 10/25/2022] [Accepted: 01/04/2023] [Indexed: 02/03/2023]
Abstract
Self-nonself discrimination is vital for the immune system to mount responses against pathogens while maintaining tolerance toward the host and innocuous commensals during homeostasis. Here, we investigated how indiscriminate DNA sensors, such as cyclic GMP-AMP synthase (cGAS), make this self-nonself distinction. Screening of a small-molecule library revealed that spermine, a well-known DNA condenser associated with viral DNA, markedly elevates cGAS activation. Mechanistically, spermine condenses DNA to enhance and stabilize cGAS-DNA binding, optimizing cGAS and downstream antiviral signaling. Spermine promotes condensation of viral, but not host nucleosome, DNA. Deletion of viral DNA-associated spermine, by propagating virus in spermine-deficient cells, reduced cGAS activation. Spermine depletion subsequently attenuated cGAS-mediated antiviral and anticancer immunity. Collectively, our results reveal a pathogenic DNA-associated molecular pattern that facilitates nonself recognition, linking metabolism and pathogen recognition.
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Affiliation(s)
- Lina Wang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Siru Li
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Kai Wang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Na Wang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Qiaoling Liu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Zhen Sun
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Li Wang
- CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Lulu Wang
- School of Life Science and Biotechnology, Dalian University of Technology, No. 2 Linggong Road, Dalian, Liaoning 116024, China
| | - Quentin Liu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangzhou 510060, China
| | - Chengli Song
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China.
| | - Qingkai Yang
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, Liaoning 116044, China.
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6
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Park CB, Sung BJ. Effects of Packaging History on the Ejection of a Polymer Chain from a Small Confinement. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00857] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Chung Bin Park
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
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7
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Brandariz-Nuñez A, Robinson SJ, Evilevitch A. Pressurized DNA state inside herpes capsids-A novel antiviral target. PLoS Pathog 2020; 16:e1008604. [PMID: 32702029 PMCID: PMC7377361 DOI: 10.1371/journal.ppat.1008604] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 05/05/2020] [Indexed: 01/25/2023] Open
Abstract
Drug resistance in viruses represents one of the major challenges of healthcare. As part of an effort to provide a treatment that avoids the possibility of drug resistance, we discovered a novel mechanism of action (MOA) and specific compounds to treat all nine human herpesviruses and animal herpesviruses. The novel MOA targets the pressurized genome state in a viral capsid, "turns off" capsid pressure, and blocks viral genome ejection into a cell nucleus, preventing viral replication. This work serves as a proof-of-concept to demonstrate the feasibility of a new antiviral target-suppressing pressure-driven viral genome ejection-that is likely impervious to developing drug resistance. This pivotal finding presents a platform for discovery of a new class of broad-spectrum treatments for herpesviruses and other viral infections with genome-pressure-dependent replication. A biophysical approach to antiviral treatment such as this is also a vital strategy to prevent the spread of emerging viruses where vaccine development is challenged by high mutation rates or other evasion mechanisms.
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Affiliation(s)
- Alberto Brandariz-Nuñez
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Scott J. Robinson
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Alex Evilevitch
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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8
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González B, Monroe L, Li K, Yan R, Wright E, Walter T, Kihara D, Weintraub ST, Thomas JA, Serwer P, Jiang W. Phage G Structure at 6.1 Å Resolution, Condensed DNA, and Host Identity Revision to a Lysinibacillus. J Mol Biol 2020; 432:4139-4153. [PMID: 32454153 DOI: 10.1016/j.jmb.2020.05.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 05/21/2020] [Accepted: 05/21/2020] [Indexed: 11/16/2022]
Abstract
Phage G has the largest capsid and genome of any known propagated phage. Many aspects of its structure, assembly, and replication have not been elucidated. Herein, we present the dsDNA-packed and empty phage G capsid at 6.1 and 9 Å resolution, respectively, using cryo-EM for structure determination and mass spectrometry for protein identification. The major capsid protein, gp27, is identified and found to share the HK97-fold universally conserved in all previously solved dsDNA phages. Trimers of the decoration protein, gp26, sit on the 3-fold axes and are thought to enhance the interactions of the hexameric capsomeres of gp27, for other phages encoding decoration proteins. Phage G's decoration protein is longer than what has been reported in other phages, and we suspect the extra interaction surface area helps stabilize the capsid. We identified several additional capsid proteins, including a candidate for the prohead protease responsible for processing gp27. Furthermore, cryo-EM reveals a range of partially full, condensed DNA densities that appear to have no contact with capsid shell. Three analyses confirm that the phage G host is a Lysinibacillus, and not Bacillus megaterium: identity of host proteins in our mass spectrometry analyses, genome sequence of the phage G host, and host range of phage G.
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Affiliation(s)
- Brenda González
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA
| | - Lyman Monroe
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA
| | - Kunpeng Li
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA
| | - Rui Yan
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA
| | - Elena Wright
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Thomas Walter
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA
| | - Daisuke Kihara
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA; Department of Computer Science, Purdue University, 305 North University Street, West Lafayette, IN 47907-2107, USA
| | - Susan T Weintraub
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Julie A Thomas
- Gosnell School of Life Sciences, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623, USA
| | - Philip Serwer
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Wen Jiang
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA; Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA; Purdue Cryo-EM Facility, Purdue University, Hockmeyer Hall of Structural Biology, 240 South Martin Jischke Drive, West Lafayette, IN 47907-1971, USA; Purdue Center for Cancer Research, Purdue University, 201 South University Street, West Lafayette, IN 47907, USA; Purdue Institute for Infectious, Immunology and Inflammatory Diseases, Purdue University, 207 South Martin Jischke Drive, West Lafayette, IN 47907, USA; Purdue Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN 47097, USA.
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9
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Martín-González N, Hernando-Pérez M, Condezo GN, Pérez-Illana M, Šiber A, Reguera D, Ostapchuk P, Hearing P, San Martín C, de Pablo PJ. Adenovirus major core protein condenses DNA in clusters and bundles, modulating genome release and capsid internal pressure. Nucleic Acids Res 2019; 47:9231-9242. [PMID: 31396624 PMCID: PMC6755088 DOI: 10.1093/nar/gkz687] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 07/10/2019] [Accepted: 08/06/2019] [Indexed: 11/23/2022] Open
Abstract
Some viruses package dsDNA together with large amounts of positively charged proteins, thought to help condense the genome inside the capsid with no evidence. Further, this role is not clear because these viruses have typically lower packing fractions than viruses encapsidating naked dsDNA. In addition, it has recently been shown that the major adenovirus condensing protein (polypeptide VII) is dispensable for genome encapsidation. Here, we study the morphology and mechanics of adenovirus particles with (Ad5-wt) and without (Ad5-VII-) protein VII. Ad5-VII- particles are stiffer than Ad5-wt, but DNA-counterions revert this difference, indicating that VII screens repulsive DNA-DNA interactions. Consequently, its absence results in increased internal pressure. The core is slightly more ordered in the absence of VII and diffuses faster out of Ad5-VII– than Ad5-wt fractured particles. In Ad5-wt unpacked cores, dsDNA associates in bundles interspersed with VII-DNA clusters. These results indicate that protein VII condenses the adenovirus genome by combining direct clustering and promotion of bridging by other core proteins. This condensation modulates the virion internal pressure and DNA release from disrupted particles, which could be crucial to keep the genome protected inside the semi-disrupted capsid while traveling to the nuclear pore.
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Affiliation(s)
| | - Mercedes Hernando-Pérez
- Department of Macromolecular Structures, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | - Gabriela N Condezo
- Department of Macromolecular Structures, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | - Marta Pérez-Illana
- Department of Macromolecular Structures, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | | | - David Reguera
- Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona, Spain.,Universitat de Barcelona Institute of Complex Systems (UBICS), 08028 Barcelona, Spain
| | - Philomena Ostapchuk
- Department of Molecular Genetics and Microbiology, School of Medicine, Stony Brook University, Stony Brook, NY 11794-5222, USA
| | - Patrick Hearing
- Department of Molecular Genetics and Microbiology, School of Medicine, Stony Brook University, Stony Brook, NY 11794-5222, USA
| | - Carmen San Martín
- Department of Macromolecular Structures, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain
| | - Pedro J de Pablo
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid 28049, Spain.,Instituto de Física de la Materia Condensada (IFIMAC), Universidad Autónoma de Madrid, Madrid 28049, Spain
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10
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Park CB, Kwon S, Sung BJ. The effects of a knot and its conformational relaxation on the ejection of a single polymer chain from confinement. J Chem Phys 2019. [DOI: 10.1063/1.5110428] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Seulki Kwon
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
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11
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Asija K, Teschke CM. Of capsid structure and stability: The partnership between charged residues of E-loop and P-domain of the bacteriophage P22 coat protein. Virology 2019; 534:45-53. [PMID: 31176063 PMCID: PMC6614003 DOI: 10.1016/j.virol.2019.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/27/2019] [Accepted: 05/31/2019] [Indexed: 01/14/2023]
Abstract
Tailed dsDNA bacteriophages and herpesviruses form capsids using coat proteins that have the HK97 fold. In these viruses, the coat proteins first assemble into procapsids, which subsequently mature during DNA packaging. Generally interactions between the coat protein E-loop of one subunit and the P-domain of an adjacent subunit help stabilize both capsomers and capsids. Based on a recent 3.3 Å cryo-EM structure of the bacteriophage P22 virion, E-loop amino acids E52, E59 and E72 were suggested to stabilize the capsid through intra-capsomer salt bridges with the P-domain residues R102, R109 and K118. The glutamic acid residues were each mutated to alanine to test this hypothesis. The substitutions resulted in a WT phenotype and did not destabilize capsids; rather, the alanine substituted coat proteins increased the stability of procapsids and virions. These results indicate that different types of interactions must be used between the E-loop and P-domain to stabilize phage P22 procapsids and virions.
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Affiliation(s)
- Kunica Asija
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA; Department of Chemistry, University of Connecticut, Storrs, CT, USA.
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12
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Zhang CY, Zhang NH. Influence of Microscopic Interactions on the Flexible Mechanical Properties of Viral DNA. Biophys J 2018; 115:763-772. [PMID: 30119833 DOI: 10.1016/j.bpj.2018.07.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 07/09/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022] Open
Abstract
During the packaging and ejection of viral DNA, its mechanical properties play an essential role in viral infection. Some of these mechanical properties originate from different microscopic interactions of the encapsulated DNA in the capsid. Based on an updated mesoscopic model of the interaction potential by Parsegian et al., an alternative continuum elastic model of the free energy of the confined DNA in the capsid is developed in this work. With this model, we not only quantitatively identify the respective contributions from hydration repulsion, electrostatic repulsion, entropy and elastic bending but also predict the ionic effect of viral DNA's mechanical properties during the packaging and ejection. The relevant predictions are quantitively or qualitatively consistent with the existing experimental results. Furthermore, the nonmonotonous or monotonous changes in the respective contributions of microscopic interactions to the ejection force and free energy at different ejection stages are revealed systematically. Among these, the nonmonotonicity in the entropic contribution implies a transition of viral DNA structure from order to disorder during the ejection.
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Affiliation(s)
- Cheng-Yin Zhang
- Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China
| | - Neng-Hui Zhang
- Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China; Department of Mechanics, College of Sciences, Shanghai University, Shanghai, China.
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13
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Evilevitch A. The mobility of packaged phage genome controls ejection dynamics. eLife 2018; 7:37345. [PMID: 30178745 PMCID: PMC6122950 DOI: 10.7554/elife.37345] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 07/29/2018] [Indexed: 12/31/2022] Open
Abstract
The cell decision between lytic and lysogenic infection is strongly influenced by dynamics of DNA injection into a cell from a phage population, as phages compete for limited resources and progeny. However, what controls the timing of viral DNA ejection events was not understood. This in vitro study reveals that DNA ejection dynamics for phages can be synchronized (occurring within seconds) or desynchronized (displaying minutes-long delays in initiation) based on mobility of encapsidated DNA, which in turn is regulated by environmental factors, such as temperature and extra-cellular ionic conditions. This mechano-regulation of ejection dynamics is suggested to influence viral replication where the cell’s decision between lytic and latent infection is associated with synchronized or desynchronized delayed ejection events from phage population adsorbed to a cell. Our findings are of significant importance for understanding regulatory mechanisms of latency in phage and Herpesviruses, where encapsidated DNA undergoes a similar mechanical transition. Viruses are tiny ‘parasites’ that smuggle their genetic material inside a cell and then hijack its resources for their own benefit. A viral infection can either be lytic or latent. In a lytic cycle, viruses make their host produce many copies of themselves, ultimately killing the cell. In contrast, during a latent infection, the viruses go ‘dormant’: for instance, some of them can insert their genetic material into the DNA of their host, which then gets passed on as the cell divides. Certain viruses are capable of both lytic and latent infections. One example is the lambda phage, which targets Escherichia coli bacteria. In the first stage of infection, the genetic material ‘shoots out’ of the virus and gets injected inside the bacterium. The dynamics of the ejection process determine the type of infection that will follow. If multiple phages release their genomes quickly and within seconds of each other into the same cell, the bacterium tends to incorporate the viral DNA into its own genome, leading to a latent cycle. If the infections take place more slowly and not all at the same time, the cell is more likely to go through a lytic phase. However, the mechanism behind the different injection behaviors is still unknown; in particular, it is unclear which factors control the specificities of the ejection process in the first place. Here, Alex Evilevitch demonstrates that the mechanical state of the phage DNA just before ejection dictates how the genetic material will then be injected in the bacteria. The experiments measured the stiffness of the DNA and the amount of heat given off during infection. Like fluid toothpaste, if the DNA is more liquid and flexible, it gets ejected quickly and simultaneously from several phages. Then, the genetic information of these viruses can be incorporated in the genome of the bacteria. On the other hand, if the DNA is more solid, it is likely to ‘stick’ and take time before it can be squeezed out: the injections become unsynchronised, which leads to a lytic phase. Evilevitch then shows that the environment can influence the properties of the phages’ genome. A little more heat, or certain chemicals, can make the DNA more fluid inside the viruses, and change the way it can be injected inside the bacteria. Many viruses that cause diseases in humans – from cold sores to glandular fever – can switch between the lytic and latent cycles. For the first time, these results show that the mechanical properties of the DNA inside a virus influence the ‘decision’ between the two types of infection. This knowledge could help us prevent infections from becoming lytic and ultimately allow us to control the spread of disease.
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Affiliation(s)
- Alex Evilevitch
- Department of Pathobiology, Division of Microbiology and Immunology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Champaign, United States.,Department of Experimental Medical Sciences, Virus Biophysics Group, Lund University, Lund, Sweden
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14
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Frutos MD, Leforestier A, Degrouard J, Zambrano N, Wien F, Boulanger P, Brasilès S, Renouard M, Durand D, Livolant F. Can Changes in Temperature or Ionic Conditions Modify the DNA Organization in the Full Bacteriophage Capsid? J Phys Chem B 2016; 120:5975-86. [PMID: 27152667 DOI: 10.1021/acs.jpcb.6b01783] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We compared four bacteriophage species, T5, λ, T7, and Φ29, to explore the possibilities of DNA reorganization in the capsid where the chain is highly concentrated and confined. First, we did not detect any change in DNA organization as a function of temperature between 20 to 40 °C. Second, the presence of spermine (4+) induces a significant enlargement of the typical size of the hexagonal domains in all phages. We interpret these changes as a reorganization of DNA by slight movements of defects in the structure, triggered by a partial screening of repulsive interactions. We did not detect any signal characteristic of a long-range chiral organization of the encapsidated DNA in the presence and in the absence of spermine.
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Affiliation(s)
- Marta de Frutos
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay , 91405 Orsay Cedex, France
| | - Amélie Leforestier
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay , 91405 Orsay Cedex, France
| | - Jéril Degrouard
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay , 91405 Orsay Cedex, France
| | - Nebraska Zambrano
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay , 91405 Orsay Cedex, France
| | - Frank Wien
- Synchrotron SOLEIL, DISCO, L'Orme des Merisiers , 91190 St Aubin, France
| | - Pascale Boulanger
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR 9198, Univ. Paris-Sud, Université Paris-Saclay , 91198 Gif sur Yvette Cedex, France
| | - Sandrine Brasilès
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR 9198, Univ. Paris-Sud, Université Paris-Saclay , 91198 Gif sur Yvette Cedex, France
| | - Madalena Renouard
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR 9198, Univ. Paris-Sud, Université Paris-Saclay , 91198 Gif sur Yvette Cedex, France
| | - Dominique Durand
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR 9198, Univ. Paris-Sud, Université Paris-Saclay , 91198 Gif sur Yvette Cedex, France
| | - Françoise Livolant
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay , 91405 Orsay Cedex, France
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15
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New Structural Insights into the Genome and Minor Capsid Proteins of BK Polyomavirus using Cryo-Electron Microscopy. Structure 2016; 24:528-536. [PMID: 26996963 PMCID: PMC4826271 DOI: 10.1016/j.str.2016.02.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 01/22/2016] [Accepted: 02/17/2016] [Indexed: 11/22/2022]
Abstract
BK polyomavirus is the causative agent of several diseases in transplant patients and the immunosuppressed. In order to better understand the structure and life cycle of BK, we produced infectious virions and VP1-only virus-like particles in cell culture, and determined their three-dimensional structures using cryo-electron microscopy (EM) and single-particle image processing. The resulting 7.6-Å resolution structure of BK and 9.1-Å resolution of the virus-like particles are the highest-resolution cryo-EM structures of any polyomavirus. These structures confirm that the architecture of the major structural protein components of these human polyomaviruses are similar to previous structures from other hosts, but give new insight into the location and role of the enigmatic minor structural proteins, VP2 and VP3. We also observe two shells of electron density, which we attribute to a structurally ordered part of the viral genome, and discrete contacts between this density and both VP1 and the minor capsid proteins.
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16
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Zhao H, Speir JA, Matsui T, Lin Z, Liang L, Lynn AY, Varnado B, Weiss TM, Tang L. Structure of a Bacterial Virus DNA-Injection Protein Complex Reveals a Decameric Assembly with a Constricted Molecular Channel. PLoS One 2016; 11:e0149337. [PMID: 26882199 PMCID: PMC4755594 DOI: 10.1371/journal.pone.0149337] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 01/29/2016] [Indexed: 12/18/2022] Open
Abstract
The multi-layered cell envelope structure of Gram-negative bacteria represents significant physical and chemical barriers for short-tailed phages to inject phage DNA into the host cytoplasm. Here we show that a DNA-injection protein of bacteriophage Sf6, gp12, forms a 465-kDa, decameric assembly in vitro. The electron microscopic structure of the gp12 assembly shows a ~150-Å, mushroom-like architecture consisting of a crown domain and a tube-like domain, which embraces a 25-Å-wide channel that could precisely accommodate dsDNA. The constricted channel suggests that gp12 mediates rapid, uni-directional injection of phage DNA into host cells by providing a molecular conduit for DNA translocation. The assembly exhibits a 10-fold symmetry, which may be a common feature among DNA-injection proteins of P22-like phages and may suggest a symmetry mismatch with respect to the 6-fold symmetric phage tail. The gp12 monomer is highly flexible in solution, supporting a mechanism for translocation of the protein through the conduit of the phage tail toward the host cell envelope, where it assembles into a DNA-injection device.
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Affiliation(s)
- Haiyan Zhao
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
| | - Jeffrey A. Speir
- National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, California, United States of America
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 14 2575 Sand Hill Road, MS69, Menlo Park, California, United States of America
| | - Zihan Lin
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
| | - Lingfei Liang
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
| | - Anna Y. Lynn
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
| | - Brittany Varnado
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
| | - Thomas M. Weiss
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 14 2575 Sand Hill Road, MS69, Menlo Park, California, United States of America
| | - Liang Tang
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, United States of America
- * E-mail:
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17
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Berndsen ZT, Keller N, Smith DE. Continuous allosteric regulation of a viral packaging motor by a sensor that detects the density and conformation of packaged DNA. Biophys J 2015; 108:315-24. [PMID: 25606680 DOI: 10.1016/j.bpj.2014.11.3469] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/31/2014] [Accepted: 11/24/2014] [Indexed: 11/28/2022] Open
Abstract
We report evidence for an unconventional type of allosteric regulation of a biomotor. We show that the genome-packaging motor of phage ϕ29 is regulated by a sensor that detects the density and conformation of the DNA packaged inside the viral capsid, and slows the motor by a mechanism distinct from the effect of a direct load force on the motor. Specifically, we show that motor-ATP interactions are regulated by a signal that is propagated allosterically from inside the viral shell to the motor mounted on the outside. This signal continuously regulates the motor speed and pausing in response to changes in either density or conformation of the packaged DNA, and slows the motor before the buildup of large forces resisting DNA confinement. Analysis of motor slipping reveals that the force resisting packaging remains low (<1 pN) until ∼ 70% and then rises sharply to ∼ 23 pN at high filling, which is a several-fold lower value than was previously estimated under the assumption that force alone slows the motor. These findings are consistent with recent studies of the stepping kinetics of the motor. The allosteric regulatory mechanism we report allows double-stranded DNA viruses to achieve rapid, high-density packing of their genomes by limiting the buildup of nonequilibrium load forces on the motor.
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Affiliation(s)
- Zachary T Berndsen
- Department of Physics, University of California, San Diego, La Jolla, California; Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - Nicholas Keller
- Department of Physics, University of California, San Diego, La Jolla, California
| | - Douglas E Smith
- Department of Physics, University of California, San Diego, La Jolla, California.
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18
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Bauer DW, Evilevitch A. Influence of Internal DNA Pressure on Stability and Infectivity of Phage λ. J Mol Biol 2015; 427:3189-3200. [PMID: 26254570 DOI: 10.1016/j.jmb.2015.07.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 07/22/2015] [Accepted: 07/26/2015] [Indexed: 11/27/2022]
Abstract
Viruses must remain infectious while in harsh extracellular environments. An important aspect of viral particle stability for double-stranded DNA viruses is the energetically unfavorable state of the tightly confined DNA chain within the virus capsid creating pressures of tens of atmospheres. Here, we study the influence of internal genome pressure on the thermal stability of viral particles. Using differential scanning calorimetry to monitor genome loss upon heating, we find that internal pressure destabilizes the virion, resulting in a smaller activation energy barrier to trigger DNA release. These experiments are complemented by plaque assay and electron microscopy measurements to determine the influence of intra-capsid DNA pressure on the rates of viral infectivity loss. At higher temperatures (65-75°C), failure to retain the packaged genome is the dominant mechanism of viral inactivation. Conversely, at lower temperatures (40-55°C), a separate inactivation mechanism dominates, which results in non-infectious particles that still retain their packaged DNA. Most significantly, both mechanisms of infectivity loss are directly influenced by internal DNA pressure, with higher pressure resulting in a more rapid rate of inactivation at all temperatures.
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Affiliation(s)
- D W Bauer
- Carnegie Mellon University Department of Physics, Pittsburgh, PA 15213, USA
| | - A Evilevitch
- Carnegie Mellon University Department of Physics, Pittsburgh, PA 15213, USA; Lund University Department of Biochemistry and Structural Biology, 221 00 Lund, Sweden.
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19
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Li D, Liu T, Zuo X, Li T, Qiu X, Evilevitch A. Ionic switch controls the DNA state in phage λ. Nucleic Acids Res 2015; 43:6348-58. [PMID: 26092697 PMCID: PMC4513876 DOI: 10.1093/nar/gkv611] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 05/31/2015] [Indexed: 01/19/2023] Open
Abstract
We have recently found that DNA packaged in phage λ undergoes a disordering transition triggered by temperature, which results in increased genome mobility. This solid-to-fluid like DNA transition markedly increases the number of infectious λ particles facilitating infection. However, the structural transition strongly depends on temperature and ionic conditions in the surrounding medium. Using titration microcalorimetry combined with solution X-ray scattering, we mapped both energetic and structural changes associated with transition of the encapsidated λ-DNA. Packaged DNA needs to reach a critical stress level in order for transition to occur. We varied the stress on DNA in the capsid by changing the temperature, packaged DNA length and ionic conditions. We found striking evidence that the intracapsid DNA transition is 'switched on' at the ionic conditions mimicking those in vivo and also at the physiologic temperature of infection at 37°C. This ion regulated on-off switch of packaged DNA mobility in turn affects viral replication. These results suggest a remarkable adaptation of phage λ to the environment of its host bacteria in the human gut. The metastable DNA state in the capsid provides a new paradigm for the physical evolution of viruses.
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Affiliation(s)
- Dong Li
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Ting Liu
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Xiaobing Zuo
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Tao Li
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Xiangyun Qiu
- Department of Physics, The George Washington University, Washington, DC 20052, USA
| | - Alex Evilevitch
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA Department of Biochemistry and Structural Biology, Lund University, SE-221 00 Lund, Sweden
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20
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Abstract
Releasing the packaged viral DNA into the host cell is an essential process to initiate viral infection. In many double-stranded DNA bacterial viruses and herpesviruses, the tightly packaged genome is hexagonally ordered and stressed in the protein shell, called the capsid. DNA condensed in this state inside viral capsids has been shown to be trapped in a glassy state, with restricted molecular motion in vitro. This limited intracapsid DNA mobility is caused by the sliding friction between closely packaged DNA strands, as a result of the repulsive interactions between the negative charges on the DNA helices. It had been unclear how this rigid crystalline structure of the viral genome rapidly ejects from the capsid, reaching rates of 60,000 bp/s. Through a combination of single-molecule and bulk techniques, we determined how the structure and energy of the encapsidated DNA in phage λ regulates the mobility required for its ejection. Our data show that packaged λ-DNA undergoes a solid-to-fluid-like disordering transition as a function of temperature, resulting locally in less densely packed DNA, reducing DNA-DNA repulsions. This process leads to a significant increase in genome mobility or fluidity, which facilitates genome release at temperatures close to that of viral infection (37 °C), suggesting a remarkable physical adaptation of bacterial viruses to the environment of Escherichia coli cells in a human host.
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21
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Solid-to-fluid DNA transition inside HSV-1 capsid close to the temperature of infection. Nat Chem Biol 2014; 10:861-7. [PMID: 25195012 DOI: 10.1038/nchembio.1628] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/31/2014] [Indexed: 01/06/2023]
Abstract
DNA in the human Herpes simplex virus type 1 (HSV-1) capsid is packaged to a tight density. This leads to tens of atmospheres of internal pressure responsible for the delivery of the herpes genome into the cell nucleus. In this study we show that, despite its liquid crystalline state inside the capsid, the DNA is fluid-like, which facilitates its ejection into the cell nucleus during infection. We found that the sliding friction between closely packaged DNA strands, caused by interstrand repulsive interactions, is reduced by the ionic environment of epithelial cells and neurons susceptible to herpes infection. However, variations in the ionic conditions corresponding to neuronal activity can restrict DNA mobility in the capsid, making it more solid-like. This can inhibit intranuclear DNA release and interfere with viral replication. In addition, the temperature of the human host (37 °C) induces a disordering transition of the encapsidated herpes genome, which reduces interstrand interactions and provides genome mobility required for infection.
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Abstract
Bacteriophages initiate infection by releasing their double-stranded DNA into the cytosol of their bacterial host. However, what controls and sets the timescales of DNA ejection? Here we provide evidence from stochastic simulations which shows that the topology and organization of DNA packed inside the capsid plays a key role in determining these properties. Even with similar osmotic pressure pushing out the DNA, we find that spatially ordered DNA spools have a much lower effective friction than disordered entangled states. Such spools are only found when the tendency of nearby DNA strands to align locally is accounted for. This topological or conformational friction also depends on DNA knot type in the packing geometry and slows down or arrests the ejection of twist knots and very complex knots. We also find that the family of (2, 2k+1) torus knots unravel gradually by simplifying their topology in a stepwise fashion. Finally, an analysis of DNA trajectories inside the capsid shows that the knots formed throughout the ejection process mirror those found in gel electrophoresis experiments for viral DNA molecules extracted from the capsids.
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23
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Bauer DW, Huffman JB, Homa FL, Evilevitch A. Herpes virus genome, the pressure is on. J Am Chem Soc 2013; 135:11216-21. [PMID: 23829592 DOI: 10.1021/ja404008r] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Herpes simplex virus type 1 (HSV-1) packages its micrometers-long double-stranded DNA genome into a nanometer-scale protein shell, termed the capsid. Upon confinement within the capsid, neighboring DNA strands experience repulsive electrostatic and hydration forces as well as bending stress associated with the tight curvature required of packaged DNA. By osmotically suppressing DNA release from HSV-1 capsids, we provide the first experimental evidence of a high internal pressure of tens of atmospheres within a eukaryotic human virus, resulting from the confined genome. Furthermore, the ejection is progressively suppressed by increasing external osmotic pressures, which reveals that internal pressure is capable of powering ejection of the entire genome from the viral capsid. Despite billions of years of evolution separating eukaryotic viruses and bacteriophages, pressure-driven DNA ejection has been conserved. This suggests it is a key mechanism for viral infection and thus presents a new target for antiviral therapies.
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Affiliation(s)
- David W Bauer
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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