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Cheng K, Sun Y, Yu H, Hu Y, He Y, Shen Y. Staphylococcus aureus SOS response: Activation, impact, and drug targets. MLIFE 2024; 3:343-366. [PMID: 39359682 PMCID: PMC11442139 DOI: 10.1002/mlf2.12137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/17/2024] [Accepted: 04/10/2024] [Indexed: 10/04/2024]
Abstract
Staphylococcus aureus is a common cause of diverse infections, ranging from superficial to invasive, affecting both humans and animals. The widespread use of antibiotics in clinical treatments has led to the emergence of antibiotic-resistant strains and small colony variants. This surge presents a significant challenge in eliminating infections and undermines the efficacy of available treatments. The bacterial Save Our Souls (SOS) response, triggered by genotoxic stressors, encompasses host immune defenses and antibiotics, playing a crucial role in bacterial survival, invasiveness, virulence, and drug resistance. Accumulating evidence underscores the pivotal role of the SOS response system in the pathogenicity of S. aureus. Inhibiting this system offers a promising approach for effective bactericidal treatments and curbing the evolution of antimicrobial resistance. Here, we provide a comprehensive review of the activation, impact, and key proteins associated with the SOS response in S. aureus. Additionally, perspectives on therapeutic strategies targeting the SOS response for S. aureus, both individually and in combination with traditional antibiotics are proposed.
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Affiliation(s)
- Kaiying Cheng
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of MedicineZhejiang UniversityHangzhouChina
| | - Yukang Sun
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
| | - Huan Yu
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
| | - Yingxuan Hu
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
| | - Yini He
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
| | - Yuanyuan Shen
- Zhejiang Key Laboratory of Medical Epigenetics, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Affiliated Hospital of Hangzhou Normal UniversityHangzhou Normal UniversityHangzhouChina
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2
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Skutel M, Yanovskaya D, Demkina A, Shenfeld A, Musharova O, Severinov K, Isaev A. RecA-dependent or independent recombination of plasmid DNA generates a conflict with the host EcoKI immunity by launching restriction alleviation. Nucleic Acids Res 2024; 52:5195-5208. [PMID: 38567730 PMCID: PMC11109961 DOI: 10.1093/nar/gkae243] [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: 09/19/2023] [Revised: 03/17/2024] [Accepted: 03/22/2024] [Indexed: 05/23/2024] Open
Abstract
Bacterial defence systems are tightly regulated to avoid autoimmunity. In Type I restriction-modification (R-M) systems, a specific mechanism called restriction alleviation (RA) controls the activity of the restriction module. In the case of the Escherichia coli Type I R-M system EcoKI, RA proceeds through ClpXP-mediated proteolysis of restriction complexes bound to non-methylated sites that appear after replication or reparation of host DNA. Here, we show that RA is also induced in the presence of plasmids carrying EcoKI recognition sites, a phenomenon we refer to as plasmid-induced RA. Further, we show that the anti-restriction behavior of plasmid-borne non-conjugative transposons such as Tn5053, previously attributed to their ardD loci, is due to plasmid-induced RA. Plasmids carrying both EcoKI and Chi sites induce RA in RecA- and RecBCD-dependent manner. However, inactivation of both RecA and RecBCD restores RA, indicating that there exists an alternative, RecA-independent, homologous recombination pathway that is blocked in the presence of RecBCD. Indeed, plasmid-induced RA in a RecBCD-deficient background does not depend on the presence of Chi sites. We propose that processing of random dsDNA breaks in plasmid DNA via homologous recombination generates non-methylated EcoKI sites, which attract EcoKI restriction complexes channeling them for ClpXP-mediated proteolysis.
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Affiliation(s)
- Mikhail Skutel
- Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Daria Yanovskaya
- Skolkovo Institute of Science and Technology, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow, Russia
| | - Alina Demkina
- Skolkovo Institute of Science and Technology, Moscow, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | | | - Olga Musharova
- Skolkovo Institute of Science and Technology, Moscow, Russia
- Institute of Molecular Genetics, National Research Center Kurchatov Institute, Moscow, Russia
| | - Konstantin Severinov
- Waksman Institute of Microbiology, Piscataway, USA
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Artem Isaev
- Skolkovo Institute of Science and Technology, Moscow, Russia
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3
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Gaydar V, Zananiri R, Saied L, Dvir O, Kaplan A, Henn A. Communication between DNA and nucleotide binding sites facilitates stepping by the RecBCD helicase. Nucleic Acids Res 2024; 52:3911-3923. [PMID: 38364872 DOI: 10.1093/nar/gkae108] [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: 05/22/2023] [Revised: 01/30/2024] [Accepted: 02/05/2024] [Indexed: 02/18/2024] Open
Abstract
Double-strand DNA breaks are the severest type of genomic damage, requiring rapid response to ensure survival. RecBCD helicase in prokaryotes initiates processive and rapid DNA unzipping, essential for break repair. The energetics of RecBCD during translocation along the DNA track are quantitatively not defined. Specifically, it's essential to understand the mechanism by which RecBCD switches between its binding states to enable its translocation. Here, we determine, by systematic affinity measurements, the degree of coupling between DNA and nucleotide binding to RecBCD. In the presence of ADP, RecBCD binds weakly to DNA that harbors a double overhang mimicking an unwinding intermediate. Consistently, RecBCD binds weakly to ADP in the presence of the same DNA. We did not observe coupling between DNA and nucleotide binding for DNA molecules having only a single overhang, suggesting that RecBCD subunits must both bind DNA to 'sense' the nucleotide state. On the contrary, AMPpNp shows weak coupling as RecBCD remains strongly bound to DNA in its presence. Detailed thermodynamic analysis of the RecBCD reaction mechanism suggests an 'energetic compensation' between RecB and RecD, which may be essential for rapid unwinding. Our findings provide the basis for a plausible stepping mechanism' during the processive translocation of RecBCD.
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Affiliation(s)
- Vera Gaydar
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Rani Zananiri
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Layla Saied
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Or Dvir
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Ariel Kaplan
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Arnon Henn
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
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4
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Mohr G, Yao J, Park SK, Markham L, Lambowitz AM. Mechanisms used for cDNA synthesis and site-specific integration of RNA into DNA genomes by a reverse transcriptase-Cas1 fusion protein. SCIENCE ADVANCES 2024; 10:eadk8791. [PMID: 38608016 PMCID: PMC11014452 DOI: 10.1126/sciadv.adk8791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 03/08/2024] [Indexed: 04/14/2024]
Abstract
Reverse transcriptase-Cas1 (RT-Cas1) fusion proteins found in some CRISPR systems enable spacer acquisition from both RNA and DNA, but the mechanism of RNA spacer acquisition has remained unclear. Here, we found that Marinomonas mediterranea RT-Cas1/Cas2 adds short 3'-DNA (dN) tails to RNA protospacers, enabling their direct integration into CRISPR arrays as 3'-dN-RNAs or 3'-dN-RNA/cDNA duplexes at rates comparable to similarly configured DNAs. Reverse transcription of RNA protospacers is initiated at 3' proximal sites by multiple mechanisms, including recently described de novo initiation, protein priming with any dNTP, and use of short exogenous or synthesized DNA oligomer primers, enabling synthesis of near full-length cDNAs of diverse RNAs without fixed sequence requirements. The integration of 3'-dN-RNAs or single-stranded DNAs (ssDNAs) is favored over duplexes at higher protospacer concentrations, potentially relevant to spacer acquisition from abundant pathogen RNAs or ssDNA fragments generated by phage defense nucleases. Our findings reveal mechanisms for site-specifically integrating RNA into DNA genomes with potential biotechnological applications.
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Affiliation(s)
- Georg Mohr
- Departments of Molecular Biosciences and Oncology, University of Texas at Austin, Austin, TX 78712, USA
| | - Jun Yao
- Departments of Molecular Biosciences and Oncology, University of Texas at Austin, Austin, TX 78712, USA
| | | | - Laura Markham
- Departments of Molecular Biosciences and Oncology, University of Texas at Austin, Austin, TX 78712, USA
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5
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Yang R, Hunker O, Wise M, Bleichert F. Multiple pathways for licensing human replication origins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.10.588796. [PMID: 38645015 PMCID: PMC11030351 DOI: 10.1101/2024.04.10.588796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The loading of replicative helicases constitutes an obligatory step in the assembly of DNA replication machineries. In eukaryotes, the MCM2-7 replicative helicase motor is deposited onto DNA by the origin recognition complex (ORC) and co-loader proteins as a head-to-head MCM double hexamer to license replication origins. Although extensively studied in the budding yeast model system, the mechanisms of origin licensing in higher eukaryotes remain poorly defined. Here, we use biochemical reconstitution and electron microscopy (EM) to reconstruct the human MCM loading pathway. Unexpectedly, we find that, unlike in yeast, ORC's Orc6 subunit is not essential for human MCM loading but can enhance loading efficiency. EM analyses identify several intermediates en route to MCM double hexamer formation in the presence and absence of Orc6, including an abundant DNA-loaded, closed-ring single MCM hexamer intermediate that can mature into a head-to-head double hexamer through different pathways. In an Orc6-facilitated pathway, ORC and a second MCM2-7 hexamer are recruited to the dimerization interface of the first hexamer through an MCM-ORC intermediate that is architecturally distinct from an analogous intermediate in yeast. In an alternative, Orc6-independent pathway, MCM double hexamer formation proceeds through dimerization of two independently loaded single MCM2-7 hexamers, promoted by a propensity of human MCM2-7 hexamers to dimerize without the help of other loading factors. This redundancy in human MCM loading pathways likely provides resilience against replication stress under cellular conditions by ensuring that enough origins are licensed for efficient DNA replication. Additionally, the biochemical reconstitution of human origin licensing paves the way to address many outstanding questions regarding DNA replication initiation and replication-coupled events in higher eukaryotes in the future.
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Affiliation(s)
| | | | - Marleigh Wise
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Franziska Bleichert
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
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6
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Amundsen SK, Smith GR. Chi hotspot Control of RecBCD Helicase-nuclease: Enzymatic Tests Support the Intramolecular Signal-transduction Model. J Mol Biol 2024; 436:168482. [PMID: 38331210 PMCID: PMC10947171 DOI: 10.1016/j.jmb.2024.168482] [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: 11/15/2023] [Revised: 01/11/2024] [Accepted: 02/02/2024] [Indexed: 02/10/2024]
Abstract
Repair of broken DNA is essential for life; the reactions involved can also promote genetic recombination to aid evolution. In Escherichia coli, RecBCD enzyme is required for the major pathway of these events. RecBCD is a complex ATP-dependent DNA helicase with nuclease activity controlled by Chi recombination hotspots (5'-GCTGGTGG-3'). During rapid DNA unwinding, when Chi is in a RecC tunnel, RecB nuclease nicks DNA at Chi. Here, we test our signal transduction model - upon binding Chi (step 1), RecC signals RecD helicase to stop unwinding (step 2); RecD then signals RecB (step 3) to nick at Chi (step 4) and to begin loading RecA DNA strand-exchange protein (step 5). We discovered that ATP-γ-S, like the small molecule RecBCD inhibitor NSAC1003, causes RecBCD to nick DNA, independent of Chi, at novel positions determined by the DNA substrate length. Two RecB ATPase-site mutants nick at novel positions determined by their RecB:RecD helicase rate ratios. In each case, we find that nicking at the novel position requires steps 3 and 4 but not step 1 or 2, as shown by mutants altered at the intersubunit contacts specific for each step; nicking also requires RecD helicase and RecB nuclease activities. Thus, altering the RecB ATPase site, by small molecules or mutation, sensitizes RecD to signal RecB to nick DNA (steps 4 and 3, respecitvely) without the signal from RecC or Chi (steps 1 and 2). These new, enzymatic results strongly support the signal transduction model and provide a paradigm for studying other complex enzymes.
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Affiliation(s)
- Susan K Amundsen
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Farview Avenue North, A1-162, Seattle, WA 98109, USA
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Farview Avenue North, A1-162, Seattle, WA 98109, USA.
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7
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Pilotto S, Sýkora M, Cackett G, Dulson C, Werner F. Structure of the recombinant RNA polymerase from African Swine Fever Virus. Nat Commun 2024; 15:1606. [PMID: 38383525 PMCID: PMC10881513 DOI: 10.1038/s41467-024-45842-7] [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: 08/17/2023] [Accepted: 02/06/2024] [Indexed: 02/23/2024] Open
Abstract
African Swine Fever Virus is a Nucleo-Cytoplasmic Large DNA Virus that causes an incurable haemorrhagic fever in pigs with a high impact on global food security. ASFV replicates in the cytoplasm of the infected cell and encodes its own transcription machinery that is independent of cellular factors, however, not much is known about how this system works at a molecular level. Here, we present methods to produce recombinant ASFV RNA polymerase, functional assays to screen for inhibitors, and high-resolution cryo-electron microscopy structures of the ASFV RNAP in different conformational states. The ASFV RNAP bears a striking resemblance to RNAPII with bona fide homologues of nine of its twelve subunits. Key differences include the fusion of the ASFV assembly platform subunits RPB3 and RPB11, and an unusual C-terminal domain of the stalk subunit vRPB7 that is related to the eukaryotic mRNA cap 2´-O-methyltransferase 1. Despite the high degree of structural conservation with cellular RNA polymerases, the ASFV RNAP is resistant to the inhibitors rifampicin and alpha-amanitin. The cryo-EM structures and fully recombinant RNAP system together provide an important tool for the design, development, and screening of antiviral drugs in a low biosafety containment environment.
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Affiliation(s)
- Simona Pilotto
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Michal Sýkora
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Gwenny Cackett
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Christopher Dulson
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Finn Werner
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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8
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Mishra G, Srivastava K, Rais J, Dixit M, Kumari Singh V, Chandra Mishra L. CRISPR-Cas9: A Potent Gene-editing Tool for the Treatment of Cancer. Curr Mol Med 2024; 24:191-204. [PMID: 36788695 DOI: 10.2174/1566524023666230213094308] [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: 06/04/2022] [Revised: 11/02/2022] [Accepted: 11/10/2022] [Indexed: 02/16/2023]
Abstract
The prokaryotic adaptive immune system has clustered regularly interspaced short palindromic repeat. CRISPR-associated protein (CRISPR-Cas) genome editing systems have been harnessed. A robust programmed technique for efficient and accurate genome editing and gene targeting has been developed. Engineered cell therapy, in vivo gene therapy, animal modeling, and cancer diagnosis and treatment are all possible applications of this ground-breaking approach. Multiple genetic and epigenetic changes in cancer cells induce malignant cell growth and provide chemoresistance. The capacity to repair or ablate such mutations has enormous potential in the fight against cancer. The CRISPR-Cas9 genome editing method has recently become popular in cancer treatment research due to its excellent efficiency and accuracy. The preceding study has shown therapeutic potential in expanding our anticancer treatments by using CRISPR-Cas9 to directly target cancer cell genomic DNA in cellular and animal cancer models. In addition, CRISPR-Cas9 can combat oncogenic infections and test anticancer medicines. It may design immune cells and oncolytic viruses for cancer immunotherapeutic applications. In this review, these preclinical CRISPRCas9- based cancer therapeutic techniques are summarised, along with the hurdles and advancements in converting therapeutic CRISPR-Cas9 into clinical use. It will increase their applicability in cancer research.
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Affiliation(s)
- Gauri Mishra
- Department of Zoology, Swami Shraddhanand College, University of Delhi-110036, Delhi, India
- Division Radiopharmaceuticals and Radiation Biology, Institute of Nuclear Medicine and Allied Sciences, Brig SK Mazumdar Road, Delhi-110054, India
| | - Kamakshi Srivastava
- Department of Zoology, Swami Shraddhanand College, University of Delhi-110036, Delhi, India
| | - Juhi Rais
- Department of Nuclear Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow-226014, India
| | - Manish Dixit
- Department of Nuclear Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow-226014, India
| | - Vandana Kumari Singh
- Department of Zoology, Hansraj College, University of Delhi- 110007, Dehli, India
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9
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Amundsen SK, Smith GR. RecBCD enzyme: mechanistic insights from mutants of a complex helicase-nuclease. Microbiol Mol Biol Rev 2023; 87:e0004123. [PMID: 38047637 PMCID: PMC10732027 DOI: 10.1128/mmbr.00041-23] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023] Open
Abstract
SUMMARYRecBCD enzyme is a multi-functional protein that initiates the major pathway of homologous genetic recombination and DNA double-strand break repair in Escherichia coli. It is also required for high cell viability and aids proper DNA replication. This 330-kDa, three-subunit enzyme is one of the fastest, most processive helicases known and contains a potent nuclease controlled by Chi sites, hotspots of recombination, in DNA. RecBCD undergoes major changes in activity and conformation when, during DNA unwinding, it encounters Chi (5'-GCTGGTGG-3') and nicks DNA nearby. Here, we discuss the multitude of mutations in each subunit that affect one or another activity of RecBCD and its control by Chi. These mutants have given deep insights into how the multiple activities of this complex enzyme are coordinated and how it acts in living cells. Similar studies could help reveal how other complex enzymes are controlled by inter-subunit interactions and conformational changes.
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Affiliation(s)
| | - Gerald R. Smith
- Fred Hutchinson Cancer Center Seattle, Seattle, Washington, USA
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10
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Aframian N, Eldar A. Abortive infection antiphage defense systems: separating mechanism and phenotype. Trends Microbiol 2023; 31:1003-1012. [PMID: 37268559 DOI: 10.1016/j.tim.2023.05.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 05/11/2023] [Accepted: 05/12/2023] [Indexed: 06/04/2023]
Abstract
Bacteria have evolved a wide array of mechanisms that allow them to eliminate phage infection. 'Abortive infection' (abi) systems are an expanding category of such mechanisms, defined as those which induce programmed cell death (or dormancy) upon infection, and thus halt phage propagation within a bacterial population. This definition entails two requirements - a phenotypic observation (cell death upon infection), and a mechanistic determination of its sources (system-induced death). The phenotypic and mechanistic aspects of abi are often implicitly assumed to be tightly linked, and studies regularly tend to establish one and deduce the other. However, recent evidence points to a complicated relationship between the mechanism of defense and the phenotype observed upon infection. We argue that rather than viewing the abi phenotype as an inherent quality of a set of defense systems, it should be more appropriately thought of as an attribute of interactions between specific phages and bacteria under given conditions. Consequently, we also point to potential pitfalls in the prevailing methods for ascertaining the abi phenotype. Overall, we propose an alternative framework for parsing interactions between attacking phages and defending bacteria.
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Affiliation(s)
- Nitzan Aframian
- Shmunis School of Biomedicine and Cancer Research, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel
| | - Avigdor Eldar
- Shmunis School of Biomedicine and Cancer Research, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel.
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11
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Mohr G, Yao J, Park SK, Markham LM, Lambowitz AM. Mechanisms used for cDNA synthesis and site-specific integration of RNA into DNA genomes by a reverse transcriptase-Cas1 fusion protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555893. [PMID: 37693417 PMCID: PMC10491204 DOI: 10.1101/2023.09.01.555893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Reverse transcriptase-Cas1 (RT-Cas1) fusion proteins found in some CRISPR systems enable spacer acquisition from both RNA and DNA, but the mechanism of RNA spacer acquisition has remained unclear. Here, we found Marinomonas mediterranea RT-Cas1/Cas2 adds short 3'-DNA (dN) tails to RNA protospacers enabling their direct integration into CRISPR arrays as 3'-dN-RNA/cDNA duplexes or 3'-dN-RNAs at rates comparable to similarly configured DNAs. Reverse transcription of RNA protospacers occurs by multiple mechanisms, including recently described de novo initiation, protein priming with any dNTP, and use of short exogenous or synthesized DNA oligomer primers, enabling synthesis of cDNAs from diverse RNAs without fixed sequence requirements. The integration of 3'-dN-RNAs or single-stranded (ss) DNAs is favored over duplexes at higher protospacer concentrations, potentially relevant to spacer acquisition from abundant pathogen RNAs or ssDNA fragments generated by phage-defense nucleases. Our findings reveal novel mechanisms for site-specifically integrating RNA into DNA genomes with potential biotechnological applications.
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Affiliation(s)
- Georg Mohr
- Departments of Molecular Biosciences and Oncology University of Texas at Austin Austin TX, 78712
| | - Jun Yao
- Departments of Molecular Biosciences and Oncology University of Texas at Austin Austin TX, 78712
| | | | - Laura M. Markham
- Departments of Molecular Biosciences and Oncology University of Texas at Austin Austin TX, 78712
| | - Alan M. Lambowitz
- Departments of Molecular Biosciences and Oncology University of Texas at Austin Austin TX, 78712
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12
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Ton WD, Wang Y, Chai P, Beauchamp-Perez C, Flint NT, Lammers LG, Xiong H, Zhang K, Markus SM. Microtubule-binding-induced allostery triggers LIS1 dissociation from dynein prior to cargo transport. Nat Struct Mol Biol 2023; 30:1365-1379. [PMID: 37322240 PMCID: PMC10590275 DOI: 10.1038/s41594-023-01010-x] [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: 11/23/2022] [Accepted: 04/28/2023] [Indexed: 06/17/2023]
Abstract
The lissencephaly-related protein LIS1 is a critical regulator of cytoplasmic dynein that governs motor function and intracellular localization (for example, to microtubule plus-ends). Although LIS1 binding is required for dynein activity, its unbinding prior to initiation of cargo transport is equally important, since preventing dissociation leads to dynein dysfunction. To understand whether and how dynein-LIS1 binding is modulated, we engineered dynein mutants locked in a microtubule-bound (MT-B) or microtubule-unbound (MT-U) state. Whereas the MT-B mutant exhibits low LIS1 affinity, the MT-U mutant binds LIS1 with high affinity, and as a consequence remains almost irreversibly associated with microtubule plus-ends. We find that a monomeric motor domain is sufficient to exhibit these opposing LIS1 affinities, and that this is evolutionarily conserved between yeast and humans. Three cryo-EM structures of human dynein with and without LIS1 reveal microtubule-binding induced conformational changes responsible for this regulation. Our work reveals key biochemical and structural insight into LIS1-mediated dynein activation.
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Affiliation(s)
- William D Ton
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Yue Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Pengxin Chai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | | | - Nicholas T Flint
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Lindsay G Lammers
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Hao Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Kai Zhang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
| | - Steven M Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.
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13
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Marini G, Poland B, Leininger C, Lukoyanova N, Spielbauer D, Barry JK, Altier D, Lum A, Scolaro E, Ortega CP, Yalpani N, Sandahl G, Mabry T, Klever J, Nowatzki T, Zhao JZ, Sethi A, Kassa A, Crane V, Lu AL, Nelson ME, Eswar N, Topf M, Saibil HR. Structural journey of an insecticidal protein against western corn rootworm. Nat Commun 2023; 14:4171. [PMID: 37443175 PMCID: PMC10344926 DOI: 10.1038/s41467-023-39891-7] [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: 01/12/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023] Open
Abstract
The broad adoption of transgenic crops has revolutionized agriculture. However, resistance to insecticidal proteins by agricultural pests poses a continuous challenge to maintaining crop productivity and new proteins are urgently needed to replace those utilized for existing transgenic traits. We identified an insecticidal membrane attack complex/perforin (MACPF) protein, Mpf2Ba1, with strong activity against the devastating coleopteran pest western corn rootworm (WCR) and a novel site of action. Using an integrative structural biology approach, we determined monomeric, pre-pore and pore structures, revealing changes between structural states at high resolution. We discovered an assembly inhibition mechanism, a molecular switch that activates pre-pore oligomerization upon gut fluid incubation and solved the highest resolution MACPF pore structure to-date. Our findings demonstrate not only the utility of Mpf2Ba1 in the development of biotechnology solutions for protecting maize from WCR to promote food security, but also uncover previously unknown mechanistic principles of bacterial MACPF assembly.
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Affiliation(s)
- Guendalina Marini
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London, WC1E 7HX, UK
- Centre for Structural Systems Biology (CSSB), Leibniz-Institut für Virologie (LIV), Universitätsklinikum Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Brad Poland
- Corteva Agriscience, Johnston, IA, 50131, USA
| | - Chris Leininger
- Corteva Agriscience, Johnston, IA, 50131, USA
- Syngenta, Research Triangle Park, NC, 27709, USA
| | - Natalya Lukoyanova
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London, WC1E 7HX, UK
| | | | | | - Dan Altier
- Corteva Agriscience, Johnston, IA, 50131, USA
| | - Amy Lum
- Corteva Agriscience, Johnston, IA, 50131, USA
- Willow Biosciences, 319 N Bernardo Ave #4, Mountain View, CA, 94043, USA
| | | | - Claudia Pérez Ortega
- Corteva Agriscience, Johnston, IA, 50131, USA
- Hologic, Inc., 250 Campus Drive, Marlborough, MA, 01752, USA
| | - Nasser Yalpani
- Corteva Agriscience, Johnston, IA, 50131, USA
- Dept. of Biology, University of British Columbia Okanagan, 3187 University Way, Kelowna, BC, V1V 1V7, Canada
| | | | - Tim Mabry
- Corteva Agriscience, Ivesdale, IL, 61851, USA
| | | | | | | | - Amit Sethi
- Corteva Agriscience, Johnston, IA, 50131, USA
| | - Adane Kassa
- Corteva Agriscience, Johnston, IA, 50131, USA
| | | | - Albert L Lu
- Corteva Agriscience, Johnston, IA, 50131, USA
| | | | | | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London, WC1E 7HX, UK.
- Centre for Structural Systems Biology (CSSB), Leibniz-Institut für Virologie (LIV), Universitätsklinikum Hamburg-Eppendorf (UKE), Hamburg, Germany.
| | - Helen R Saibil
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London, WC1E 7HX, UK.
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14
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Gao Z, Feng Y. Bacteriophage strategies for overcoming host antiviral immunity. Front Microbiol 2023; 14:1211793. [PMID: 37362940 PMCID: PMC10286901 DOI: 10.3389/fmicb.2023.1211793] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/17/2023] [Indexed: 06/28/2023] Open
Abstract
Phages and their bacterial hosts together constitute a vast and diverse ecosystem. Facing the infection of phages, prokaryotes have evolved a wide range of antiviral mechanisms, and phages in turn have adopted multiple tactics to circumvent or subvert these mechanisms to survive. An in-depth investigation into the interaction between phages and bacteria not only provides new insight into the ancient coevolutionary conflict between them but also produces precision biotechnological tools based on anti-phage systems. Moreover, a more complete understanding of their interaction is also critical for the phage-based antibacterial measures. Compared to the bacterial antiviral mechanisms, studies into counter-defense strategies adopted by phages have been a little slow, but have also achieved important advances in recent years. In this review, we highlight the numerous intracellular immune systems of bacteria as well as the countermeasures employed by phages, with an emphasis on the bacteriophage strategies in response to host antiviral immunity.
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Affiliation(s)
| | - Yue Feng
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing Key Laboratory of Bioprocess, State Key Laboratory of Chemical Resource Engineering, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
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15
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Moura de Sousa J, Lourenço M, Gordo I. Horizontal gene transfer among host-associated microbes. Cell Host Microbe 2023; 31:513-527. [PMID: 37054673 DOI: 10.1016/j.chom.2023.03.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Abstract
Horizontal gene transfer is an important evolutionary force, facilitating bacterial diversity. It is thought to be pervasive in host-associated microbiomes, where bacterial densities are high and mobile elements are frequent. These genetic exchanges are also key for the rapid dissemination of antibiotic resistance. Here, we review recent studies that have greatly extended our knowledge of the mechanisms underlying horizontal gene transfer, the ecological complexities of a network of interactions involving bacteria and their mobile elements, and the effect of host physiology on the rates of genetic exchanges. Furthermore, we discuss other, fundamental challenges in detecting and quantifying genetic exchanges in vivo, and how studies have contributed to start overcoming these challenges. We highlight the importance of integrating novel computational approaches and theoretical models with experimental methods where multiple strains and transfer elements are studied, both in vivo and in controlled conditions that mimic the intricacies of host-associated environments.
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Affiliation(s)
- Jorge Moura de Sousa
- Institut Pasteur, Université Paris Cité, CNRS, UMR3525, Microbial Evolutionary Genomics, Paris, 75015 Paris, France
| | - Marta Lourenço
- Institut Pasteur, Université Paris Cité, Biodiversity and Epidemiology of Bacterial Pathogens, F-75015 Paris, France
| | - Isabel Gordo
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande,6, Oeiras, Portugal.
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16
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Amundsen SK, Richardson A, Ha K, Smith GR. A flexible RecC surface loop required for Chi hotspot control of RecBCD enzyme. Genetics 2023; 223:iyac175. [PMID: 36521180 PMCID: PMC9991510 DOI: 10.1093/genetics/iyac175] [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: 08/12/2022] [Revised: 11/11/2022] [Accepted: 11/14/2022] [Indexed: 12/23/2022] Open
Abstract
Escherichia coli RecBCD helicase-nuclease promotes vital homologous recombination-based repair of DNA double-strand breaks. The RecB nuclease domain (Nuc) is connected to the RecB helicase domain by a 19-amino-acid tether. When DNA binds to RecBCD, published evidence suggests that Nuc moves ∼50 Å from the exit of a RecC tunnel, from which the 3'-ended strand emerges during unwinding, to a distant position on RecC's surface. During subsequent ATP-dependent unwinding of DNA, Nuc nicks the 3'-ended strand near 5'-GCTGGTGG-3' (Chi recombination hotspot). Here, we test our model of Nuc swinging on the tether from the RecC tunnel exit to the RecC distant surface and back to the RecC tunnel exit to cut at Chi. We identify positions in a flexible surface loop on RecC and on RecB Nuc with complementary charges, mutation of which strongly reduces but does not eliminate Chi hotspot activity in cells. The recC loop mutation interacts with recB mutations hypothesized to be in the Chi-activated intramolecular signal transduction pathway; the double mutants, but not the single mutants, eliminate Chi hotspot activity. A RecC amino acid near the flexible loop is also essential for full Chi activity; its alteration likewise synergizes with a signal transduction mutation to eliminate Chi activity. We infer that altering the RecC surface loop reduces coordination among the subunits, which is critical for Chi hotspot activity. We discuss other RecBCD mutants with related properties.
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Affiliation(s)
- Susan K Amundsen
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | | | - Khoi Ha
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
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17
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Wilkinson M, Gallardo RU, Martinez RM, Guthertz N, So M, Aubrey LD, Radford SE, Ranson NA. Disease-relevant β 2-microglobulin variants share a common amyloid fold. Nat Commun 2023; 14:1190. [PMID: 36864041 PMCID: PMC9981686 DOI: 10.1038/s41467-023-36791-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 02/16/2023] [Indexed: 03/04/2023] Open
Abstract
β2-microglobulin (β2m) and its truncated variant ΔΝ6 are co-deposited in amyloid fibrils in the joints, causing the disorder dialysis-related amyloidosis (DRA). Point mutations of β2m result in diseases with distinct pathologies. β2m-D76N causes a rare systemic amyloidosis with protein deposited in the viscera in the absence of renal failure, whilst β2m-V27M is associated with renal failure, with amyloid deposits forming predominantly in the tongue. Here we use cryoEM to determine the structures of fibrils formed from these variants under identical conditions in vitro. We show that each fibril sample is polymorphic, with diversity arising from a 'lego-like' assembly of a common amyloid building block. These results suggest a 'many sequences, one amyloid fold' paradigm in contrast with the recently reported 'one sequence, many amyloid folds' behaviour of intrinsically disordered proteins such as tau and Aβ.
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Affiliation(s)
- Martin Wilkinson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Rodrigo U Gallardo
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Aelin Therapeutics, Bio-Incubator Leuven, Gaston Geenslaan 1, 3001, Leuven, Belgium
| | - Roberto Maya Martinez
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Peak Proteins, Birchwood House, Larkwood Way, Macclesfield, Cheshire, SK10 2XR, UK
| | - Nicolas Guthertz
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Bicycle Therapeutics, Blocks A & B, Portway Building, Grant Park, Abingdon, Cambridge, CB21 6GS, UK
| | - Masatomo So
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Nara Medical University, 840 Shijo-cho, Kashihara, Nara, 634-8521, Japan
| | - Liam D Aubrey
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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18
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Troman L, Alvira S, Daum B, Gold VAM, Collinson I. Interaction of the periplasmic chaperone SurA with the inner membrane protein secretion (SEC) machinery. Biochem J 2023; 480:283-296. [PMID: 36701201 PMCID: PMC9987972 DOI: 10.1042/bcj20220480] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 01/11/2023] [Accepted: 01/25/2023] [Indexed: 01/27/2023]
Abstract
Gram-negative bacteria are surrounded by two protein-rich membranes with a peptidoglycan layer sandwiched between them. Together they form the envelope (or cell wall), crucial for energy production, lipid biosynthesis, structural integrity, and for protection against physical and chemical environmental challenges. To achieve envelope biogenesis, periplasmic and outer-membrane proteins (OMPs) must be transported from the cytosol and through the inner-membrane, via the ubiquitous SecYEG protein-channel. Emergent proteins either fold in the periplasm or cross the peptidoglycan (PG) layer towards the outer-membrane for insertion through the β-barrel assembly machinery (BAM). Trafficking of hydrophobic proteins through the periplasm is particularly treacherous given the high protein density and the absence of energy (ATP or chemiosmotic potential). Numerous molecular chaperones assist in the prevention and recovery from aggregation, and of these SurA is known to interact with BAM, facilitating delivery to the outer-membrane. However, it is unclear how proteins emerging from the Sec-machinery are received and protected from aggregation and proteolysis prior to an interaction with SurA. Through biochemical analysis and electron microscopy we demonstrate the binding capabilities of the unoccupied and substrate-engaged SurA to the inner-membrane translocation machinery complex of SecYEG-SecDF-YidC - aka the holo-translocon (HTL). Supported by AlphaFold predictions, we suggest a role for periplasmic domains of SecDF in chaperone recruitment to the protein translocation exit site in SecYEG. We propose that this immediate interaction with the enlisted chaperone helps to prevent aggregation and degradation of nascent envelope proteins, facilitating their safe passage to the periplasm and outer-membrane.
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Affiliation(s)
- Lucy Troman
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K
| | - Sara Alvira
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K
| | - Bertram Daum
- Living Systems Institute, University of Exeter, Exeter, U.K
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, U.K
| | - Vicki A. M. Gold
- Living Systems Institute, University of Exeter, Exeter, U.K
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, U.K
| | - Ian Collinson
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K
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19
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Yang J, Sun Y, Wang Y, Hao W, Cheng K. Structural and DNA end resection study of the bacterial NurA-HerA complex. BMC Biol 2023; 21:42. [PMID: 36829173 PMCID: PMC9960219 DOI: 10.1186/s12915-023-01542-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 02/10/2023] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND The nuclease NurA and the ATPase/translocase HerA play a vital role in repair of double-strand breaks (DSB) during the homologous recombination in archaea. A NurA-HerA complex is known to mediate DSB DNA end resection, leading to formation of a free 3' end used to search for the homologous sequence. Despite the structures of individual archaeal types of NurA and HerA having been reported, there is limited information regarding the molecular mechanisms underlying this process. Some bacteria also possess homologs of NurA and HerA; however, the bacterial type of this complex, as well as the detailed mechanisms underlying the joining of NurA-HerA in DSB DNA end resection, remains unclear. RESULTS We report for the first time the crystal structures of Deinococcus radiodurans HerA (drHerA) in the nucleotide-free and ADP-binding modes. A D. radiodurans NurA-HerA complex structure was constructed according to a low-resolution cryo-electron microscopy map. We performed site-directed mutagenesis to map the drNurA-HerA interaction sites, suggesting that their interaction is mainly mediated by ionic links, in contrast to previously characterized archaeal NurA-HerA interactions. The key residues responsible for the DNA translocation activity, DNA unwinding activity, and catalytic activities of the drNurA-HerA complex were identified. A HerA/FtsK-specific translocation-related motif (TR motif) that guarantees the processivity of double-stranded DNA (dsDNA) translocation was identified. Moreover, a mechanism for the translocation-regulated resection of the 5' tail of broken dsDNA and the corresponding generation of a recombinogenic 3' single-stranded DNA tail by the drNurA-HerA complex was elucidated. CONCLUSIONS Our work provides new insights into the mechanism underlying bacterial NurA-HerA-mediated DSB DNA end resection, and the way this complex digests the 5' tail of a DNA duplex and provides long 3' free end for strand invasion in the bacterial homologous recombination process.
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Affiliation(s)
- Jieyu Yang
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Yiyang Sun
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Ying Wang
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Wanshan Hao
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Kaiying Cheng
- Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121, China. .,State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China.
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20
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Wilkinson M, Wilkinson OJ, Feyerherm C, Fletcher EE, Wigley DB, Dillingham MS. Structures of RecBCD in complex with phage-encoded inhibitor proteins reveal distinctive strategies for evasion of a bacterial immunity hub. eLife 2022; 11:e83409. [PMID: 36533901 PMCID: PMC9836394 DOI: 10.7554/elife.83409] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 12/18/2022] [Indexed: 12/23/2022] Open
Abstract
Following infection of bacterial cells, bacteriophage modulate double-stranded DNA break repair pathways to protect themselves from host immunity systems and prioritise their own recombinases. Here, we present biochemical and structural analysis of two phage proteins, gp5.9 and Abc2, which target the DNA break resection complex RecBCD. These exemplify two contrasting mechanisms for control of DNA break repair in which the RecBCD complex is either inhibited or co-opted for the benefit of the invading phage. Gp5.9 completely inhibits RecBCD by preventing it from binding to DNA. The RecBCD-gp5.9 structure shows that gp5.9 acts by substrate mimicry, binding predominantly to the RecB arm domain and competing sterically for the DNA binding site. Gp5.9 adopts a parallel coiled-coil architecture that is unprecedented for a natural DNA mimic protein. In contrast, binding of Abc2 does not substantially affect the biochemical activities of isolated RecBCD. The RecBCD-Abc2 structure shows that Abc2 binds to the Chi-recognition domains of the RecC subunit in a position that might enable it to mediate the loading of phage recombinases onto its single-stranded DNA products.
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Affiliation(s)
- Martin Wilkinson
- Section of Structural Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College LondonLondonUnited Kingdom
| | - Oliver J Wilkinson
- DNA:protein Interactions Unit, School of Biochemistry, University of BristolBristolUnited Kingdom
| | - Connie Feyerherm
- DNA:protein Interactions Unit, School of Biochemistry, University of BristolBristolUnited Kingdom
| | - Emma E Fletcher
- DNA:protein Interactions Unit, School of Biochemistry, University of BristolBristolUnited Kingdom
| | - Dale B Wigley
- Section of Structural Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College LondonLondonUnited Kingdom
| | - Mark S Dillingham
- DNA:protein Interactions Unit, School of Biochemistry, University of BristolBristolUnited Kingdom
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21
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The coordination of anti-phage immunity mechanisms in bacterial cells. Nat Commun 2022; 13:7412. [PMID: 36456580 PMCID: PMC9715693 DOI: 10.1038/s41467-022-35203-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 11/18/2022] [Indexed: 12/02/2022] Open
Abstract
Bacterial cells are equipped with a variety of immune strategies to fight bacteriophage infections. Such strategies include unspecific mechanisms directed against any phage infecting the cell, ranging from the identification and cleavage of the viral DNA by restriction nucleases (restriction-modification systems) to the suicidal death of infected host cells (abortive infection, Abi). In addition, CRISPR-Cas systems generate an immune memory that targets specific phages in case of reinfection. However, the timing and coordination of different antiviral systems in bacterial cells are poorly understood. Here, we use simple mathematical models of immune responses in individual bacterial cells to propose that the intracellular dynamics of phage infections are key to addressing these questions. Our models suggest that the rates of viral DNA replication and cleavage inside host cells define functional categories of phages that differ in their susceptibility to bacterial anti-phage mechanisms, which could give raise to alternative phage strategies to escape bacterial immunity. From this viewpoint, the combined action of diverse bacterial defenses would be necessary to reduce the chances of phage immune evasion. The decision of individual infected cells to undergo suicidal cell death or to incorporate new phage sequences into their immune memory would be determined by dynamic interactions between the host's immune mechanisms and the phage DNA. Our work highlights the importance of within-cell dynamics to understand bacterial immunity, and formulates hypotheses that may inspire future research in this area.
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22
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Verdú C, Pérez-Arnaiz P, Peropadre A, Berenguer J, Mencía M. Deletion of the primase-polymerases encoding gene, located in a mobile element in Thermus thermophilus HB27, leads to loss of function mutation of addAB genes. Front Microbiol 2022; 13:1005862. [DOI: 10.3389/fmicb.2022.1005862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 11/08/2022] [Indexed: 12/03/2022] Open
Abstract
DNA primase-polymerases (Ppol) have been shown to play active roles in DNA repair and damage tolerance, both in prokaryotes and eukaryotes. The ancestral thermophilic bacterium Thermus thermophilus strain HB27 encodes a Ppol protein among the genes present in mobile element ICETh2, absent in other T. thermophilus strains. Using different strategies we ablated the function of Ppol in HB27 cells, either by knocking out the gene through insertional mutagenesis, markerless deletion or through abolition of its catalytic activity. Whole genome sequencing of this diverse collection of Ppol mutants showed spontaneous loss of function mutation in the helicase-nuclease AddAB in every ppol mutant isolated. Given that AddAB is a major player in recombinational repair in many prokaryotes, with similar activity to the proteobacterial RecBCD complex, we have performed a detailed characterization of the ppol mutants in combination with addAB mutants. The results show that knockout addAB mutants are more sensitive to DNA damage agents than the wild type, and present a dramatic three orders of magnitude increase in natural transformation efficiencies with both plasmid and lineal DNA, whereas ppol mutants show defects in plasmid stability. Interestingly, DNA-integrity comet assays showed that the genome of all the ppol and/or addAB mutants was severely affected by widespread fragmentation, however, this did not translate in neat loss of viability of the strains. All these data support that Ppol appears to keep in balance the activity of AddAB as a part of the DNA housekeeping maintenance in T. thermophilus HB27, thus, playing a key role in its genome stability.
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23
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Subramaniam S, Smith GR. RecBCD enzyme and Chi recombination hotspots as determinants of self vs. non-self: Myths and mechanisms. ADVANCES IN GENETICS 2022; 109:1-37. [PMID: 36334915 PMCID: PMC10047805 DOI: 10.1016/bs.adgen.2022.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bacteria face a challenge when DNA enters their cells by transformation, mating, or phage infection. Should they treat this DNA as an invasive foreigner and destroy it, or consider it one of their own and potentially benefit from incorporating new genes or alleles to gain useful functions? It is frequently stated that the short nucleotide sequence Chi (5' GCTGGTGG 3'), a hotspot of homologous genetic recombination recognized by Escherichia coli's RecBCD helicase-nuclease, allows E. coli to distinguish its DNA (self) from any other DNA (non-self) and to destroy non-self DNA, and that Chi is "over-represented" in the E. coli genome. We show here that these latter statements (dogmas) are not supported by available evidence. We note Chi's wide-spread occurrence and activity in distantly related bacterial species and phages. We illustrate multiple, highly non-random features of the genomes of E. coli and coliphage P1 that account for Chi's high frequency and genomic position, leading us to propose that P1 selects for Chi's enhancement of recombination, whereas E. coli selects for the preferred codons in Chi. We discuss other, previously described mechanisms for self vs. non-self determination involving RecBCD and for RecBCD's destruction of DNA that cannot recombine, whether foreign or domestic, with or without Chi.
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Affiliation(s)
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA, United States.
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24
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Wang BB, Xu JZ, Zhang F, Liu S, Liu J, Zhang WG. Review of DNA repair enzymes in bacteria: With a major focus on AddAB and RecBCD. DNA Repair (Amst) 2022; 118:103389. [PMID: 36030574 DOI: 10.1016/j.dnarep.2022.103389] [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: 03/14/2022] [Revised: 07/18/2022] [Accepted: 08/20/2022] [Indexed: 11/03/2022]
Abstract
DNA recombination repair systems are essential for organisms to maintain genomic stability. In recent years, we have improved our understanding of the mechanisms of RecBCD/AddAB family-mediated DNA double-strand break repair. In E. coli, it is RecBCD that plays a central role, and in Firmicute Bacillus subtilis it is the AddAB complex that functions. However, there are open questions about the mechanism of DNA repair in bacteria. For example, how bacteria containing crossover hotspot instigator (Chi) sites regulate the activity of proteins. In addition, we still do not know the exact process by which the RecB nuclease or AddA nuclease structural domains load RecA onto DNA. We also know little about the mechanism of DNA repair in the industrially important production bacterium Corynebacterium glutamicum (C. glutamicum). Therefore, exploring DNA repair mechanisms in bacteria may not only deepen our understanding of the DNA repair process in this species but also guide us in the targeted treatment of diseases associated with recombination defects, such as cancer. In this paper, we firstly review the classical proteins RecBCD and AddAB involved in DNA recombination repair, secondly focus on the novel helical nuclease AdnAB found in the genus Mycobacterium.
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Affiliation(s)
- Bing-Bing Wang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China
| | - Jian-Zhong Xu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China.
| | - Feng Zhang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China
| | - Shuai Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China
| | - Jie Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China
| | - Wei-Guo Zhang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, WuXi 214122, People's Republic of China.
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25
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Abstract
Bacterial conjugation is the fundamental process of unidirectional transfer of DNAs, often plasmid DNAs, from a donor cell to a recipient cell1. It is the primary means by which antibiotic resistance genes spread among bacterial populations2,3. In Gram-negative bacteria, conjugation is mediated by a large transport apparatus—the conjugative type IV secretion system (T4SS)—produced by the donor cell and embedded in both its outer and inner membranes. The T4SS also elaborates a long extracellular filament—the conjugative pilus—that is essential for DNA transfer4,5. Here we present a high-resolution cryo-electron microscopy (cryo-EM) structure of a 2.8 megadalton T4SS complex composed of 92 polypeptides representing 8 of the 10 essential T4SS components involved in pilus biogenesis. We added the two remaining components to the structural model using co-evolution analysis of protein interfaces, to enable the reconstitution of the entire system including the pilus. This structure describes the exceptionally large protein–protein interaction network required to assemble the many components that constitute a T4SS and provides insights on the unique mechanism by which they elaborate pili. Cryo-electron microscopy structures of a 2.8 megadalton bacterial type IV secretion system encoded by the plasmid R388 and comprising 92 polypeptides provide insights into the stepwise mechanism of pilus assembly.
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26
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Structural basis for broad anti-phage immunity by DISARM. Nat Commun 2022; 13:2987. [PMID: 35624106 PMCID: PMC9142583 DOI: 10.1038/s41467-022-30673-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 05/12/2022] [Indexed: 11/08/2022] Open
Abstract
In the evolutionary arms race against phage, bacteria have assembled a diverse arsenal of antiviral immune strategies. While the recently discovered DISARM (Defense Island System Associated with Restriction-Modification) systems can provide protection against a wide range of phage, the molecular mechanisms that underpin broad antiviral targeting but avoiding autoimmunity remain enigmatic. Here, we report cryo-EM structures of the core DISARM complex, DrmAB, both alone and in complex with an unmethylated phage DNA mimetic. These structures reveal that DrmAB core complex is autoinhibited by a trigger loop (TL) within DrmA and binding to DNA substrates containing a 5′ overhang dislodges the TL, initiating a long-range structural rearrangement for DrmAB activation. Together with structure-guided in vivo studies, our work provides insights into the mechanism of phage DNA recognition and specific activation of this widespread antiviral defense system. DISARM (Defense Island System Associated with Restriction Modification) systems can provide bacteria with protection against a wide range of phage. Here, Bravo et al. determine cryo-EM structures of the core DISARM complex that shed light onto phage DNA recognition and activation of this widespread defense system.
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Ivanova ME, Lukoyanova N, Malhotra S, Topf M, Trapani JA, Voskoboinik I, Saibil HR. The pore conformation of lymphocyte perforin. SCIENCE ADVANCES 2022; 8:eabk3147. [PMID: 35148176 PMCID: PMC8836823 DOI: 10.1126/sciadv.abk3147] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 12/17/2021] [Indexed: 05/05/2023]
Abstract
Perforin is a pore-forming protein that facilitates rapid killing of pathogen-infected or cancerous cells by the immune system. Perforin is released from cytotoxic lymphocytes, together with proapoptotic granzymes, to bind to a target cell membrane where it oligomerizes and forms pores. The pores allow granzyme entry, which rapidly triggers the apoptotic death of the target cell. Here, we present a 4-Å resolution cryo-electron microscopy structure of the perforin pore, revealing previously unidentified inter- and intramolecular interactions stabilizing the assembly. During pore formation, the helix-turn-helix motif moves away from the bend in the central β sheet to form an intermolecular contact. Cryo-electron tomography shows that prepores form on the membrane surface with minimal conformational changes. Our findings suggest the sequence of conformational changes underlying oligomerization and membrane insertion, and explain how several pathogenic mutations affect function.
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Affiliation(s)
- Marina E. Ivanova
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London WC1E 7HX, UK
- Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
| | - Natalya Lukoyanova
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London WC1E 7HX, UK
| | - Sony Malhotra
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London WC1E 7HX, UK
- Scientific Computing Department, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Fermi Ave, Harwell, Didcot OX11 0QX, UK
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London WC1E 7HX, UK
- Centre for Structural Systems Biology, Leibniz-Institut für Experimentelle Virologie and Universitätsklinikum Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Joseph A. Trapani
- Peter MacCallum Cancer Centre, 305 Grattan St, Melbourne, VIC 3000, Australia
| | - Ilia Voskoboinik
- Peter MacCallum Cancer Centre, 305 Grattan St, Melbourne, VIC 3000, Australia
| | - Helen R. Saibil
- Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet St, London WC1E 7HX, UK
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Coppola N, Cordeiro NF, Trenchi G, Esposito F, Fuga B, Fuentes-Castillo D, Lincopan N, Iriarte A, Bado I, Vignoli R. Imported One-Day-Old Chicks as Trojan Horses for Multidrug-Resistant Priority Pathogens Harboring mcr-9, rmtG, and Extended-Spectrum β-Lactamase Genes. Appl Environ Microbiol 2022; 88:e0167521. [PMID: 34731047 PMCID: PMC8788672 DOI: 10.1128/aem.01675-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/29/2021] [Indexed: 11/20/2022] Open
Abstract
Antimicrobial resistance is a critical issue that is no longer restricted to hospital settings but also represents a growing problem involving intensive animal production systems. In this study, we performed a microbiological and molecular investigation of priority pathogens carrying transferable resistance genes to critical antimicrobials in 1-day-old chickens imported from Brazil to Uruguay. Bacterial identification was performed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, and antibiotic susceptibility was determined by Sensititre. Antimicrobial resistance genes were sought by PCR, and clonality was assessed by pulsed-field gel electrophoresis (PFGE). Four multidrug-resistant (MDR) representative strains were sequenced by an Illumina and/or Oxford Nanopore Technologies device. Twenty-eight MDR isolates were identified as Escherichia coli (n = 14), Enterobacter cloacae (n = 11), or Klebsiella pneumoniae (n = 3). While resistance to oxyiminocephalosporins was due to blaCTX-M-2, blaCTX-M-8, blaCTX-M-15, blaCTX-M-55, and blaCMY-2, plasmid-mediated quinolone resistance was associated with the qnrB19, qnrE1, and qnrB2 genes. Finally, resistance to aminoglycosides and fosfomycin was due to the presence of 16S rRNA methyltransferase rmtG and fosA-type genes, respectively. Short- and long-read genome sequencing of E. cloacae strain ODC_Eclo3 revealed the presence of IncQ/rmtG (pUR-EC3.1; 7,400 bp), IncHI2A/mcr-9.1/blaCTX-M-2 (pUR-EC3.2, ST16 [pMLST; 408,436 bp), and IncN2/qnrB19/aacC3/aph(3″)-Ib (pUR-EC3.3) resistance plasmids. Strikingly, the blaCTX-M-2 gene was carried by a novel Tn1696-like composite transposon designated Tn7337. In summary, we report that imported 1-day-old chicks can act as Trojan horses for the hidden spread of WHO critical-priority MDR pathogens harboring mcr-9, rmtG, and extended-spectrum β-lactamase genes in poultry farms, which is a critical issue from a One Health perspective. IMPORTANCE Antimicrobial resistance is considered a significant problem for global health, including within the concept of One Health; therefore, the food chain connects human health and animal health directly. In this work, we searched for microorganisms resistant to antibiotics considered critical for human health in intestinal microbiota of 1-day-old baby chicks imported to Uruguay from Brazil. We describe genes for resistance to antibiotics whose use the WHO has indicated to "watch" or "reserve" (AWaRe classification), such as rmtG and mcr9.1, which confer resistance to all the aminoglycosides and colistin, respectively, among other genes, and their presence in new mobile genetic elements that favor its dissemination. The sustained entry of these microorganisms evades the sanitary measures implemented by the countries and production establishments to reduce the selection of resistant microorganisms. These silently imported resistant microorganisms could explain a considerable part of the antimicrobial resistance problems found in the production stages of the system.
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Affiliation(s)
- Nadia Coppola
- Departamento de Bacteriología y Virología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Nicolás F. Cordeiro
- Departamento de Bacteriología y Virología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | | | - Fernanda Esposito
- Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, Brazil
| | - Bruna Fuga
- Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Danny Fuentes-Castillo
- Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Nilton Lincopan
- Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, Brazil
- Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Andrés Iriarte
- Departamento de Desarrollo Biotecnológico, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Inés Bado
- Departamento de Bacteriología y Virología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Rafael Vignoli
- Departamento de Bacteriología y Virología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
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Rocha EPC, Bikard D. Microbial defenses against mobile genetic elements and viruses: Who defends whom from what? PLoS Biol 2022; 20:e3001514. [PMID: 35025885 PMCID: PMC8791490 DOI: 10.1371/journal.pbio.3001514] [Citation(s) in RCA: 80] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 01/26/2022] [Indexed: 12/27/2022] Open
Abstract
Prokaryotes have numerous mobile genetic elements (MGEs) that mediate horizontal gene transfer (HGT) between cells. These elements can be costly, even deadly, and cells use numerous defense systems to filter, control, or inactivate them. Recent studies have shown that prophages, conjugative elements, their parasites (phage satellites and mobilizable elements), and other poorly described MGEs encode defense systems homologous to those of bacteria. These constitute a significant fraction of the repertoire of cellular defense genes. As components of MGEs, these defense systems have presumably evolved to provide them, not the cell, adaptive functions. While the interests of the host and MGEs are aligned when they face a common threat such as an infection by a virulent phage, defensive functions carried by MGEs might also play more selfish roles to fend off other antagonistic MGEs or to ensure their maintenance in the cell. MGEs are eventually lost from the surviving host genomes by mutational processes and their defense systems can be co-opted when they provide an advantage to the cell. The abundance of defense systems in MGEs thus sheds new light on the role, effect, and fate of the so-called "cellular defense systems," whereby they are not only merely microbial defensive weapons in a 2-partner arms race, but also tools of intragenomic conflict between multiple genetic elements with divergent interests that shape cell fate and gene flow at the population level.
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Affiliation(s)
- Eduardo P. C. Rocha
- Institut Pasteur, Université de Paris, CNRS UMR3525, Microbial Evolutionary Genomics, Paris, France
| | - David Bikard
- Institut Pasteur, Université de Paris, Synthetic Biology, Department of Microbiology, Paris, France
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Ni T, Zhu Y, Yang Z, Xu C, Chaban Y, Nesterova T, Ning J, Böcking T, Parker MW, Monnie C, Ahn J, Perilla JR, Zhang P. Structure of native HIV-1 cores and their interactions with IP6 and CypA. SCIENCE ADVANCES 2021; 7:eabj5715. [PMID: 34797722 PMCID: PMC8604400 DOI: 10.1126/sciadv.abj5715] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 10/01/2021] [Indexed: 05/24/2023]
Abstract
The viral capsid plays essential roles in HIV replication and is a major platform engaging host factors. To overcome challenges in study native capsid structure, we used the perfringolysin O to perforate the membrane of HIV-1 particles, thus allowing host proteins and small molecules to access the native capsid while improving cryo–electron microscopy image quality. Using cryo–electron tomography and subtomogram averaging, we determined the structures of native capsomers in the presence and absence of inositol hexakisphosphate (IP6) and cyclophilin A and constructed an all-atom model of a complete HIV-1 capsid. Our structures reveal two IP6 binding sites and modes of cyclophilin A interactions. Free energy calculations substantiate the two binding sites at R18 and K25 and further show a prohibitive energy barrier for IP6 to pass through the pentamer. Our results demonstrate that perfringolysin O perforation is a valuable tool for structural analyses of enveloped virus capsids and interactions with host cell factors.
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Affiliation(s)
- Tao Ni
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Yanan Zhu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Zhengyi Yang
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| | - Chaoyi Xu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Yuriy Chaban
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| | - Tanya Nesterova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Jiying Ning
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, UNSW, Sydney, Australia
| | - Michael W. Parker
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
- St. Vincent’s Institute of Medical Research, Fitzroy, Victoria 3065, Australia
| | - Christina Monnie
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Juan R. Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Peijun Zhang
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
- Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, Oxford OX3 7BN, UK
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Unwinding of a DNA replication fork by a hexameric viral helicase. Nat Commun 2021; 12:5535. [PMID: 34545080 PMCID: PMC8452682 DOI: 10.1038/s41467-021-25843-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 08/31/2021] [Indexed: 11/16/2022] Open
Abstract
Hexameric helicases are motor proteins that unwind double-stranded DNA (dsDNA) during DNA replication but how they are optimised for strand separation is unclear. Here we present the cryo-EM structure of the full-length E1 helicase from papillomavirus, revealing all arms of a bound DNA replication fork and their interactions with the helicase. The replication fork junction is located at the entrance to the helicase collar ring, that sits above the AAA + motor assembly. dsDNA is escorted to and the 5´ single-stranded DNA (ssDNA) away from the unwinding point by the E1 dsDNA origin binding domains. The 3´ ssDNA interacts with six spirally-arranged β-hairpins and their cyclical top-to-bottom movement pulls the ssDNA through the helicase. Pulling of the RF against the collar ring separates the base-pairs, while modelling of the conformational cycle suggest an accompanying movement of the collar ring has an auxiliary role, helping to make efficient use of ATP in duplex unwinding. Replicative hexameric helicases are fundamental components of replisomes. Here the authors resolve a cryo-EM structure of the E1 helicase from papillomavirus bound to a DNA replication fork, providing insights into the mechanism of DNA unwinding by these hexameric enzymes.
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32
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Pilotto S, Fouqueau T, Lukoyanova N, Sheppard C, Lucas-Staat S, Díaz-Santín LM, Matelska D, Prangishvili D, Cheung ACM, Werner F. Structural basis of RNA polymerase inhibition by viral and host factors. Nat Commun 2021; 12:5523. [PMID: 34535646 PMCID: PMC8448823 DOI: 10.1038/s41467-021-25666-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/19/2021] [Indexed: 12/26/2022] Open
Abstract
RNA polymerase inhibition plays an important role in the regulation of transcription in response to environmental changes and in the virus-host relationship. Here we present the high-resolution structures of two such RNAP-inhibitor complexes that provide the structural bases underlying RNAP inhibition in archaea. The Acidianus two-tailed virus encodes the RIP factor that binds inside the DNA-binding channel of RNAP, inhibiting transcription by occlusion of binding sites for nucleic acid and the transcription initiation factor TFB. Infection with the Sulfolobus Turreted Icosahedral Virus induces the expression of the host factor TFS4, which binds in the RNAP funnel similarly to eukaryotic transcript cleavage factors. However, TFS4 allosterically induces a widening of the DNA-binding channel which disrupts trigger loop and bridge helix motifs. Importantly, the conformational changes induced by TFS4 are closely related to inactivated states of RNAP in other domains of life indicating a deep evolutionary conservation of allosteric RNAP inhibition.
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Affiliation(s)
- Simona Pilotto
- RNAP Laboratory, Institute for Structural and Molecular Biology, University College London, London, UK
| | - Thomas Fouqueau
- RNAP Laboratory, Institute for Structural and Molecular Biology, University College London, London, UK
| | - Natalya Lukoyanova
- Institute for Structural and Molecular Biology, Birkbeck College, London, UK
| | - Carol Sheppard
- Section of Virology, Department of Infectious disease, Imperial College London, London, UK
| | | | | | - Dorota Matelska
- RNAP Laboratory, Institute for Structural and Molecular Biology, University College London, London, UK
| | | | | | - Finn Werner
- RNAP Laboratory, Institute for Structural and Molecular Biology, University College London, London, UK.
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33
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Hao L, Zhang R, Lohman TM. Heterogeneity in E. coli RecBCD Helicase-DNA Binding and Base Pair Melting. J Mol Biol 2021; 433:167147. [PMID: 34246654 DOI: 10.1016/j.jmb.2021.167147] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/14/2021] [Accepted: 07/05/2021] [Indexed: 11/17/2022]
Abstract
E. coli RecBCD, a helicase/nuclease involved in double stranded (ds) DNA break repair, binds to a dsDNA end and melts out several DNA base pairs (bp) using only its binding free energy. We examined RecBCD-DNA initiation complexes using thermodynamic and structural approaches. Measurements of enthalpy changes for RecBCD binding to DNA ends possessing pre-melted ssDNA tails of increasing length suggest that RecBCD interacts with ssDNA as long as 17-18 nucleotides and can melt at least 10-11 bp upon binding a blunt DNA end. Cryo-EM structures of RecBCD alone and in complex with a blunt-ended dsDNA show significant conformational heterogeneities associated with the RecB nuclease domain (RecBNuc) and the RecD subunit. In the absence of DNA, 56% of RecBCD molecules show no density for the RecB nuclease domain, RecBNuc, and all RecBCD molecules show only partial density for RecD. DNA binding reduces these conformational heterogeneities, with 63% of the molecules showing density for both RecD and RecBNuc. This suggests that the RecBNuc domain is dynamic and influenced by DNA binding. The major RecBCD-DNA structural class in which RecBNuc is docked onto RecC shows melting of at least 11 bp from a blunt DNA end, much larger than previously observed. A second structural class in which RecBNuc is not docked shows only four bp melted suggesting that RecBCD complexes transition between states with different extents of DNA melting and that the extent of melting regulates initiation of helicase activity.
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Affiliation(s)
- Linxuan Hao
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Avenue, Box 8231, Saint Louis, MO 63110, United States
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Avenue, Box 8231, Saint Louis, MO 63110, United States
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Avenue, Box 8231, Saint Louis, MO 63110, United States.
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Isaev AB, Musharova OS, Severinov KV. Microbial Arsenal of Antiviral Defenses - Part I. BIOCHEMISTRY (MOSCOW) 2021; 86:319-337. [PMID: 33838632 DOI: 10.1134/s0006297921030081] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Bacteriophages or phages are viruses that infect bacterial cells (for the scope of this review we will also consider viruses that infect Archaea). Constant threat of phage infection is a major force that shapes evolution of the microbial genomes. To withstand infection, bacteria had evolved numerous strategies to avoid recognition by phages or to directly interfere with phage propagation inside the cell. Classical molecular biology and genetic engineering have been deeply intertwined with the study of phages and host defenses. Nowadays, owing to the rise of phage therapy, broad application of CRISPR-Cas technologies, and development of bioinformatics approaches that facilitate discovery of new systems, phage biology experiences a revival. This review describes variety of strategies employed by microbes to counter phage infection, with a focus on novel systems discovered in recent years. First chapter covers defense associated with cell surface, role of small molecules, and innate immunity systems relying on DNA modification.
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Affiliation(s)
- Artem B Isaev
- Skolkovo Institute of Science and Technology, Moscow, 143028, Russia.
| | - Olga S Musharova
- Skolkovo Institute of Science and Technology, Moscow, 143028, Russia. .,Institute of Molecular Genetics, Moscow, 119334, Russia
| | - Konstantin V Severinov
- Skolkovo Institute of Science and Technology, Moscow, 143028, Russia. .,Waksman Institute of Microbiology, Piscataway, NJ 08854, USA
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35
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Bianco PR, Lu Y. Single-molecule insight into stalled replication fork rescue in Escherichia coli. Nucleic Acids Res 2021; 49:4220-4238. [PMID: 33744948 PMCID: PMC8096234 DOI: 10.1093/nar/gkab142] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/22/2021] [Indexed: 01/05/2023] Open
Abstract
DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.
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Affiliation(s)
- Piero R Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
| | - Yue Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
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36
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Atherton J, Moores CA. Cryo-EM of kinesin-binding protein: challenges and opportunities from protein-surface interactions. Acta Crystallogr D Struct Biol 2021; 77:411-423. [PMID: 33825702 PMCID: PMC8025885 DOI: 10.1107/s2059798321001935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 02/17/2021] [Indexed: 11/10/2022] Open
Abstract
Kinesin-binding protein (KBP) is an important selective inhibitor of specific kinesin family members and its genetic disruption causes Goldberg-Shprintzen syndrome. Cryo-electron microscopy (cryo-EM) has recently been used to reveal the structure of KBP alone (72 kDa) and in complex with the motor domain of the mitotic kinesin-12 KIF15 (110 kDa). KBP is an α-solenoid, tetratricopeptide-repeat protein that interacts with the microtubule-binding region of the kinesin motor domain and blocks microtubule attachment. Numerous challenges arose relating to the behavior of KBP and KBP-kinesin complexes during cryo-EM sample preparation. These included the partial denaturation of KBP by air-water interfaces, protein aggregation resulting from carbon interaction and preferential orientation. Sample preparation with a graphene oxide substrate enabled the eventual structure determination. Here, experiences with preparing these samples are detailed, bringing attention to some of the challenges and opportunities that are likely to arise from protein-surface interactions.
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Affiliation(s)
- Joseph Atherton
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
- Institute of Structural and Molecular Biology, Birkbeck, University of London, London, United Kingdom
| | - Carolyn A. Moores
- Institute of Structural and Molecular Biology, Birkbeck, University of London, London, United Kingdom
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37
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Clutch mechanism of chemomechanical coupling in a DNA resecting motor nuclease. Proc Natl Acad Sci U S A 2021; 118:2023955118. [PMID: 33836607 DOI: 10.1073/pnas.2023955118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mycobacterial AdnAB is a heterodimeric helicase-nuclease that initiates homologous recombination by resecting DNA double-strand breaks (DSBs). The N-terminal motor domain of the AdnB subunit hydrolyzes ATP to drive rapid and processive 3' to 5' translocation of AdnAB on the tracking DNA strand. ATP hydrolysis is mechanically productive when oscillating protein domain motions synchronized with the ATPase cycle propel the DNA tracking strand forward by a single-nucleotide step, in what is thought to entail a pawl-and-ratchet-like fashion. By gauging the effects of alanine mutations of the 16 amino acids at the AdnB-DNA interface on DNA-dependent ATP hydrolysis, DNA translocation, and DSB resection in ensemble and single-molecule assays, we gained key insights into which DNA contacts couple ATP hydrolysis to motor activity. The results implicate AdnB Trp325, which intercalates into the tracking strand and stacks on a nucleobase, as the singular essential constituent of the ratchet pawl, without which ATP hydrolysis on ssDNA is mechanically futile. Loss of Thr663 and Thr118 contacts with tracking strand phosphates and of His665 with a nucleobase drastically slows the AdnAB motor during DSB resection. Our findings for AdnAB prompt us to analogize its mechanism to that of an automobile clutch.
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38
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Atherton J, Hummel JJA, Olieric N, Locke J, Peña A, Rosenfeld SS, Steinmetz MO, Hoogenraad CC, Moores CA. The mechanism of kinesin inhibition by kinesin-binding protein. eLife 2020; 9:e61481. [PMID: 33252036 PMCID: PMC7746232 DOI: 10.7554/elife.61481] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 11/28/2020] [Indexed: 12/25/2022] Open
Abstract
Subcellular compartmentalisation is necessary for eukaryotic cell function. Spatial and temporal regulation of kinesin activity is essential for building these local environments via control of intracellular cargo distribution. Kinesin-binding protein (KBP) interacts with a subset of kinesins via their motor domains, inhibits their microtubule (MT) attachment, and blocks their cellular function. However, its mechanisms of inhibition and selectivity have been unclear. Here we use cryo-electron microscopy to reveal the structure of KBP and of a KBP-kinesin motor domain complex. KBP is a tetratricopeptide repeat-containing, right-handed α-solenoid that sequesters the kinesin motor domain's tubulin-binding surface, structurally distorting the motor domain and sterically blocking its MT attachment. KBP uses its α-solenoid concave face and edge loops to bind the kinesin motor domain, and selected structure-guided mutations disrupt KBP inhibition of kinesin transport in cells. The KBP-interacting motor domain surface contains motifs exclusively conserved in KBP-interacting kinesins, suggesting a basis for kinesin selectivity.
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Affiliation(s)
- Joseph Atherton
- Randall Centre for Cell and Molecular Biophysics, King’s CollegeLondonUnited Kingdom
- Institute of Structural and Molecular Biology, Birkbeck, University of LondonLondonUnited Kingdom
| | - Jessica JA Hummel
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Natacha Olieric
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer InstitutVilligen PSISwitzerland
| | - Julia Locke
- Institute of Structural and Molecular Biology, Birkbeck, University of LondonLondonUnited Kingdom
| | - Alejandro Peña
- Institute of Structural and Molecular Biology, Birkbeck, University of LondonLondonUnited Kingdom
| | | | - Michel O Steinmetz
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer InstitutVilligen PSISwitzerland
- University of Basel, BiozentrumBaselSwitzerland
| | - Casper C Hoogenraad
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Carolyn A Moores
- Institute of Structural and Molecular Biology, Birkbeck, University of LondonLondonUnited Kingdom
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Pavankumar TL, Mittal P, Hallsworth JE. Molecular insights into the ecology of a psychrotolerant
Pseudomonas syringae. Environ Microbiol 2020; 23:3665-3681. [DOI: 10.1111/1462-2920.15304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/01/2020] [Accepted: 11/03/2020] [Indexed: 02/06/2023]
Affiliation(s)
- Theetha L. Pavankumar
- Department of Microbiology and Molecular Genetics, Briggs Hall, One Shields Avenue University of California Davis CA USA
| | - Pragya Mittal
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine University of Edinburgh Crewe Road South, Edinburgh, EH42XU, Scotland UK
| | - John E. Hallsworth
- Institute for Global Food Security, School of Biological Sciences Queen's University Belfast 19 Chlorine Gardens, Belfast, BT9 5DL Northern Ireland UK
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40
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Millman A, Bernheim A, Stokar-Avihail A, Fedorenko T, Voichek M, Leavitt A, Oppenheimer-Shaanan Y, Sorek R. Bacterial Retrons Function In Anti-Phage Defense. Cell 2020; 183:1551-1561.e12. [PMID: 33157039 DOI: 10.1016/j.cell.2020.09.065] [Citation(s) in RCA: 181] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 08/04/2020] [Accepted: 09/28/2020] [Indexed: 01/06/2023]
Abstract
Retrons are bacterial genetic elements comprised of a reverse transcriptase (RT) and a non-coding RNA (ncRNA). The RT uses the ncRNA as template, generating a chimeric RNA/DNA molecule in which the RNA and DNA components are covalently linked. Although retrons were discovered three decades ago, their function remained unknown. We report that retrons function as anti-phage defense systems. The defensive unit is composed of three components: the RT, the ncRNA, and an effector protein. We examined multiple retron systems and show that they confer defense against a broad range of phages via abortive infection. Focusing on retron Ec48, we show evidence that it "guards" RecBCD, a complex with central anti-phage functions in bacteria. Inhibition of RecBCD by phage proteins activates the retron, leading to abortive infection and cell death. Thus, the Ec48 retron forms a second line of defense that is triggered if the first lines of defense have collapsed.
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Affiliation(s)
- Adi Millman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Aude Bernheim
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | - Taya Fedorenko
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Maya Voichek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Azita Leavitt
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | - Rotem Sorek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
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41
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Amundsen SK, Taylor AF, Smith GR. Chi hotspot control of RecBCD helicase-nuclease by long-range intramolecular signaling. Sci Rep 2020; 10:19415. [PMID: 33154402 PMCID: PMC7644769 DOI: 10.1038/s41598-020-73078-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 09/08/2020] [Indexed: 11/09/2022] Open
Abstract
Repair of broken DNA by homologous recombination requires coordinated enzymatic reactions to prepare it for interaction with intact DNA. The multiple activities of enterobacterial RecBCD helicase-nuclease are coordinated by Chi recombination hotspots (5′ GCTGGTGG 3′) recognized during DNA unwinding. Chi is recognized in a tunnel in RecC but activates the RecB nuclease, > 25 Ǻ away. How the Chi-dependent signal travels this long distance has been unknown. We found a Chi hotspot-deficient mutant in the RecB helicase domain located > 45 Ǻ from both the Chi-recognition site and the nuclease active site. This unexpected observation led us to find additional mutations that reduced or eliminated Chi hotspot activity in each subunit and widely scattered throughout RecBCD. Each mutation alters the intimate contact between one or another pair of subunits in crystal or cryoEM structures of RecBCD bound to DNA. Collectively, these mutations span a path about 185 Ǻ long from the Chi recognition site to the nuclease active site. We discuss these surprising results in the context of an intramolecular signal transduction accounting for many previous observations.
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Affiliation(s)
- Susan K Amundsen
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Andrew F Taylor
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
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42
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Gurung D, Blumenthal RM. Distribution of RecBCD and AddAB recombination-associated genes among bacteria in 33 phyla. MICROBIOLOGY-SGM 2020; 166:1047-1064. [PMID: 33085588 DOI: 10.1099/mic.0.000980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Homologous recombination plays key roles in fundamental processes such as recovery from DNA damage and in bacterial horizontal gene transfer, yet there are still open questions about the distribution of recognized components of recombination machinery among bacteria and archaea. RecBCD helicase-nuclease plays a central role in recombination among Gammaproteobacteria like Escherichia coli; while bacteria in other phyla, like the Firmicute Bacillus subtilis, use the related AddAB complex. The activity of at least some of these complexes is controlled by short DNA sequences called crossover hotspot instigator (Chi) sites. When RecBCD or AddAB complexes encounter an autologous Chi site during unwinding, they introduce a nick such that ssDNA with a free end is available to invade another duplex. If homologous DNA is present, RecA-dependent homologous recombination is promoted; if not (or if no autologous Chi site is present) the RecBCD/AddAB complex eventually degrades the DNA. We examined the distribution of recBCD and addAB genes among bacteria, and sought ways to distinguish them unambiguously. We examined bacterial species among 33 phyla, finding some unexpected distribution patterns. RecBCD and addAB are less conserved than recA, with the orthologous recB and addA genes more conserved than the recC or addB genes. We were able to classify RecB vs. AddA and RecC vs. AddB in some bacteria where this had not previously been done. We used logo analysis to identify sequence segments that are conserved, but differ between the RecBC and AddAB proteins, to help future differentiation between members of these two families.
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Affiliation(s)
- Deepti Gurung
- Present address: Department of Cancer Biology, College of Medicine & Life Sciences, The University of Toledo, Toledo OH 43614-1021, USA.,Department of Medical Microbiology & Immunology, and Program in Bioinformatics, College of Medicine & Life Sciences, The University of Toledo, Toledo OH 43614-1021, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology & Immunology, and Program in Bioinformatics, College of Medicine & Life Sciences, The University of Toledo, Toledo OH 43614-1021, USA
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Karabulut AC, Cirz RT, Taylor AF, Smith GR. Small-molecule sensitization of RecBCD helicase-nuclease to a Chi hotspot-activated state. Nucleic Acids Res 2020; 48:7973-7980. [PMID: 32597964 PMCID: PMC7641324 DOI: 10.1093/nar/gkaa534] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/22/2020] [Accepted: 06/10/2020] [Indexed: 11/13/2022] Open
Abstract
Coordinating multiple activities of complex enzymes is critical for life, including transcribing, replicating and repairing DNA. Bacterial RecBCD helicase-nuclease must coordinate DNA unwinding and cutting to repair broken DNA. Starting at a DNA end, RecBCD unwinds DNA with its fast RecD helicase on the 5'-ended strand and its slower RecB helicase on the 3'-ended strand. At Chi hotspots (5' GCTGGTGG 3'), RecB's nuclease cuts the 3'-ended strand and loads RecA strand-exchange protein onto it. We report that a small molecule NSAC1003, a sulfanyltriazolobenzimidazole, mimics Chi sites by sensitizing RecBCD to cut DNA at a Chi-independent position a certain percent of the DNA substrate's length. This percent decreases with increasing NSAC1003 concentration. Our data indicate that NSAC1003 slows RecB relative to RecD and sensitizes it to cut DNA when the leading helicase RecD stops at the DNA end. Two previously described RecBCD mutants altered in the RecB ATP-binding site also have this property, but uninhibited wild-type RecBCD lacks it. ATP and NSAC1003 are competitive; computation docks NSAC1003 into RecB's ATP-binding site, suggesting NSAC1003 acts directly on RecB. NSAC1003 will help elucidate molecular mechanisms of RecBCD-Chi regulation and DNA repair. Similar studies could help elucidate other DNA enzymes with activities coordinated at chromosomal sites.
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Affiliation(s)
- Ahmet C Karabulut
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | | | - Andrew F Taylor
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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