1
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Adams MC, Schiltz C, Sun J, Hosford C, Johnson V, Pan H, Borbat P, Freed J, Thomason L, Court C, Court D, Chappie J. The crystal structure of bacteriophage λ RexA provides novel insights into the DNA binding properties of Rex-like phage exclusion proteins. Nucleic Acids Res 2024; 52:4659-4675. [PMID: 38554102 PMCID: PMC11077077 DOI: 10.1093/nar/gkae212] [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: 09/05/2023] [Revised: 03/07/2024] [Accepted: 03/12/2024] [Indexed: 04/01/2024] Open
Abstract
RexA and RexB function as an exclusion system that prevents bacteriophage T4rII mutants from growing on Escherichia coli λ phage lysogens. Recent data established that RexA is a non-specific DNA binding protein that can act independently of RexB to bias the λ bistable switch toward the lytic state, preventing conversion back to lysogeny. The molecular interactions underlying these activities are unknown, owing in part to a dearth of structural information. Here, we present the 2.05-Å crystal structure of the λ RexA dimer, which reveals a two-domain architecture with unexpected structural homology to the recombination-associated protein RdgC. Modelling suggests that our structure adopts a closed conformation and would require significant domain rearrangements to facilitate DNA binding. Mutagenesis coupled with electromobility shift assays, limited proteolysis, and double electron-electron spin resonance spectroscopy support a DNA-dependent conformational change. In vivo phenotypes of RexA mutants suggest that DNA binding is not a strict requirement for phage exclusion but may directly contribute to modulation of the bistable switch. We further demonstrate that RexA homologs from other temperate phages also dimerize and bind DNA in vitro. Collectively, these findings advance our mechanistic understanding of Rex functions and provide new evolutionary insights into different aspects of phage biology.
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Affiliation(s)
- Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Carl J Schiltz
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Jing Sun
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | | | - Virginia M Johnson
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Hao Pan
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
- National Biomedical Resource for Advanced Electron Spin Resonance Spectroscopy, Cornell University, Ithaca, NY 14853, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
- National Biomedical Resource for Advanced Electron Spin Resonance Spectroscopy, Cornell University, Ithaca, NY 14853, USA
| | - Lynn C Thomason
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Carolyn Court
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Donald L Court
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
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2
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Patel PH, Taylor VL, Zhang C, Getz LJ, Fitzpatrick AD, Davidson AR, Maxwell KL. Anti-phage defence through inhibition of virion assembly. Nat Commun 2024; 15:1644. [PMID: 38388474 PMCID: PMC10884400 DOI: 10.1038/s41467-024-45892-x] [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: 11/21/2023] [Accepted: 02/06/2024] [Indexed: 02/24/2024] Open
Abstract
Bacteria have evolved diverse antiviral defence mechanisms to protect themselves against phage infection. Phages integrated into bacterial chromosomes, known as prophages, also encode defences that protect the bacterial hosts in which they reside. Here, we identify a type of anti-phage defence that interferes with the virion assembly pathway of invading phages. The protein that mediates this defence, which we call Tab (for 'Tail assembly blocker'), is constitutively expressed from a Pseudomonas aeruginosa prophage. Tab allows the invading phage replication cycle to proceed, but blocks assembly of the phage tail, thus preventing formation of infectious virions. While the infected cell dies through the activity of the replicating phage lysis proteins, there is no release of infectious phage progeny, and the bacterial community is thereby protected from a phage epidemic. Prophages expressing Tab are not inhibited during their own lytic cycle because they express a counter-defence protein that interferes with Tab function. Thus, our work reveals an anti-phage defence that operates by blocking virion assembly, thereby both preventing formation of phage progeny and allowing destruction of the infected cell due to expression of phage lysis genes.
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Affiliation(s)
| | | | - Chi Zhang
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Landon J Getz
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | | | - Alan R Davidson
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Karen L Maxwell
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
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3
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Mohammed HT, Mageeney C, Korenberg J, Graham L, Ware VC. Characterization of novel recombinant mycobacteriophages derived from homologous recombination between two temperate phages. G3 (BETHESDA, MD.) 2023; 13:jkad210. [PMID: 37713616 PMCID: PMC10700106 DOI: 10.1093/g3journal/jkad210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 08/15/2023] [Accepted: 08/31/2023] [Indexed: 09/17/2023]
Abstract
Comparative analyses of mycobacteriophage genomes reveals extensive genetic diversity in genome organization and gene content, contributing to widespread mosaicism. We previously reported that the prophage of mycobacteriophage Butters (cluster N) provides defense against infection by Island3 (subcluster I1). To explore the anti-Island3 defense mechanism, we attempted to isolate Island3 defense escape mutants on a Butters lysogen, but only uncovered phages with recombinant genomes comprised of regions of Butters and Island3 arranged from left arm to right arm as Butters-Island3-Butters (BIBs). Recombination occurs within two distinct homologous regions that encompass lysin A, lysin B, and holin genes in one segment, and RecE and RecT genes in the other. Structural genes of mosaic BIB genomes are contributed by Butters while the immunity cassette is derived from Island3. Consequently, BIBs are morphologically identical to Butters (as shown by transmission electron microscopy) but are homoimmune with Island3. Recombinant phages overcome antiphage defense and silencing of the lytic cycle. We leverage this observation to propose a stratagem to generate novel phages for potential therapeutic use.
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Affiliation(s)
- Hamidu T Mohammed
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
- Memsel, Inc., 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA
| | - Catherine Mageeney
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
- Biotechnology and Bioengineering Department, Sandia National Laboratories, Livermore, CA 94551, USA
| | - Jamie Korenberg
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
- New York Institute of Technology College of Osteopathic Medicine, 101 Northern Blvd., Glen Head, NY 11545, USA
| | - Lee Graham
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
| | - Vassie C Ware
- Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
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4
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Dot EW, Thomason LC, Chappie JS. Everything OLD is new again: How structural, functional, and bioinformatic advances have redefined a neglected nuclease family. Mol Microbiol 2023; 120:122-140. [PMID: 37254295 DOI: 10.1111/mmi.15074] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 04/28/2023] [Accepted: 04/30/2023] [Indexed: 06/01/2023]
Abstract
Overcoming lysogenization defect (OLD) proteins are a conserved family of ATP-powered nucleases that function in anti-phage defense. Recent bioinformatic, genetic, and crystallographic studies have yielded new insights into the structure, function, and evolution of these enzymes. Here we review these developments and propose a new classification scheme to categorize OLD homologs that relies on gene neighborhoods, biochemical properties, domain organization, and catalytic machinery. This taxonomy reveals important similarities and differences between family members and provides a blueprint to contextualize future in vivo and in vitro findings. We also detail how OLD nucleases are related to PARIS and Septu anti-phage defense systems and discuss important mechanistic questions that remain unanswered.
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Affiliation(s)
- Elena Wanvig Dot
- Department of Molecular Medicine, Cornell University, Ithaca, New York, USA
| | - Lynn C Thomason
- Molecular Control and Genetics Section, RNA Biology Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, New York, USA
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5
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Georjon H, Tesson F, Shomar H, Bernheim A. Genomic characterization of the antiviral arsenal of Actinobacteria. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001374. [PMID: 37531269 PMCID: PMC10482375 DOI: 10.1099/mic.0.001374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/18/2023] [Indexed: 08/04/2023]
Abstract
Phages are ubiquitous in nature, and bacteria with very different genomics, metabolisms, and lifestyles are subjected to their predation. Yet, the defence systems that allow bacteria to resist their phages have rarely been explored experimentally outside a very limited number of model organisms. Actinobacteria (Actinomycetota) are a phylum of GC-rich Gram-positive bacteria, which often produce an important diversity of secondary metabolites. Despite being ubiquitous in a wide range of environments, from soil to fresh and sea water but also the gut microbiome, relatively little is known about the anti-phage arsenal of Actinobacteria. In this work, we used DefenseFinder to systematically detect 131 anti-phage defence systems in 22803 fully sequenced prokaryotic genomes, among which are 2253 Actinobacteria of more than 700 species. We show that, like other bacteria, Actinobacteria encode many diverse anti-phage systems that are often encoded on mobile genetic elements. We further demonstrate that most detected defence systems are absent or rarer in Actinobacteria than in other bacteria, while a few rare systems are enriched (notably gp29-gp30 and Wadjet). We characterize the spatial distribution of anti-phage systems on Streptomyces chromosomes and show that some defence systems (e.g. RM systems) tend to be encoded in the core region, while others (e.g. Lamassu and Wadjet) are enriched towards the extremities. Overall, our results suggest that Actinobacteria might be a source of novel anti-phage systems and provide clues to characterize mechanistic aspects of known anti-phage systems.
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Affiliation(s)
- Héloïse Georjon
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, Inserm U1284, Paris, France
| | - Florian Tesson
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, Inserm U1284, Paris, France
- UMR 1137, IAME, Université de Paris, INSERM, Paris, France
| | - Helena Shomar
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, Inserm U1284, Paris, France
| | - Aude Bernheim
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, Inserm U1284, Paris, France
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Patel PH, Maxwell KL. Prophages provide a rich source of antiphage defense systems. Curr Opin Microbiol 2023; 73:102321. [PMID: 37121062 DOI: 10.1016/j.mib.2023.102321] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/26/2023] [Accepted: 03/27/2023] [Indexed: 05/02/2023]
Abstract
Temperate phages are pervasive in nature, existing within bacterial cells in a form known as prophages. In this state, survival of the phage is intricately tied to the survival of the bacterial host. As a result, prophages often encode genes that increase bacterial fitness. One important way to increase survival is to provide defense against competing phages. Recent work reviewed here reveals that prophages provide a diverse and robust reservoir of antiphage defense systems that likely play a major role in bacterial-phage dynamics.
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Affiliation(s)
- Pramalkumar H Patel
- Department of Biochemistry, University of Toronto, MaRS West Tower, 661 University Avenue, Toronto, ON M5G 1M1, Canada
| | - Karen L Maxwell
- Department of Biochemistry, University of Toronto, MaRS West Tower, 661 University Avenue, Toronto, ON M5G 1M1, Canada.
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7
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Thomason LC, Schiltz CJ, Court C, Hosford CJ, Adams MC, Chappie JS, Court DL. Bacteriophage λ RexA and RexB Functions Assist the Transition from Lysogeny to Lytic Growth. Mol Microbiol 2021; 116:1044-1063. [PMID: 34379857 DOI: 10.1111/mmi.14792] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 11/26/2022]
Abstract
The CI and Cro repressors of bacteriophage λ create a bistable switch between lysogenic and lytic growth. In λ lysogens, CI repressor expressed from the PRM promoter blocks expression of the lytic promoters PL and PR to allow stable maintenance of the lysogenic state. When lysogens are induced, CI repressor is inactivated and Cro repressor is expressed from the lytic PR promoter. Cro repressor blocks PRM transcription and CI repressor synthesis to ensure that the lytic state proceeds. RexA and RexB proteins, like CI, are expressed from the PRM promoter in λ lysogens; RexB is also expressed from a second promoter, PLIT , embedded in rexA. Here we show that RexA binds CI repressor and assists the transition from lysogenic to lytic growth, using both intact lysogens and defective prophages with reporter genes under control of the lytic PL and PR promoters. Once lytic growth begins, if the bistable switch does return to the immune state, RexA expression lessens the probability that it will remain there, thus stabilizing the lytic state and activation of the lytic PL and PR promoters. RexB modulates the effect of RexA and may also help establish phage DNA replication as lytic growth ensues.
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Affiliation(s)
- Lynn C Thomason
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, 21702.,RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
| | - Carl J Schiltz
- Department of Molecular Medicine, Cornell University, Ithaca, 14850.,Department of Biological Sciences and Center for Structural Biology, Vanderbilt University, Nashville, TN, 37232, USA
| | - Carolyn Court
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
| | - Christopher J Hosford
- Department of Molecular Medicine, Cornell University, Ithaca, 14850.,New England Biolabs, Inc, Ipswich, MA, USA
| | - Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, 14850
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, 14850
| | - Donald L Court
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
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