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Kutnowski N, Ghanim GE, Lee Y, Rio DC. Activity of zebrafish THAP9 transposase and zebrafish P element-like transposons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.22.586318. [PMID: 38562726 PMCID: PMC10983969 DOI: 10.1101/2024.03.22.586318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Transposable elements are mobile DNA segments that are found ubiquitously across the three domains of life. One family of transposons, called P elements, were discovered in the fruit fly Drosophila melanogaster. Since their discovery, P element transposase-homologous genes (called THAP-domain containing 9 or THAP9) have been discovered in other animal genomes. Here, we show that the zebrafish (Danio rerio) genome contains both an active THAP9 transposase (zfTHAP9) and mobile P-like transposable elements (called Pdre). zfTHAP9 transposase can excise one of its own elements (Pdre2) and Drosophila P elements. Drosophila P element transposase (DmTNP) is also able to excise the zebrafish Pdre2 element, even though it's distinct from the Drosophila P element. However, zfTHAP9 cannot transpose Pdre2 or Drosophila P elements, indicating partial transposase activity. Characterization of the N-terminal THAP DNA binding domain of zfTHAP9 shows distinct DNA binding site preferences from DmTNP and mutation of the zfTHAP9, based on known mutations in DmTNP, generated a hyperactive protein,. These results define an active vertebrate THAP9 transposase that can act on the endogenous zebrafish Pdre and Drosophila P elements.
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Affiliation(s)
- Nitzan Kutnowski
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA
| | - George E Ghanim
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA
| | - Yeon Lee
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA
| | - Donald C Rio
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA
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2
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Hoffmann FT, Kim M, Beh LY, Wang J, Vo PLH, Gelsinger DR, George JT, Acree C, Mohabir JT, Fernández IS, Sternberg SH. Selective TnsC recruitment enhances the fidelity of RNA-guided transposition. Nature 2022; 609:384-393. [PMID: 36002573 PMCID: PMC10583602 DOI: 10.1038/s41586-022-05059-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 06/29/2022] [Indexed: 01/25/2023]
Abstract
Bacterial transposons are pervasive mobile genetic elements that use distinct DNA-binding proteins for horizontal transmission. For example, Escherichia coli Tn7 homes to a specific attachment site using TnsD1, whereas CRISPR-associated transposons use type I or type V Cas effectors to insert downstream of target sites specified by guide RNAs2,3. Despite this targeting diversity, transposition invariably requires TnsB, a DDE-family transposase that catalyses DNA excision and insertion, and TnsC, a AAA+ ATPase that is thought to communicate between transposase and targeting proteins4. How TnsC mediates this communication and thereby regulates transposition fidelity has remained unclear. Here we use chromatin immunoprecipitation with sequencing to monitor in vivo formation of the type I-F RNA-guided transpososome, enabling us to resolve distinct protein recruitment events before integration. DNA targeting by the TniQ-Cascade complex is surprisingly promiscuous-hundreds of genomic off-target sites are sampled, but only a subset of those sites is licensed for TnsC and TnsB recruitment, revealing a crucial proofreading checkpoint. To advance the mechanistic understanding of interactions responsible for transpososome assembly, we determined structures of TnsC using cryogenic electron microscopy and found that ATP binding drives the formation of heptameric rings that thread DNA through the central pore, thereby positioning the substrate for downstream integration. Collectively, our results highlight the molecular specificity imparted by consecutive factor binding to genomic target sites during RNA-guided transposition, and provide a structural roadmap to guide future engineering efforts.
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Affiliation(s)
- Florian T Hoffmann
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Minjoo Kim
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Department of Biomedical Engineering, New York University Tandon School of Engineering, New York, NY, USA
| | - Leslie Y Beh
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Illumina Singapore Pte, Ltd., Singapore, Singapore
| | - Jing Wang
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- The National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Phuc Leo H Vo
- Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, NY, USA
- Vertex Pharmaceuticals, Boston, MA, USA
| | - Diego R Gelsinger
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Jerrin Thomas George
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Christopher Acree
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Jason T Mohabir
- Department of Computer Science, Columbia University, New York, NY, USA
- Genomic Center for Infectious Diseases, Broad Institute, Cambridge, MA, USA
| | - Israel S Fernández
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
| | - Samuel H Sternberg
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
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3
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Park JU, Tsai AWL, Chen TH, Peters JE, Kellogg EH. Mechanistic details of CRISPR-associated transposon recruitment and integration revealed by cryo-EM. Proc Natl Acad Sci U S A 2022; 119:e2202590119. [PMID: 35914146 PMCID: PMC9371665 DOI: 10.1073/pnas.2202590119] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 06/04/2022] [Indexed: 11/18/2022] Open
Abstract
CRISPR-associated transposons (CASTs) are Tn7-like elements that are capable of RNA-guided DNA integration. Although structural data are known for nearly all core transposition components, the transposase component, TnsB, remains uncharacterized. Using cryo-electron microscopy (cryo-EM) structure determination, we reveal the conformation of TnsB during transposon integration for the type V-K CAST system from Scytonema hofmanni (ShCAST). Our structure of TnsB is a tetramer, revealing strong mechanistic relationships with the overall architecture of RNaseH transposases/integrases in general, and in particular the MuA transposase from bacteriophage Mu. However, key structural differences in the C-terminal domains indicate that TnsB's tetrameric architecture is stabilized by a different set of protein-protein interactions compared with MuA. We describe the base-specific interactions along the TnsB binding site, which explain how different CAST elements can function on cognate mobile elements independent of one another. We observe that melting of the 5' nontransferred strand of the transposon end is a structural feature stabilized by TnsB and furthermore is crucial for donor-DNA integration. Although not observed in the TnsB strand-transfer complex, the C-terminal end of TnsB serves a crucial role in transposase recruitment to the target site. The C-terminal end of TnsB adopts a short, structured 15-residue "hook" that decorates TnsC filaments. Unlike full-length TnsB, C-terminal fragments do not appear to stimulate filament disassembly using two different assays, suggesting that additional interactions between TnsB and TnsC are required for redistributing TnsC to appropriate targets. The structural information presented here will help guide future work in modifying these important systems as programmable gene integration tools.
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Affiliation(s)
- Jung-Un Park
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
| | - Amy Wei-Lun Tsai
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
| | - Tiffany H Chen
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
| | - Joseph E Peters
- Department of Microbiology, Cornell University, Ithaca, NY 14853
| | - Elizabeth H Kellogg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
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4
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Kaczmarska Z, Czarnocki-Cieciura M, Górecka-Minakowska KM, Wingo RJ, Jackiewicz J, Zajko W, Poznański JT, Rawski M, Grant T, Peters JE, Nowotny M. Structural basis of transposon end recognition explains central features of Tn7 transposition systems. Mol Cell 2022; 82:2618-2632.e7. [PMID: 35654042 PMCID: PMC9308760 DOI: 10.1016/j.molcel.2022.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 03/02/2022] [Accepted: 05/03/2022] [Indexed: 02/06/2023]
Abstract
Tn7 is a bacterial transposon with relatives containing element-encoded CRISPR-Cas systems mediating RNA-guided transposon insertion. Here, we present the 2.7 Å cryoelectron microscopy structure of prototypic Tn7 transposase TnsB interacting with the transposon end DNA. When TnsB interacts across repeating binding sites, it adopts a beads-on-a-string architecture, where the DNA-binding and catalytic domains are arranged in a tiled and intertwined fashion. The DNA-binding domains form few base-specific contacts leading to a binding preference that requires multiple weakly conserved sites at the appropriate spacing to achieve DNA sequence specificity. TnsB binding imparts differences in the global structure of the protein-bound DNA ends dictated by the spacing or overlap of binding sites explaining functional differences in the left and right ends of the element. We propose a model of the strand-transfer complex in which the terminal TnsB molecule is rearranged so that its catalytic domain is in a position conducive to transposition.
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Affiliation(s)
- Zuzanna Kaczmarska
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Mariusz Czarnocki-Cieciura
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | | | - Robert J Wingo
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Justyna Jackiewicz
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Weronika Zajko
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Jarosław T Poznański
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Michał Rawski
- Malopolska Centre of Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Timothy Grant
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, WI 53715, USA; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Joseph E Peters
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA.
| | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland.
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5
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Miskey C, Kesselring L, Querques I, Abrusán G, Barabas O, Ivics Z. OUP accepted manuscript. Nucleic Acids Res 2022; 50:2807-2825. [PMID: 35188569 PMCID: PMC8934666 DOI: 10.1093/nar/gkac092] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/24/2022] [Accepted: 02/08/2022] [Indexed: 11/14/2022] Open
Abstract
The Sleeping Beauty (SB) transposon system is a popular tool for genome engineering, but random integration into the genome carries a certain genotoxic risk in therapeutic applications. Here we investigate the role of amino acids H187, P247 and K248 in target site selection of the SB transposase. Structural modeling implicates these three amino acids located in positions analogous to amino acids with established functions in target site selection in retroviral integrases and transposases. Saturation mutagenesis of these residues in the SB transposase yielded variants with altered target site selection properties. Transposon integration profiling of several mutants reveals increased specificity of integrations into palindromic AT repeat target sequences in genomic regions characterized by high DNA bendability. The H187V and K248R mutants redirect integrations away from exons, transcriptional regulatory elements and nucleosomal DNA in the human genome, suggesting enhanced safety and thus utility of these SB variants in gene therapy applications.
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Affiliation(s)
| | | | - Irma Querques
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
- Department of Biochemistry, University of Zurich, Zurich 8057, Switzerland
| | - György Abrusán
- Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, Szeged 6726, Hungary
| | - Orsolya Barabas
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
- Department of Molecular Biology, University of Geneva, Geneva 1211, Switzerland
| | - Zoltán Ivics
- To whom correspondence should be addressed. Tel: +49 6103 77 6000; Fax: +49 6103 77 1280;
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6
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Badel C, Da Cunha V, Oberto J. Archaeal tyrosine recombinases. FEMS Microbiol Rev 2021; 45:fuab004. [PMID: 33524101 PMCID: PMC8371274 DOI: 10.1093/femsre/fuab004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 01/13/2021] [Indexed: 12/16/2022] Open
Abstract
The integration of mobile genetic elements into their host chromosome influences the immediate fate of cellular organisms and gradually shapes their evolution. Site-specific recombinases catalyzing this integration have been extensively characterized both in bacteria and eukarya. More recently, a number of reports provided the in-depth characterization of archaeal tyrosine recombinases and highlighted new particular features not observed in the other two domains. In addition to being active in extreme environments, archaeal integrases catalyze reactions beyond site-specific recombination. Some of these integrases can catalyze low-sequence specificity recombination reactions with the same outcome as homologous recombination events generating deep rearrangements of their host genome. A large proportion of archaeal integrases are termed suicidal due to the presence of a specific recombination target within their own gene. The paradoxical maintenance of integrases that disrupt their gene upon integration implies novel mechanisms for their evolution. In this review, we assess the diversity of the archaeal tyrosine recombinases using a phylogenomic analysis based on an exhaustive similarity network. We outline the biochemical, ecological and evolutionary properties of these enzymes in the context of the families we identified and emphasize similarities and differences between archaeal recombinases and their bacterial and eukaryal counterparts.
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Affiliation(s)
- Catherine Badel
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Violette Da Cunha
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Jacques Oberto
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
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7
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Park JU, Tsai AWL, Mehrotra E, Petassi MT, Hsieh SC, Ke A, Peters JE, Kellogg EH. Structural basis for target site selection in RNA-guided DNA transposition systems. Science 2021; 373:768-774. [PMID: 34385391 DOI: 10.1126/science.abi8976] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 07/07/2021] [Indexed: 12/31/2022]
Abstract
CRISPR-associated transposition systems allow guide RNA-directed integration of a single DNA cargo in one orientation at a fixed distance from a programmable target sequence. We used cryo-electron microscopy (cryo-EM) to define the mechanism that underlies this process by characterizing the transposition regulator, TnsC, from a type V-K CRISPR-transposase system. In this scenario, polymerization of adenosine triphosphate-bound TnsC helical filaments could explain how polarity information is passed to the transposase. TniQ caps the TnsC filament, representing a universal mechanism for target information transfer in Tn7/Tn7-like elements. Transposase-driven disassembly establishes delivery of the element only to unused protospacers. Finally, TnsC transitions to define the fixed point of insertion, as revealed by structures with the transition state mimic ADP•AlF3 These mechanistic findings provide the underpinnings for engineering CRISPR-associated transposition systems for research and therapeutic applications.
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Affiliation(s)
- Jung-Un Park
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Amy Wei-Lun Tsai
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Eshan Mehrotra
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Michael T Petassi
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Shan-Chi Hsieh
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Ailong Ke
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Joseph E Peters
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA.
| | - Elizabeth H Kellogg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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8
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Chen X, Gellert M, Yang W. Inner workings of RAG recombinase and its specialization for adaptive immunity. Curr Opin Struct Biol 2021; 71:79-86. [PMID: 34245989 DOI: 10.1016/j.sbi.2021.05.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 05/31/2021] [Indexed: 01/03/2023]
Abstract
RAG1/2 (RAG) is an RNH-type DNA recombinase specially evolved to initiate V(D)J gene rearrangement for generating the adaptive immune response in jawed vertebrates. After decades of frustration with little mechanistic understanding of RAG, the crystal structure of mouse RAG recombinase opened the flood gates in early 2015. Structures of three different chordate RAG recombinases, including protoRAG, and the evolutionarily preceding transib transposase have been determined in complex with various DNA substrates. Biochemical studies along with the abundant structural data have shed light on how RAG has evolved from an ordinary transposase to a specialized recombinase in initiating gene rearrangement. RAG has also become one of the best characterized RNH-type recombinases, illustrating how a single active site can cleave the two antiparallel DNA strands of a double helix.
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Affiliation(s)
- Xuemin Chen
- Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Martin Gellert
- Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Yang
- Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA.
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9
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Callens M, Pradier L, Finnegan M, Rose C, Bedhomme S. Read between the lines: Diversity of non-translational selection pressures on local codon usage. Genome Biol Evol 2021; 13:6263832. [PMID: 33944930 PMCID: PMC8410138 DOI: 10.1093/gbe/evab097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2021] [Indexed: 12/14/2022] Open
Abstract
Protein coding genes can contain specific motifs within their nucleotide sequence that function as a signal for various biological pathways. The presence of such sequence motifs within a gene can have beneficial or detrimental effects on the phenotype and fitness of an organism, and this can lead to the enrichment or avoidance of this sequence motif. The degeneracy of the genetic code allows for the existence of alternative synonymous sequences that exclude or include these motifs, while keeping the encoded amino acid sequence intact. This implies that locally, there can be a selective pressure for preferentially using a codon over its synonymous alternative in order to avoid or enrich a specific sequence motif. This selective pressure could -in addition to mutation, drift and selection for translation efficiency and accuracy- contribute to shape the codon usage bias. In this review, we discuss patterns of avoidance of (or enrichment for) the various biological signals contained in specific nucleotide sequence motifs: transcription and translation initiation and termination signals, mRNA maturation signals, and antiviral immune system targets. Experimental data on the phenotypic or fitness effects of synonymous mutations in these sequence motifs confirm that they can be targets of local selection pressures on codon usage. We also formulate the hypothesis that transposable elements could have a similar impact on codon usage through their preferred integration sequences. Overall, selection on codon usage appears to be a combination of a global selection pressure imposed by the translation machinery, and a patchwork of local selection pressures related to biological signals contained in specific sequence motifs.
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Affiliation(s)
- Martijn Callens
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Léa Pradier
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Michael Finnegan
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Caroline Rose
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Stéphanie Bedhomme
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
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10
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Harris HMB, Hill C. A Place for Viruses on the Tree of Life. Front Microbiol 2021; 11:604048. [PMID: 33519747 PMCID: PMC7840587 DOI: 10.3389/fmicb.2020.604048] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/14/2020] [Indexed: 12/15/2022] Open
Abstract
Viruses are ubiquitous. They infect almost every species and are probably the most abundant biological entities on the planet, yet they are excluded from the Tree of Life (ToL). However, there can be no doubt that viruses play a significant role in evolution, the force that facilitates all life on Earth. Conceptually, viruses are regarded by many as non-living entities that hijack living cells in order to propagate. A strict separation between living and non-living entities places viruses far from the ToL, but this may be theoretically unsound. Advances in sequencing technology and comparative genomics have expanded our understanding of the evolutionary relationships between viruses and cellular organisms. Genomic and metagenomic data have revealed that co-evolution between viral and cellular genomes involves frequent horizontal gene transfer and the occasional co-option of novel functions over evolutionary time. From the giant, ameba-infecting marine viruses to the tiny Porcine circovirus harboring only two genes, viruses and their cellular hosts are ecologically and evolutionarily intertwined. When deciding how, if, and where viruses should be placed on the ToL, we should remember that the Tree functions best as a model of biological evolution on Earth, and it is important that models themselves evolve with our increasing understanding of biological systems.
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Affiliation(s)
- Hugh M B Harris
- APC Microbiome Ireland, College of Medicine and Health, University College Cork, Cork, Ireland
| | - Colin Hill
- APC Microbiome Ireland, College of Medicine and Health, University College Cork, Cork, Ireland.,School of Microbiology, University College Cork, Cork, Ireland
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11
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Zhang Y, Corbett E, Wu S, Schatz DG. Structural basis for the activation and suppression of transposition during evolution of the RAG recombinase. EMBO J 2020; 39:e105857. [PMID: 32945578 DOI: 10.15252/embj.2020105857] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 08/17/2020] [Accepted: 08/20/2020] [Indexed: 11/09/2022] Open
Abstract
Jawed vertebrate adaptive immunity relies on the RAG1/RAG2 (RAG) recombinase, a domesticated transposase, for assembly of antigen receptor genes. Using an integration-activated form of RAG1 with methionine at residue 848 and cryo-electron microscopy, we determined structures that capture RAG engaged with transposon ends and U-shaped target DNA prior to integration (the target capture complex) and two forms of the RAG strand transfer complex that differ based on whether target site DNA is annealed or dynamic. Target site DNA base unstacking, flipping, and melting by RAG1 methionine 848 explain how this residue activates transposition, how RAG can stabilize sharp bends in target DNA, and why replacement of residue 848 by arginine during RAG domestication led to suppression of transposition activity. RAG2 extends a jawed vertebrate-specific loop to interact with target site DNA, and functional assays demonstrate that this loop represents another evolutionary adaptation acquired during RAG domestication to inhibit transposition. Our findings identify mechanistic principles of the final step in cut-and-paste transposition and the molecular and structural logic underlying the transformation of RAG from transposase to recombinase.
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Affiliation(s)
- Yuhang Zhang
- Department of Immunobiology, Yale School of Medicine, New Haven, CT, USA
| | - Elizabeth Corbett
- Department of Immunobiology, Yale School of Medicine, New Haven, CT, USA
| | - Shenping Wu
- Department of Pharmacology, Yale School of Medicine West Haven, New Haven, CT, USA
| | - David G Schatz
- Department of Immunobiology, Yale School of Medicine, New Haven, CT, USA
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12
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Garrett S, Shiimori M, Watts EA, Clark L, Graveley BR, Terns MP. Primed CRISPR DNA uptake in Pyrococcus furiosus. Nucleic Acids Res 2020; 48:6120-6135. [PMID: 32421777 PMCID: PMC7293040 DOI: 10.1093/nar/gkaa381] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 04/15/2020] [Accepted: 05/11/2020] [Indexed: 12/19/2022] Open
Abstract
CRISPR-Cas adaptive immune systems are used by prokaryotes to defend against invaders like viruses and other mobile genetic elements. Immune memories are stored in the form of 'spacers' which are short DNA sequences that are captured from invaders and added to the CRISPR array during a process called 'adaptation'. Spacers are transcribed and the resulting CRISPR (cr)RNAs assemble with different Cas proteins to form effector complexes that recognize matching nucleic acid and destroy it ('interference'). Adaptation can be 'naïve', i.e. independent of any existing spacer matches, or it can be 'primed', i.e. spurred by the crRNA-mediated detection of a complete or partial match to an invader sequence. Here we show that primed adaptation occurs in Pyrococcus furiosus. Although P. furiosus has three distinct CRISPR-Cas interference systems (I-B, I-A and III-B), only the I-B system and Cas3 were necessary for priming. Cas4, which is important for selection and processing of new spacers in naïve adaptation, was also essential for priming. Loss of either the I-B effector proteins or Cas3 reduced naïve adaptation. However, when Cas3 and all crRNP genes were deleted, uptake of correctly processed spacers was observed, indicating that none of these interference proteins are necessary for naïve adaptation.
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Affiliation(s)
- Sandra Garrett
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, UConn Stem Cell Institute, UConn Health, Farmington, CT 06030, USA
| | - Masami Shiimori
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Elizabeth A Watts
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Landon Clark
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Brenton R Graveley
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, UConn Stem Cell Institute, UConn Health, Farmington, CT 06030, USA
| | - Michael P Terns
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.,Department of Microbiology, University of Georgia, Athens, GA 30602, USA.,Department of Genetics, University of Georgia, Athens, GA 30602, USA
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