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Waldern JM, Smith D, Piazza CL, Bailey EJ, Schiraldi NJ, Nemati R, Fabris D, Belfort M, Novikova O. Methylation of rRNA as a host defense against rampant group II intron retrotransposition. Mob DNA 2021; 12:9. [PMID: 33678171 PMCID: PMC7938551 DOI: 10.1186/s13100-021-00237-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/22/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Group II introns are mobile retroelements, capable of invading new sites in DNA. They are self-splicing ribozymes that complex with an intron-encoded protein to form a ribonucleoprotein that targets DNA after splicing. These molecules can invade DNA site-specifically, through a process known as retrohoming, or can invade ectopic sites through retrotransposition. Retrotransposition, in particular, can be strongly influenced by both environmental and cellular factors. RESULTS To investigate host factors that influence retrotransposition, we performed random insertional mutagenesis using the ISS1 transposon to generate a library of over 1000 mutants in Lactococcus lactis, the native host of the Ll.LtrB group II intron. By screening this library, we identified 92 mutants with increased retrotransposition frequencies (RTP-ups). We found that mutations in amino acid transport and metabolism tended to have increased retrotransposition frequencies. We further explored a subset of these RTP-up mutants, the most striking of which is a mutant in the ribosomal RNA methyltransferase rlmH, which exhibited a reproducible 20-fold increase in retrotransposition frequency. In vitro and in vivo experiments revealed that ribosomes in the rlmH mutant were defective in the m3Ψ modification and exhibited reduced binding to the intron RNA. CONCLUSIONS Taken together, our results reinforce the importance of the native host organism in regulating group II intron retrotransposition. In particular, the evidence from the rlmH mutant suggests a role for ribosome modification in limiting rampant retrotransposition.
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Affiliation(s)
- Justin M. Waldern
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Current address: Department of Biology, University of North Carolina, 270 Bell Tower Drive, Chapel Hill, NC 27599 USA
| | - Dorie Smith
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
| | - Carol Lyn Piazza
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
| | - E. Jake Bailey
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
| | - Nicholas J. Schiraldi
- Academic and Research Computing Center, Information Technology Services, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
| | - Reza Nemati
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Current address: Biogen, 125 Broadway, Cambridge, MA 02142 USA
| | - Dan Fabris
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Current address: Department of Chemistry, University of Connecticut, 55 N. Eagleville Road, Storrs, CT 06268 USA
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Department of Biomedical Sciences, School of Public Health, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
| | - Olga Novikova
- Department of Biological Sciences and RNA Institute, University at Albany, 1400 Washington Avenue, Albany, NY 12222 USA
- Current address: Biology Department, SUNY Buffalo State College, 1300 Elmwood Avenue, Buffalo, NY 14222 USA
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Liu N, Dong X, Hu C, Zeng J, Wang J, Wang J, Wang HW, Belfort M. Exon and protein positioning in a pre-catalytic group II intron RNP primed for splicing. Nucleic Acids Res 2020; 48:11185-11198. [PMID: 33021674 PMCID: PMC7641739 DOI: 10.1093/nar/gkaa773] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/30/2020] [Accepted: 09/30/2020] [Indexed: 11/13/2022] Open
Abstract
Group II introns are the putative progenitors of nuclear spliceosomal introns and use the same two-step splicing pathway. In the cell, the intron RNA forms a ribonucleoprotein (RNP) complex with the intron-encoded protein (IEP), which is essential for splicing. Although structures of spliced group II intron RNAs and RNP complexes have been characterized, structural insights into the splicing process remain enigmatic due to lack of pre-catalytic structural models. Here, we report two cryo-EM structures of endogenously produced group II intron RNPs trapped in their pre-catalytic state. Comparison of the catalytically activated precursor RNP to its previously reported spliced counterpart allowed identification of key structural rearrangements accompanying splicing, including a remodeled active site and engagement of the exons. Importantly, altered RNA-protein interactions were observed upon splicing among the RNP complexes. Furthermore, analysis of the catalytically inert precursor RNP demonstrated the structural impact of the formation of the active site on RNP architecture. Taken together, our results not only fill a gap in understanding the structural basis of IEP-assisted group II intron splicing, but also provide parallels to evolutionarily related spliceosomal splicing.
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Affiliation(s)
- Nan Liu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaolong Dong
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Cuixia Hu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jianwei Zeng
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jiawei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY 12222, USA
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Dong X, Qu G, Piazza CL, Belfort M. Group II intron as cold sensor for self-preservation and bacterial conjugation. Nucleic Acids Res 2020; 48:6198-6209. [PMID: 32379323 PMCID: PMC7293003 DOI: 10.1093/nar/gkaa313] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 04/01/2020] [Accepted: 04/20/2020] [Indexed: 01/18/2023] Open
Abstract
Group II introns are self-splicing ribozymes and mobile genetic elements. Splicing is required for both expression of the interrupted host gene and intron retromobility. For the pRS01 plasmid-encoded Lactococcus lactis group II intron, Ll.LtrB, splicing enables expression of the intron's host relaxase protein. Relaxase, in turn, initiates horizontal transfer of the conjugative pRS01 plasmid and stimulates retrotransposition of the intron. Little is known about how splicing of bacterial group II introns is influenced by environmental conditions. Here, we show that low temperatures can inhibit Ll.LtrB intron splicing. Whereas autocatalysis is abolished in the cold, splicing is partially restored by the intron-encoded protein (IEP). Structure profiling reveals cold-induced disruptions of key tertiary interactions, suggesting that a kinetic trap prevents the intron RNA from assuming its native state. Interestingly, while reduced levels of transcription and splicing lead to a paucity of excised intron in the cold, levels of relaxase mRNA are maintained, partially due to diminished intron-mediated mRNA targeting, allowing intron spread by conjugal transfer. Taken together, this study demonstrates not only the intrinsic cold sensitivity of group II intron splicing and the role of the IEP for cold-stress adaptation, but also maintenance of horizontal plasmid and intron transfer under cold-shock.
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Affiliation(s)
- Xiaolong Dong
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Guosheng Qu
- College of Life Sciences, Hebei University, Baoding, Hebei 071002, China
| | - Carol Lyn Piazza
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY 12222, USA
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Wu Y, Zheng YY, Lin Q, Sheng J. Detection and Quantification of RNA Phosphorothioate Modifications Using Mass Spectrometry. CURRENT PROTOCOLS IN NUCLEIC ACID CHEMISTRY 2020; 82:e113. [PMID: 32822120 PMCID: PMC7700719 DOI: 10.1002/cpnc.113] [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] [Indexed: 11/09/2022]
Abstract
This article describes a protocol for detecting and quantifying RNA phosphorothioate modifications in cellular RNA samples. Starting from solid-phase synthesis of phosphorothioate RNA dinucleotides, followed by purification with reversed-phase HPLC, phosphorothioate RNA dinucleotide standards are prepared for UPLC-MS and LC-MS/MS methods. RNA samples are extracted from cells using TRIzol reagent, then digested with a nuclease mixture and analyzed by mass spectrometry. UPLC-MS is employed first to identify RNA phosphorothioate modifications. An optimized LC-MS/MS method is then employed to quantify the frequency of RNA phosphorothioate modifications in a series of model cells. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Synthesis, purification, and characterization of RNA phosphorothioate dinucleotides Basic Protocol 2: Digestion of RNA samples extracted from cells Basic Protocol 3: Detection and quantification of RNA phosphorothioate modifications by mass spectrometry.
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Affiliation(s)
- Ying Wu
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, New York
| | - Ya Ying Zheng
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, New York
| | - Qishan Lin
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, New York
| | - Jia Sheng
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, New York
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Belfort M, Lambowitz AM. Group II Intron RNPs and Reverse Transcriptases: From Retroelements to Research Tools. Cold Spring Harb Perspect Biol 2019; 11:11/4/a032375. [PMID: 30936187 DOI: 10.1101/cshperspect.a032375] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Group II introns, self-splicing retrotransposons, serve as both targets of investigation into their structure, splicing, and retromobility and a source of tools for genome editing and RNA analysis. Here, we describe the first cryo-electron microscopy (cryo-EM) structure determination, at 3.8-4.5 Å, of a group II intron ribozyme complexed with its encoded protein, containing a reverse transcriptase (RT), required for RNA splicing and retromobility. We also describe a method called RIG-seq using a retrotransposon indicator gene for high-throughput integration profiling of group II introns and other retrotransposons. Targetrons, RNA-guided gene targeting agents widely used for bacterial genome engineering, are described next. Finally, we detail thermostable group II intron RTs, which synthesize cDNAs with high accuracy and processivity, for use in various RNA-seq applications and relate their properties to a 3.0-Å crystal structure of the protein poised for reverse transcription. Biological insights from these group II intron revelations are discussed.
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Affiliation(s)
- Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, State University of New York, Albany, New York 12222
| | - Alan M Lambowitz
- Institute for Cellular and Molecular Biology and Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712
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Villarreal LP, Witzany G. That is life: communicating RNA networks from viruses and cells in continuous interaction. Ann N Y Acad Sci 2019; 1447:5-20. [PMID: 30865312 DOI: 10.1111/nyas.14040] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 01/13/2019] [Accepted: 01/31/2019] [Indexed: 02/06/2023]
Abstract
All the conserved detailed results of evolution stored in DNA must be read, transcribed, and translated via an RNA-mediated process. This is required for the development and growth of each individual cell. Thus, all known living organisms fundamentally depend on these RNA-mediated processes. In most cases, they are interconnected with other RNAs and their associated protein complexes and function in a strictly coordinated hierarchy of temporal and spatial steps (i.e., an RNA network). Clearly, all cellular life as we know it could not function without these key agents of DNA replication, namely rRNA, tRNA, and mRNA. Thus, any definition of life that lacks RNA functions and their networks misses an essential requirement for RNA agents that inherently regulate and coordinate (communicate to) cells, tissues, organs, and organisms. The precellular evolution of RNAs occurred at the core of the emergence of cellular life and the question remained of how both precellular and cellular levels are interconnected historically and functionally. RNA networks and RNA communication can interconnect these levels. With the reemergence of virology in evolution, it became clear that communicating viruses and subviral infectious genetic parasites are bridging these two levels by invading, integrating, coadapting, exapting, and recombining constituent parts in host genomes for cellular requirements in gene regulation and coordination aims. Therefore, a 21st century understanding of life is of an inherently social process based on communicating RNA networks, in which viruses and cells continuously interact.
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Affiliation(s)
- Luis P Villarreal
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California
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