1
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Rousseau M, Oulavallickal T, Williamson A, Arcus V, Patrick WM, Hicks J. Characterisation and engineering of a thermophilic RNA ligase from Palaeococcus pacificus. Nucleic Acids Res 2024; 52:3924-3937. [PMID: 38421610 DOI: 10.1093/nar/gkae149] [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: 11/27/2023] [Revised: 01/23/2024] [Accepted: 02/19/2024] [Indexed: 03/02/2024] Open
Abstract
RNA ligases are important enzymes in molecular biology and are highly useful for the manipulation and analysis of nucleic acids, including adapter ligation in next-generation sequencing of microRNAs. Thermophilic RNA ligases belonging to the RNA ligase 3 family are gaining attention for their use in molecular biology, for example a thermophilic RNA ligase from Methanobacterium thermoautotrophicum is commercially available for the adenylation of nucleic acids. Here we extensively characterise a newly identified RNA ligase from the thermophilic archaeon Palaeococcus pacificus (PpaRnl). PpaRnl exhibited significant substrate adenylation activity but low ligation activity across a range of oligonucleotide substrates. Mutation of Lys92 in motif I to alanine, resulted in an enzyme that lacked adenylation activity, but demonstrated improved ligation activity with pre-adenylated substrates (ATP-independent ligation). Subsequent structural characterisation revealed that in this mutant enzyme Lys238 was found in two alternate positions for coordination of the phosphate tail of ATP. In contrast mutation of Lys238 in motif V to glycine via structure-guided engineering enhanced ATP-dependent ligation activity via an arginine residue compensating for the absence of Lys238. Ligation activity for both mutations was higher than the wild-type, with activity observed across a range of oligonucleotide substrates with varying sequence and secondary structure.
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Affiliation(s)
- Meghan Rousseau
- School of Science, The University of Waikato, Hamilton 3216, New Zealand
| | - Tifany Oulavallickal
- School of Biological Sciences, Victoria University of Wellington, Wellington 6140, New Zealand
| | - Adele Williamson
- School of Science, The University of Waikato, Hamilton 3216, New Zealand
| | - Vic Arcus
- School of Science, The University of Waikato, Hamilton 3216, New Zealand
| | - Wayne M Patrick
- School of Biological Sciences, Victoria University of Wellington, Wellington 6140, New Zealand
| | - Joanna Hicks
- Te Huataki Waiora School of Health, The University of Waikato, Hamilton 3216, New Zealand
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2
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Yang Z, Zhang C, Lian G, Dong S, Song M, Shao H, Wang J, Zhong T, Luo Z, Jin S, Ding C. Direct adenylation from 5'-OH-terminated oligonucleotides by a fusion enzyme containing Pfu RNA ligase and T4 polynucleotide kinase. Nucleic Acids Res 2022; 50:7560-7569. [PMID: 35819229 PMCID: PMC9303275 DOI: 10.1093/nar/gkac604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 06/23/2022] [Accepted: 06/30/2022] [Indexed: 11/14/2022] Open
Abstract
5′-Adenylated oligonucleotides (AppOligos) are widely used for single-stranded DNA/RNA ligation in next-generation sequencing (NGS) applications such as microRNA (miRNA) profiling. The ligation between an AppOligo adapter and target molecules (such as miRNA) no longer requires ATP, thereby minimizing potential self-ligations and simplifying library preparation procedures. AppOligos can be produced by chemical synthesis or enzymatic modification. However, adenylation via chemical synthesis is inefficient and expensive, while enzymatic modification requires pre-phosphorylated substrate and additional purification. Here we cloned and characterized the Pfu RNA ligase encoded by the PF0353 gene in the hyperthermophilic archaea Pyrococcus furiosus. We further engineered fusion enzymes containing both Pfu RNA ligase and T4 polynucleotide kinase. One fusion enzyme, 8H-AP, was thermostable and can directly catalyze 5′-OH-terminated DNA substrates to adenylated products. The newly discovered Pfu RNA ligase and the engineered fusion enzyme may be useful tools for applications using AppOligos.
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Affiliation(s)
- Zhengquan Yang
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Chengliang Zhang
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China.,Department of Clinical Laboratory, Kunming Third People's Hospital, Kunming, Yunnan, 650041, China
| | - Guojun Lian
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Shijie Dong
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Menghui Song
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Hengrong Shao
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Jingmei Wang
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Tao Zhong
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Zhenni Luo
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Shengnan Jin
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Chunming Ding
- Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
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3
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Liu Y, Takagi Y, Sugijanto M, Nguyen KDM, Hirata A, Hori H, Ho CK. Genetic and Functional Analyses of Archaeal ATP-Dependent RNA Ligase in C/D Box sRNA Circularization and Ribosomal RNA Processing. Front Mol Biosci 2022; 9:811548. [PMID: 35445080 PMCID: PMC9014305 DOI: 10.3389/fmolb.2022.811548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 02/08/2022] [Indexed: 11/24/2022] Open
Abstract
RNA ligases play important roles in repairing and circularizing RNAs post-transcriptionally. In this study, we generated an allelic knockout of ATP-dependent RNA ligase (Rnl) in the hyperthermophilic archaeon Thermococcus kodakarensis to identify its biological targets. A comparative analysis of circular RNA reveals that the Rnl-knockout strain represses circularization of C/D box sRNAs without affecting the circularization of tRNA and rRNA processing intermediates. Recombinant archaeal Rnl could circularize C/D box sRNAs with a mutation in the conserved C/D box sequence element but not when the terminal stem structures were disrupted, suggesting that proximity of the two ends could be critical for intramolecular ligation. Furthermore, T. kodakarensis accumulates aberrant RNA fragments derived from ribosomal RNA in the absence of Rnl. These results suggest that Rnl is responsible for C/D box sRNA circularization and may also play a role in ribosomal RNA processing.
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Affiliation(s)
- Yancheng Liu
- Human Biology Program, University of Tsukuba, Tsukuba, Japan
| | - Yuko Takagi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Milyadi Sugijanto
- Doctoral Program in Medical Sciences, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | | | - Akira Hirata
- Department of Natural Science, Graduate School of Technology, Industrial and Social Science, Tokushima University, Tokushima, Japan
| | - Hiroyuki Hori
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
| | - C. Kiong Ho
- Human Biology Program, University of Tsukuba, Tsukuba, Japan
- Doctoral Program in Medical Sciences, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
- *Correspondence: C. Kiong Ho,
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4
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Kroupova A, Ackle F, Asanović I, Weitzer S, Boneberg FM, Faini M, Leitner A, Chui A, Aebersold R, Martinez J, Jinek M. Molecular architecture of the human tRNA ligase complex. eLife 2021; 10:e71656. [PMID: 34854379 PMCID: PMC8668186 DOI: 10.7554/elife.71656] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/01/2021] [Indexed: 01/23/2023] Open
Abstract
RtcB enzymes are RNA ligases that play essential roles in tRNA splicing, unfolded protein response, and RNA repair. In metazoa, RtcB functions as part of a five-subunit tRNA ligase complex (tRNA-LC) along with Ddx1, Cgi-99, Fam98B, and Ashwin. The human tRNA-LC or its individual subunits have been implicated in additional cellular processes including microRNA maturation, viral replication, DNA double-strand break repair, and mRNA transport. Here, we present a biochemical analysis of the inter-subunit interactions within the human tRNA-LC along with crystal structures of the catalytic subunit RTCB and the N-terminal domain of CGI-99. We show that the core of the human tRNA-LC is assembled from RTCB and the C-terminal alpha-helical regions of DDX1, CGI-99, and FAM98B, all of which are required for complex integrity. The N-terminal domain of CGI-99 displays structural homology to calponin-homology domains, and CGI-99 and FAM98B associate via their N-terminal domains to form a stable subcomplex. The crystal structure of GMP-bound RTCB reveals divalent metal coordination geometry in the active site, providing insights into its catalytic mechanism. Collectively, these findings shed light on the molecular architecture and mechanism of the human tRNA ligase complex and provide a structural framework for understanding its functions in cellular RNA metabolism.
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Affiliation(s)
- Alena Kroupova
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Fabian Ackle
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Igor Asanović
- Max Perutz Labs, Vienna BioCenter (VBC)ViennaAustria
| | | | | | - Marco Faini
- Department of Biology, Institute of Molecular Systems Biology, ETH ZurichZurichSwitzerland
| | - Alexander Leitner
- Department of Biology, Institute of Molecular Systems Biology, ETH ZurichZurichSwitzerland
| | - Alessia Chui
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Ruedi Aebersold
- Department of Biology, Institute of Molecular Systems Biology, ETH ZurichZurichSwitzerland
| | | | - Martin Jinek
- Department of Biochemistry, University of ZurichZurichSwitzerland
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5
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Banerjee A, Ghosh S, Goldgur Y, Shuman S. Structure and two-metal mechanism of fungal tRNA ligase. Nucleic Acids Res 2019; 47:1428-1439. [PMID: 30590734 PMCID: PMC6379707 DOI: 10.1093/nar/gky1275] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 12/10/2018] [Accepted: 12/11/2018] [Indexed: 02/06/2023] Open
Abstract
Fungal tRNA ligase (Trl1) is an essential enzyme that repairs RNA breaks with 2′,3′-cyclic-PO4 and 5′-OH ends inflicted during tRNA splicing and non-canonical mRNA splicing in the fungal unfolded protein response. Trl1 is composed of C-terminal cyclic phosphodiesterase (CPD) and central GTP-dependent polynucleotide kinase (KIN) domains that heal the broken ends to generate the 3′-OH,2′-PO4 and 5′-PO4 termini required for sealing by an N-terminal ATP-dependent ligase domain (LIG). Here we report crystal structures of the Trl1-LIG domain from Chaetomium thermophilum at two discrete steps along the reaction pathway: the covalent LIG-(lysyl-Nζ)–AMP•Mn2+ intermediate and a LIG•ATP•(Mn2+)2 Michaelis complex. The structures highlight a two-metal mechanism whereby a penta-hydrated metal complex stabilizes the transition state of the ATP α phosphate and a second metal bridges the β and γ phosphates to help orient the pyrophosphate leaving group. A LIG-bound sulfate anion is a plausible mimetic of the essential RNA terminal 2′-PO4. Trl1-LIG has a distinctive C-terminal domain that instates fungal Trl1 as the founder of an Rnl6 clade of ATP-dependent RNA ligase. We discuss how the Trl1-LIG structure rationalizes the large body of in vivo structure–function data for Saccharomyces cerevisiae Trl1.
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Affiliation(s)
- Ankan Banerjee
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Shreya Ghosh
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Yehuda Goldgur
- Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Stewart Shuman
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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6
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Becker HF, L'Hermitte-Stead C, Myllykallio H. Diversity of circular RNAs and RNA ligases in archaeal cells. Biochimie 2019; 164:37-44. [PMID: 31212038 DOI: 10.1016/j.biochi.2019.06.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 06/13/2019] [Indexed: 01/16/2023]
Abstract
Circular RNAs (circRNAs) differ structurally from other types of RNAs and are resistant against exoribonucleases. Although they have been detected in all domains of life, it remains unclear how circularization affects or changes functions of these ubiquitous nucleic acid circles. The biogenesis of circRNAs has been mostly described as a backsplicing event, but in archaea, where RNA splicing is a rare phenomenon, a second pathway for circRNA formation was described in the cases of rRNAs processing, tRNA intron excision, and Box C/D RNAs formation. At least in some archaeal species, circRNAs are formed by a ligation step catalyzed by an atypic homodimeric RNA ligase belonging to Rnl3 family. In this review, we describe archaeal circRNA transcriptomes obtained using high throughput sequencing technologies on Sulfolobus solfataricus, Pyrococcus abyssi and Nanoarchaeum equitans cells. We will discuss the distribution of circular RNAs among the different RNA categories and present the Rnl3 ligase family implicated in the circularization activity. Special focus is given for the description of phylogenetic distributions, protein structures, and substrate specificities of archaeal RNA ligases.
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Affiliation(s)
- Hubert F Becker
- LOB, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France; Sorbonne Université, Faculté des Sciences et Ingénierie, 75005, Paris, France.
| | | | - Hannu Myllykallio
- LOB, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
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7
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Unciuleac MC, Goldgur Y, Shuman S. Structures of ATP-bound DNA ligase D in a closed domain conformation reveal a network of amino acid and metal contacts to the ATP phosphates. J Biol Chem 2019; 294:5094-5104. [PMID: 30718283 PMCID: PMC6442053 DOI: 10.1074/jbc.ra119.007445] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 02/01/2019] [Indexed: 01/07/2023] Open
Abstract
DNA ligases are the sine qua non of genome integrity and essential for DNA replication and repair in all organisms. DNA ligases join 3'-OH and 5'-PO4 ends via a series of three nucleotidyl transfer steps. In step 1, ligase reacts with ATP or NAD+ to form a covalent ligase-(lysyl-Nζ)-AMP intermediate and release pyrophosphate (PPi) or nicotinamide mononucleotide. In step 2, AMP is transferred from ligase-adenylate to the 5'-PO4 DNA end to form a DNA-adenylate intermediate (AppDNA). In step 3, ligase catalyzes attack by a DNA 3'-OH on the DNA-adenylate to seal the two ends via a phosphodiester bond and release AMP. Eukaryal, archaeal, and many bacterial and viral DNA ligases are ATP-dependent. The catalytic core of ATP-dependent DNA ligases consists of an N-terminal nucleotidyltransferase domain fused to a C-terminal OB domain. Here we report crystal structures at 1.4-1.8 Å resolution of Mycobacterium tuberculosis LigD, an ATP-dependent DNA ligase dedicated to nonhomologous end joining, in complexes with ATP that highlight large movements of the OB domain (∼50 Å), from a closed conformation in the ATP complex to an open conformation in the covalent ligase-AMP intermediate. The LigD·ATP structures revealed a network of amino acid contacts to the ATP phosphates that stabilize the transition state and orient the PPi leaving group. A complex with ATP and magnesium suggested a two-metal mechanism of lysine adenylylation driven by a catalytic Mg2+ that engages the ATP α phosphate and a second metal that bridges the ATP β and γ phosphates.
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Affiliation(s)
| | - Yehuda Goldgur
- Structural Biology Programs, Sloan Kettering Institute, New York, New York 10065
| | - Stewart Shuman
- From the Molecular Biology and , To whom correspondence should be addressed:
Molecular Biology Program, Sloan Kettering Institute, 1275 York Ave., New York, NY 10065. E-mail:
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8
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Yoshinari S, Liu Y, Gollnick P, Ho CK. Cleavage of 3'-terminal adenosine by archaeal ATP-dependent RNA ligase. Sci Rep 2017; 7:11662. [PMID: 28912583 PMCID: PMC5599603 DOI: 10.1038/s41598-017-11693-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 08/29/2017] [Indexed: 01/15/2023] Open
Abstract
Methanothermobacter thermoautotrophicus RNA ligase (MthRnl) catalyzes formation of phosphodiester bonds between the 5′-phosphate and 3′-hydroxyl termini of single-stranded RNAs. It can also react with RNA with a 3′-phosphate end to generate a 2′,3′-cyclic phosphate. Here, we show that MthRnl can additionally remove adenosine from the 3′-terminus of the RNA to produce 3′-deadenylated RNA, RNA(3′-rA). This 3′-deadenylation activity is metal-dependent and requires a 2′-hydroxyl at both the terminal adenosine and the penultimate nucleoside. Residues that contact the ATP/AMP in the MthRnl crystal structures are essential for the 3′-deadenylation activity, suggesting that 3′-adenosine may occupy the ATP-binding pocket. The 3′-end of cleaved RNA(3′-rA) consists of 2′,3′-cyclic phosphate which protects RNA(3′-rA) from ligation and further deadenylation. These findings suggest that ATP-dependent RNA ligase may act on a specific set of 3′-adenylated RNAs to regulate their processing and downstream biological events.
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Affiliation(s)
- Shigeo Yoshinari
- Department of Biological Sciences, State University of New York, Buffalo, NY, 14260, United States of America
| | - Yancheng Liu
- Human Biology Program, School of Integrative and Global Majors, University of Tsukuba, Ibaraki, 305-8575, Japan
| | - Paul Gollnick
- Department of Biological Sciences, State University of New York, Buffalo, NY, 14260, United States of America
| | - C Kiong Ho
- Department of Biological Sciences, State University of New York, Buffalo, NY, 14260, United States of America. .,Human Biology Program, School of Integrative and Global Majors, University of Tsukuba, Ibaraki, 305-8575, Japan. .,Department of Infection Biology, Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan.
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9
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Becker HF, Héliou A, Djaout K, Lestini R, Regnier M, Myllykallio H. High-throughput sequencing reveals circular substrates for an archaeal RNA ligase. RNA Biol 2017; 14:1075-1085. [PMID: 28277897 DOI: 10.1080/15476286.2017.1302640] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
It is only recently that the abundant presence of circular RNAs (circRNAs) in all kingdoms of Life, including the hyperthermophilic archaeon Pyrococcus abyssi, has emerged. This led us to investigate the physiologic significance of a previously observed weak intramolecular ligation activity of Pab1020 RNA ligase. Here we demonstrate that this enzyme, despite sharing significant sequence similarity with DNA ligases, is indeed an RNA-specific polynucleotide ligase efficiently acting on physiologically significant substrates. Using a combination of RNA immunoprecipitation assays and RNA-seq, our genome-wide studies revealed 133 individual circRNA loci in P. abyssi. The large majority of these loci interacted with Pab1020 in cells and circularization of selected C/D Box and 5S rRNA transcripts was confirmed biochemically. Altogether these studies revealed that Pab1020 is required for RNA circularization. Our results further suggest the functional speciation of an ancestral NTase domain and/or DNA ligase toward RNA ligase activity and prompt for further characterization of the widespread functions of circular RNAs in prokaryotes. Detailed insight into the cellular substrates of Pab1020 may facilitate the development of new biotechnological applications e.g. in ligation of preadenylated adaptors to RNA molecules.
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Affiliation(s)
- Hubert F Becker
- a LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau , France.,b Sorbonne Universités, UPMC Univ Paris 06 , 4 Place Jussieu, Paris , France
| | - Alice Héliou
- a LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau , France.,c LIX, Ecole Polytechnique, CNRS, Université Paris-Saclay, INRIA , Palaiseau , France
| | - Kamel Djaout
- a LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau , France
| | - Roxane Lestini
- a LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau , France
| | - Mireille Regnier
- c LIX, Ecole Polytechnique, CNRS, Université Paris-Saclay, INRIA , Palaiseau , France
| | - Hannu Myllykallio
- a LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau , France
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Two-metal versus one-metal mechanisms of lysine adenylylation by ATP-dependent and NAD +-dependent polynucleotide ligases. Proc Natl Acad Sci U S A 2017; 114:2592-2597. [PMID: 28223499 DOI: 10.1073/pnas.1619220114] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Polynucleotide ligases comprise a ubiquitous superfamily of nucleic acid repair enzymes that join 3'-OH and 5'-PO4 DNA or RNA ends. Ligases react with ATP or NAD+ and a divalent cation cofactor to form a covalent enzyme-(lysine-Nζ)-adenylate intermediate. Here, we report crystal structures of the founding members of the ATP-dependent RNA ligase family (T4 RNA ligase 1; Rnl1) and the NAD+-dependent DNA ligase family (Escherichia coli LigA), captured as their respective Michaelis complexes, which illuminate distinctive catalytic mechanisms of the lysine adenylylation reaction. The 2.2-Å Rnl1•ATP•(Mg2+)2 structure highlights a two-metal mechanism, whereby: a ligase-bound "catalytic" Mg2+(H2O)5 coordination complex lowers the pKa of the lysine nucleophile and stabilizes the transition state of the ATP α phosphate; a second octahedral Mg2+ coordination complex bridges the β and γ phosphates; and protein elements unique to Rnl1 engage the γ phosphate and associated metal complex and orient the pyrophosphate leaving group for in-line catalysis. By contrast, the 1.55-Å LigA•NAD+•Mg2+ structure reveals a one-metal mechanism in which a ligase-bound Mg2+(H2O)5 complex lowers the lysine pKa and engages the NAD+ α phosphate, but the β phosphate and the nicotinamide nucleoside of the nicotinamide mononucleotide (NMN) leaving group are oriented solely via atomic interactions with protein elements that are unique to the LigA clade. The two-metal versus one-metal dichotomy demarcates a branchpoint in ligase evolution and favors LigA as an antibacterial drug target.
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