1
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Ahammed KS, van Hoof A. Fungi of the order Mucorales express a "sealing-only" tRNA ligase. RNA (NEW YORK, N.Y.) 2024; 30:354-366. [PMID: 38307611 PMCID: PMC10946435 DOI: 10.1261/rna.079957.124] [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: 11/16/2023] [Accepted: 01/20/2024] [Indexed: 02/04/2024]
Abstract
Some eukaryotic pre-tRNAs contain an intron that is removed by a dedicated set of enzymes. Intron-containing pre-tRNAs are cleaved by tRNA splicing endonuclease, followed by ligation of the two exons and release of the intron. Fungi use a "heal and seal" pathway that requires three distinct catalytic domains of the tRNA ligase enzyme, Trl1. In contrast, humans use a "direct ligation" pathway carried out by RTCB, an enzyme completely unrelated to Trl1. Because of these mechanistic differences, Trl1 has been proposed as a promising drug target for fungal infections. To validate Trl1 as a broad-spectrum drug target, we show that fungi from three different phyla contain Trl1 orthologs with all three domains. This includes the major invasive human fungal pathogens, and these proteins can each functionally replace yeast Trl1. In contrast, species from the order Mucorales, including the pathogens Rhizopus arrhizus and Mucor circinelloides, have an atypical Trl1 that contains the sealing domain but lacks both healing domains. Although these species contain fewer tRNA introns than other pathogenic fungi, they still require splicing to decode three of the 61 sense codons. These sealing-only Trl1 orthologs can functionally complement defects in the corresponding domain of yeast Trl1 and use a conserved catalytic lysine residue. We conclude that Mucorales use a sealing-only enzyme together with unidentified nonorthologous healing enzymes for their heal and seal pathway. This implies that drugs that target the sealing activity are more likely to be broader-spectrum antifungals than drugs that target the healing domains.
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Affiliation(s)
- Khondakar Sayef Ahammed
- Department of Microbiology and Molecular Genetics, UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Ambro van Hoof
- Department of Microbiology and Molecular Genetics, UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Texas 77030, USA
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2
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Ghosh S, Dantuluri S, Jacewicz A, Sanchez AM, Abdullahu L, Damha MJ, Schwer B, Shuman S. Characterization of tRNA splicing enzymes RNA ligase and tRNA 2'-phosphotransferase from the pathogenic fungi Mucorales. RNA (NEW YORK, N.Y.) 2024; 30:367-380. [PMID: 38238085 PMCID: PMC10946426 DOI: 10.1261/rna.079911.123] [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: 12/04/2023] [Accepted: 01/09/2024] [Indexed: 03/20/2024]
Abstract
Fungal Trl1 is an essential trifunctional tRNA splicing enzyme that heals and seals tRNA exons with 2',3'-cyclic-PO4 and 5'-OH ends. Trl1 is composed of C-terminal cyclic phosphodiesterase and central polynucleotide kinase end-healing domains that generate the 3'-OH,2'-PO4 and 5'-PO4 termini required for sealing by an N-terminal ATP-dependent ligase domain. Trl1 enzymes are present in many human fungal pathogens and are promising targets for antifungal drug discovery because their domain structures and biochemical mechanisms are unique compared to the mammalian RtcB-type tRNA splicing enzyme. Here we report that Mucorales species (deemed high-priority human pathogens by WHO) elaborate a noncanonical tRNA splicing apparatus in which a monofunctional RNA ligase enzyme is encoded separately from any end-healing enzymes. We show that Mucor circinelloides RNA ligase (MciRNL) is active in tRNA splicing in vivo in budding yeast in lieu of the Trl1 ligase domain. Biochemical and kinetic characterization of recombinant MciRNL underscores its requirement for a 2'-PO4 terminus in the end-joining reaction, whereby the 2'-PO4 enhances the rates of RNA 5'-adenylylation (step 2) and phosphodiester synthesis (step 3) by ∼125-fold and ∼6200-fold, respectively. In the canonical fungal tRNA splicing pathway, the splice junction 2'-PO4 installed by RNA ligase is removed by a dedicated NAD+-dependent RNA 2'-phosphotransferase Tpt1. Here we identify and affirm by genetic complementation in yeast the biological activity of Tpt1 orthologs from three Mucorales species. Recombinant M. circinelloides Tpt1 has vigorous NAD+-dependent RNA 2'-phosphotransferase activity in vitro.
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Affiliation(s)
- Shreya Ghosh
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Swathi Dantuluri
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Agata Jacewicz
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Ana M Sanchez
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York 10065, USA
| | - Leonora Abdullahu
- Department of Chemistry, McGill University, Montreal, Quebec H3A0B8, Canada
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, Quebec H3A0B8, Canada
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065, USA
| | - Stewart Shuman
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
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3
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Shuman S. RNA Repair: Hiding in Plain Sight. Annu Rev Genet 2023; 57:461-489. [PMID: 37722686 DOI: 10.1146/annurev-genet-071719-021856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/20/2023]
Abstract
Enzymes that phosphorylate, dephosphorylate, and ligate RNA 5' and 3' ends were discovered more than half a century ago and were eventually shown to repair purposeful site-specific endonucleolytic breaks in the RNA phosphodiester backbone. The pace of discovery and characterization of new candidate RNA repair activities in taxa from all phylogenetic domains greatly exceeds our understanding of the biological pathways in which they act. The key questions anent RNA break repair in vivo are (a) identifying the triggers, agents, and targets of RNA cleavage and (b) determining whether RNA repair results in restoration of the original RNA, modification of the RNA (by loss or gain at the ends), or rearrangements of the broken RNA segments (i.e., RNA recombination). This review provides a perspective on the discovery, mechanisms, and physiology of purposeful RNA break repair, highlighting exemplary repair pathways (e.g., tRNA restriction-repair and tRNA splicing) for which genetics has figured prominently in their elucidation.
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Affiliation(s)
- Stewart Shuman
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA;
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4
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Ahammed KS, van Hoof A. Fungi of the order Mucorales express a "sealing-only" tRNA ligase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.16.567474. [PMID: 38014270 PMCID: PMC10680797 DOI: 10.1101/2023.11.16.567474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Some eukaryotic pre-tRNAs contain an intron that is removed by a dedicated set of enzymes. Intron-containing pre-tRNAs are cleaved by tRNA splicing endonuclease (TSEN), followed by ligation of the two exons and release of the intron. Fungi use a "heal and seal" pathway that requires three distinct catalytic domains of the tRNA ligase enzyme, Trl1. In contrast, humans use a "direct ligation" pathway carried out by RTCB, an enzyme completely unrelated to Trl1. Because of these mechanistic differences, Trl1 has been proposed as a promising drug target for fungal infections. To validate Trl1 as a broad-spectrum drug target, we show that fungi from three different phyla contain Trl1 orthologs with all three domains. This includes the major invasive human fungal pathogens, and these proteins each can functionally replace yeast Trl1. In contrast, species from the order Mucorales, including the pathogens Rhizopus arrhizus and Mucor circinelloides, contain an atypical Trl1 that contains the sealing domain, but lack both healing domains. Although these species contain fewer tRNA introns than other pathogenic fungi, they still require splicing to decode three of the 61 sense codons. These sealing-only Trl1 orthologs can functionally complement defects in the corresponding domain of yeast Trl1 and use a conserved catalytic lysine residue. We conclude that Mucorales use a sealing-only enzyme together with unidentified non-orthologous healing enzymes for their heal and seal pathway. This implies that drugs that target the sealing activity are more likely to be broader-spectrum antifungals than drugs that target the healing domains.
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Affiliation(s)
- Khondakar Sayef Ahammed
- Department of Microbiology and Molecular Genetics. UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences. University of Texas Health Science Center at Houston
| | - Ambro van Hoof
- Department of Microbiology and Molecular Genetics. UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences. University of Texas Health Science Center at Houston
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5
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El-Gendi H, Saleh AK, Badierah R, Redwan EM, El-Maradny YA, El-Fakharany EM. A Comprehensive Insight into Fungal Enzymes: Structure, Classification, and Their Role in Mankind's Challenges. J Fungi (Basel) 2021; 8:23. [PMID: 35049963 PMCID: PMC8778853 DOI: 10.3390/jof8010023] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/22/2021] [Accepted: 12/25/2021] [Indexed: 11/16/2022] Open
Abstract
Enzymes have played a crucial role in mankind's challenges to use different types of biological systems for a diversity of applications. They are proteins that break down and convert complicated compounds to produce simple products. Fungal enzymes are compatible, efficient, and proper products for many uses in medicinal requests, industrial processing, bioremediation purposes, and agricultural applications. Fungal enzymes have appropriate stability to give manufactured products suitable shelf life, affordable cost, and approved demands. Fungal enzymes have been used from ancient times to today in many industries, including baking, brewing, cheese making, antibiotics production, and commodities manufacturing, such as linen and leather. Furthermore, they also are used in other fields such as paper production, detergent, the textile industry, and in drinks and food technology in products manufacturing ranging from tea and coffee to fruit juice and wine. Recently, fungi have been used for the production of more than 50% of the needed enzymes. Fungi can produce different types of enzymes extracellularly, which gives a great chance for producing in large amounts with low cost and easy viability in purified forms using simple purification methods. In the present review, a comprehensive trial has been advanced to elaborate on the different types and structures of fungal enzymes as well as the current status of the uses of fungal enzymes in various applications.
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Affiliation(s)
- Hamada El-Gendi
- Bioprocess Development Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications (SRTA-City), Universities and Research Institutes Zone, New Borg El-Arab, Alexandria 21934, Egypt;
| | - Ahmed K. Saleh
- Cellulose and Paper Department, National Research Centre, El-Tahrir St., Dokki, Giza 12622, Egypt;
| | - Raied Badierah
- Biological Science Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia; (R.B.); (E.M.R.)
- Medical Laboratory, King Abdulaziz University Hospital, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - Elrashdy M. Redwan
- Biological Science Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia; (R.B.); (E.M.R.)
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications (SRTA-City), New Borg EL-Arab, Alexandria 21934, Egypt;
| | - Yousra A. El-Maradny
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications (SRTA-City), New Borg EL-Arab, Alexandria 21934, Egypt;
| | - Esmail M. El-Fakharany
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications (SRTA-City), New Borg EL-Arab, Alexandria 21934, Egypt;
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6
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Syed Abuthakir MH, Sharmila V, Jeyam M. Screening Balanites aegyptiaca for inhibitors against putative drug targets in Microsporum gypseum - Subtractive proteome, docking and simulation approach. INFECTION GENETICS AND EVOLUTION 2021; 90:104755. [PMID: 33549764 DOI: 10.1016/j.meegid.2021.104755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/31/2020] [Accepted: 01/31/2021] [Indexed: 02/07/2023]
Abstract
Microsporum gypseum is a keratinophilic fungi grouped under dermatophytes infecting skin, hair and nail portions in human and animals causing tinea corporis, tinea facei and tinea capitis. As both human and fungi are eukaryotes, the available drugs for treating dermatophytes produce some side effects due to drug interaction with human also. Apart from this, the gut microbiota has a very big role in the health of human which should not be affected by the drugs. Hence this study focused on finding a target which is unique and essential to M. gypseum and non-homologous to human and gut microbiota, non-homologous to human domain architecture, highly interacting with other proteins, sub-cellular localization of proteins and non-druggability analysis of the targets using subtractive proteomics approach which resulted with 3 novel drug targets from M. gypseum which were modeled using I-TASSER, refined by ModRefiner and validated by PROCHECK. Further these targets were docked with compounds identified through LC-MS of fractioned methanol extract of B. aegyptiaca fruit pulp using Glide module and the stability of the docked complex was analyzed by molecular dynamics simulation using Desmond module of Schrodinger. Cyanidin-3-O-rhamnoside had better interaction with all the targets and Taurocholic acid had better result with ECCP which suggests the multi-targeting potency of these two compounds against M. gypseum which has to be confirmed by in vitro and in vivo studies.
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Affiliation(s)
| | - Velusamy Sharmila
- Biochematics Lab, Department of Bioinformatics, Bharathiar University, Coimbatore., India
| | - Muthusamy Jeyam
- Biochematics Lab, Department of Bioinformatics, Bharathiar University, Coimbatore., India.
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7
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Dantuluri S, Schwer B, Abdullahu L, Damha MJ, Shuman S. Activity and substrate specificity of Candida, Aspergillus, and Coccidioides Tpt1: essential tRNA splicing enzymes and potential anti-fungal targets. RNA (NEW YORK, N.Y.) 2021; 27:rna.078660.120. [PMID: 33509912 PMCID: PMC8051265 DOI: 10.1261/rna.078660.120] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
The enzyme Tpt1 is an essential agent of fungal tRNA splicing that removes an internal RNA 2'-PO4 generated by fungal tRNA ligase. Tpt1 performs a two-step reaction in which: (i) the 2'-PO4 attacks NAD+ to form an RNA-2'-phospho-(ADP-ribose) intermediate; and (ii) transesterification of the ADP-ribose O2'' to the RNA 2'-phosphodiester yields 2'-OH RNA and ADP-ribose-1'',2''-cyclic phosphate. Because Tpt1 does not participate in metazoan tRNA splicing, and Tpt1 knockout has no apparent impact on mammalian physiology, Tpt1 is considered a potential anti-fungal drug target. Here we characterize Tpt1 enzymes from four human fungal pathogens: Coccidioides immitis, the agent of Valley Fever; Aspergillus fumigatus and Candida albicans, which cause invasive, often fatal, infections in immunocompromised hosts; and Candida auris, an emerging pathogen that is resistant to current therapies. All four pathogen Tpt1s were active in vivo in complementing a lethal Saccharomyces cerevisiae tpt1∆ mutation and in vitro in NAD+-dependent conversion of a 2'-PO4 to a 2'-OH. The fungal Tpt1s utilized nicotinamide hypoxanthine dinucleotide as a substrate in lieu of NAD+, albeit with much lower affinity, whereas nicotinic acid adenine dinucleotide was ineffective. Fungal Tpt1s efficiently removed an internal ribonucleotide 2'-phosphate from an otherwise all-DNA substrate. Replacement of an RNA ribose-2'-PO4 nucleotide with arabinose-2'-PO4 diminished enzyme specific activity by ≥2000-fold and selectively slowed step 2 of the reaction pathway, resulting in transient accumulation of an ara-2'-phospho-ADP-ribosylated intermediate. Our results implicate the 2'-PO4 ribonucleotide as the principal determinant of fungal Tpt1 nucleic acid substrate specificity.
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8
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Banerjee A, Goldgur Y, Schwer B, Shuman S. Atomic structures of the RNA end-healing 5'-OH kinase and 2',3'-cyclic phosphodiesterase domains of fungal tRNA ligase: conformational switches in the kinase upon binding of the GTP phosphate donor. Nucleic Acids Res 2020; 47:11826-11838. [PMID: 31722405 PMCID: PMC7145591 DOI: 10.1093/nar/gkz1049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/16/2019] [Accepted: 11/07/2019] [Indexed: 01/17/2023] Open
Abstract
Fungal tRNA ligase (Trl1) rectifies RNA breaks with 2′,3′-cyclic-PO4 and 5′-OH termini. Trl1 consists of three catalytic modules: an N-terminal ligase (LIG) domain; a central polynucleotide kinase (KIN) domain; and a C-terminal cyclic phosphodiesterase (CPD) domain. Trl1 enzymes found in all human fungal pathogens are untapped targets for antifungal drug discovery. Here we report a 1.9 Å crystal structure of Trl1 KIN-CPD from the pathogenic fungus Candida albicans, which adopts an extended conformation in which separate KIN and CPD domains are connected by an unstructured linker. CPD belongs to the 2H phosphotransferase superfamily by dint of its conserved central concave β sheet and interactions of its dual HxT motif histidines and threonines with phosphate in the active site. Additional active site motifs conserved among the fungal CPD clade of 2H enzymes are identified. We present structures of the Candida Trl1 KIN domain at 1.5 to 2.0 Å resolution—as apoenzyme and in complexes with GTP•Mg2+, IDP•PO4, and dGDP•PO4—that highlight conformational switches in the G-loop (which recognizes the guanine base) and lid-loop (poised over the nucleotide phosphates) that accompany nucleotide binding.
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Affiliation(s)
- Ankan Banerjee
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Yehuda Goldgur
- Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Beate Schwer
- Microbiology and Immunology Department, Weill Cornell Medical College, New York, NY 10065, USA
| | - Stewart Shuman
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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9
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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: 16] [Impact Index Per Article: 3.2] [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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10
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Pillon MC, Sobhany M, Stanley RE. Characterization of the molecular crosstalk within the essential Grc3/Las1 pre-rRNA processing complex. RNA (NEW YORK, N.Y.) 2018; 24:721-738. [PMID: 29440475 PMCID: PMC5900568 DOI: 10.1261/rna.065037.117] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 02/06/2018] [Indexed: 06/08/2023]
Abstract
Grc3 is an essential well-conserved eukaryotic polynucleotide kinase (PNK) that cooperates with the endoribonuclease Las1 to process the preribosomal RNA (rRNA). Aside from being dependent upon Las1 for coordinated kinase and nuclease function, little is known about Grc3 substrate specificity and the molecular mechanisms governing kinase activity. Here we characterize the kinase activity of Grc3 and identify key similarities and differences between Grc3 and other polynucleotide kinase family members. In contrast to other PNK family members, Grc3 has distinct substrate preference for RNA substrates in vitro. By disrupting conserved residues found at the Grc3 kinase active site, we identified specific residues required to support Grc3-directed Las1-mediated pre-rRNA cleavage in vitro and in vivo. The crosstalk between Grc3 and Las1 ensures the direct coupling of cleavage and phosphorylation during pre-rRNA processing. Taken together, our studies provide key insight into the polynucleotide kinase activity of the essential enzyme Grc3 and its molecular crosstalk with the endoribonuclease Las1.
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Affiliation(s)
- Monica C Pillon
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
| | - Mack Sobhany
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
| | - Robin E Stanley
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
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11
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Remus BS, Goldgur Y, Shuman S. Structural basis for the GTP specificity of the RNA kinase domain of fungal tRNA ligase. Nucleic Acids Res 2018; 45:12945-12953. [PMID: 29165709 PMCID: PMC5728400 DOI: 10.1093/nar/gkx1159] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 11/04/2017] [Indexed: 01/10/2023] 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 and central polynucleotide kinase domains that heal the broken ends to generate the 3′-OH,2′-PO4 and 5′-PO4 termini required for sealing by an N-terminal ligase domain. Trl1 enzymes are found in all human fungal pathogens and are promising targets for antifungal drug discovery because their domain compositions and biochemical mechanisms are unique compared to the mammalian RtcB-type tRNA splicing enzyme. A distinctive feature of Trl1 is its preferential use of GTP as phosphate donor for the RNA kinase reaction. Here we report the 2.2 Å crystal structure of the kinase domain of Trl1 from the fungal pathogen Candida albicans with GDP and Mg2+ in the active site. The P-loop phosphotransferase fold of the kinase is embellished by a unique ‘G-loop’ element that accounts for guanine nucleotide specificity. Mutations of amino acids that contact the guanine nucleobase efface kinase activity in vitro and Trl1 function in vivo. Our findings fortify the case for the Trl1 kinase as an antifungal target.
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Affiliation(s)
- Barbara S Remus
- 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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12
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Characterization of Runella slithyformis HD-Pnk, a Bifunctional DNA/RNA End-Healing Enzyme Composed of an N-Terminal 2',3'-Phosphoesterase HD Domain and a C-Terminal 5'-OH Polynucleotide Kinase Domain. J Bacteriol 2017; 199:JB.00739-16. [PMID: 27895092 DOI: 10.1128/jb.00739-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 11/18/2016] [Indexed: 11/20/2022] Open
Abstract
5'- and 3'-end-healing reactions are key steps in nucleic acid break repair in which 5'-OH ends are phosphorylated by a polynucleotide kinase (Pnk) and 3'-PO4 or 2',3'-cyclic-PO4 ends are hydrolyzed by a phosphoesterase to generate the 5'-PO4 and 3'-OH termini required for sealing by classic polynucleotide ligases. End-healing and sealing enzymes are present in diverse bacterial taxa, often organized as modular units within a single multifunctional polypeptide or as subunits of a repair complex. Here we identify and characterize Runella slithyformis HD-Pnk as a novel bifunctional end-healing enzyme composed of an N-terminal 2',3'-phosphoesterase HD domain and a C-terminal 5'-OH polynucleotide kinase P-loop domain. HD-Pnk phosphorylates 5'-OH polynucleotides (9-mers or longer) in the presence of magnesium and any nucleoside triphosphate donor. HD-Pnk dephosphorylates RNA 2',3'-cyclic phosphate, RNA 3'-phosphate, RNA 2'-phosphate, and DNA 3'-phosphate ends in the presence of a transition metal cofactor, which can be nickel, copper, or cobalt. HD-Pnk homologs are present in genera from 11 bacterial phyla and are often encoded in an operon with a putative ATP-dependent polynucleotide ligase. IMPORTANCE The present study provides insights regarding the diversity of nucleic acid repair strategies via the characterization of Runella slithyformis HD-Pnk as the exemplar of a novel clade of dual 5'- and 3'-end-healing enzymes that phosphorylate 5'-OH termini and dephosphorylate 2',3'-cyclic-PO4, 3'-PO4, and 2'-PO4 ends. The distinctive feature of HD-Pnk is its domain composition, i.e., a fusion of an N-terminal HD phosphohydrolase module and a C-terminal P-loop polynucleotide kinase module. Homologs of Runella HD-Pnk with the same domain composition, same domain order, and similar polypeptide sizes are distributed widely among genera from 11 bacterial phyla.
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