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Rostamighadi M, Kamelshahroudi A, Mehta V, Zeng FY, Pass I, Chung TDY, Salavati R. High-throughput screening of compounds targeting RNA editing in Trypanosoma brucei: Novel molecular scaffolds with broad trypanocidal effects. Biochem Pharmacol 2024; 219:115937. [PMID: 37995979 DOI: 10.1016/j.bcp.2023.115937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/15/2023] [Accepted: 11/16/2023] [Indexed: 11/25/2023]
Abstract
Mitochondrial uridine insertion/deletion RNA editing, catalyzed by a multiprotein complex (editosome), is essential for gene expression in trypanosomes and Leishmania parasites. As this process is absent in the human host, a drug targeting this mechanism promises high selectivity and reduced toxicity. Here, we successfully miniaturized our FRET-based full-round RNA editing assay, which replicates the complete RNA editing process, adapting it into a 1536-well format. Leveraging this assay, we screened over 100,000 compounds against purified editosomes derived from Trypanosoma brucei, identifying seven confirmed primary hits. We sourced and evaluated various analogs to enhance the inhibitory and parasiticidal effects of these primary hits. In combination with secondary assays, our compounds marked inhibition of essential catalytic activities, including the RNA editing ligase and interactions of editosome proteins. Although the primary hits did not exhibit any growth inhibitory effect on parasites, we describe eight analog compounds capable of effectively killing T. brucei and/or Leishmania donovani parasites within a low micromolar concentration. Whether parasite killing is - at least in part - due to inhibition of RNA editing in vivo remains to be assessed. Our findings introduce novel molecular scaffolds with the potential for broad antitrypanosomal effects.
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Affiliation(s)
- Mojtaba Rostamighadi
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada
| | - Arezou Kamelshahroudi
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada
| | - Vaibhav Mehta
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada; Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Fu-Yue Zeng
- Sanford Burnham Prebys Medical Discovery Institute, Conrad Prebys Center for Chemical Genomics, La Jolla, CA, USA
| | - Ian Pass
- Sanford Burnham Prebys Medical Discovery Institute, Conrad Prebys Center for Chemical Genomics, La Jolla, CA, USA
| | - Thomas D Y Chung
- Sanford Burnham Prebys Medical Discovery Institute, Conrad Prebys Center for Chemical Genomics, La Jolla, CA, USA
| | - Reza Salavati
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada; Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada.
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2
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Lukeš J, Speijer D, Zíková A, Alfonzo JD, Hashimi H, Field MC. Trypanosomes as a magnifying glass for cell and molecular biology. Trends Parasitol 2023; 39:902-912. [PMID: 37679284 DOI: 10.1016/j.pt.2023.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/08/2023] [Accepted: 08/09/2023] [Indexed: 09/09/2023]
Abstract
The African trypanosome, Trypanosoma brucei, has developed into a flexible and robust experimental model for molecular and cellular parasitology, allowing us to better combat these and related parasites that cause worldwide suffering. Diminishing case numbers, due to efficient public health efforts, and recent development of new drug treatments have reduced the need for continued study of T. brucei in a disease context. However, we argue that this pathogen has been instrumental in revolutionary discoveries that have widely informed molecular and cellular biology and justifies continuing research as an experimental model. Ongoing work continues to contribute towards greater understanding of both diversified and conserved biological features. We discuss multiple examples where trypanosomes pushed the boundaries of cell biology and hope to inspire researchers to continue exploring these remarkable protists as tools for magnifying the inner workings of cells.
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Affiliation(s)
- Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic.
| | - Dave Speijer
- Medical Biochemistry, University of Amsterdam, AMC, Amsterdam, The Netherlands
| | - Alena Zíková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Juan D Alfonzo
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA
| | - Hassan Hashimi
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Mark C Field
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; School of Life Sciences, University of Dundee, Dundee, UK
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3
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Liu S, Wang H, Li X, Zhang F, Lee JKJ, Li Z, Yu C, Hu JJ, Zhao X, Suematsu T, Alvarez-Cabrera AL, Liu Q, Zhang L, Huang L, Aphasizheva I, Aphasizhev R, Zhou ZH. Structural basis of gRNA stabilization and mRNA recognition in trypanosomal RNA editing. Science 2023; 381:eadg4725. [PMID: 37410820 DOI: 10.1126/science.adg4725] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 05/17/2023] [Indexed: 07/08/2023]
Abstract
In Trypanosoma brucei, the editosome, composed of RNA-editing substrate-binding complex (RESC) and RNA-editing catalytic complex (RECC), orchestrates guide RNA (gRNA)-programmed editing to recode cryptic mitochondrial transcripts into messenger RNAs (mRNAs). The mechanism of information transfer from gRNA to mRNA is unclear owing to a lack of high-resolution structures for these complexes. With cryo-electron microscopy and functional studies, we have captured gRNA-stabilizing RESC-A and gRNA-mRNA-binding RESC-B and RESC-C particles. RESC-A sequesters gRNA termini, thus promoting hairpin formation and blocking mRNA access. The conversion of RESC-A into RESC-B or -C unfolds gRNA and allows mRNA selection. The ensuing gRNA-mRNA duplex protrudes from RESC-B, likely exposing editing sites to RECC-catalyzed cleavage, uridine insertion or deletion, and ligation. Our work reveals a remodeling event facilitating gRNA-mRNA hybridization and assembly of a macromolecular substrate for the editosome's catalytic modality.
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Affiliation(s)
- Shiheng Liu
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Hong Wang
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA
| | - Xiaorun Li
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Fan Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jane K J Lee
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Zihang Li
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Clinton Yu
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Jason J Hu
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Xiaojing Zhao
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA
| | - Ana L Alvarez-Cabrera
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Qiushi Liu
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA
| | - Liye Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- Shanghai Clinical Research and Trial Center, Shanghai 201210, China
| | - Lan Huang
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA
- Department of Biochemistry, Boston University Medical Campus, Boston, MA, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, USA
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4
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Acquah FA, Mooers BHM. Targeting RNA Structure to Inhibit Editing in Trypanosomes. Int J Mol Sci 2023; 24:10110. [PMID: 37373258 PMCID: PMC10298474 DOI: 10.3390/ijms241210110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/01/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
Mitochondrial RNA editing in trypanosomes represents an attractive target for developing safer and more efficient drugs for treating infections with trypanosomes because this RNA editing pathway is not found in humans. Other workers have targeted several enzymes in this editing system, but not the RNA. Here, we target a universal domain of the RNA editing substrate, which is the U-helix formed between the oligo-U tail of the guide RNA and the target mRNA. We selected a part of the U-helix that is rich in G-U wobble base pairs as the target site for the virtual screening of 262,000 compounds. After chemoinformatic filtering of the top 5000 leads, we subjected 50 representative complexes to 50 nanoseconds of molecular dynamics simulations. We identified 15 compounds that retained stable interactions in the deep groove of the U-helix. The microscale thermophoresis binding experiments on these five compounds show low-micromolar to nanomolar binding affinities. The UV melting studies show an increase in the melting temperatures of the U-helix upon binding by each compound. These five compounds can serve as leads for drug development and as research tools to probe the role of the RNA structure in trypanosomal RNA editing.
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Affiliation(s)
- Francis A. Acquah
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
| | - Blaine H. M. Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
- Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Laboratory of Biomolecular Structure and Function, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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5
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Gaona-López C, Vazquez-Jimenez LK, Gonzalez-Gonzalez A, Delgado-Maldonado T, Ortiz-Pérez E, Nogueda-Torres B, Moreno-Rodríguez A, Vázquez K, Saavedra E, Rivera G. Advances in Protozoan Epigenetic Targets and Their Inhibitors for the Development of New Potential Drugs. Pharmaceuticals (Basel) 2023; 16:ph16040543. [PMID: 37111300 PMCID: PMC10143871 DOI: 10.3390/ph16040543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/29/2023] [Accepted: 03/31/2023] [Indexed: 04/29/2023] Open
Abstract
Protozoan parasite diseases cause significant mortality and morbidity worldwide. Factors such as climate change, extreme poverty, migration, and a lack of life opportunities lead to the propagation of diseases classified as tropical or non-endemic. Although there are several drugs to combat parasitic diseases, strains resistant to routinely used drugs have been reported. In addition, many first-line drugs have adverse effects ranging from mild to severe, including potential carcinogenic effects. Therefore, new lead compounds are needed to combat these parasites. Although little has been studied regarding the epigenetic mechanisms in lower eukaryotes, it is believed that epigenetics plays an essential role in vital aspects of the organism, from controlling the life cycle to the expression of genes involved in pathogenicity. Therefore, using epigenetic targets to combat these parasites is foreseen as an area with great potential for development. This review summarizes the main known epigenetic mechanisms and their potential as therapeutics for a group of medically important protozoal parasites. Different epigenetic mechanisms are discussed, highlighting those that can be used for drug repositioning, such as histone post-translational modifications (HPTMs). Exclusive parasite targets are also emphasized, including the base J and DNA 6 mA. These two categories have the greatest potential for developing drugs to treat or eradicate these diseases.
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Affiliation(s)
- Carlos Gaona-López
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
| | - Lenci K Vazquez-Jimenez
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
| | - Alonzo Gonzalez-Gonzalez
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
| | - Timoteo Delgado-Maldonado
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
| | - Eyrá Ortiz-Pérez
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
| | - Benjamín Nogueda-Torres
- Departamento de Parasitología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Adriana Moreno-Rodríguez
- Laboratorio de Estudios Epidemiológicos, Clínicos, Diseños Experimentales e Investigación, Facultad de Ciencias Químicas, Universidad Autónoma "Benito Juárez" de Oaxaca, Avenida Universidad S/N, Ex Hacienda Cinco Señores, Oaxaca 68120, Mexico
| | - Karina Vázquez
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Nuevo León, Francisco Villa 20, General Escobedo 66054, Mexico
| | - Emma Saavedra
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City 14080, Mexico
| | - Gildardo Rivera
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Reynosa 88710, Mexico
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6
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Wang JF, Lin RH, Zhang X, Hide G, Lun ZR, Lai DH. Novel insertions in the mitochondrial maxicircle of Trypanosoma musculi, a mouse trypanosome. Parasitology 2022; 149:1546-1555. [PMID: 35924587 PMCID: PMC11093713 DOI: 10.1017/s0031182022001019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 07/14/2022] [Accepted: 07/17/2022] [Indexed: 11/07/2022]
Abstract
Trypanosoma musculi is a, globally distributed, mouse-specific haemoflagellate, of the family Trypanosomatidae, which shares similar characteristics in morphology with Trypanosoma lewisi. The kinetoplast (mitochondrial) DNA of Trypanosomatidae flagellates is comprised of catenated maxicircles and minicircles. However, genetic information on the T. musculi kinetoplast remains largely unknown. In this study, the T. musculi maxicircle genome was completely assembled, with PacBio and Illumina sequencing, and the size was confirmed at 34 606 bp. It consisted of 2 distinct parts: the coding region and the divergent regions (DRs, DRI and II). In comparison with other trypanosome maxicircles (Trypanosoma brucei, Trypanosoma cruzi and T. lewisi), the T. musculi maxicircle has a syntenic distribution of genes and shares 73.9, 78.0 and 92.7% sequence identity, respectively, over the whole coding region. Moreover, novel insertions in MURF2 (630 bp) and in ND5 (1278 bp) were found, respectively, which are homologous to minicircles. These findings support an evolutionary scenario similar to the one proposed for insertions in Trypanosoma cruzi, the pathogen of American trypanosomiasis. These novel insertions, together with a deletion (281 bp) in ND4, question the role of Complex I in T. musculi. A detailed analysis of DRII indicated that it contains numerous repeat motifs and palindromes, the latter of which are highly conservative and contain A5C elements. The comprehensively annotated kinetoplast maxicircle of T. musculi reveals a high degree of similarity between this parasite and the maxicircle of T. lewisi and suggests that the DRII could be a valuable marker for distinguishing these evolutionarily related species.
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Affiliation(s)
- Ju-Feng Wang
- Guangdong Provincial Key Laboratory of Aquatic Economic Animals, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, The People's Republic of China
| | - Ruo-Hong Lin
- Guangdong Provincial Key Laboratory of Aquatic Economic Animals, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, The People's Republic of China
| | - Xuan Zhang
- Guangdong Provincial Key Laboratory of Aquatic Economic Animals, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, The People's Republic of China
| | - Geoff Hide
- Ecosystems and Environment Research Centre and Biomedical Research Centre, School of Science, Engineering and Environment, University of Salford, Salford M5 4WT, UK
| | - Zhao-Rong Lun
- Guangdong Provincial Key Laboratory of Aquatic Economic Animals, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, The People's Republic of China
- Ecosystems and Environment Research Centre and Biomedical Research Centre, School of Science, Engineering and Environment, University of Salford, Salford M5 4WT, UK
| | - De-Hua Lai
- Guangdong Provincial Key Laboratory of Aquatic Economic Animals, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, The People's Republic of China
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7
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Current Status of Regulatory Non-Coding RNAs Research in the Tritryp. Noncoding RNA 2022; 8:ncrna8040054. [PMID: 35893237 PMCID: PMC9326685 DOI: 10.3390/ncrna8040054] [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: 05/14/2022] [Revised: 07/01/2022] [Accepted: 07/02/2022] [Indexed: 11/23/2022] Open
Abstract
Trypanosomatids are protozoan parasites that cause devastating vector-borne human diseases. Gene expression regulation of these organisms depends on post-transcriptional control in responding to diverse environments while going through multiple developmental stages of their complex life cycles. In this scenario, non-coding RNAs (ncRNAs) are excellent candidates for a very efficient, quick, and economic strategy to regulate gene expression. The advent of high throughput RNA sequencing technologies show the presence and deregulation of small RNA fragments derived from canonical ncRNAs. This review seeks to depict the ncRNA landscape in trypanosomatids, focusing on the small RNA fragments derived from functional RNA molecules observed in RNA sequencing studies. Small RNA fragments derived from canonical ncRNAs (tsRNAs, snsRNAs, sdRNAs, and sdrRNAs) were identified in trypanosomatids. Some of these RNAs display changes in their levels associated with different environments and developmental stages, demanding further studies to determine their functional characterization and potential roles. Nevertheless, a comprehensive and detailed ncRNA annotation for most trypanosomatid genomes is still needed, allowing better and more extensive comparative and functional studies.
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Aphasizheva I, Aphasizhev R. Mitochondrial RNA quality control in trypanosomes. WILEY INTERDISCIPLINARY REVIEWS. RNA 2021; 12:e1638. [PMID: 33331073 PMCID: PMC9805618 DOI: 10.1002/wrna.1638] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/27/2020] [Accepted: 11/29/2020] [Indexed: 01/04/2023]
Abstract
Unicellular parasites Trypanosoma brucei spp. cause African human and animal trypanosomiasis, a spectrum of diseases that jeopardize public health and afflict the economy in sub-Saharan Africa. These hemoflagellates are distinguished by a single mitochondrion, which contains a kinetoplast nucleoid composed of DNA and histone-like proteins. Kinetoplast DNA (kDNA) represents a densely packed network of interlinked relaxed circular molecules: a few ~23-kb maxicircles encoding ribosomal RNAs (rRNAs) and proteins, and approximately 5,000 1-kb minicircles bearing guide RNA (gRNA) genes. The transcription start site defines the mRNA's 5' terminus while the primary RNA is remodeled into a monocistronic messenger by 3'-5' exonucleolytic trimming, 5' and 3' end modifications, and, in most cases, by internal U-insertion/deletion editing. Ribosomal and guide RNA precursors are also trimmed, and the processed molecules are uridylated. For 35 years, mRNA editing has attracted a major effort, but more recently the essential pre- and postediting processing and turnover events have been discovered and the key effectors have been identified. Among these, pentatricopeptide repeat (PPR) RNA binding proteins emerged as conduits coupling modifications of mRNA termini with internal sequence changes introduced by editing. Among 39 annotated PPRs, 20 belong to ribosomal subunits or assembly intermediates, four function as polyadenylation factors, a single factor directs 5' mRNA modification, and one protein is found in F1-ATPase. Nuclear and mitochondrial RNases P consist of a single PPR polypeptide, PRORP1 and PROP2, respectively. Here, we review PPR-mediated mitochondrial processes and discuss their potential roles in mRNA maturation, quality control, translational activation, and decay. This article is categorized under: RNA Processing > Capping and 5' End Modifications RNA Processing > 3' End Processing RNA Processing > RNA Editing and Modification.
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Affiliation(s)
- Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, Massachusetts
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, Massachusetts,Department of Biochemistry, Boston University Medical Campus, Boston, Massachusetts
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9
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Abstract
Complex I (NADH dehydrogenase) is the first enzyme in the respiratory chain. It catalyses the electron transfer from NADH to ubiquinone that is associated with proton pumping out of the matrix. In this study, we characterized NADH dehydrogenase activity in seven monoxenous trypanosomatid species: Blechomonas ayalai, Herpetomonas tarakana, Kentomonas sorsogonicus, Leptomonas seymouri, Novymonas esmeraldas, Sergeia podlipaevi and Wallacemonas raviniae. We also investigated the subunit composition of the complex I in dixenous Phytomonas serpens, in which its presence and activity have been previously documented. In addition to P. serpens, the complex I is functionally active in N. esmeraldas and S. podlipaevi. We also identified 24-32 subunits of the complex I in individual species by using mass spectrometry. Among them, for the first time, we recognized several proteins of the mitochondrial DNA origin.
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10
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Aphasizheva I, Suematsu T, Vacas A, Wang H, Fan C, Zhao X, Zhang L, Aphasizhev R. CTS tag-based methods for investigating mitochondrial RNA modification factors in Trypanosoma brucei. Methods Enzymol 2021; 658:83-109. [PMID: 34517961 PMCID: PMC9805619 DOI: 10.1016/bs.mie.2021.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Unicellular parasite Trypanosoma brucei maintains an elaborate mitochondrial mRNA processing pathway including 3'-5' exonucleolytic trimming of primary precursors, 5' and 3' modifications, and, in most cases, massive U-insertion/deletion editing. Whereas the role of editing in restoring protein coding sequence is apparent, recent developments suggest that terminal modifications are equally critical for generating a stable translationally competent messenger. The enzymatic activities responsible for 5' pyrophosphate hydrolysis, 3' adenylation and uridylation, and 3'-5' decay are positively and negatively regulated by pentatricopeptide repeat-containing (PPR) proteins. These sequence-specific RNA binding factors typically contain arrays of 35-amino acid repeats each of which recognizes a single nucleotide. Here, we introduce a combinatorial CTS affinity tag, which underlies a suite of methods for PPR proteins purification, in vivo RNA binding sites mapping and sub-cellular localization studies. These approaches should be applicable to most trypanosomal RNA binding proteins.
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Affiliation(s)
- Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, United States,Corresponding author:
| | - Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, United States
| | - Andres Vacas
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, United States
| | - Hong Wang
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, United States
| | - Chenyu Fan
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xiaojing Zhao
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Liye Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, United States,Department of Biochemistry, Boston University Medical Campus, Boston, MA, United States
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11
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Cooper S, Wadsworth ES, Ochsenreiter T, Ivens A, Savill NJ, Schnaufer A. Assembly and annotation of the mitochondrial minicircle genome of a differentiation-competent strain of Trypanosoma brucei. Nucleic Acids Res 2019; 47:11304-11325. [PMID: 31665448 PMCID: PMC6868439 DOI: 10.1093/nar/gkz928] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/03/2019] [Accepted: 10/08/2019] [Indexed: 01/10/2023] Open
Abstract
Kinetoplastids are protists defined by one of the most complex mitochondrial genomes in nature, the kinetoplast. In the sleeping sickness parasite Trypanosoma brucei, the kinetoplast is a chain mail-like network of two types of interlocked DNA molecules: a few dozen ∼23-kb maxicircles (homologs of the mitochondrial genome of other eukaryotes) and thousands of ∼1-kb minicircles. Maxicircles encode components of respiratory chain complexes and the mitoribosome. Several maxicircle-encoded mRNAs undergo extensive post-transcriptional RNA editing via addition and deletion of uridines. The process is mediated by hundreds of species of minicircle-encoded guide RNAs (gRNAs), but the precise number of minicircle classes and gRNA genes was unknown. Here we present the first essentially complete assembly and annotation of the kinetoplast genome of T. brucei. We have identified 391 minicircles, encoding not only ∼930 predicted 'canonical' gRNA genes that cover nearly all known editing events (accessible via the web at http://hank.bio.ed.ac.uk), but also ∼370 'non-canonical' gRNA genes of unknown function. Small RNA transcriptome data confirmed expression of the majority of both categories of gRNAs. Finally, we have used our data set to refine definitions for minicircle structure and to explore dynamics of minicircle copy numbers.
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Affiliation(s)
- Sinclair Cooper
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, Scotland EH9 3FL, UK
| | - Elizabeth S Wadsworth
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, Scotland EH9 3FL, UK
| | | | - Alasdair Ivens
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, Scotland EH9 3FL, UK
| | - Nicholas J Savill
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, Scotland EH9 3FL, UK
| | - Achim Schnaufer
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, Scotland EH9 3FL, UK
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12
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Maslov DA. Separating the Wheat from the Chaff: RNA Editing and Selection of Translatable mRNA in Trypanosome Mitochondria. Pathogens 2019; 8:E105. [PMID: 31323762 PMCID: PMC6789859 DOI: 10.3390/pathogens8030105] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/14/2019] [Accepted: 07/16/2019] [Indexed: 11/16/2022] Open
Abstract
In the mitochondria of trypanosomes and related kinetoplastid protists, most mRNAs undergo a long and sophisticated maturation pathway before they can be productively translated by mitochondrial ribosomes. Some of the aspects of this pathway (identity of the promotors, transcription initiation, and termination signals) remain obscure, and some (post-transcriptional modification by U-insertion/deletion, RNA editing, 3'-end maturation) have been illuminated by research during the last decades. The RNA editing creates an open reading frame for a productive translation, but the fully edited mRNA often represents a minor fraction in the pool of pre-edited and partially edited precursors. Therefore, it has been expected that the final stages of the mRNA processing generate molecular hallmarks, which allow for the efficient and selective recognition of translation-competent templates. The general contours and several important details of this process have become known only recently and represent the subject of this review.
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Affiliation(s)
- Dmitri A Maslov
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, CA 92521, USA.
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13
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Nikpour N, Salavati R. The RNA binding activity of the first identified trypanosome protein with Z-DNA-binding domains. Sci Rep 2019; 9:5904. [PMID: 30976048 PMCID: PMC6459835 DOI: 10.1038/s41598-019-42409-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 03/25/2019] [Indexed: 12/22/2022] Open
Abstract
RNA-binding proteins play a particularly important role in regulating gene expression in trypanosomes. A map of the network of protein complexes in Trypanosoma brucei uncovered an essential protein (Tb927.10.7910) that is postulated to be an RNA-binding protein implicated in the regulation of the mitochondrial post-transcriptional gene regulatory network by its association with proteins that participate in a multi-protein RNA editing complex. However, the mechanism by which this protein interacts with its multiple target transcripts remained unknown. Using sensitive database searches and experimental data, we identify Z-DNA-binding domains in T. brucei in the N- and C-terminal regions of Tb927.10.7910. RNA-binding studies of the wild-type protein, now referred to as RBP7910 (RNA binding protein 7910), and site-directed mutagenesis of residues important for the Z-DNA binding domains show that it preferentially interacts with RNA molecules containing poly(U) and poly(AU)-rich sequences. The interaction of RBP7910 with these regions may be involved in regulation of RNA editing of mitochondrial transcripts.
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Affiliation(s)
- Najmeh Nikpour
- Institute of Parasitology, McGill University, Quebec, H9X3V9, Canada
| | - Reza Salavati
- Department of Biochemistry, McGill University, McIntyre Medical Building, 3655 Promenade Sir William Osler, Montreal, Quebec, H3G 1Y6, Canada.
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14
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Mesitov MV, Yu T, Suematsu T, Sement FM, Zhang L, Yu C, Huang L, Aphasizheva I. Pentatricopeptide repeat poly(A) binding protein KPAF4 stabilizes mitochondrial mRNAs in Trypanosoma brucei. Nat Commun 2019; 10:146. [PMID: 30635574 PMCID: PMC6329795 DOI: 10.1038/s41467-018-08137-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 12/19/2018] [Indexed: 01/25/2023] Open
Abstract
In Trypanosoma brucei, most mitochondrial mRNAs undergo editing, and 3′ adenylation and uridylation. The internal sequence changes and terminal extensions are coordinated: pre-editing addition of the short (A) tail protects the edited transcript against 3′-5′ degradation, while post-editing A/U-tailing renders mRNA competent for translation. Participation of a poly(A) binding protein (PABP) in coupling of editing and 3′ modification processes has been inferred, but its identity and mechanism of action remained elusive. We report identification of KPAF4, a pentatricopeptide repeat-containing PABP which sequesters the A-tail and impedes mRNA degradation. Conversely, KPAF4 inhibits uridylation of A-tailed transcripts and, therefore, premature A/U-tailing of partially-edited mRNAs. This quality check point likely prevents translation of incompletely edited mRNAs. We also find that RNA editing substrate binding complex (RESC) mediates the interaction between the 5′ end-bound pyrophosphohydrolase MERS1 and 3′ end-associated KPAF4 to enable mRNA circularization. This event appears to be critical for edited mRNA stability. Polyadenylation stabilizes edited mitochondrial mRNAs in Trypanosoma brucei, but the involved poly(A) binding protein is unknown. Here, Mesitov et al. show that a pentatricopeptide repeat factor KPAF4 binds to A-tail and prevents exonucleolytic degradation as well as translation of incompletely edited mRNAs.
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Affiliation(s)
- Mikhail V Mesitov
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, 02118, USA
| | - Tian Yu
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, 02118, USA.,Bioinformatics Program, Boston University, Boston, MA, 02215, USA
| | - Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, 02118, USA
| | - Francois M Sement
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, 02118, USA
| | - Liye Zhang
- School of Life Science and Technology, ShanghaiTechUniversity, 201210, Shanghai, China
| | - Clinton Yu
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, 92697, USA
| | - Lan Huang
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, 92697, USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, 02118, USA.
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15
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Cruz-Reyes J, Mooers BHM, Doharey PK, Meehan J, Gulati S. Dynamic RNA holo-editosomes with subcomplex variants: Insights into the control of trypanosome editing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1502. [PMID: 30101566 DOI: 10.1002/wrna.1502] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/03/2018] [Accepted: 07/09/2018] [Indexed: 12/14/2022]
Abstract
RNA editing causes massive remodeling of the mitochondrial mRNA transcriptome in trypanosomes and related kinetoplastid protozoa. This type of editing involves the specific insertion or deletion of uridylates (U) directed by small noncoding guide RNAs (gRNAs). Because U-insertion exceeds U-deletion by a factor of 10, editing increases the nascent mRNA size by up to 55%. In Trypanosoma brucei, the editing apparatus uses ~40 proteins and >1,200 gRNAs to create the functional open reading frame in 12 mRNAs. Thousands of sites are specifically recognized in the pre-edited mRNAs and a myriad of partially edited transcript intermediates accumulates in mitochondria. The control of editing is poorly understood, but past work suggests that it occurs during substrate recognition, the initiation and progression of editing, and during the life-cycle in different hosts. The growing understanding of the editing proteins offers clues about editing control. Most editing proteins reside in the "RNA-free" RNA editing core complex (RECC) and in the accessory RNA editing substrate complex (RESC) that contains gRNA. Two accessory RNA helicases are known, including one in the RNA editing helicase 2 complex (REH2C). Both the RESC and the REH2C associate with mRNA, providing a rationale for the assembly of mRNA or its mRNPs, RESC, and the RECC enzyme. Identified variants of the canonical editing complexes further complicate the model of RNA editing. We examine specific examples of complex variants, differential effects of editing proteins on the mRNAs within and between T. brucei life stages, and possible control points in RNA holo-editosomes. This article is categorized under: RNA Processing > RNA Editing and Modification RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Jorge Cruz-Reyes
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Blaine H M Mooers
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Pawan K Doharey
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Joshua Meehan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Shelly Gulati
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
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16
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Recent advances in trypanosomatid research: genome organization, expression, metabolism, taxonomy and evolution. Parasitology 2018; 146:1-27. [PMID: 29898792 DOI: 10.1017/s0031182018000951] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Unicellular flagellates of the family Trypanosomatidae are obligatory parasites of invertebrates, vertebrates and plants. Dixenous species are aetiological agents of a number of diseases in humans, domestic animals and plants. Their monoxenous relatives are restricted to insects. Because of the high biological diversity, adaptability to dramatically different environmental conditions, and omnipresence, these protists have major impact on all biotic communities that still needs to be fully elucidated. In addition, as these organisms represent a highly divergent evolutionary lineage, they are strikingly different from the common 'model system' eukaryotes, such as some mammals, plants or fungi. A number of excellent reviews, published over the past decade, were dedicated to specialized topics from the areas of trypanosomatid molecular and cell biology, biochemistry, host-parasite relationships or other aspects of these fascinating organisms. However, there is a need for a more comprehensive review that summarizing recent advances in the studies of trypanosomatids in the last 30 years, a task, which we tried to accomplish with the current paper.
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17
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McAdams NM, Simpson RM, Chen R, Sun Y, Read LK. MRB7260 is essential for productive protein-RNA interactions within the RNA editing substrate binding complex during trypanosome RNA editing. RNA (NEW YORK, N.Y.) 2018; 24:540-556. [PMID: 29330168 PMCID: PMC5855954 DOI: 10.1261/rna.065169.117] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 01/08/2018] [Indexed: 05/20/2023]
Abstract
The trypanosome RNA editing substrate binding complex (RESC) acts as the platform for mitochondrial uridine insertion/deletion RNA editing and facilitates the protein-protein and protein-RNA interactions required for the editing process. RESC is broadly comprised of two subcomplexes: GRBC (guide RNA binding complex) and REMC (RNA editing mediator complex). Here, we characterize the function and position in RESC organization of a previously unstudied RESC protein, MRB7260. We show that MRB7260 forms numerous RESC-related complexes, including a novel, small complex with the guide RNA binding protein, GAP1, which is a canonical GRBC component, and REMC components MRB8170 and TbRGG2. RNA immunoprecipitations in MRB7260-depleted cells show that MRB7260 is critical for normal RNA trafficking between REMC and GRBC. Analysis of protein-protein interactions also reveals an important role for MRB7260 in promoting stable association of the two subcomplexes. High-throughput sequencing analysis of RPS12 mRNAs from MRB7260 replete and depleted cells demonstrates that MRB7260 is critical for gRNA exchange and early gRNA utilization, with the exception of the initiating gRNA. Together, these data demonstrate that MRB7260 is essential for productive protein-RNA interactions with RESC during RNA editing.
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Affiliation(s)
- Natalie M McAdams
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York 14203, USA
| | - Rachel M Simpson
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York 14203, USA
| | - Runpu Chen
- Department of Computer Science and Engineering, University at Buffalo, Buffalo, New York 14260, USA
| | - Yijun Sun
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York 14203, USA
| | - Laurie K Read
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York 14203, USA
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18
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19
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McDermott SM, Stuart K. The essential functions of KREPB4 are developmentally distinct and required for endonuclease association with editosomes. RNA (NEW YORK, N.Y.) 2017; 23:1672-1684. [PMID: 28802260 PMCID: PMC5648035 DOI: 10.1261/rna.062786.117] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 08/07/2017] [Indexed: 05/20/2023]
Abstract
Uridine insertion and deletion RNA editing generates functional mitochondrial mRNAs in Trypanosoma brucei, and several transcripts are differentially edited in bloodstream (BF) and procyclic form (PF) cells correlating with changes in mitochondrial function. Editing is catalyzed by three ∼20S editosomes that have a common set of 12 proteins, but are typified by mutually exclusive RNase III KREN1, N2, and N3 endonucleases with distinct cleavage specificities. KREPB4 is a common editosome protein that has a degenerate RNase III domain lacking conserved catalytic residues, in addition to zinc-finger and Pumilio/fem-3 mRNA binding factor (PUF) motifs. Here we show that KREPB4 is essential for BF and PF growth, in vivo RNA editing, and editosome integrity, but that loss of KREPB4 has differential effects on editosome components and complexes between BF and PF cells. We used targeted mutagenesis to investigate the functions of the conserved PUF and RNase III domains in both life-cycle stages and show that the PUF motif is not essential for function in BF or PF. In contrast, specific mutations in the RNase III domain severely inhibit BF and PF growth and editing, and disrupt ∼20S editosomes, while others indicate that the RNase III domain is noncatalytic. We further show that KREPB4, specifically the noncatalytic RNase III domain, is required for the association of KREN1, N2, and N3 with PF editosomes. These results, combined with previous studies, support a model in which KREPB4 acts as a pseudoenzyme to form the noncatalytic half of an RNase III heterodimer with the editing endonucleases.
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Affiliation(s)
- Suzanne M McDermott
- Center for Infectious Disease Research (formerly Seattle BioMed), Seattle, Washington 98109, USA
| | - Kenneth Stuart
- Center for Infectious Disease Research (formerly Seattle BioMed), Seattle, Washington 98109, USA
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20
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Simpson RM, Bruno AE, Chen R, Lott K, Tylec BL, Bard JE, Sun Y, Buck MJ, Read LK. Trypanosome RNA Editing Mediator Complex proteins have distinct functions in gRNA utilization. Nucleic Acids Res 2017; 45:7965-7983. [PMID: 28535252 PMCID: PMC5737529 DOI: 10.1093/nar/gkx458] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 05/01/2017] [Accepted: 05/10/2017] [Indexed: 11/13/2022] Open
Abstract
Uridine insertion/deletion RNA editing is an essential process in kinetoplastid parasites whereby mitochondrial mRNAs are modified through the specific insertion and deletion of uridines to generate functional open reading frames, many of which encode components of the mitochondrial respiratory chain. The roles of numerous non-enzymatic editing factors have remained opaque given the limitations of conventional methods to interrogate the order and mechanism by which editing progresses and thus roles of individual proteins. Here, we examined whole populations of partially edited sequences using high throughput sequencing and a novel bioinformatic platform, the Trypanosome RNA Editing Alignment Tool (TREAT), to elucidate the roles of three proteins in the RNA Editing Mediator Complex (REMC). We determined that the factors examined function in the progression of editing through a gRNA; however, they have distinct roles and REMC is likely heterogeneous in composition. We provide the first evidence that editing can proceed through numerous paths within a single gRNA and that non-linear modifications are essential, generating commonly observed junction regions. Our data support a model in which RNA editing is executed via multiple paths that necessitate successive re-modification of junction regions facilitated, in part, by the REMC variant containing TbRGG2 and MRB8180.
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Affiliation(s)
- Rachel M. Simpson
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 3435 Main Street, Buffalo, NY 14214, USA
| | - Andrew E. Bruno
- Center for Computational Research, University at Buffalo, 701 Ellicott St., Buffalo, NY 14203, USA
| | - Runpu Chen
- Department of Computer Science and Engineering, New York State Center of Excellence in Bioinformatics and Life Sciences, 701 Ellicott St., Buffalo, NY 14203, USA
| | - Kaylen Lott
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 3435 Main Street, Buffalo, NY 14214, USA
| | - Brianna L. Tylec
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 3435 Main Street, Buffalo, NY 14214, USA
| | - Jonathan E. Bard
- Genomics and Bioinformatics Core, University at Buffalo, 701 Ellicott St., Buffalo, NY 14203, USA
| | - Yijun Sun
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 3435 Main Street, Buffalo, NY 14214, USA
- Center for Computational Research, University at Buffalo, 701 Ellicott St., Buffalo, NY 14203, USA
| | - Michael J. Buck
- Department of Biochemistry, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 701 Ellicott St., Buffalo, NY 14203, USA
| | - Laurie K. Read
- Department of Microbiology and Immunology, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 3435 Main Street, Buffalo, NY 14214, USA
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21
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Zhang L, Sement FM, Suematsu T, Yu T, Monti S, Huang L, Aphasizhev R, Aphasizheva I. PPR polyadenylation factor defines mitochondrial mRNA identity and stability in trypanosomes. EMBO J 2017; 36:2435-2454. [PMID: 28684539 DOI: 10.15252/embj.201796808] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/10/2017] [Accepted: 05/22/2017] [Indexed: 11/09/2022] Open
Abstract
In Trypanosoma brucei, most mitochondrial mRNAs undergo internal changes by RNA editing and 3' end modifications. The temporally separated and functionally distinct modifications are manifested by adenylation prior to editing, and by post-editing extension of a short A-tail into a long A/U-heteropolymer. The A-tail stabilizes partially and fully edited mRNAs, while the A/U-tail enables mRNA binding to the ribosome. Here, we identify an essential pentatricopeptide repeat-containing RNA binding protein, kinetoplast polyadenylation factor 3 (KPAF3), and demonstrate its role in protecting pre-mRNA against degradation by the processome. We show that KPAF3 recruits KPAP1 poly(A) polymerase to the 3' terminus, thus leading to pre-mRNA stabilization, or decay depending on the occurrence and extent of editing. In vitro, KPAF3 stimulates KPAP1 activity and inhibits mRNA uridylation by RET1 TUTase. Our findings indicate that KPAF3 selectively directs pre-mRNA toward adenylation rather than uridylation, which is a default post-trimming modification characteristic of ribosomal and guide RNAs. As a quality control mechanism, KPAF3 binding ensures that mRNAs entering the editing pathway are adenylated and, therefore, competent for post-editing A/U-tailing and translational activation.
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Affiliation(s)
- Liye Zhang
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA.,Section of Computational Biomedicine, Boston University School of Medicine, Boston, MA, USA
| | - Francois M Sement
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
| | - Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
| | - Tian Yu
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
| | - Stefano Monti
- Section of Computational Biomedicine, Boston University School of Medicine, Boston, MA, USA
| | - Lan Huang
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA.,Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
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22
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Aphasizhev R, Suematsu T, Zhang L, Aphasizheva I. Constructive edge of uridylation-induced RNA degradation. RNA Biol 2016; 13:1078-1083. [PMID: 27715485 PMCID: PMC5100348 DOI: 10.1080/15476286.2016.1229736] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 08/06/2016] [Accepted: 08/24/2016] [Indexed: 12/18/2022] Open
Abstract
RNA uridylation is a significant transcriptome-shaping factor in protists, fungi, metazoans, and plants. The 3' U-additions are catalyzed by terminal uridyltransferases (TUTases), a diverse group of enzymes that along with non-canonical poly(A) polymerases form a distinct group in the superfamily of DNA polymerase β-like nucleotidyl transferases. Within and across studied organisms and subcellular compartments, TUTases differ in nucleotide triphosphate selectivity, interacting partners, and RNA targets. A general premise linking RNA uridylation to 3'-5' degradation received support from several studies of small RNAs and mRNA turnover. However, recent work on kinetoplastid protists typified by Trypanosoma brucei provides evidence that RNA uridylation may play a more nuanced role in generating functional small RNAs. In this pathogen's mitochondrion, most mRNAs are internally edited by U-insertions and deletions, and subjected to 3' adenylation/uridylation; guide RNAs (gRNAs) required for editing are U-tailed. The prominent role of uridylation in mitochondrial RNA metabolism stimulated identification of the first TUTase, RNA editing TUTase 1 (RET1). Here we discuss functional studies of mitochondrial uridylation in trypanosomes that have revealed an unorthodox pathway of small RNA biogenesis. The current model accentuates physical coupling of RET1 and 3'-5' RNase II/RNB-type exonuclease DSS1 within a stable complex termed the mitochondrial 3' processome (MPsome). In the confines of this complex, RET1 initially uridylates a long precursor to activate its 3'-5' degradation by DSS1, and then uridylates trimmed guide RNA to disengage the processing complex from the mature molecule. We also discuss a potential role of antisense transcription in the MPsome pausing at a fixed distance from gRNA's 5' end. This step likely defines the mature 3' end by enabling kinetic competition between TUTase and exonuclease activities.
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Affiliation(s)
- Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
- Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
| | - Liye Zhang
- Section of Computational Biomedicine, Boston University School of Medicine, Boston, MA, USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA, USA
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23
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Abstract
Uridine insertion and deletion RNA editing generates functional mitochondrial mRNAs in Trypanosoma brucei Editing is catalyzed by three distinct ∼20S editosomes that have a common set of 12 proteins, but are typified by mutually exclusive RNase III endonucleases with distinct cleavage specificities and unique partner proteins. Previous studies identified a network of protein-protein interactions among a subset of common editosome proteins, but interactions among the endonucleases and their partner proteins, and their interactions with common subunits were not identified. Here, chemical cross-linking and mass spectrometry, comparative structural modeling, and genetic and biochemical analyses were used to define the molecular architecture and subunit organization of purified editosomes. We identified intra- and interprotein cross-links for all editosome subunits that are fully consistent with editosome protein structures and previously identified interactions, which we validated by genetic and biochemical studies. The results were used to create a highly detailed map of editosome protein domain proximities, leading to identification of molecular interactions between subunits, insights into the functions of noncatalytic editosome proteins, and a global understanding of editosome architecture.
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24
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Suematsu T, Zhang L, Aphasizheva I, Monti S, Huang L, Wang Q, Costello CE, Aphasizhev R. Antisense Transcripts Delimit Exonucleolytic Activity of the Mitochondrial 3' Processome to Generate Guide RNAs. Mol Cell 2016; 61:364-378. [PMID: 26833087 PMCID: PMC4744118 DOI: 10.1016/j.molcel.2016.01.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 11/16/2015] [Accepted: 12/24/2015] [Indexed: 12/21/2022]
Abstract
Small, noncoding RNA biogenesis typically involves cleavage of structured precursor by RNase III-like endonucleases. However, guide RNAs (gRNAs) that direct U-insertion/deletion mRNA editing in mitochondria of trypanosomes maintain 5' triphosphate characteristic of the transcription initiation and possess a U-tail indicative of 3' processing and uridylation. Here, we identified a protein complex composed of RET1 TUTase, DSS1 3'-5' exonuclease, and three additional subunits. This complex, termed mitochondrial 3' processome (MPsome), is responsible for primary uridylation of ∼800 nt gRNA precursors, their processive degradation to a mature size of 40-60 nt, and secondary U-tail addition. Both strands of the gRNA gene are transcribed into sense and antisense precursors of similar lengths. Head-to-head hybridization of these transcripts blocks symmetrical 3'-5' degradation at a fixed distance from the double-stranded region. Together, our findings suggest a model in which gRNA is derived from the 5' extremity of a primary molecule by uridylation-induced, antisense transcription-controlled 3'-5' exonucleolytic degradation.
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Affiliation(s)
- Takuma Suematsu
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA
| | - Liye Zhang
- Section of Computational Biomedicine, Boston University School of Medicine, Boston, MA 02118, USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA
| | - Stefano Monti
- Section of Computational Biomedicine, Boston University School of Medicine, Boston, MA 02118, USA
| | - Lan Huang
- Department of Physiology & Biophysics, School of Medicine, University of California, Irvine, Irvine, CA 92697, USA
| | - Qi Wang
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Catherine E Costello
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA; Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA.
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25
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Aphasizheva I, Aphasizhev R. U-Insertion/Deletion mRNA-Editing Holoenzyme: Definition in Sight. Trends Parasitol 2015; 32:144-156. [PMID: 26572691 DOI: 10.1016/j.pt.2015.10.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 10/06/2015] [Accepted: 10/12/2015] [Indexed: 11/16/2022]
Abstract
RNA editing is a process that alters DNA-encoded sequences and is distinct from splicing, 5' capping, and 3' additions. In 30 years since editing was discovered in mitochondria of trypanosomes, several functionally and evolutionarily unrelated mechanisms have been described in eukaryotes, archaea, and viruses. Editing events are predominantly post-transcriptional and include nucleoside insertions and deletions, and base substitutions and modifications. Here, we review the mechanism of uridine insertion/deletion mRNA editing in kinetoplastid protists typified by Trypanosoma brucei. This type of editing corrects frameshifts, introduces translation punctuation signals, and often adds hundreds of uridines to create protein-coding sequences. We focus on protein complexes responsible for editing reactions and their interactions with other elements of the mitochondrial gene expression pathway.
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Affiliation(s)
- Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA.
| | - Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, Boston, MA 02118, USA; Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
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Dietrich A, Wallet C, Iqbal RK, Gualberto JM, Lotfi F. Organellar non-coding RNAs: Emerging regulation mechanisms. Biochimie 2015; 117:48-62. [DOI: 10.1016/j.biochi.2015.06.027] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/29/2015] [Indexed: 02/06/2023]
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Viegas SC, Silva IJ, Apura P, Matos RG, Arraiano CM. Surprises in the 3'-end: 'U' can decide too! FEBS J 2015; 282:3489-99. [PMID: 26183531 DOI: 10.1111/febs.13377] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 06/22/2015] [Accepted: 07/10/2015] [Indexed: 12/27/2022]
Abstract
RNA molecules are subjected to post-transcriptional modifications that might determine their maturation, activity, localization and stability. These alterations can occur within the RNA molecule or at its 5'- or 3'- extremities, and are essential for gene regulation and proper function of the RNA. One major type of modification is the 3'-end addition of nontemplated nucleotides. Polyadenylation is the most well studied type of 3'-RNA modification, both in eukaryotes and prokaryotes. The importance of 3'-oligouridylation has recently gained attention through the discovery of several types of uridylated-RNAs, by the existence of enzymes that specifically add poly(U) tails and others that preferentially degrade these tails. Namely, Dis3L2 is a 3'-5' exoribonuclease from the RNase II/RNB family that has been shown to act preferentially on oligo(U)-tailed transcripts. Our understanding of this process is still at the beginning, but it is already known to interfere in the regulation of diverse RNA species in most eukaryotes. Now that we are aware of the prevalence of RNA uridylation and the techniques available to globally evaluate the 3'-terminome, we can expect to make rapid progress in determining the extent of terminal oligouridylation in different RNA populations and unravel its impact on RNA decay mechanisms. Here, we sum up what is known about 3'-RNA modification in the different cellular compartments of eukaryotic cells, the conserved enzymes that perform this 3'-end modification and the effectors that are selectively activated by this process.
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Affiliation(s)
- Sandra C Viegas
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Inês J Silva
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Patricia Apura
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Rute G Matos
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Cecilia M Arraiano
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
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Czerwoniec A, Kasprzak JM, Bytner P, Dobrychłop M, Bujnicki JM. Structure and intrinsic disorder of the proteins of the Trypanosoma brucei editosome. FEBS Lett 2015; 589:2603-10. [PMID: 26226426 DOI: 10.1016/j.febslet.2015.07.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/21/2015] [Accepted: 07/22/2015] [Indexed: 01/02/2023]
Abstract
Mitochondrial pre-mRNAs in trypanosomatids undergo RNA editing to be converted into translatable mRNAs. The reaction is characterized by the insertion and deletion of uridine residues and is catalyzed by a macromolecular protein complex called the editosome. Despite intensive research, structural information for the majority of editosome proteins is still missing and no high resolution structure for the editosome exists. Here we present a comprehensive structural bioinformatics analysis of all proteins of the Trypanosoma brucei editosome. We specifically focus on the interplay between intrinsic order and disorder. According to computational predictions, editosome proteins involved in the basal reaction steps of the processing cycle are mostly ordered. By contrast, thirty percent of the amino acid content of the editosome is intrinsically disordered, which includes most prominently proteins with OB-fold domains. Based on the data we suggest a functional model, in which the structurally disordered domains of the complex are correlated with the RNA binding and RNA unfolding activity of the T. brucei editosome.
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Affiliation(s)
- Anna Czerwoniec
- Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland.
| | - Joanna M Kasprzak
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Trojdena 4, PL-02-109 Warsaw, Poland; Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland
| | - Patrycja Bytner
- Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland
| | - Mateusz Dobrychłop
- Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland
| | - Janusz M Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Trojdena 4, PL-02-109 Warsaw, Poland; Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland.
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Mooers BHM. Fusion RNAs in crystallographic studies of double-stranded RNA from trypanosome RNA editing. Methods Mol Biol 2015; 1240:191-216. [PMID: 25352146 DOI: 10.1007/978-1-4939-1896-6_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Head-to-head fusions of two identical double-stranded fragments of RNA can be designed to self-assemble from a single RNA species and form a double-stranded helix with a twofold rotation axis relating the two strands. These symmetrical RNA molecules are more likely to crystallize without end-on-end statistical packing disorder because the two halves of the molecule are identical. This approach can be used to study many fragments of double-stranded RNA or many isolated helical domains from large single-stranded RNAs that may not yet be amenable to high-resolution studies by crystallography or NMR. We used fusion RNAs to study one (the U-helix) of three functional domains formed when guide RNA binds to its cognate pre-edited mRNA from the trypanosome RNA editing system. The U-helix forms when the 3' oligo(U) tail of the guide RNA (gRNA) binds to the purine-rich, pre-edited mRNA upstream from the current RNA editing site. Fusion RNAs 16-and 32-base pairs in length formed crystals that gave diffraction to 1.37 and 1.05 Å respectively. We provide the composition of a fusion RNA crystallization screen and describe the X-ray data collection, structure determination, and refinement of the crystal structures of fusion RNAs.
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Affiliation(s)
- Blaine H M Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 975 NE 10th St., Stanton L. Young Biomedical Research Center Rm. 466, Oklahoma City, OK, 73104-5419, USA,
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Polyuridylation in Eukaryotes: A 3'-End Modification Regulating RNA Life. BIOMED RESEARCH INTERNATIONAL 2015; 2015:968127. [PMID: 26078976 PMCID: PMC4442281 DOI: 10.1155/2015/968127] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/23/2015] [Accepted: 04/15/2015] [Indexed: 12/22/2022]
Abstract
In eukaryotes, mRNA polyadenylation is a well-known modification that is essential for many aspects of the protein-coding RNAs life cycle. However, modification of the 3′ terminal nucleotide within various RNA molecules is a general and conserved process that broadly modulates RNA function in all kingdoms of life. Numerous types of modifications have been characterized, which are generally specific for a given type of RNA such as the CCA addition found in tRNAs. In recent years, the addition of nontemplated uridine nucleotides or uridylation has been shown to occur in various types of RNA molecules and in various cellular compartments with significantly different outcomes. Indeed, uridylation is able to alter RNA half-life both in positive and in negative ways, highlighting the importance of the enzymes in charge of performing this modification. The present review aims at summarizing the current knowledge on the various processes leading to RNA 3′-end uridylation and on their potential impacts in various diseases.
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31
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Madina BR, Kumar V, Mooers BHM, Cruz-Reyes J. Native Variants of the MRB1 Complex Exhibit Specialized Functions in Kinetoplastid RNA Editing. PLoS One 2015; 10:e0123441. [PMID: 25928631 PMCID: PMC4415780 DOI: 10.1371/journal.pone.0123441] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/04/2015] [Indexed: 12/20/2022] Open
Abstract
Adaptation and survival of Trypanosoma brucei requires editing of mitochondrial mRNA by uridylate (U) insertion and deletion. Hundreds of small guide RNAs (gRNAs) direct the mRNA editing at over 3,000 sites. RNA editing is controlled during the life cycle but the regulation of substrate and stage specificity remains unknown. Editing progresses in the 3' to 5' direction along the pre-mRNA in blocks, each targeted by a unique gRNA. A critical editing factor is the mitochondrial RNA binding complex 1 (MRB1) that binds gRNA and transiently interacts with the catalytic RNA editing core complex (RECC). MRB1 is a large and dynamic complex that appears to be comprised of distinct but related subcomplexes (termed here MRBs). MRBs seem to share a 'core' complex of proteins but differ in the composition of the 'variable' proteins. Since some proteins associate transiently the MRBs remain imprecisely defined. MRB1 controls editing by unknown mechanisms, and the functional relevance of the different MRBs is unclear. We previously identified two distinct MRBs, and showed that they carry mRNAs that undergo editing. We proposed that editing takes place in the MRBs because MRBs stably associate with mRNA and gRNA but only transiently interact with RECC, which is RNA free. Here, we identify the first specialized functions in MRBs: 1) 3010-MRB is a major scaffold for RNA editing, and 2) REH2-MRB contains a critical trans-acting RNA helicase (REH2) that affects multiple steps of editing function in 3010-MRB. These trans effects of the REH2 include loading of unedited mRNA and editing in the first block and in subsequent blocks as editing progresses. REH2 binds its own MRB via RNA, and conserved domains in REH2 were critical for REH2 to associate with the RNA and protein components of its MRB. Importantly, REH2 associates with a ~30 kDa RNA-binding protein in a novel ~15S subcomplex in RNA-depleted mitochondria. We use these new results to update our model of MRB function and organization.
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Affiliation(s)
- Bhaskara R. Madina
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, United States of America
| | - Vikas Kumar
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, United States of America
| | - Blaine H. M. Mooers
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States of America
| | - Jorge Cruz-Reyes
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, United States of America
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Carnes J, Lerch M, Kurtz I, Stuart K. Bloodstream form Trypanosoma brucei do not require mRPN1 for gRNA processing. RNA (NEW YORK, N.Y.) 2015; 21:28-35. [PMID: 25404564 PMCID: PMC4274635 DOI: 10.1261/rna.045708.114] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 10/06/2014] [Indexed: 06/04/2023]
Abstract
Mitochondrial RNA processing in the kinetoplastid parasite Trypanosoma brucei involves numerous specialized catalytic activities that are incompletely understood. The mitochondrial genome consists of maxicircles that primarily encode rRNAs and mRNAs, and minicircles that encode a diverse array of guide RNAs (gRNAs). RNA editing uses these gRNAs as templates to recode mRNAs by insertion and deletion of uridine (U) residues. While the multiprotein complex that catalyzes RNA editing has been extensively studied, other players involved in mitochondrial RNA processing have remained enigmatic. The proteins required for processing mitochondrial polycistronic transcripts into mature species was essentially unknown until an RNase III endonuclease, called mRPN1, was reported to be involved in gRNA processing in procyclic form parasites. In this work, we examine the role of mRPN1 in gRNA processing in bloodstream form parasites, and show that complete elimination of mRPN1 by gene knockout does not alter gRNA maturation. These results indicate that another enzyme must be involved in gRNA processing.
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Affiliation(s)
- Jason Carnes
- Seattle Biomedical Research Institute, Seattle, Washington 98109, USA
| | - Melissa Lerch
- Seattle Biomedical Research Institute, Seattle, Washington 98109, USA
| | - Irina Kurtz
- Seattle Biomedical Research Institute, Seattle, Washington 98109, USA
| | - Ken Stuart
- Seattle Biomedical Research Institute, Seattle, Washington 98109, USA
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Abstract
I knew nothing and had thought nothing about parasites until 1971. In fact, if you had asked me before then, I might have commented that parasites were rather disgusting. I had been at the Johns Hopkins School of Medicine for three years, and I was on the lookout for a new project. In 1971, I came across a paper in the Journal of Molecular Biology by Larry Simpson, a classmate of mine in graduate school. Larry's paper described a remarkable DNA structure known as kinetoplast DNA (kDNA), isolated from a parasite. kDNA, the mitochondrial genome of trypanosomatids, is a DNA network composed of several thousand interlocked DNA rings. Almost nothing was known about it. I was looking for a project on DNA replication, and I wanted it to be both challenging and important. I had no doubt that working with kDNA would be a challenge, as I would be exploring uncharted territory. I was also sure that the project would be important when I learned that parasites with kDNA threaten huge populations in underdeveloped tropical countries. Looking again at Larry's paper, I found the electron micrographs of the kDNA networks to be rather beautiful. I decided to take a chance on kDNA. Little did I know then that I would devote the next forty years of my life to studying kDNA replication.
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Affiliation(s)
- Paul T Englund
- From the Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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34
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Madina BR, Kumar V, Metz R, Mooers BH, Bundschuh R, Cruz-Reyes J. Native mitochondrial RNA-binding complexes in kinetoplastid RNA editing differ in guide RNA composition. RNA (NEW YORK, N.Y.) 2014; 20:1142-52. [PMID: 24865612 PMCID: PMC4114691 DOI: 10.1261/rna.044495.114] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 04/25/2014] [Indexed: 05/20/2023]
Abstract
Mitochondrial mRNAs in kinetoplastids require extensive U-insertion/deletion editing that progresses 3'-to-5' in small blocks, each directed by a guide RNA (gRNA), and exhibits substrate and developmental stage-specificity by unsolved mechanisms. Here, we address compositionally related factors, collectively known as the mitochondrial RNA-binding complex 1 (MRB1) or gRNA-binding complex (GRBC), that contain gRNA, have a dynamic protein composition, and transiently associate with several mitochondrial factors including RNA editing core complexes (RECC) and ribosomes. MRB1 controls editing by still unknown mechanisms. We performed the first next-generation sequencing study of native subcomplexes of MRB1, immunoselected via either RNA helicase 2 (REH2), that binds RNA and associates with unwinding activity, or MRB3010, that affects an early editing step. The particles contain either REH2 or MRB3010 but share the core GAP1 and other proteins detected by RNA photo-crosslinking. Analyses of the first editing blocks indicate an enrichment of several initiating gRNAs in the MRB3010-purified complex. Our data also indicate fast evolution of mRNA 3' ends and strain-specific alternative 3' editing within 3' UTR or C-terminal protein-coding sequence that could impact mitochondrial physiology. Moreover, we found robust specific copurification of edited and pre-edited mRNAs, suggesting that these particles may bind both mRNA and gRNA editing substrates. We propose that multiple subcomplexes of MRB1 with different RNA/protein composition serve as a scaffold for specific assembly of editing substrates and RECC, thereby forming the editing holoenzyme. The MRB3010-subcomplex may promote early editing through its preferential recruitment of initiating gRNAs.
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MESH Headings
- Amino Acid Sequence
- Base Composition
- Base Sequence
- Cells, Cultured
- Kinetoplastida/genetics
- Kinetoplastida/metabolism
- Molecular Sequence Data
- Protozoan Proteins/genetics
- Protozoan Proteins/metabolism
- RNA/chemistry
- RNA/metabolism
- RNA Editing
- RNA, Guide, Kinetoplastida/chemistry
- RNA, Guide, Kinetoplastida/genetics
- RNA, Guide, Kinetoplastida/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/metabolism
- RNA, Mitochondrial
- RNA, Protozoan/chemistry
- RNA, Protozoan/metabolism
- Trypanosoma brucei brucei/genetics
- Trypanosoma brucei brucei/metabolism
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Affiliation(s)
- Bhaskara R. Madina
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Vikas Kumar
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Richard Metz
- Texas AgriLife Genomics and Bioinformatics Service, Texas A&M University, College Station, Texas 77845, USA
| | - Blaine H.M. Mooers
- Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Ralf Bundschuh
- Department of Physics, Department of Chemistry & Biochemistry, Division of Hematology, Center of RNA Biology, The Ohio State University, Columbus, Ohio 43210-1117, USA
| | - Jorge Cruz-Reyes
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
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35
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Aphasizhev R, Aphasizheva I. Mitochondrial RNA editing in trypanosomes: small RNAs in control. Biochimie 2014; 100:125-31. [PMID: 24440637 PMCID: PMC4737708 DOI: 10.1016/j.biochi.2014.01.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 01/06/2014] [Indexed: 12/29/2022]
Abstract
Mitochondrial mRNA editing in trypanosomes is a posttranscriptional processing pathway thereby uridine residues (Us) are inserted into, or deleted from, messenger RNA precursors. By correcting frameshifts, introducing start and stop codons, and often adding most of the coding sequence, editing restores open reading frames for mitochondrially-encoded mRNAs. There can be hundreds of editing events in a single pre-mRNA, typically spaced by few nucleotides, with U-insertions outnumbering U-deletions by approximately 10-fold. The mitochondrial genome is composed of ∼50 maxicircles and thousands of minicircles. Catenated maxi- and minicircles are packed into a dense structure called the kinetoplast; maxicircles yield rRNA and mRNA precursors while guide RNAs (gRNAs) are produced predominantly from minicircles, although varying numbers of maxicircle-encoded gRNAs have been identified in kinetoplastids species. Guide RNAs specify positions and the numbers of inserted or deleted Us by hybridizing to pre-mRNA and forming series of mismatches. These 50-60 nucleotide (nt) molecules are 3' uridylated by RET1 TUTase and stabilized via association with the gRNA binding complex (GRBC). Editing reactions of mRNA cleavage, U-insertion or deletion, and ligation are catalyzed by the RNA editing core complex (RECC). To function in mitochondrial translation, pre-mRNAs must further undergo post-editing 3' modification by polyadenylation/uridylation. Recent studies revealed a highly compound nature of mRNA editing and polyadenylation complexes and their interactions with the translational machinery. Here we focus on mechanisms of RNA editing and its functional coupling with pre- and post-editing 3' mRNA modification and gRNA maturation pathways.
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Affiliation(s)
- Ruslan Aphasizhev
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, 72 East Concord Street, Evans 4th Floor, E426, Boston, MA 02118, USA.
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology, Boston University School of Dental Medicine, 72 East Concord Street, Evans 4th Floor, E426, Boston, MA 02118, USA
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36
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Burroughs AM, Ando Y, Aravind L. New perspectives on the diversification of the RNA interference system: insights from comparative genomics and small RNA sequencing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 5:141-81. [PMID: 24311560 DOI: 10.1002/wrna.1210] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/03/2013] [Accepted: 11/01/2013] [Indexed: 12/19/2022]
Abstract
Our understanding of the pervasive involvement of small RNAs in regulating diverse biological processes has been greatly augmented by recent application of deep-sequencing technologies to small RNA across diverse eukaryotes. We review the currently known small RNA classes and place them in context of the reconstructed evolutionary history of the RNA interference (RNAi) protein machinery. This synthesis indicates that the earliest versions of eukaryotic RNAi systems likely utilized small RNA processed from three types of precursors: (1) sense-antisense transcriptional products, (2) genome-encoded, imperfectly complementary hairpin sequences, and (3) larger noncoding RNA precursor sequences. Structural dissection of PIWI proteins along with recent discovery of novel families (including Med13 of the Mediator complex) suggest that emergence of a distinct architecture with the N-terminal domains (also occurring separately fused to endoDNases in prokaryotes) formed via duplication of an ancestral unit was key to their recruitment as primary RNAi effectors and use of small RNAs of certain preferred lengths. Prokaryotic PIWI proteins are typically components of several RNA-directed DNA restriction or CRISPR/Cas systems. However, eukaryotic versions appear to have emerged from a subset that evolved RNA-directed RNAi. They were recruited alongside RNaseIII domains and RNA-dependent RNA polymerase (RdRP) domains, also from prokaryotic systems, to form the core eukaryotic RNAi system. Like certain regulatory systems, RNAi diversified into two distinct but linked arms concomitant with eukaryotic nucleocytoplasmic compartmentalization. Subsequent elaboration of RNAi proceeded via diversification of the core protein machinery through lineage-specific expansions and recruitment of new components from prokaryotes (nucleases and small RNA-modifying enzymes), allowing for diversification of associating small RNAs.
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Affiliation(s)
- Alexander Maxwell Burroughs
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
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37
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Knüsel S, Roditi I. Insights into the regulation of GPEET procyclin during differentiation from early to late procyclic forms of Trypanosoma brucei. Mol Biochem Parasitol 2013; 191:66-74. [PMID: 24076427 DOI: 10.1016/j.molbiopara.2013.09.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/17/2013] [Accepted: 09/18/2013] [Indexed: 11/19/2022]
Abstract
The procyclic form of Trypanosoma brucei colonises the gut of its insect vector, the tsetse fly. GPEET and EP procyclins constitute the parasite's surface coat at this stage of the life cycle, and the presence or absence of GPEET distinguishes between early and late procyclic forms, respectively. Differentiation from early to late procyclic forms in vivo occurs in the fly midgut and can be mimicked in culture. Our analysis of this transition in vitro delivered new insights into the process of GPEET repression. First, we could show that parasites followed a concrete sequence of events upon triggering differentiation: after undergoing an initial growth arrest, cells lost GPEET protein, and finally late procyclic forms resumed proliferation. Second, we determined the stability of both GPEET and EP mRNA during differentiation. GPEET mRNA is exceptionally stable in early procyclic forms, with a half-life >6h. The GPEET mRNA detected in late procyclic form cultures is a mixture of transcripts from both bona fide late procyclic forms and GPEET-positive 'laggard' parasites present in these cultures. However, its stability was clearly reduced during differentiation and in late procyclic form cultures. Alternatively processed GPEET transcripts were enriched in samples from late procyclic forms, suggesting that altered mRNA processing might contribute to repression of GPEET in this developmental stage. In addition, we detected GPEET transcripts with non-templated oligo(U) tails that were enriched in late procyclic forms. To the best of our knowledge, this is the first study reporting a uridylyl-tailed, nuclear-encoded mRNA species in trypanosomatids or any other protozoa.
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Affiliation(s)
- Sebastian Knüsel
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland; Graduate School of Cellular and Biomedical Sciences, University of Bern, Freiestrasse 1, CH-3012 Bern, Switzerland
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38
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Aphasizhev R, Aphasizheva I. Emerging roles of PPR proteins in trypanosomes: switches, blocks, and triggers. RNA Biol 2013; 10:1495-500. [PMID: 24055869 PMCID: PMC3858432 DOI: 10.4161/rna.26215] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 08/16/2013] [Accepted: 08/19/2013] [Indexed: 01/05/2023] Open
Abstract
Mitochondrial genomes of trypanosomes are composed of catenated maxicircles and mini-circles that are densely packed into a nucleoprotein structure called the kinetoplast. Maxicircle DNA (~25 kb long, 20-50 copies) resembles a typical mitochondrial genome bearing rRNA and respiratory complex subunits genes, and also contains 12 cryptogenes whose transcripts require U-insertion/deletion editing to assemble protein-coding sequences. Production of guide RNAs for the editing process remains the only established function of mini-circle DNA (~1 kb, ~10000 copies). Although editing remains the most studied step in mRNA biogenesis, recent investigations illuminated complex nucleolytic processing and pre- and post-editing 3' modification events that ultimately create translation-competent mRNAs. Key mRNA 3' processing enzymes, such as KPAP1 poly(A) polymerase and RET1 TUTase, have been identified but the mechanisms regulating their activities remain poorly understood. Discoveries of multiple pentatricopeptide repeat-containing (PPR) proteins populating polyadenylation complex and ribosomal subunits opened exciting experimental prospects that may ultimately lead to an integrated picture of mitochondrial gene expression.
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Affiliation(s)
- Ruslan Aphasizhev
- Department of Molecular and Cell Biology; Boston University Goldman School of Dental Medicine; Boston, MA USA
| | - Inna Aphasizheva
- Department of Molecular and Cell Biology; Boston University Goldman School of Dental Medicine; Boston, MA USA
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39
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Kolesnikov AA, Gerasimov ES. Diversity of mitochondrial genome organization. BIOCHEMISTRY (MOSCOW) 2013; 77:1424-35. [PMID: 23379519 DOI: 10.1134/s0006297912130020] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In this review, we discuss types of mitochondrial genome structural organization (architecture), which includes the following characteristic features: size and the shape of DNA molecule, number of encoded genes, presence of cryptogenes, and editing of primary transcripts.
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Affiliation(s)
- A A Kolesnikov
- Biological Faculty, Lomonosov Moscow State University, Moscow, 119234, Russia.
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40
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Hashimi H, Zimmer SL, Ammerman ML, Read LK, Lukeš J. Dual core processing: MRB1 is an emerging kinetoplast RNA editing complex. Trends Parasitol 2013; 29:91-9. [PMID: 23305619 PMCID: PMC3558622 DOI: 10.1016/j.pt.2012.11.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 11/28/2012] [Accepted: 11/28/2012] [Indexed: 12/17/2022]
Abstract
Our understanding of kinetoplastid RNA (kRNA) editing has centered on this paradigm: guide RNAs (gRNAs) provide a blueprint for uridine insertion/deletion into mitochondrial mRNAs by the RNA editing core complex (RECC). The characterization of constituent subunits of the mitochondrial RNA-binding complex 1 (MRB1) implies that it too is vital to the editing process. The recently elucidated MRB1 architecture will be instrumental in putting functional data from individual subunits into context. Our model depicts two functions for MRB1: mediating multi-round kRNA editing by coordinating the exchange of multiple gRNAs required by RECC to edit lengthy regions of mRNAs, and then linking kRNA editing with other RNA processing events.
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Affiliation(s)
- Hassan Hashimi
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, and Faculty of Science, University of South Bohemia, České Budějovice (Budweis) 370 05, Czech Republic
| | - Sara L. Zimmer
- Department of Microbiology and Immunology, School of Medicine, State University of New York at Buffalo, NY 14214, USA
| | - Michelle L. Ammerman
- Department of Microbiology and Immunology, School of Medicine, State University of New York at Buffalo, NY 14214, USA
| | - Laurie K. Read
- Department of Microbiology and Immunology, School of Medicine, State University of New York at Buffalo, NY 14214, USA
| | - Julius Lukeš
- Institute of Parasitology, Biology Center, Czech Academy of Sciences, and Faculty of Science, University of South Bohemia, České Budějovice (Budweis) 370 05, Czech Republic
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Abstract
RNA editing describes a chemically diverse set of biomolecular reactions in which the nucleotide sequence of RNA molecules is altered. Editing reactions have been identified in many organisms and frequently contribute to the maturation of organellar transcripts. A special editing reaction has evolved within the mitochondria of the kinetoplastid protozoa. The process is characterized by the insertion and deletion of uridine nucleotides into otherwise nontranslatable messenger RNAs. Kinetoplastid RNA editing involves an exclusive class of small, noncoding RNAs known as guide RNAs. Furthermore, a unique molecular machinery, the editosome, catalyzes the process. Editosomes are megadalton multienzyme assemblies that provide a catalytic surface for the individual steps of the reaction cycle. Here I review the current mechanistic understanding and molecular inventory of kinetoplastid RNA editing and the editosome machinery. Special emphasis is placed on the molecular morphology of the editing complex in order to correlate structural features with functional characteristics.
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Affiliation(s)
- H Ulrich Göringer
- Department of Genetics, Darmstadt University of Technology, Germany.
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42
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Kiethega GN, Yan Y, Turcotte M, Burger G. RNA-level unscrambling of fragmented genes in Diplonema mitochondria. RNA Biol 2013; 10:301-13. [PMID: 23324603 DOI: 10.4161/rna.23340] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We previously reported a unique genome with systematically fragmented genes and gene pieces dispersed across numerous circular chromosomes, occurring in mitochondria of diplonemids. Genes are split into up to 12 short fragments (modules), which are separately transcribed and joined in a way that differs from known trans-splicing. Further, cox1 mRNA includes six non-encoded uridines indicating RNA editing. In the absence of recognizable cis-elements, we postulated that trans-splicing and RNA editing are directed by trans-acting molecules. Here, we provide insight into the post-transcriptional processes by investigating transcription, RNA processing, trans-splicing and RNA editing in cox1 and at a newly discovered site in cob. We show that module precursor transcripts are up to several thousand nt long and processed accurately at their 5' and 3' termini to yield the short coding-only regions. Processing at 5' and 3' ends occurs independently, and a processed terminus engages in trans-splicing even if the module's other terminus is yet unprocessed. Moreover, only cognate module transcripts join, though without directionality. In contrast, module transcripts requiring RNA editing only trans-splice when editing is completed. Finally, experimental and computational analyses suggest the existence of RNA trans-factors with the potential for guiding both trans-splicing and RNA editing.
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Crumple: a method for complete enumeration of all possible pseudoknot-free RNA secondary structures. PLoS One 2012; 7:e52414. [PMID: 23300665 PMCID: PMC3531468 DOI: 10.1371/journal.pone.0052414] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 11/16/2012] [Indexed: 12/28/2022] Open
Abstract
The diverse landscape of RNA conformational space includes many canyons and crevices that are distant from the lowest minimum free energy valley and remain unexplored by traditional RNA structure prediction methods. A complete description of the entire RNA folding landscape can facilitate identification of biologically important conformations. The Crumple algorithm rapidly enumerates all possible non-pseudoknotted structures for an RNA sequence without consideration of thermodynamics while filtering the output with experimental data. The Crumple algorithm provides an alternative approach to traditional free energy minimization programs for RNA secondary structure prediction. A complete computation of all non-pseudoknotted secondary structures can reveal structures that would not be predicted by methods that sample the RNA folding landscape based on thermodynamic predictions. The free energy minimization approach is often successful but is limited by not considering RNA tertiary and protein interactions and the possibility that kinetics rather than thermodynamics determines the functional RNA fold. Efficient parallel computing and filters based on experimental data make practical the complete enumeration of all non-pseudoknotted structures. Efficient parallel computing for Crumple is implemented in a ring graph approach. Filters for experimental data include constraints from chemical probing of solvent accessibility, enzymatic cleavage of paired or unpaired nucleotides, phylogenetic covariation, and the minimum number and lengths of helices determined from crystallography or cryo-electron microscopy. The minimum number and length of helices has a significant effect on reducing conformational space. Pairing constraints reduce conformational space more than single nucleotide constraints. Examples with Alfalfa Mosaic Virus RNA and Trypanosome brucei guide RNA demonstrate the importance of evaluating all possible structures when pseduoknots, RNA-protein interactions, and metastable structures are important for biological function. Crumple software is freely available at http://adenosine.chem.ou.edu/software.html.
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45
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Mooers BHM, Singh A. The crystal structure of an oligo(U):pre-mRNA duplex from a trypanosome RNA editing substrate. RNA (NEW YORK, N.Y.) 2011; 17:1870-1883. [PMID: 21878548 PMCID: PMC3185919 DOI: 10.1261/rna.2880311] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 07/30/2011] [Indexed: 05/31/2023]
Abstract
Guide RNAs bind antiparallel to their target pre-mRNAs to form editing substrates in reaction cycles that insert or delete uridylates (Us) in most mitochondrial transcripts of trypanosomes. The 5' end of each guide RNA has an anchor sequence that binds to the pre-mRNA by base-pair complementarity. The template sequence in the middle of the guide RNA directs the editing reactions. The 3' ends of most guide RNAs have ∼15 contiguous Us that bind to the purine-rich unedited pre-mRNA upstream of the editing site. The resulting U-helix is rich in G·U wobble base pairs. To gain insights into the structure of the U-helix, we crystallized 8 bp of the U-helix in one editing substrate for the A6 mRNA of Trypanosoma brucei. The fragment provides three samples of the 5'-AGA-3'/5'-UUU-3' base-pair triple. The fusion of two identical U-helices head-to-head promoted crystallization. We obtained X-ray diffraction data with a resolution limit of 1.37 Å. The U-helix had low and high twist angles before and after each G·U wobble base pair; this variation was partly due to shearing of the wobble base pairs as revealed in comparisons with a crystal structure of a 16-nt RNA with all Watson-Crick base pairs. Both crystal structures had wider major grooves at the junction between the poly(U) and polypurine tracts. This junction mimics the junction between the template helix and the U-helix in RNA-editing substrates and may be a site of major groove invasion by RNA editing proteins.
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Affiliation(s)
- Blaine H M Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104-5419, USA.
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46
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Madina BR, Kuppan G, Vashisht AA, Liang YH, Downey KM, Wohlschlegel JA, Ji X, Sze SH, Sacchettini JC, Read LK, Cruz-Reyes J. Guide RNA biogenesis involves a novel RNase III family endoribonuclease in Trypanosoma brucei. RNA (NEW YORK, N.Y.) 2011; 17:1821-30. [PMID: 21810935 PMCID: PMC3185915 DOI: 10.1261/rna.2815911] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 06/29/2011] [Indexed: 05/29/2023]
Abstract
The mitochondrial genome of kinetoplastids, including species of Trypanosoma and Leishmania, is an unprecedented DNA structure of catenated maxicircles and minicircles. Maxicircles represent the typical mitochondrial genome encoding components of the respiratory complexes and ribosomes. However, most mRNA sequences are cryptic, and their maturation requires a unique U insertion/deletion RNA editing. Minicircles encode hundreds of small guide RNAs (gRNAs) that partially anneal with unedited mRNAs and direct the extensive editing. Trypanosoma brucei gRNAs and mRNAs are transcribed as polycistronic precursors, which undergo processing preceding editing; however, the relevant nucleases are unknown. We report the identification and functional characterization of a close homolog of editing endonucleases, mRPN1 (mitochondrial RNA precursor-processing endonuclease 1), which is involved in gRNA biogenesis. Recombinant mRPN1 is a dimeric dsRNA-dependent endonuclease that requires Mg(2+), a critical catalytic carboxylate, and generates 2-nucleotide 3' overhangs. The cleavage specificity of mRPN1 is reminiscent of bacterial RNase III and thus is fundamentally distinct from editing endonucleases, which target a single scissile bond just 5' of short duplexes. An inducible knockdown of mRPN1 in T. brucei results in loss of gRNA and accumulation of precursor transcripts (pre-gRNAs), consistent with a role of mRPN1 in processing. mRPN1 stably associates with three proteins previously identified in relatively large complexes that do not contain mRPN1, and have been linked with multiple aspects of mitochondrial RNA metabolism. One protein, TbRGG2, directly binds mRPN1 and is thought to modulate gRNA utilization by editing complexes. The proposed participation of mRPN1 in processing of polycistronic RNA and its specific protein interactions in gRNA expression are discussed.
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Affiliation(s)
- Bhaskara Reddy Madina
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Gokulan Kuppan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Ajay A. Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095-1737, USA
| | - Yu-He Liang
- Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Kurtis M. Downey
- Department of Microbiology and Immunology, University at Buffalo, State University of New York, Buffalo, New York 14214, USA
| | - James A. Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095-1737, USA
| | - Xinhua Ji
- Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Sing-Hoi Sze
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
- Department of Computer Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
| | - James C. Sacchettini
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Laurie K. Read
- Department of Microbiology and Immunology, University at Buffalo, State University of New York, Buffalo, New York 14214, USA
| | - Jorge Cruz-Reyes
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
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47
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Aphasizhev R, Aphasizheva I. Uridine insertion/deletion editing in trypanosomes: a playground for RNA-guided information transfer. WILEY INTERDISCIPLINARY REVIEWS. RNA 2011; 2:669-85. [PMID: 21823228 PMCID: PMC3154072 DOI: 10.1002/wrna.82] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
RNA editing is a collective term referring to enzymatic processes that change RNA sequence apart from splicing, 5' capping or 3' extension. In this article, we focus on uridine insertion/deletion mRNA editing found exclusively in mitochondria of kinetoplastid protists. This type of editing corrects frameshifts, introduces start and stops codons, and often adds much of the coding sequence to create an open reading frame. The mitochondrial genome of trypanosomatids, the most extensively studied clade within the order Kinetoplastida, is composed of ∼50 maxicircles with limited coding capacity and thousands of minicircles. To produce functional mRNAs, a multitude of nuclear-encoded factors mediate interactions of maxicircle-encoded pre-mRNAs with a vast repertoire of minicircle-encoded guide RNAs. Editing reactions of mRNA cleavage, U-insertions or U-deletions, and ligation are catalyzed by the RNA editing core complex (RECC, the 20S editosome) while each step of this enzymatic cascade is directed by guide RNAs. These 50-60 nucleotide (nt) molecules are 3' uridylated by RET1 TUTase and stabilized via association with the gRNA binding complex (GRBC). Remarkably, the information transfer between maxicircle and minicircle transcriptomes does not rely on template-dependent polymerization of nucleic acids. Instead, intrinsic substrate specificities of key enzymes are largely responsible for the fidelity of editing. Conversely, the efficiency of editing is enhanced by assembling enzymes and RNA binding proteins into stable multiprotein complexes. WIREs RNA 2011 2 669-685 DOI: 10.1002/wrna.82 For further resources related to this article, please visit the WIREs website.
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MESH Headings
- Endonucleases/chemistry
- Endonucleases/genetics
- Endonucleases/metabolism
- Models, Biological
- Models, Molecular
- Protozoan Proteins/chemistry
- Protozoan Proteins/genetics
- Protozoan Proteins/metabolism
- RNA Editing/genetics
- RNA Editing/physiology
- RNA Helicases/chemistry
- RNA Helicases/genetics
- RNA Helicases/metabolism
- RNA, Guide, Kinetoplastida/genetics
- RNA, Guide, Kinetoplastida/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Protozoan/chemistry
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Trypanosoma/genetics
- Trypanosoma/metabolism
- Uridine/chemistry
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Affiliation(s)
- Ruslan Aphasizhev
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, USA.
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48
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Göringer HU, Katari VS, Böhm C. The structural landscape of native editosomes in African trypanosomes. WILEY INTERDISCIPLINARY REVIEWS. RNA 2011; 2:395-407. [PMID: 21957025 DOI: 10.1002/wrna.67] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The majority of mitochondrial pre-messenger RNAs in African trypanosomes are substrates of a U-nucleotide-specific insertion/deletion-type RNA editing reaction. The process converts nonfunctional pre-mRNAs into translation-competent molecules and can generate protein diversity by alternative editing. High molecular mass protein complexes termed editosomes catalyze the processing reaction. They stably interact with pre-edited mRNAs and small noncoding RNAs, known as guide RNAs (gRNAs), which act as templates in the reaction. Editosomes provide a molecular surface for the individual steps of the catalytic reaction cycle and although the protein inventory of the complexes has been studied in detail, a structural analysis of the processing machinery has only recently been accomplished. Electron microscopy in combination with single particle reconstruction techniques has shown that steady state isolates of editosomes contain ensembles of two classes of stable complexes with calculated apparent hydrodynamic sizes of 20S and 35-40S. 20S editosomes are free of substrate RNAs, whereas 35-40S editosomes are associated with endogenous mRNA and gRNA molecules. Both complexes are characterized by a diverse structural landscape, which include complexes that lack or possess defined subdomains. Here, we summarize the consensus models and structural landmarks of both complexes. We correlate structural features with functional characteristics and provide an outlook into dynamic aspects of the editing reaction cycle.
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Affiliation(s)
- H Ulrich Göringer
- Department of Microbiology and Genetics, Darmstadt University of Technology, Darmstadt, Germany.
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49
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Aphasizhev R, Aphasizheva I. Mitochondrial RNA processing in trypanosomes. Res Microbiol 2011; 162:655-63. [PMID: 21596134 DOI: 10.1016/j.resmic.2011.04.015] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 04/04/2011] [Indexed: 01/20/2023]
Abstract
The mitochondrial genome of trypanosomes is composed of ∼50 maxicircles and thousands of minicircles. Maxi-(∼25 kb) and mini-(∼1 kb)circles are catenated and packed into a dense structure called a kinetoplast. Both types of circular DNA are transcribed by a phage-like RNA polymerase: maxicircles yield multicistronic rRNA and mRNA precursors, while guide RNA (gRNA) precursors are produced from minicircles. To function in mitochondrial translation, pre-mRNAs must undergo a nucleolytic processing and 3' modifications, and often uridine insertion/deletion editing. gRNAs, which represent short (50-60 nt) RNAs directing editing reactions, are produced by 3' nucleolytic processing of a much longer precursor followed by 3' uridylation. Ribosomal RNAs are excised from precursors and their 3' ends are also trimmed and uridylated. All tRNAs are imported from the cytoplasm and some are further modified and edited in the mitochondrial matrix. Historically, the fascinating phenomenon of RNA editing has been extensively studied as an isolated pathway in which nuclear-encoded proteins mediate interactions of maxi- and minicircle transcripts to create open reading frames. However, recent studies unraveled a highly integrated network of mitochondrial genome expression including critical pre- and post-editing 3' mRNA processing, and gRNA and rRNA maturation steps. Here we focus on RNA 3' adenylation and uridylation as processes essential for biogenesis, stability and functioning of mitochondrial RNAs.
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Affiliation(s)
- Ruslan Aphasizhev
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, B240 Medical Sciences I, Irvine, CA 92697, USA.
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50
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Ammerman ML, Hashimi H, Novotná L, Cicová Z, McEvoy SM, Lukes J, Read LK. MRB3010 is a core component of the MRB1 complex that facilitates an early step of the kinetoplastid RNA editing process. RNA (NEW YORK, N.Y.) 2011; 17:865-77. [PMID: 21451155 PMCID: PMC3078736 DOI: 10.1261/rna.2446311] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 02/17/2011] [Indexed: 05/20/2023]
Abstract
Gene expression in the mitochondria of the kinetoplastid parasite Trypanosoma brucei is regulated primarily post-transcriptionally at the stages of RNA processing, editing, and turnover. The mitochondrial RNA-binding complex 1 (MRB1) is a recently identified multiprotein complex containing components with distinct functions during different aspects of RNA metabolism, such as guide RNA (gRNA) and mRNA turnover, precursor transcript processing, and RNA editing. In this study we examined the function of the MRB1 protein, Tb927.5.3010, which we term MRB3010. We show that MRB3010 is essential for growth of both procyclic form and bloodstream form life-cycle stages of T. brucei. Down-regulation of MRB3010 by RNAi leads to a dramatic inhibition of RNA editing, yet its depletion does not impact total gRNA levels. Rather, it appears to affect the editing process at an early stage, as indicated by the accumulation of pre-edited and small partially edited RNAs. MRB3010 is present in large (>20S) complexes and exhibits both RNA-dependent and RNA-independent interactions with other MRB1 complex proteins. Comparison of proteins isolated with MRB3010 tagged at its endogenous locus to those reported from other MRB1 complex purifications strongly suggests the presence of an MRB1 "core" complex containing five to six proteins, including MRB3010. Together, these data further our understanding of the function and composition of the imprecisely defined MRB1 complex.
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Affiliation(s)
- Michelle L Ammerman
- Department of Microbiology and Immunology, School of Medicine, State University of New York at Buffalo, Buffalo, New York 14214, USA
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