1
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Khalifah BA, Alghamdi SA, Alhasan AH. Unleashing the potential of catalytic RNAs to combat mis-spliced transcripts. Front Bioeng Biotechnol 2023; 11:1244377. [PMID: 38047291 PMCID: PMC10690607 DOI: 10.3389/fbioe.2023.1244377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/23/2023] [Indexed: 12/05/2023] Open
Abstract
Human transcriptome can undergo RNA mis-splicing due to spliceopathies contributing to the increasing number of genetic diseases including muscular dystrophy (MD), Alzheimer disease (AD), Huntington disease (HD), myelodysplastic syndromes (MDS). Intron retention (IR) is a major inducer of spliceopathies where two or more introns remain in the final mature mRNA and account for many intronic expansion diseases. Potential removal of such introns for therapeutic purposes can be feasible when utilizing bioinformatics, catalytic RNAs, and nano-drug delivery systems. Overcoming delivery challenges of catalytic RNAs was discussed in this review as a future perspective highlighting the significance of utilizing synthetic biology in addition to high throughput deep sequencing and computational approaches for the treatment of mis-spliced transcripts.
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Affiliation(s)
- Bashayer A. Khalifah
- Institute for Bioengineering, Health Sector, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia
- Faculty of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Ali H. Alhasan
- Institute for Bioengineering, Health Sector, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia
- College of Science and General Studies, Alfaisal University, Riyadh, Saudi Arabia
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2
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Cervera A, de la Peña M. Small circRNAs with self-cleaving ribozymes are highly expressed in diverse metazoan transcriptomes. Nucleic Acids Res 2020; 48:5054-5064. [PMID: 32198887 PMCID: PMC7229834 DOI: 10.1093/nar/gkaa187] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 03/09/2020] [Accepted: 03/11/2020] [Indexed: 12/13/2022] Open
Abstract
Ribozymes are catalytic RNAs present in modern genomes but regarded as remnants of a prebiotic RNA world. The paradigmatic hammerhead ribozyme (HHR) is a small self-cleaving motif widespread from bacterial to human genomes. Here, we report that most of the classical type I HHRs frequently found in the genomes of animals are contained within a novel family of non-autonomous non-LTR retrotransposons of the retrozyme class. These retroelements are expressed as abundant linear and circular RNAs of ∼170-400 nt in different animal tissues. Bioinformatic and in vitro analyses indicate an efficient self-cleavage of the HHRs harboured in most invertebrate retrozymes, whereas HHRs in retrozymes of vertebrates, such as the axolotl and other amphibians, require to act as dimeric motifs to reach higher self-cleavage rates. Ligation assays of retrozyme RNAs with a protein ligase versus HHR self-ligation indicate that, most likely, tRNA ligases and not the ribozymes are involved in the step of RNA circularization. Altogether, these results confirm the existence of a new and conserved pathway in animals and, likely, eukaryotes in general, for the efficient biosynthesis of RNA circles through small ribozymes, which opens the door for the development of new tools in the emerging field of study of circRNAs.
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Affiliation(s)
- Amelia Cervera
- IBMCP (CSIC-UPV). C/ Ingeniero Fausto Elio s/n, 46022 Valencia, Spain
| | - Marcos de la Peña
- IBMCP (CSIC-UPV). C/ Ingeniero Fausto Elio s/n, 46022 Valencia, Spain
- To whom correspondence should be addressed. Tel: +34 963 877 915; Fax: +34 963 877 859;
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3
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Chu H, Perea W, Greenbaum NL. Role of the central junction in folding topology of the protein-free human U2-U6 snRNA complex. RNA (NEW YORK, N.Y.) 2020; 26:836-850. [PMID: 32220895 PMCID: PMC7297123 DOI: 10.1261/rna.073379.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 03/16/2020] [Indexed: 06/02/2023]
Abstract
U2 and U6 small nuclear (sn)RNAs are the only snRNAs directly implicated in catalyzing the splicing of pre-mRNA, but assembly and rearrangement steps prior to catalysis require numerous proteins. Previous studies have shown that the protein-free U2-U6 snRNA complex adopts two conformations in equilibrium, characterized by four and three helices surrounding a central junction. The four-helix conformer is strongly favored in the in vitro protein-free state, but the three-helix conformer predominates in spliceosomes. To analyze the role of the central junction in positioning elements forming the active site, we derived three-dimensional models of the two conformations from distances measured between fluorophores at selected locations in constructs representing the protein-free human U2-U6 snRNA complex by time-resolved fluorescence resonance energy transfer. Data describing four angles in the four-helix conformer suggest tetrahedral geometry; addition of Mg2+ results in shortening of the distances between neighboring helices, indicating compaction of the complex around the junction. In contrast, the three-helix conformer shows a closer approach between helices bearing critical elements, but the addition of Mg2+ widens the distance between them; thus in neither conformer are the critical helices positioned to favor the proposed triplex interaction. The presence of Mg2+ also enhances the fraction of the three-helix conformer, as does incubation with the Prp19-related protein RBM22, which has been implicated in the remodeling of the U2-U6 snRNA complex to render it catalytically active. These data suggest that although the central junction assumes a significant role in orienting helices, spliceosomal proteins and Mg2+ facilitate formation of the catalytically active conformer.
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Affiliation(s)
- Huong Chu
- Department of Chemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, New York 10016, USA
| | - William Perea
- Department of Chemistry, Hunter College of the City University of New York, New York, New York 10065, USA
| | - Nancy L Greenbaum
- Department of Chemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, New York 10016, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, New York 10016, USA
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4
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Izumikawa K, Nobe Y, Ishikawa H, Yamauchi Y, Taoka M, Sato K, Nakayama H, Simpson RJ, Isobe T, Takahashi N. TDP-43 regulates site-specific 2'-O-methylation of U1 and U2 snRNAs via controlling the Cajal body localization of a subset of C/D scaRNAs. Nucleic Acids Res 2019; 47:2487-2505. [PMID: 30759234 PMCID: PMC6412121 DOI: 10.1093/nar/gkz086] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 01/29/2019] [Accepted: 02/01/2019] [Indexed: 12/12/2022] Open
Abstract
TDP-43 regulates cellular levels of Cajal bodies (CBs) that provide platforms for the assembly and RNA modifications of small nuclear ribonucleoproteins (snRNPs) involved in pre-mRNA splicing. Alterations in these snRNPs may be linked to pathogenesis of amyotrophic lateral sclerosis. However, specific roles for TDP-43 in CBs remain unknown. Here, we demonstrate that TDP-43 regulates the CB localization of four UG-rich motif-bearing C/D-box-containing small Cajal body-specific RNAs (C/D scaRNAs; i.e. scaRNA2, 7, 9 and 28) through the direct binding to these scaRNAs. TDP-43 enhances binding of a CB-localizing protein, WD40-repeat protein 79 (WDR79), to a subpopulation of scaRNA2 and scaRNA28; the remaining population of the four C/D scaRNAs was localized to CB-like structures even with WDR79 depletion. Depletion of TDP-43, in contrast, shifted the localization of these C/D scaRNAs, mainly into the nucleolus, as well as destabilizing scaRNA2, and reduced the site-specific 2'-O-methylation of U1 and U2 snRNAs, including at 70A in U1 snRNA and, 19G, 25G, 47U and 61C in U2 snRNA. Collectively, we suggest that TDP-43 and WDR79 have separate roles in determining CB localization of subsets of C/D and H/ACA scaRNAs.
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Affiliation(s)
- Keiichi Izumikawa
- Department of Applied Biological Science and Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183–8509, Japan
| | - Yuko Nobe
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan
| | - Hideaki Ishikawa
- Department of Applied Biological Science and Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183–8509, Japan
| | - Yoshio Yamauchi
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan
| | - Masato Taoka
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan
| | - Ko Sato
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan
| | - Hiroshi Nakayama
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
| | - Richard J Simpson
- Department of Applied Biological Science and Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183–8509, Japan
- La Trobe Institute for Molecular Science (LIMS), LIMS Building 1, Room 412 La Trobe University, Melbourne Victoria 3086, Australia
| | - Toshiaki Isobe
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan
| | - Nobuhiro Takahashi
- Department of Applied Biological Science and Global Innovation Research Organizations, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183–8509, Japan
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5
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Proximity-CLIP provides a snapshot of protein-occupied RNA elements in subcellular compartments. Nat Methods 2018; 15:1074-1082. [PMID: 30478324 PMCID: PMC6289640 DOI: 10.1038/s41592-018-0220-y] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 09/25/2018] [Indexed: 12/22/2022]
Abstract
Methods to systematically study subcellular RNA localization are limited and lagging behind proteomic tools. Here, we combined APEX2-mediated proximity biotinylation of proteins with photoactivatable ribonucleoside-enhanced crosslinking to simultaneously profile the proteome, as well as the transcriptome bound by RNA-binding proteins in any given subcellular compartment. Our approach is fractionation-independent and enables to study the localization of RNA processing intermediates, as well as the identification of regulatory RNA cis-acting elements occupied by proteins in a cellular compartment-specific manner. We applied Proximity-CLIP to study RNA and protein in the nucleus, cytoplasm and at cell-cell interfaces. Among other insights, we observed frequent transcriptional readthrough continuing for several kilobases downstream of the canonical cleavage and polyadenylation site and a differential RBP occupancy pattern for mRNAs in the nucleus and cytoplasm. Surprisingly, mRNAs localized to cell-cell interfaces often encoded regulatory proteins and contained protein-occupied CUG sequence elements in their 3’ untranslated region.
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6
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Nguyen TC, Zaleta-Rivera K, Huang X, Dai X, Zhong S. RNA, Action through Interactions. Trends Genet 2018; 34:867-882. [PMID: 30177410 DOI: 10.1016/j.tig.2018.08.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/10/2018] [Accepted: 08/03/2018] [Indexed: 12/18/2022]
Abstract
As transcription of the human genome is quite pervasive, it is possible that many novel functions of the noncoding genome have yet to be identified. Often the noncoding genome's functions are carried out by their RNA transcripts, which may rely on their structures and/or extensive interactions with other molecules. Recent technology developments are transforming the fields of RNA biology from studying one RNA at a time to transcriptome-wide mapping of structures and interactions. Here, we highlight the recent advances in transcriptome-wide RNA interaction analysis. These technologies revealed surprising versatility of RNA to participate in diverse molecular systems. For example, tens of thousands of RNA-RNA interactions have been revealed in cultured cells as well as in mouse brain, including interactions between transposon-produced transcripts and mRNAs. In addition, most transcription start sites in the human genome are associated with noncoding RNA transcribed from other genomic loci. These recent discoveries expanded our understanding of RNAs' roles in chromatin organization, gene regulation, and intracellular signaling.
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Affiliation(s)
- Tri C Nguyen
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Kathia Zaleta-Rivera
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Xuerui Huang
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Xiaofeng Dai
- Wuxi School of Medicine, Jiangnan University, Wuxi Shi, Jiangsu Sheng, P.R. China.
| | - Sheng Zhong
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.
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7
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Circular RNAs Biogenesis in Eukaryotes Through Self-Cleaving Hammerhead Ribozymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1087:53-63. [PMID: 30259357 DOI: 10.1007/978-981-13-1426-1_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Circular DNAs are frequent genomic molecules, especially among the simplest life beings, whereas circular RNAs have been regarded as weird nucleic acids in biology. Now we know that eukaryotes are able to express circRNAs, mostly derived from backsplicing mechanisms, and playing different biological roles such as regulation of RNA splicing and transcription, among others. However, a second natural and highly efficient pathway for the expression in vivo of circRNAs has been recently reported, which allows the accumulation of abundant small (100-1000 nt) non-coding RNA circles through the participation of small self-cleaving RNAs or ribozymes called hammerhead ribozymes. These genome-encoded circRNAs with ribozymes seem to be a new family of small and nonautonomous retrotransposable elements of plants and animals (so-called retrozymes), which will offer functional clues to the biology and evolution of circular RNA molecules as well as new biotechnological tools in this emerging field.
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8
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DeHaven AC, Norden IS, Hoskins AA. Lights, camera, action! Capturing the spliceosome and pre-mRNA splicing with single-molecule fluorescence microscopy. WILEY INTERDISCIPLINARY REVIEWS. RNA 2016; 7:683-701. [PMID: 27198613 PMCID: PMC4990488 DOI: 10.1002/wrna.1358] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/20/2016] [Accepted: 04/04/2016] [Indexed: 11/06/2022]
Abstract
The process of removing intronic sequences from a precursor to messenger RNA (pre-mRNA) to yield a mature mRNA transcript via splicing is an integral step in eukaryotic gene expression. Splicing is carried out by a cellular nanomachine called the spliceosome that is composed of RNA components and dozens of proteins. Despite decades of study, many fundamentals of spliceosome function have remained elusive. Recent developments in single-molecule fluorescence microscopy have afforded new tools to better probe the spliceosome and the complex, dynamic process of splicing by direct observation of single molecules. These cutting-edge technologies enable investigators to monitor the dynamics of specific splicing components, whole spliceosomes, and even cotranscriptional splicing within living cells. WIREs RNA 2016, 7:683-701. doi: 10.1002/wrna.1358 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Alexander C. DeHaven
- Integrated Program in Biochemistry, U. Wisconsin-Madison, Madison, WI 53706
- Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706
| | - Ian S. Norden
- Integrated Program in Biochemistry, U. Wisconsin-Madison, Madison, WI 53706
- Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706
| | - Aaron A. Hoskins
- Department of Biochemistry, U. Wisconsin-Madison, Madison, WI 53706
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9
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Cervera A, Urbina D, de la Peña M. Retrozymes are a unique family of non-autonomous retrotransposons with hammerhead ribozymes that propagate in plants through circular RNAs. Genome Biol 2016; 17:135. [PMID: 27339130 PMCID: PMC4918200 DOI: 10.1186/s13059-016-1002-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/07/2016] [Indexed: 11/16/2022] Open
Abstract
Background Catalytic RNAs, or ribozymes, are regarded as fossils of a prebiotic RNA world that have remained in the genomes of modern organisms. The simplest ribozymes are the small self-cleaving RNAs, like the hammerhead ribozyme, which have been historically considered biological oddities restricted to some RNA pathogens. Recent data, however, indicate that small self-cleaving ribozymes are widespread in genomes, although their functions are still unknown. Results We reveal that hammerhead ribozyme sequences in plant genomes form part of a new family of small non-autonomous retrotransposons with hammerhead ribozymes, referred to as retrozymes. These elements contain two long terminal repeats of approximately 350 bp, each harbouring a hammerhead ribozyme that delimitates a variable region of 600–1000 bp with no coding capacity. Retrozymes are actively transcribed, which gives rise to heterogeneous linear and circular RNAs that accumulate differentially depending on the tissue or developmental stage of the plant. Genomic and transcriptomic retrozyme sequences are highly heterogeneous and share almost no sequence homology among species except the hammerhead ribozyme motif and two small conserved domains typical of Ty3-gypsy long terminal repeat retrotransposons. Moreover, we detected the presence of RNAs of both retrozyme polarities, which suggests events of independent RNA-RNA rolling-circle replication and evolution, similarly to that of infectious circular RNAs like viroids and viral satellite RNAs. Conclusions Our work reveals that circular RNAs with hammerhead ribozymes are frequently occurring molecules in plant and, most likely, metazoan transcriptomes, which explains the ubiquity of these genomic ribozymes and suggests a feasible source for the emergence of circular RNA plant pathogens. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-1002-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amelia Cervera
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Denisse Urbina
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Marcos de la Peña
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain.
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10
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McNeil BA, Semper C, Zimmerly S. Group II introns: versatile ribozymes and retroelements. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 7:341-55. [PMID: 26876278 DOI: 10.1002/wrna.1339] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 12/10/2015] [Accepted: 12/22/2015] [Indexed: 01/10/2023]
Abstract
Group II introns are catalytic RNAs (ribozymes) and retroelements found in the genomes of bacteria, archaebacteria, and organelles of some eukaryotes. The prototypical retroelement form consists of a structurally conserved RNA and a multidomain reverse transcriptase protein, which interact with each other to mediate splicing and mobility reactions. A wealth of biochemical, cross-linking, and X-ray crystal structure studies have helped to reveal how the two components cooperate to carry out the splicing and mobility reactions. In addition to the standard retroelement form, group II introns have evolved into derivative forms by either losing specific splicing or mobility characteristics, or becoming functionally specialized. Of particular interest are the eukaryotic derivatives-the spliceosome, spliceosomal introns, and non-LTR retroelements-which together make up approximately half of the human genome. On a practical level, the properties of group II introns have been exploited to develop group II intron-based biotechnological tools. WIREs RNA 2016, 7:341-355. doi: 10.1002/wrna.1339 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Bonnie A McNeil
- Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Cameron Semper
- Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Steven Zimmerly
- Department of Biological Sciences, University of Calgary, Calgary, Canada
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11
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Hang J, Wan R, Yan C, Shi Y. Structural basis of pre-mRNA splicing. Science 2015; 349:1191-8. [PMID: 26292705 DOI: 10.1126/science.aac8159] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 08/10/2015] [Indexed: 01/27/2023]
Abstract
Splicing of precursor messenger RNA is performed by the spliceosome. In the cryogenic electron microscopy structure of the yeast spliceosome, U5 small nuclear ribonucleoprotein acts as a central scaffold onto which U6 and U2 small nuclear RNAs (snRNAs) are intertwined to form a catalytic center next to Loop I of U5 snRNA. Magnesium ions are coordinated by conserved nucleotides in U6 snRNA. The intron lariat is held in place through base-pairing interactions with both U2 and U6 snRNAs, leaving the variable-length middle portion on the solvent-accessible surface of the catalytic center. The protein components of the spliceosome anchor both 5' and 3' ends of the U2 and U6 snRNAs away from the active site, direct the RNA sequences, and allow sufficient flexibility between the ends and the catalytic center. Thus, the spliceosome is in essence a protein-directed ribozyme, with the protein components essential for the delivery of critical RNA molecules into close proximity of one another at the right time for the splicing reaction.
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Affiliation(s)
- Jing Hang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ruixue Wan
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Chuangye Yan
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yigong Shi
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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12
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Abstract
Precursor messenger RNA (pre-mRNA) splicing is a critical step in the posttranscriptional regulation of gene expression, providing significant expansion of the functional proteome of eukaryotic organisms with limited gene numbers. Split eukaryotic genes contain intervening sequences or introns disrupting protein-coding exons, and intron removal occurs by repeated assembly of a large and highly dynamic ribonucleoprotein complex termed the spliceosome, which is composed of five small nuclear ribonucleoprotein particles, U1, U2, U4/U6, and U5. Biochemical studies over the past 10 years have allowed the isolation as well as compositional, functional, and structural analysis of splicing complexes at distinct stages along the spliceosome cycle. The average human gene contains eight exons and seven introns, producing an average of three or more alternatively spliced mRNA isoforms. Recent high-throughput sequencing studies indicate that 100% of human genes produce at least two alternative mRNA isoforms. Mechanisms of alternative splicing include RNA-protein interactions of splicing factors with regulatory sites termed silencers or enhancers, RNA-RNA base-pairing interactions, or chromatin-based effects that can change or determine splicing patterns. Disease-causing mutations can often occur in splice sites near intron borders or in exonic or intronic RNA regulatory silencer or enhancer elements, as well as in genes that encode splicing factors. Together, these studies provide mechanistic insights into how spliceosome assembly, dynamics, and catalysis occur; how alternative splicing is regulated and evolves; and how splicing can be disrupted by cis- and trans-acting mutations leading to disease states. These findings make the spliceosome an attractive new target for small-molecule, antisense, and genome-editing therapeutic interventions.
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Affiliation(s)
- Yeon Lee
- Center for RNA Systems Biology; Division of Biochemistry, Biophysics, and Structural Biology; Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3204;
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13
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Abstract
The emergence of catalysis in early genetic polymers like RNA is considered a key transition in the origin of life1, predating the appearance of protein enzymes. DNA also demonstrates the capacity to fold into three-dimensional structures and form catalysts in vitro2. However, to what degree these natural biopolymers comprise functionally privileged chemical scaffolds3 for folding or the evolution of catalysis is not known. The ability of synthetic genetic polymers (XNAs) with alternative backbone chemistries not found in nature to fold into defined structures and bind ligands4 raises the possibility that these too might be capable of forming catalysts (XNAzymes). Here we report the discovery of such XNAzymes, elaborated in four different chemistries (ANA (arabino nucleic acids)5, FANA (2′-fluoroarabino nucleic acids)6, HNA (hexitol nucleic acids) and CeNA (cyclohexene nucleic acids)7 directly from random XNA oligomer pools, exhibiting in trans RNA endonuclease and ligase activities. We also describe an XNA-XNA ligase metalloenzyme in the FANA framework, establishing catalysis in an entirely synthetic system and enabling the synthesis of FANA oligomers and an active RNA endonuclease FANAzyme from its constituent parts. These results extend catalysis beyond biopolymers and establish technologies for the discovery of catalysts in a wide range of polymer scaffolds not found in nature8. Evolution of catalysis independent of any natural polymer has implications for the definition of chemical boundary conditions for the emergence of life on earth and elsewhere in the universe9.
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14
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Collier SE, Voehler M, Peng D, Ohi R, Gould KL, Reiter NJ, Ohi MD. Structural and functional insights into the N-terminus of Schizosaccharomyces pombe Cdc5. Biochemistry 2014; 53:6439-51. [PMID: 25263959 PMCID: PMC4204884 DOI: 10.1021/bi5008639] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
The
spliceosome is a dynamic macromolecular machine composed of
five small nuclear ribonucleoparticles (snRNPs), the NineTeen Complex
(NTC), and other proteins that catalyze the removal of introns mature
to form the mature message. The NTC, named after its founding member Saccharomyces cerevisiae Prp19, is a conserved spliceosome
subcomplex composed of at least nine proteins. During spliceosome
assembly, the transition to an active spliceosome correlates with
stable binding of the NTC, although the mechanism of NTC function
is not understood. Schizosaccharomyces pombe Cdc5, a core subunit of the NTC, is an essential protein required
for pre-mRNA splicing. The highly conserved Cdc5 N-terminus contains
two canonical Myb (myeloblastosis) repeats (R1 and R2) and a third
domain (D3) that was previously classified as a Myb-like repeat. Although
the N-terminus of Cdc5 is required for its function, how R1, R2, and
D3 each contribute to functionality is unclear. Using a combination
of yeast genetics, structural approaches, and RNA binding assays,
we show that R1, R2, and D3 are all required for the function of Cdc5
in cells. We also show that the N-terminus of Cdc5 binds RNA in vitro. Structural and functional analyses of Cdc5-D3
show that, while this domain does not adopt a Myb fold, Cdc5-D3 preferentially
binds double-stranded RNA. Our data suggest that the Cdc5 N-terminus
interacts with RNA structures proposed to be near the catalytic core
of the spliceosome.
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Affiliation(s)
- Scott E Collier
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center , Nashville, Tennessee 37232, United States
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15
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The noncoding RNA revolution-trashing old rules to forge new ones. Cell 2014; 157:77-94. [PMID: 24679528 DOI: 10.1016/j.cell.2014.03.008] [Citation(s) in RCA: 1647] [Impact Index Per Article: 164.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 03/07/2014] [Indexed: 12/14/2022]
Abstract
Noncoding RNAs (ncRNAs) accomplish a remarkable variety of biological functions. They regulate gene expression at the levels of transcription, RNA processing, and translation. They protect genomes from foreign nucleic acids. They can guide DNA synthesis or genome rearrangement. For ribozymes and riboswitches, the RNA structure itself provides the biological function, but most ncRNAs operate as RNA-protein complexes, including ribosomes, snRNPs, snoRNPs, telomerase, microRNAs, and long ncRNAs. Many, though not all, ncRNAs exploit the power of base pairing to selectively bind and act on other nucleic acids. Here, we describe the pathway of ncRNA research, where every established "rule" seems destined to be overturned.
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Valadkhan S. The role of snRNAs in spliceosomal catalysis. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 120:195-228. [PMID: 24156945 DOI: 10.1016/b978-0-12-381286-5.00006-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The spliceosomes, large ribonucleoprotein (RNP) assemblies that remove the intervening sequences from pre-mRNAs, contain a large number of proteins and five small nuclear RNAs (snRNAs). One snRNA, U6, contains highly conserved sequences that are thought to be the functional counterparts of the RNA elements that form the active site of self-splicing group II intron ribozymes. An in vitro-assembled, protein-free complex of U6 with U2, the base-pairing partner in the spliceosomal catalytic core, can catalyze a two-step splicing reaction in the absence of all other spliceosomal factors, suggesting that the two snRNAs may form all or a large share of the spliceosomal active site. On the other hand, several spliceosomal proteins are thought to help in the formation of functionally required RNA-RNA interactions in the catalytic core. Whether they also contribute functional groups to the spliceosomal active site, and thus whether the spliceosomes are RNA or RNP enzymes remain uncertain.
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Affiliation(s)
- Saba Valadkhan
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, USA
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17
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Karunatilaka KS, Rueda D. Post-transcriptional modifications modulate conformational dynamics in human U2-U6 snRNA complex. RNA (NEW YORK, N.Y.) 2014; 20:16-23. [PMID: 24243115 PMCID: PMC3866641 DOI: 10.1261/rna.041806.113] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The spliceosome catalyzes precursor-mRNA splicing in all eukaryotes. It consists of over 100 proteins and five small nuclear RNAs (snRNAs), including U2 and U6 snRNAs, which are essential for catalysis. Human and yeast snRNAs share structural similarities despite the fact that human snRNAs contain numerous post-transcriptional modifications. Although functions for these modifications have been proposed, their exact roles are still not well understood. To help elucidate these roles in pre-mRNA splicing, we have used single-molecule fluorescence to characterize the effect of several post-transcriptional modifications in U2 snRNA on the conformation and dynamics of the U2-U6 complex in vitro. Consistent with yeast, the human U2-U6 complex reveals the presence of a magnesium-dependent dynamic equilibrium among three conformations. Interestingly, our data show that modifications in human U2 stem I modulate the dynamic equilibrium of the U2-U6 complex by stabilizing the four-helix structure. However, the small magnitude of this effect suggests that post-transcriptional modifications in human snRNAs may have a primary role in the mediation of specific RNA-protein interactions in vivo.
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Affiliation(s)
| | - David Rueda
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
- Department of Medicine, Section of Virology, Imperial College London, London W12 0NN, United Kingdom
- Single Molecule Imaging Group, MRC Clinical Sciences Center, Imperial College London, London W12 0NN, United Kingdom
- Corresponding authorE-mail
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18
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Abstract
A new study adds to the evidence for a common evolutionary origin of the spliceosome and group II introns, but RNA-world questions remain.
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19
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Fica SM, Tuttle N, Novak T, Li NS, Lu J, Koodathingal P, Dai Q, Staley JP, Piccirilli JA. RNA catalyses nuclear pre-mRNA splicing. Nature 2013; 503:229-34. [PMID: 24196718 PMCID: PMC4666680 DOI: 10.1038/nature12734] [Citation(s) in RCA: 249] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 10/03/2013] [Indexed: 12/24/2022]
Abstract
In nuclear pre-messenger RNA splicing, introns are excised by the spliceosome, a multi-megadalton machine composed of both proteins and small nuclear RNAs (snRNAs). Over thirty years ago, following the discovery of self-splicing group II intron RNAs, the snRNAs were hypothesized to catalyze splicing. However, no definitive evidence for a role of either RNA or protein in catalysis by the spliceosome has been reported to date. By using metal rescue strategies, here we show that the U6 snRNA catalyzes both splicing reactions by positioning divalent metals that stabilize the leaving groups during each reaction. Strikingly, all of the U6 catalytic metal ligands we identified correspond to the ligands observed to position catalytic, divalent metals in crystal structures of a group II intron RNA. These findings indicate that group II introns and the spliceosome share common catalytic mechanisms, and likely common evolutionary origins. Our results demonstrate that RNA mediates catalysis within the spliceosome.
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Affiliation(s)
- Sebastian M Fica
- 1] Graduate Program in Cell and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA [2] Department of Molecular Genetics and Cell Biology, Cummings Life Sciences Center, 920 East 58th Street, The University of Chicago, Chicago, Illinois 60637, USA [3]
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20
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Cheng CC, Hung KC, Huang-Fu WC. Differentiate RNA Single-Stranded Region of the Branched Structures and Hairpin Loops by an Octahedral Cobalt(II) Complex. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200500186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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21
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Affiliation(s)
- Sophie Bonnal
- 1] Centre de Regulació Genòmica, Barcelona, Spain [2] Universitat Pompeu Fabra, Barcelona, Spain
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22
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Mroczek S, Dziembowski A. U6 RNA biogenesis and disease association. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 4:581-92. [PMID: 23776162 DOI: 10.1002/wrna.1181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/14/2013] [Accepted: 05/15/2013] [Indexed: 12/15/2022]
Abstract
U6 snRNA is one of five uridine-rich noncoding RNAs that form the major spliceosome complex. Unlike other U-snRNAs, it reveals many distinctive aspects of biogenesis such as transcription by RNA polymerase III, transcript nuclear retention and particular features of transcript ends: monomethylated 5'-guanosine triphosphate as cap structure and a 2',3'-cyclic phosphate moiety (>P) at the 3' termini. U6-snRNA plays a central role in splicing and thus its transcription, maturation, snRNP formation, and recycling are essential for cellular homeostasis. U6 snRNA enters the splicing cycle as part of the tri-U4/U6.U5snRNP complex, and after significant structural arrangements forms the catalytic site of the spliceosome together with U2 snRNA and Prp8. U6 snRNA also contributes to the splicing reaction by coordinating metal cations required for catalysis. Many human diseases are associated with altered splicing processes. Disruptions of the basal splicing machinery can be lethal or lead to severe diseases such as spinal muscular atrophy, amyotrophic lateral sclerosis, or retinitis pigmentosa. Recent studies have identified a new U6 snRNA biogenesis factor Usb1, the absence of which leads to poikiloderma with neutropenia (PN) (OMIM 604173), an autosomal recessive skin disease. Usb1 is an evolutionarily conserved 3'→5' exoribonuclease that is responsible for removing 3'-terminal uridines from U6 snRNA transcripts, which leads to the formation of a 2',3' cyclic phosphate moiety (>P). This maturation step is fundamental for U6 snRNP assembly and recycling. Usb1 represents the first example of a direct association between a spliceosomal U6 snRNA biogenesis factor and human genetic disease.
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Affiliation(s)
- Seweryn Mroczek
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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23
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Zhao C, Bachu R, Popović M, Devany M, Brenowitz M, Schlatterer JC, Greenbaum NL. Conformational heterogeneity of the protein-free human spliceosomal U2-U6 snRNA complex. RNA (NEW YORK, N.Y.) 2013; 19:561-73. [PMID: 23426875 PMCID: PMC3677266 DOI: 10.1261/rna.038265.113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 05/24/2023]
Abstract
The complex formed between the U2 and U6 small nuclear (sn)RNA molecules of the eukaryotic spliceosome plays a critical role in the catalysis of precursor mRNA splicing. Here, we have used enzymatic structure probing, (19)F NMR, and analytical ultracentrifugation techniques to characterize the fold of a protein-free biophysically tractable paired construct representing the human U2-U6 snRNA complex. Results from enzymatic probing and (19)F NMR for the complex in the absence of Mg(2+) are consistent with formation of a four-helix junction structure as a predominant conformation. However, (19)F NMR data also identify a lesser fraction (up to 14% at 25°C) of a three-helix conformation. Based upon this distribution, the calculated ΔG for inter-conversion to the four-helix structure from the three-helix structure is approximately -4.6 kJ/mol. In the presence of 5 mM Mg(2+), the fraction of the three-helix conformation increased to ∼17% and the Stokes radius, measured by analytical ultracentrifugation, decreased by 2%, suggesting a slight shift to an alternative conformation. NMR measurements demonstrated that addition of an intron fragment to the U2-U6 snRNA complex results in displacement of U6 snRNA from the region of Helix III immediately 5' of the ACAGAGA sequence of U6 snRNA, which may facilitate binding of the segment of the intron adjacent to the 5' splice site to the ACAGAGA sequence. Taken together, these observations indicate conformational heterogeneity in the protein-free human U2-U6 snRNA complex consistent with a model in which the RNA has sufficient conformational flexibility to facilitate inter-conversion between steps of splicing in situ.
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Affiliation(s)
- Caijie Zhao
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- The Graduate Center, City University of New York, New York, New York 10016, USA
| | - Ravichandra Bachu
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- The Graduate Center, City University of New York, New York, New York 10016, USA
| | - Milena Popović
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA
| | - Matthew Devany
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, New York 10065, USA
| | - Michael Brenowitz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Jörg C. Schlatterer
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Nancy L. Greenbaum
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, New York, New York 10065, USA
- The Graduate Center, City University of New York, New York, New York 10016, USA
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24
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Carlomagno T, Amata I, Codutti L, Falb M, Fohrer J, Masiewicz P, Simon B. Structural principles of RNA catalysis in a 2'-5' lariat-forming ribozyme. J Am Chem Soc 2013; 135:4403-11. [PMID: 23472843 DOI: 10.1021/ja311868t] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA-catalyzed lariat formation is present in both eukaryotes and prokaryotes. To date we lack structural insights into the catalytic mechanism of lariat-forming ribozymes. Here, we study an artificial 2'-5' AG1 lariat-forming ribozyme that shares the sequence specificity of lariat formation with the pre-mRNA splicing reaction. Using NMR, we solve the structure of the inactive state of the ribozyme in the absence of magnesium. The reaction center 5'-guanosine appears to be part of a helix with an exceptionally widened major groove, while the lariat-forming A48 is looped out at the apex of a pseudoknot. The model of the active state built by mutational analysis, molecular modeling, and small-angle X-ray scattering suggests that A48 is recognized by a conserved adenosine, juxtaposed to the 5'-guanosine in one base-pair step distance, while the G1-N7 coordinates a magnesium ion essential for the activation of the nucleophile. Our findings offer implications for lariat formation in RNA enzymes including the mechanism of the recognition of the branch-site adenosine.
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Affiliation(s)
- Teresa Carlomagno
- Structural and Computational Biology Unit, EMBL, Meyerhofstraße 1, D-69117 Heidelberg, Germany.
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25
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Fixation and accumulation of thermotolerant catalytic competence of a pair of ligase ribozymes through complex formation and cross ligation. J Mol Evol 2013; 76:48-58. [PMID: 23288433 DOI: 10.1007/s00239-012-9536-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 12/05/2012] [Indexed: 12/11/2022]
Abstract
In the early stages of the hypothetical RNA world, some primitive RNA catalysts (ribozymes) may have emerged through self-assembly of short RNA oligomers. Although they may be unstable against temperature fluctuations and other environmental changes, ligase ribozymes (ribozymes with RNA strand-joining activity) may resolve structural instability of self-assembling RNAs by converting them to the corresponding unimolecular formats. To investigate this possibility, we constructed a model system using a cross-ligation system composed of a pair of self-assembling ligase ribozymes. Their abilities to act as catalysts, substrates, and a cross-ligation system were analyzed with or without thermal pretreatment before the reactions. A pair of self-assembling ligase ribozymes, each of which can form multiple conformations, demonstrated that thermotolerance was acquired and accumulated through complex-formation that stabilized the active forms of the bimolecular ribozymes and also cross-ligation that produced the unimolecular ribozymes.
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26
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Lönnberg TA. Can phosphate-branched RNA persist under physiological conditions? Chembiochem 2012; 13:2690-700. [PMID: 23255258 DOI: 10.1002/cbic.201200629] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Indexed: 11/10/2022]
Abstract
A 2'-O-methyl-RNA oligonucleotide containing a single free 2'-OH group flanking a branching phosphotriester linkage was prepared as a model for phosphate-branched RNA by using an orthogonally protected dimeric phosphoramidite building block in solid-phase synthesis. The strategy allows the synthesis of phosphate-branched oligonucleotides, the three branches of which may be of any desired sequence. Hydrolytic reactions of the phosphotriester linkages in such oligonucleotides were studied at physiological pH in the presence (and absence) of various complementary oligonucleotides. The fully hybridized oligonucleotide model is an order of magnitude more stable than its single-stranded counterpart, which, in turn, is an order of magnitude more stable than its trinucleoside phosphotriester core lacking any oligonucleotide arms. Furthermore, kinked structures obtained by hybridizing the phosphate-branched oligonucleotide with partially complementary oligonucleotides are three to five times more stable than fully double-stranded ones and only approximately three times less stable than the so-called RNA X structure, which has been postulated to incorporate an RNA phosphotriester linkage. The results indicate that when the intrinsically unstable RNA phosphotriester linkage is embedded in an oligonucleotide of appropriate tertiary structure, its half-life can be at least several hours.
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27
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Schmitzová J, Pena V. Emerging views about the molecular structure of the spliceosomal catalytic center. RNA Biol 2012; 9:1311-8. [PMID: 23064115 DOI: 10.4161/rna.22359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Pre-mRNA splicing occurs in two chemical steps that are catalyzed by a large, dynamic RNA-protein complex called the spliceosome. Initially assembled in a catalytically inactive form, the spliceosome undergoes massive compositional and conformational remodeling, through which disparate RNA elements are re-configured and juxtaposed into a functional catalytic center. The intricate construction of the catalytic center requires the assistance of spliceosomal proteins. Recent structure-function analyses have demonstrated that the yeast-splicing factor Cwc2 is a main player that contacts and shapes the catalytic center of the spliceosome into a functional conformation. With this advance, corroborated by the atomic structure of the evolutionarily related group IIC introns, our understanding of the organization and formation of the spliceosomal catalytic center has progressed to a new level.
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Affiliation(s)
- Jana Schmitzová
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical, Macromolecular Crystallography Group, Göttingen, Germany
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28
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Bompfünewerer AF, Flamm C, Fried C, Fritzsch G, Hofacker IL, Lehmann J, Missal K, Mosig A, Müller B, Prohaska SJ, Stadler BMR, Stadler PF, Tanzer A, Washietl S, Witwer C. Evolutionary patterns of non-coding RNAs. Theory Biosci 2012; 123:301-69. [PMID: 18202870 DOI: 10.1016/j.thbio.2005.01.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Accepted: 01/24/2005] [Indexed: 01/04/2023]
Abstract
A plethora of new functions of non-coding RNAs (ncRNAs) have been discovered in past few years. In fact, RNA is emerging as the central player in cellular regulation, taking on active roles in multiple regulatory layers from transcription, RNA maturation, and RNA modification to translational regulation. Nevertheless, very little is known about the evolution of this "Modern RNA World" and its components. In this contribution, we attempt to provide at least a cursory overview of the diversity of ncRNAs and functional RNA motifs in non-translated regions of regular messenger RNAs (mRNAs) with an emphasis on evolutionary questions. This survey is complemented by an in-depth analysis of examples from different classes of RNAs focusing mostly on their evolution in the vertebrate lineage. We present a survey of Y RNA genes in vertebrates and study the molecular evolution of the U7 snRNA, the snoRNAs E1/U17, E2, and E3, the Y RNA family, the let-7 microRNA (miRNA) family, and the mRNA-like evf-1 gene. We furthermore discuss the statistical distribution of miRNAs in metazoans, which suggests an explosive increase in the miRNA repertoire in vertebrates. The analysis of the transcription of ncRNAs suggests that small RNAs in general are genetically mobile in the sense that their association with a hostgene (e.g. when transcribed from introns of a mRNA) can change on evolutionary time scales. The let-7 family demonstrates, that even the mode of transcription (as intron or as exon) can change among paralogous ncRNA.
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29
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van der Feltz C, Anthony K, Brilot A, Pomeranz Krummel DA. Architecture of the Spliceosome. Biochemistry 2012; 51:3321-33. [DOI: 10.1021/bi201215r] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Clarisse van der Feltz
- Department of Biochemistry, Brandeis University, 415 South Street, Waltham, Massachusetts
02454, United States
| | - Kelsey Anthony
- Department of Biochemistry, Brandeis University, 415 South Street, Waltham, Massachusetts
02454, United States
| | - Axel Brilot
- Department of Biochemistry, Brandeis University, 415 South Street, Waltham, Massachusetts
02454, United States
| | - Daniel A. Pomeranz Krummel
- Department of Biochemistry, Brandeis University, 415 South Street, Waltham, Massachusetts
02454, United States
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30
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Burke JE, Sashital DG, Zuo X, Wang YX, Butcher SE. Structure of the yeast U2/U6 snRNA complex. RNA (NEW YORK, N.Y.) 2012; 18:673-83. [PMID: 22328579 PMCID: PMC3312555 DOI: 10.1261/rna.031138.111] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The U2/U6 snRNA complex is a conserved and essential component of the active spliceosome that interacts with the pre-mRNA substrate and essential protein splicing factors to promote splicing catalysis. Here we have elucidated the solution structure of a 111-nucleotide U2/U6 complex using an approach that integrates SAXS, NMR, and molecular modeling. The U2/U6 structure contains a three-helix junction that forms an extended "Y" shape. The U6 internal stem-loop (ISL) forms a continuous stack with U2/U6 Helices Ib, Ia, and III. The coaxial stacking of Helix Ib on the U6 ISL is a configuration that is similar to the Domain V structure in group II introns. Interestingly, essential features of the complex--including the U80 metal binding site, AGC triad, and pre-mRNA recognition sites--localize to one face of the molecule. This observation suggests that the U2/U6 structure is well-suited for orienting substrate and cofactors during splicing catalysis.
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Affiliation(s)
- Jordan E. Burke
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Dipali G. Sashital
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Xiaobing Zuo
- Advanced Photon Source, Argonne National Laboratory, Chicago, Illinois 60437, USA
| | - Yun-Xing Wang
- National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702, USA
| | - Samuel E. Butcher
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
- Corresponding author.E-mail .
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31
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Piccirilli JA, Koldobskaya Y. Crystal structure of an RNA polymerase ribozyme in complex with an antibody fragment. Philos Trans R Soc Lond B Biol Sci 2012; 366:2918-28. [PMID: 21930583 DOI: 10.1098/rstb.2011.0144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
All models of the RNA world era invoke the presence of ribozymes that can catalyse RNA polymerization. The class I ligase ribozyme selected in vitro 15 years ago from a pool of random RNA sequences catalyses formation of a 3',5'-phosphodiester linkage analogous to a single step of RNA polymerization. Recently, the three-dimensional structure of the ligase was solved in complex with U1A RNA-binding protein and independently in complex with an antibody fragment. The RNA adopts a tripod arrangement and appears to use a two-metal ion mechanism similar to protein polymerases. Here, we discuss structural implications for engineering a true polymerase ribozyme and describe the use of the antibody framework both as a portable chaperone for crystallization of other RNAs and as a platform for exploring steps in evolution from the RNA world to the RNA-protein world.
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Affiliation(s)
- Joseph A Piccirilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Gordon Center for Integrative Science, Room W406, Chicago, IL 60637, USA.
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32
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Ariza-Mateos A, Prieto-Vega S, Díaz-Toledano R, Birk A, Szeto H, Mena I, Berzal-Herranz A, Gómez J. RNA self-cleavage activated by ultraviolet light-induced oxidation. Nucleic Acids Res 2011; 40:1748-66. [PMID: 21989404 PMCID: PMC3287179 DOI: 10.1093/nar/gkr822] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A novel UV-C-light-induced ribozyme activity was discovered within the highly structured 5'-genomic regions of both Hepatitis C Virus (HCV) and the related Classic Swine Fever Virus (CSFV). Cleavage is mediated by exposure to UV-C light but not by exogenous oxygen radicals. It is also very selective, occurring at base positions HCV C(79) and CSFV A(45) in some molecules and at the immediately adjacent 5'-positions HCV U(78) and CSFV U(44) in others. Among other reaction products, the majority of biochemically active products detected contained 3'-phosphate and 5'-phosphate-end groups at the newly generated termini, along with a much lower amount of 3'-hydroxyl end group. While preservation of an E-loop RNA structure in the vicinity of the cleavage site was a requisite for HCV RNA self-cleavage, this was not the case for CSFV RNA. The short size of the reactive domains (~33 nt), which are compatible with primitive RNA motifs, and the lack of sequence homology, indicate that as-yet unidentified UV-activated ribozymes are likely to be found throughout structured RNAs, thereby providing clues to whether early RNA self-cleavage events were mediated by photosensitive RNA structures.
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Affiliation(s)
- Ascensión Ariza-Mateos
- Laboratory of RNA Archeology, Instituto de Parasitología y Biomedicina 'López-Neyra', CSIC, Armilla, 18100 Granada, Spain
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33
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Wu G, Yu AT, Kantartzis A, Yu YT. Functions and mechanisms of spliceosomal small nuclear RNA pseudouridylation. WILEY INTERDISCIPLINARY REVIEWS. RNA 2011; 2:571-81. [PMID: 21957045 PMCID: PMC4161978 DOI: 10.1002/wrna.77] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Pseudouridines are the most abundant and highly conserved modified nucleotides identified in spliceosomal small nuclear RNAs (snRNAs). Most pseudouridines are also clustered in functionally important regions of spliceosomal snRNAs. Experiments carried out in several independent experimental systems show that the pseudouridines in spliceosomal snRNAs are functionally important for pre-messenger RNA (mRNA) splicing. Experimental data also indicate that spliceosomal snRNA pseudouridylation can be catalyzed by both RNA-dependent (box H/ACA Ribonucleoproteins) and RNA-independent (protein-only enzymes) mechanisms.
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Affiliation(s)
- Guowei Wu
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, USA
| | - Andrew T. Yu
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, USA
| | - Athena Kantartzis
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, USA
| | - Yi-Tao Yu
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, USA
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34
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Abstract
Pre-mRNA splicing is catalyzed by the spliceosome, a multimegadalton ribonucleoprotein (RNP) complex comprised of five snRNPs and numerous proteins. Intricate RNA-RNA and RNP networks, which serve to align the reactive groups of the pre-mRNA for catalysis, are formed and repeatedly rearranged during spliceosome assembly and catalysis. Both the conformation and composition of the spliceosome are highly dynamic, affording the splicing machinery its accuracy and flexibility, and these remarkable dynamics are largely conserved between yeast and metazoans. Because of its dynamic and complex nature, obtaining structural information about the spliceosome represents a major challenge. Electron microscopy has revealed the general morphology of several spliceosomal complexes and their snRNP subunits, and also the spatial arrangement of some of their components. X-ray and NMR studies have provided high resolution structure information about spliceosomal proteins alone or complexed with one or more binding partners. The extensive interplay of RNA and proteins in aligning the pre-mRNA's reactive groups, and the presence of both RNA and protein at the core of the splicing machinery, suggest that the spliceosome is an RNP enzyme. However, elucidation of the precise nature of the spliceosome's active site, awaits the generation of a high-resolution structure of its RNP core.
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Affiliation(s)
- Cindy L Will
- Max Planck Institute for Biophysical Chemistry, Department of Cellular Biochemistry, Am Fassberg 11, 37077 Göttingen, Germany
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Jaladat Y, Zhang B, Mohammadi A, Valadkhan S. Splicing of an intervening sequence by protein-free human snRNAs. RNA Biol 2011; 8:372-7. [PMID: 21445000 DOI: 10.4161/rna.8.3.15386] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Significant structural and mechanistic similarities between the spliceosomal snRNAs and catalytically critical domains of self-splicing group II introns have led to the hypothesis that the spliceosomes and group II introns may be evolutionarily related. We have previously shown that in vitro-transcribed, protein-free U6 and U2 snRNAs can catalyze a two-step splicing reaction in trans on two short RNA oligonucleotides that is identical to the splicing reactions performed by many self-splicing group II introns. Here we show that the same two snRNAs can perform splicing in cis by removal of an intervening sequence from a model substrate. These results prove that the protein-free snRNAs are competent to perform splicing on pre-mRNAs and further strengthen the possibility of an evolutionary relationship to group II introns.
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Affiliation(s)
- Yasaman Jaladat
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
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Wochner A, Attwater J, Coulson A, Holliger P. Ribozyme-catalyzed transcription of an active ribozyme. Science 2011; 332:209-12. [PMID: 21474753 DOI: 10.1126/science.1200752] [Citation(s) in RCA: 262] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A critical event in the origin of life is thought to have been the emergence of an RNA molecule capable of replicating a primordial RNA "genome." Here we describe the evolution and engineering of an RNA polymerase ribozyme capable of synthesizing RNAs of up to 95 nucleotides in length. To overcome its sequence dependence, we recombined traits evolved separately in different ribozyme lineages. This yielded a more general polymerase ribozyme that was able to synthesize a wider spectrum of RNA sequences, as we demonstrate by the accurate synthesis of an enzymatically active RNA, a hammerhead endonuclease ribozyme. This recapitulates a central aspect of an RNA-based genetic system: the RNA-catalyzed synthesis of an active ribozyme from an RNA template.
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Affiliation(s)
- Aniela Wochner
- Medical Research Council (MRC) Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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37
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Abstract
The spliceosome is a massive complex of 5 RNAs and many proteins that associate to catalyze precursor messenger RNA splicing. The process of splicing involves two phosphoryl transfer reactions that result in intron excision and ligation of the flanking exons. Since it is required for normal protein production in eukaryotic cells, pre-mRNA splicing is an essential step in gene expression. Although high resolution structural views of the spliceosome do not yet exist, a growing body of evidence indicates that the spliceosome is a magnesium-dependent enzyme that utilizes catalytic metal ions to stabilize both transition states during the two phosphoryl transfer steps of splicing. A wealth of data also indicate that the core of the spliceosome is comprised of RNA, and suggest that the spliceosome may be a ribozyme. This chapter presents the evidence for metal ion catalysis by the spliceosome, draws comparisons to similar RNA enzymes, and discusses the future directions for research into the mechanism of pre-mRNA splicing.
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Affiliation(s)
- Samuel E Butcher
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA.
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Abstract
Ribonucleoproteins (RNPs) play key roles in many cellular processes and often function as RNP enzymes. Similar to proteins, some of these RNPs exist and function as multimers, either homomeric or heteromeric. While in some cases the mechanistic function of multimerization is well understood, the functional consequences of multimerization of other RNPs remain enigmatic. In this review we will discuss the function and organization of small RNPs that exist as stable multimers, including RNPs catalyzing RNA chemical modifications, telomerase RNP, and RNPs involved in pre-mRNA splicing.
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Lee C, Jaladat Y, Mohammadi A, Sharifi A, Geisler S, Valadkhan S. Metal binding and substrate positioning by evolutionarily invariant U6 sequences in catalytically active protein-free snRNAs. RNA (NEW YORK, N.Y.) 2010; 16:2226-38. [PMID: 20826700 PMCID: PMC2957061 DOI: 10.1261/rna.2170910] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Accepted: 07/31/2010] [Indexed: 05/20/2023]
Abstract
We have previously shown that a base-paired complex formed by two of the spliceosomal RNA components, U6 and U2 small nuclear RNAs (snRNAs), can catalyze a two-step splicing reaction that depended on an evolutionarily invariant region in U6, the ACAGAGA box. Here we further analyze this RNA-catalyzed reaction and show that while the 5' and 3' splice site substrates are juxtaposed and positioned near the ACAGAGA sequence in U6, the role of the snRNAs in the reaction is beyond mere juxtaposition of the substrates and likely involves the formation of a sophisticated active site. Interestingly, the snRNA-catalyzed reaction is metal dependent, as is the case with other known splicing RNA enzymes, and terbium(III) cleavage reactions indicate metal binding by the U6/U2 complex within the evolutionarily conserved regions of U6. The above results, combined with the structural similarities between U6 and catalytically critical domains in group II self-splicing introns, suggest that the base-paired complex of U6 and U2 snRNAs is a vestigial ribozyme and a likely descendant of a group II-like self-splicing intron.
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Affiliation(s)
- Caroline Lee
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Gene expression profiling of U12-type spliceosome mutant Drosophila reveals widespread changes in metabolic pathways. PLoS One 2010; 5:e13215. [PMID: 20949011 PMCID: PMC2952598 DOI: 10.1371/journal.pone.0013215] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 09/15/2010] [Indexed: 01/31/2023] Open
Abstract
Background The U12-type spliceosome is responsible for the removal of a subset of introns from eukaryotic mRNAs. U12-type introns are spliced less efficiently than normal U2-type introns, which suggests a rate-limiting role in gene expression. The Drosophila genome contains about 20 U12-type introns, many of them in essential genes, and the U12-type spliceosome has previously been shown to be essential in the fly. Methodology/Principal Findings We have used a Drosophila line with a P-element insertion in U6atac snRNA, an essential component of the U12-type spliceosome, to investigate the impact of U12-type introns on gene expression at the organismal level during fly development. This line exhibits progressive accumulation of unspliced U12-type introns during larval development and the death of larvae at the third instar stage. Surprisingly, microarray and RT-PCR analyses revealed that most genes containing U12-type introns showed only mild perturbations in the splicing of U12-type introns. In contrast, we detected widespread downstream effects on genes that do not contain U12-type introns, with genes related to various metabolic pathways constituting the largest group. Conclusions/Significance U12-type intron-containing genes exhibited variable gene-specific responses to the splicing defect, with some genes showing up- or downregulation, while most did not change significantly. The observed residual U12-type splicing activity could be explained with the mutant U6atac allele having a low level of catalytic activity. Detailed analysis of all genes suggested that a defect in the splicing of the U12-type intron of the mitochondrial prohibitin gene may be the primary cause of the various downstream effects detected in the microarray analysis.
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Koodathingal P, Novak T, Piccirilli JA, Staley JP. The DEAH box ATPases Prp16 and Prp43 cooperate to proofread 5' splice site cleavage during pre-mRNA splicing. Mol Cell 2010; 39:385-95. [PMID: 20705241 DOI: 10.1016/j.molcel.2010.07.014] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 03/31/2010] [Accepted: 06/03/2010] [Indexed: 12/24/2022]
Abstract
To investigate the mechanisms underlying accurate pre-mRNA splicing, we developed an in vitro assay sensitive to proofreading of 5' splice site cleavage. We inactivated spliceosomes by disrupting a metal-ligand interaction at the catalytic center and discovered that, when the DEAH box ATPase Prp16 was disabled, these spliceosomes catalyzed 5' splice site cleavage but at a reduced rate. Although Prp16 does not promote splicing of a genuine substrate until after 5' splice site cleavage, we found that Prp16 can associate with spliceosomes before 5' splice site cleavage, consistent with a role for Prp16 in proofreading 5' splice site cleavage. We established that Prp16-mediated rejection is reversible, necessitating a downstream discard pathway that we found requires the DEAH box ATPase Prp43, a spliceosome disassembly factor. These data indicate that spliceosomes distinguish slow substrates and that the mechanisms for establishing the fidelity of 5' splice site cleavage and exon ligation share a common ATP-dependent framework.
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Affiliation(s)
- Prakash Koodathingal
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
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43
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Fahey ME, Moore TF, Higgins DG. Overlapping antisense transcription in the human genome. Comp Funct Genomics 2010; 3:244-53. [PMID: 18628857 PMCID: PMC2447278 DOI: 10.1002/cfg.173] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Accepted: 04/11/2002] [Indexed: 11/23/2022] Open
Abstract
Accumulating evidence indicates an important role for non-coding RNA molecules in
eukaryotic cell regulation. A small number of coding and non-coding overlapping antisense
transcripts (OATs) in eukaryotes have been reported, some of which regulate expression of
the corresponding sense transcript. The prevalence of this phenomenon is unknown, but
there may be an enrichment of such transcripts at imprinted gene loci. Taking a bioinformatics
approach, we systematically searched a human mRNA database (RefSeq) for complementary
regions that might facilitate pairing with other transcripts. We report 56 pairs
of overlapping transcripts, in which each member of the pair is transcribed from the same
locus. This allows us to make an estimate of 1000 for the minimum number of such
transcript pairs in the entire human genome. This is a surprisingly large number of
overlapping gene pairs and, clearly, some of the overlaps may not be functionally
significant. Nonetheless, this may indicate an important general role for overlapping
antisense control in gene regulation. EST databases were also investigated in order to
address the prevalence of cases of imprinted genes with associated non-coding overlapping,
antisense transcripts. However, EST databases were found to be completely inappropriate
for this purpose.
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Affiliation(s)
- M E Fahey
- Department of Biochemistry, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland
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Abstract
Spliceosomal snRNAs are extensively 2'-O-methylated and pseudouridylated. The modified nucleotides are relatively highly conserved across species, and are often clustered in regions of functional importance in pre-mRNA splicing. Over the past decade, the study of the mechanisms and functions of spliceosomal snRNA modifications has intensified. Two independent mechanisms behind these modifications, RNA-independent (protein-only) and RNA-dependent (RNA-guided), have been discovered. The role of spliceosomal snRNA modifications in snRNP biogenesis and spliceosome assembly has also been verified.
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Affiliation(s)
- John Karijolich
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, USA
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Abstract
Accuracy in the flow of genetic information from DNA to protein, or gene expression, is essential to the viability of an organisms. Pre-mRNA splicing and protein translation are two major steps in eukaryotic gene expression that necessitate the production of accurate gene products. Both processes occur in large complexes, consisting of both proteins and noncoding RNAs. Interestingly, the RNA components contain a large number of posttranscriptional modifications, including 2'-O-methylation and pseudouridylation, which are functionally important. In this chapter, we highlight the functional aspects of the modifications of spliceosomal snRNA and rRNA and provide a framework for understanding how posttranscriptional modifications are capable of influencing gene expression.
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Congenital erythropoietic porphyria: a novel uroporphyrinogen III synthase branchpoint mutation reveals underlying wild-type alternatively spliced transcripts. Blood 2009; 115:1062-9. [PMID: 19965637 DOI: 10.1182/blood-2009-04-218016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Splicing mutations account for approximately 10% of lesions causing genetic diseases, but few branchpoint sequence (BPS) lesions have been reported. In 3 families with autosomal recessive congenital erythropoietic porphyria (CEP) resulting from uroporphyrinogen III synthase (URO-synthase) deficiency, sequencing the promoter, all 10 exons and the intron/exon boundaries did not detect a mutation. Northern analyses of lymphoblast mRNAs from 2 patients and reverse-transcribed polymerase chain reaction (RT-PCR) of lymphoblast mRNAs from all 3 patients revealed multiple longer transcripts involving intron 9 and low levels of wild-type message. Sequencing intron 9 RT-PCR products and genomic DNA in each case revealed homozygosity for a novel BPS mutation (c.661-31T-->G) and alternatively spliced transcripts containing 81, 246, 358, and 523 nucleotides from intron 9. RT-PCR revealed aberrant transcripts in both wild-type and CEP lymphoblasts, whereas BPS mutation reduced the wild-type transcript and enzyme activity in CEP lymphoblasts to approximately 10% and 15% of normal, respectively. Although the +81-nucleotide alternative transcript was in-frame, it only contributed approximately 0.2% of the lymphoblast URO-synthase activity. Thus, the BPS mutation markedly reduced the wild-type transcript and enzyme activity, thereby causing the disease. This is the first BPS mutation in the last intron, presumably accounting for the observed 100% intron retention without exon skipping.
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Single-molecule analysis of protein-free U2-U6 snRNAs. Nat Struct Mol Biol 2009; 16:1154-9. [PMID: 19881500 PMCID: PMC2784090 DOI: 10.1038/nsmb.1672] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 08/17/2009] [Indexed: 02/06/2023]
Abstract
Spliceosomes catalyze the maturation of precursor mRNAs from yeast to humans. Their catalytic core comprises three small nuclear RNAs (U2, U5 and U6) involved in substrate positioning and catalysis. It has been postulated, but never shown experimentally, that the U2/U6 complex adopts at least two conformations that reflect different activation states. We have used single-molecule fluorescence to probe the structural dynamics of a protein-free RNA complex modeling U2/U6 from yeast and mutants of highly conserved regions. Our data show the presence of at least three distinct conformations in equilibrium. The minimal folding pathway consists of a two-step process with an obligatory intermediate. The first step is strongly magnesium dependent and we provide evidence suggesting the second corresponds to the formation of the genetically conserved helix IB. Site-specific mutations in the highly conserved AGC triad and the U80 base in U6 suggest that the observed conformational dynamics correlate with residues that play an important role in splicing.
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Rios AC, Tor Y. Model systems: how chemical biologists study RNA. Curr Opin Chem Biol 2009; 13:660-8. [PMID: 19879179 DOI: 10.1016/j.cbpa.2009.09.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 09/14/2009] [Accepted: 09/25/2009] [Indexed: 11/30/2022]
Abstract
Ribonucleic acids are structurally and functionally sophisticated biomolecules and the use of models, frequently truncated or modified sequences representing functional domains of the natural systems, is essential to their exploration. Functional noncoding RNAs such as miRNAs, riboswitches, and, in particular, ribozymes, have changed the view of RNA's role in biology and its catalytic potential. The well-known truncated hammerhead model has recently been refined and new data provide a clearer molecular picture of the elements responsible for its catalytic power. A model for the spliceosome, a massive and highly intricate ribonucleoprotein, is also emerging, although its true utility is yet to be cemented. Such catalytic model systems could also serve as 'chemo-paleontological' tools, further refining the RNA world hypothesis and its relevance to the origin and evolution of life.
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Affiliation(s)
- Andro C Rios
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0358, USA
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49
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Zhao R, Rueda D. RNA folding dynamics by single-molecule fluorescence resonance energy transfer. Methods 2009; 49:112-7. [DOI: 10.1016/j.ymeth.2009.04.017] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 04/17/2009] [Accepted: 04/23/2009] [Indexed: 01/05/2023] Open
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50
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Hostetter AA, Chapman EG, DeRose VJ. Rapid cross-linking of an RNA internal loop by the anticancer drug cisplatin. J Am Chem Soc 2009; 131:9250-7. [PMID: 19566097 DOI: 10.1021/ja809637e] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Cisplatin is the most prominent member of a series of platinum(II) antitumor drugs that demonstrate activity based on binding to adjacent purines on genomic DNA. The interactions between cisplatin and alternate biomolecules, including chemically similar RNA, are less understood than are those for DNA. In order to investigate potential implications of platinum(II) drug binding to a structurally complex RNA, we have characterized the reaction between cisplatin and the internal loop of a 41-nucleotide subdomain derived from the U2:U6 spliceosomal RNAs. This "BBD" RNA subdomain consists of a hairpin structure containing a purine-rich asymmetric internal loop. Aquated cisplatin is found to cross-link G nucleobases on opposing sides of the internal loop, forming an intramolecular internal loop cross-link in BBD and an analogous intermolecular cross-link in a two-piece construct containing the same internal loop sequence. The two opposing guanine residues involved in the cross-link were identified via limited alkaline hydrolysis. The kinetics of aquated cisplatin binding to the BBD RNA, a related RNA hairpin, and its DNA hairpin analogue were investigated in an ionic background of 0.1 M NaNO(3) and 1 mM Mg(NO(3))(2). Both BBD and the RNA hairpin react 5-6-fold faster than the DNA hairpin, with calculated second-order rate constants of 2.0(2), 1.7(3), and 0.33(3) M(-1) s(-1), respectively, at 37 degrees C, pH 7.8. MALDI-MS data corroborate the biochemical studies and support a model in which kinetically preferred platinum binding sites compete with less reactive sites in these oligonucleotides. Taken together, these data indicate that cisplatin treatment has potential to create internal loop and other unusual cross-links in structurally complex RNAs, on a time scale that is relevant for RNA-dependent biological processes.
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