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He Y, Andersen GR, Nielsen KH. The function and architecture of DEAH/RHA helicases. Biomol Concepts 2015; 2:315-26. [PMID: 25962039 DOI: 10.1515/bmc.2011.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 05/24/2011] [Indexed: 12/11/2022] Open
Abstract
Helicases are ubiquitous enzymes that participate in every aspect of nucleic acid metabolism. The DEAH/RHA family of helicases are involved in a variety of cellular processes including transcriptional and translational regulation, pre-mRNA splicing, pre-rRNA processing, mRNA export and decay, in addition to the innate immune response. Recently, the first crystal structures of a DEAH/RHA helicase unveiled the unique structural features of this helicase family. These structures furthermore illuminate the molecular mechanism of these proteins and provide a framework for analysis of their interaction with nucleic acids, regulatory proteins and large macromolecular complexes.
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Liu YC, Cheng SC. Functional roles of DExD/H-box RNA helicases in Pre-mRNA splicing. J Biomed Sci 2015; 22:54. [PMID: 26173448 PMCID: PMC4503299 DOI: 10.1186/s12929-015-0161-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 06/29/2015] [Indexed: 01/30/2023] Open
Abstract
Splicing of precursor mRNA takes place via two consecutive steps of transesterification catalyzed by a large ribonucleoprotein complex called the spliceosome. The spliceosome is assembled through ordered binding to the pre-mRNA of five small nuclear RNAs and numerous protein factors, and is disassembled after completion of the reaction to recycle all components. Throughout the splicing cycle, the spliceosome changes its structure, rearranging RNA-RNA, RNA-protein and protein-protein interactions, for positioning and repositioning of splice sites. DExD/H-box RNA helicases play important roles in mediating structural changes of the spliceosome by unwinding of RNA duplexes or disrupting RNA-protein interactions. DExD/H-box proteins are also implicated in the fidelity control of the splicing process at various steps. This review summarizes the functional roles of DExD/H-box proteins in pre-mRNA splicing according to studies conducted mostly in yeast and will discuss the concept of the complicated splicing reaction based on recent findings.
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Affiliation(s)
- Yen-Chi Liu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, 115, Republic of China.
| | - Soo-Chen Cheng
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, 115, Republic of China.
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Liang WW, Cheng SC. A novel mechanism for Prp5 function in prespliceosome formation and proofreading the branch site sequence. Genes Dev 2015; 29:81-93. [PMID: 25561497 PMCID: PMC4281567 DOI: 10.1101/gad.253708.114] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The DEAD-box RNA helicase Prp5 is required for the formation of the prespliceosome through an ATP-dependent function to remodel U2 snRNPs and an ATP-independent function of unknown mechanism. Liang and Cheng show that Prp5 binds to the spliceosome in association with U2 by interacting with the branchpoint-interacting stem–loop and is released upon base-pairing of U2 with the branch site to allow the recruitment of the tri-snRNP. The DEAD-box RNA helicase Prp5 is required for the formation of the prespliceosome through an ATP-dependent function to remodel U2 small nuclear ribonucleoprotein particles (snRNPs) and an ATP-independent function of unknown mechanism. Prp5 has also been implicated in proofreading the branch site sequence, but the molecular mechanism has not been well characterized. Using actin precursor mRNA (pre-mRNA) carrying branch site mutations, we identified a Prp5-containing prespliceosome with Prp5 directly bound to U2 small nuclear RNA (snRNA). Prp5 is in contact with U2 in regions on and near the branchpoint-interacting stem–loop (BSL), suggesting that Prp5 may function in stabilizing the BSL. Regardless of its ATPase activity, Prp5 mutants that suppress branch site mutations associate with the spliceosome less tightly and allow more tri-snRNP binding for the reaction to proceed. Our results suggest a novel mechanism for how Prp5 functions in prespliceosome formation and proofreading of the branch site sequence. Prp5 binds to the spliceosome in association with U2 by interacting with the BSL and is released upon the base-pairing of U2 with the branch site to allow the recruitment of the tri-snRNP. Mutations impairing U2–branch site base-pairing retard Prp5 release and impede tri-snRNP association. Prp5 mutations that destabilize the Prp5–U2 interaction suppress branch site mutations by allowing progression of the pathway.
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Affiliation(s)
- Wen-Wei Liang
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan; Institute of Microbiology and Immunology, National Yang-Ming University, Taipei 112, Taiwan
| | - Soo-Chen Cheng
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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Tsugeki R, Tanaka-Sato N, Maruyama N, Terada S, Kojima M, Sakakibara H, Okada K. CLUMSY VEIN, the Arabidopsis DEAH-box Prp16 ortholog, is required for auxin-mediated development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:183-97. [PMID: 25384462 DOI: 10.1111/tpj.12721] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 10/29/2014] [Accepted: 10/31/2014] [Indexed: 05/25/2023]
Abstract
Pre-messenger RNA (pre-mRNA) splicing is essential in eukaryotic cells. In animals and yeasts, the DEAH-box RNA-dependent ATPase Prp16 mediates conformational change of the spliceosome, thereby facilitating pre-mRNA splicing. In yeasts, Prp16 also plays an important role in splicing fidelity. Conversely, PRP16 orthologs in Chlamydomonas reinhardtii and nematode do not have an important role in general pre-mRNA splicing, but are required for gene silencing and sex determination, respectively. Functions of PRP16 orthologs in higher plants have not been described until now. Here we show that the CLUMSY VEIN (CUV) gene encoding the unique Prp16 ortholog in Arabidopsis thaliana facilitates auxin-mediated development including male-gametophyte transmission, apical-basal patterning of embryonic and gynoecium development, stamen development, phyllotactic flower positioning, and vascular development. cuv-1 mutation differentially affects splicing and expression of genes involved in auxin biosynthesis, polar auxin transport, auxin perception and auxin signaling. The cuv-1 mutation does not have an equal influence on pre-mRNA substrates. We propose that Arabidopsis PRP16/CUV differentially facilitates expression of genes, which include genes involved in auxin biosynthesis, transport, perception and signaling, thereby collectively influencing auxin-mediated development.
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Affiliation(s)
- Ryuji Tsugeki
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
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Tsugeki R, Terada S. The Arabidopsis ortholog of the DEAH-box ATPase Prp16 influences auxin-mediated development. PLANT SIGNALING & BEHAVIOR 2015; 10:e1074369. [PMID: 26237376 PMCID: PMC4883861 DOI: 10.1080/15592324.2015.1074369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In animals and yeasts, the DEAH-box RNA-dependent ATPase Prp16 facilitates pre-mRNA splicing. However, in Chlamydomonas reinhardtii and Caenorhabditis elegans, Prp16 orthologs are not important for general pre-mRNA splicing, but are required for gene silencing and sex determination, respectively. The CLUMSY VEIN (CUV) gene, which encodes a unique Prp16 ortholog in Arabidopsis thaliana, influences auxin-mediated development. A loss-of-function cuv-1 mutation tells us that CUV does not facilitate splicing of pre-mRNA substrates indiscriminately, but differentially effects splicing and expression of genes. Here we show that CUV influences root-meristem maintenance and planar polarity of root-hair positioning, both of which are processes regulated by auxin. We propose that Arabidopsis PRP16/CUV differentially facilitates the expression of genes, including genes involved in auxin biosynthesis, transport, perception and signaling, and that in this way it influences auxin-mediated development.
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Affiliation(s)
- Ryuji Tsugeki
- Department of Botany; Graduate School of Science; Kyoto University; Sakyo-ku, Kyoto, Japan
- Correspondence to: Ryuji Tsugeki;
| | - Shiho Terada
- Department of Botany; Graduate School of Science; Kyoto University; Sakyo-ku, Kyoto, Japan
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56
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Chen HC, Chang KJ, Su YL, Huang YH, Cheng SC. Structural requirement of Ntc77 for spliceosome activation and first catalytic step. Nucleic Acids Res 2014; 42:12261-71. [PMID: 25294830 PMCID: PMC4231770 DOI: 10.1093/nar/gku914] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The Prp19-associated complex is required for spliceosome activation by stabilizing the binding of U5 and U6 on the spliceosome after the release of U4. The complex comprises at least eight proteins, among which Ntc90 and Ntc77 contain multiple tetratricopeptide repeat (TPR) elements. We have previously shown that Ntc90 is not involved in spliceosome activation, but is required for the recruitment of essential first-step factor Yju2 to the spliceosome. We demonstrate here that Ntc77 has dual functions in both spliceosome activation and the first catalytic step in recruiting Yju2. We have identified an amino-terminal region of Ntc77, which encompasses the N-terminal domain and the first three TPR motifs, dispensable for spliceosome activation but required for stable interaction of Yju2 with the spliceosome. Deletion of this region had no severe effect on the integrity of the NTC, binding of NTC to the spliceosome or spliceosome activation, but impaired splicing and exhibited a dominant-negative growth phenotype. Our data reveal functional roles of Ntc77 in both spliceosome activation and the first catalytic step, and distinct structural domains of Ntc77 required for these two steps.
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Affiliation(s)
- Hsin-Chou Chen
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China Institute of Microbiology and Immunology, National Yang-Ming University, Shih-Pai, Taipei, Taiwan 112, Republic of China
| | - Kae-Jiun Chang
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China
| | - Yu-Lun Su
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China
| | - Yu-Hsin Huang
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China
| | - Soo-Chen Cheng
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China
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Hogg R, de Almeida RA, Ruckshanthi JPD, O'Keefe RT. Remodeling of U2-U6 snRNA helix I during pre-mRNA splicing by Prp16 and the NineTeen Complex protein Cwc2. Nucleic Acids Res 2014; 42:8008-23. [PMID: 24848011 PMCID: PMC4081067 DOI: 10.1093/nar/gku431] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Removal of intron regions from pre-messenger RNA (pre-mRNA) requires spliceosome assembly with pre-mRNA, then subsequent spliceosome remodeling to allow activation for the two steps of intron removal. Spliceosome remodeling is carried out through the action of DExD/H-box ATPases that modulate RNA-RNA and protein-RNA interactions. The ATPase Prp16 remodels the spliceosome between the first and second steps of splicing by catalyzing release of first step factors Yju2 and Cwc25 as well as destabilizing U2-U6 snRNA helix I. How Prp16 destabilizes U2-U6 helix I is not clear. We show that the NineTeen Complex (NTC) protein Cwc2 displays genetic interactions with the U6 ACAGAGA, the U6 internal stem loop (ISL) and the U2-U6 helix I, all RNA elements that form the spliceosome active site. We find that one function of Cwc2 is to stabilize U2-U6 snRNA helix I during splicing. Cwc2 also functionally cooperates with the NTC protein Isy1/NTC30. Mutation in Cwc2 can suppress the cold sensitive phenotype of the prp16-302 mutation indicating a functional link between Cwc2 and Prp16. Specifically the prp16-302 mutation in Prp16 stabilizes Cwc2 interactions with U6 snRNA and destabilizes Cwc2 interactions with pre-mRNA, indicating antagonistic functions of Cwc2 and Prp16. We propose that Cwc2 is a target for Prp16-mediated spliceosome remodeling during pre-mRNA splicing.
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Affiliation(s)
- Rebecca Hogg
- Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT
| | | | | | - Raymond T O'Keefe
- Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT
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58
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Ajmal M, Khan MI, Neveling K, Khan YM, Azam M, Waheed NK, Hamel CP, Ben-Yosef T, De Baere E, Koenekoop RK, Collin RWJ, Qamar R, Cremers FPM. A missense mutation in the splicing factor gene DHX38 is associated with early-onset retinitis pigmentosa with macular coloboma. J Med Genet 2014; 51:444-8. [PMID: 24737827 DOI: 10.1136/jmedgenet-2014-102316] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND Retinitis pigmentosa (RP) is the most frequent inherited retinal disease, which shows a relatively high incidence of the autosomal-recessive form in Pakistan. METHODS Genome-wide high-density single-nucleotide polymorphism (SNP) microarrays were used to identify homozygous regions shared by affected individuals of one consanguineous family. DNA of three affected and two healthy siblings was used for SNP genotyping. Genotyping data were then analysed by Homozygosity Mapper. DNA of the proband was further analysed employing exome sequencing. RESULTS Homozygosity mapping revealed a single homozygous region on chromosome 16, shared by three affected individuals. Subsequent exome sequencing identified a novel missense mutation, c.995G>A; p.(Gly332Asp), in DHX38. This mutation was found to be present in a homozygous state in four affected individuals while two healthy siblings and the parents of the affected persons were heterozygous for this mutation. This variant thereby yields a logarithm of the odds (LOD) score of 3.25, which is highly suggestive for linkage. This variant was neither detected in 180 ethnically matched control individuals, nor in 7540 Africans or Caucasians and an in-house database that contained the exome data of 400 individuals. CONCLUSIONS By combining genome-wide homozygosity mapping and exome sequencing, a novel missense mutation was identified in the DHX38 gene that encodes the pre-mRNA splicing factor PRP16, in a Pakistani family with early-onset autosomal-recessive RP. The phenotype is different from those associated with other retinal pre-mRNA splicing factors and DHX38 is the first pre-mRNA splicing gene that is putatively associated with autosomal-recessive inherited RP.
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Affiliation(s)
- Muhammad Ajmal
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Muhammad Imran Khan
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Kornelia Neveling
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Yar Muhammad Khan
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Department of Chemistry, University of Science and Technology, Bannu, Pakistan
| | - Maleeha Azam
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Christian P Hamel
- Department of Genetics, Institut National de la Santé et de la Recherche Médicale U, Université Paris Descartes-Sorbonne Paris Cité, Montpellier, France
| | - Tamar Ben-Yosef
- Department of Genetics, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Elfride De Baere
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium
| | - Robert K Koenekoop
- Department of Paediatric Surgery, Human Genetics and Ophthalmology, McGill University Health Centre, Montreal, Canada
| | - Rob W J Collin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Raheel Qamar
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Al-Nafees Medical College & Hospital, Isra University, Islamabad, Pakistan
| | - Frans P M Cremers
- Faculty of Science, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands
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Abstract
Superfamily 2 helicase proteins are ubiquitous in RNA biology and have an extraordinarily broad set of functional roles. Central among these roles are the promotion of rearrangements of structured RNAs and the remodeling of ribonucleoprotein complexes (RNPs), allowing formation of native RNA structure or progression through a functional cycle of structures. Although all superfamily 2 helicases share a conserved helicase core, they are divided evolutionarily into several families, and it is principally proteins from three families, the DEAD-box, DEAH/RHA, and Ski2-like families, that function to manipulate structured RNAs and RNPs. Strikingly, there are emerging differences in the mechanisms of these proteins, both between families and within the largest family (DEAD-box), and these differences appear to be tuned to their RNA or RNP substrates and their specific roles. This review outlines basic mechanistic features of the three families and surveys individual proteins and the current understanding of their biological substrates and mechanisms.
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Affiliation(s)
- Inga Jarmoskaite
- Department of Molecular Biosciences and the Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712; ,
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60
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Wlodaver AM, Staley JP. The DExD/H-box ATPase Prp2p destabilizes and proofreads the catalytic RNA core of the spliceosome. RNA (NEW YORK, N.Y.) 2014; 20:282-94. [PMID: 24442613 PMCID: PMC3923124 DOI: 10.1261/rna.042598.113] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/30/2013] [Indexed: 05/25/2023]
Abstract
After undergoing massive RNA and protein rearrangements during assembly, the spliceosome undergoes a final, more subtle, ATP-dependent rearrangement that is essential for catalysis. This rearrangement requires the DEAH-box protein Prp2p, an RNA-dependent ATPase. Prp2p has been implicated in destabilizing interactions between the spliceosome and the protein complexes SF3 and RES, but a role for Prp2p in destabilizing RNA-RNA interactions has not been explored. Using directed molecular genetics in budding yeast, we have found that a cold-sensitive prp2 mutation is suppressed not only by mutations in SF3 and RES components but also by a range of mutations that disrupt the spliceosomal catalytic core element U2/U6 helix I, which is implicated in juxtaposing the 5' splice site and branch site and in positioning metal ions for catalysis within the context of a putative catalytic triplex; indeed, mutations in this putative catalytic triplex also suppressed a prp2 mutation. Remarkably, we also found that prp2 mutations rescue lethal mutations in U2/U6 helix I. These data provide evidence that RNA elements that comprise the catalytic core are already formed at the Prp2p stage and that Prp2p destabilizes these elements, directly or indirectly, both to proofread spliceosome activation and to promote reconfiguration of the spliceosome to a fully competent, catalytic conformation.
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61
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Biased Brownian ratcheting leads to pre-mRNA remodeling and capture prior to first-step splicing. Nat Struct Mol Biol 2013; 20:1450-7. [PMID: 24240612 PMCID: PMC3867266 DOI: 10.1038/nsmb.2704] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 09/27/2013] [Indexed: 12/31/2022]
Abstract
The spliceosome is a dynamic ribonucleoprotein (RNP) machine that catalyzes the removal of introns in the two transesterification steps of eukaryotic pre-mRNA splicing. Here we used single molecule fluorescence resonance energy transfer to monitor the distance of the 5′ splice site (5′SS) and branchpoint (BP) of pre-mRNA in affinity-purified spliceosomes stalled by a mutation in the DExD/H-box helicase Prp2 immediately prior to the first splicing step. Addition of recombinant Prp2 together with NTP and protein cofactor Spp2 rearranges the spliceosome-substrate complex to reversibly explore conformations with proximal 5′SS and BP that accommodate chemistry. Addition of Cwc25 then strongly biases this equilibrium towards the proximal conformation, promoting efficient first-step splicing. The spliceosome thus functions as a biased Brownian ratchet machine where a helicase unlocks thermal fluctuations subsequently rectified by a cofactor “pawl”, a principle possibly widespread among the many helicase-driven RNPs.
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62
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Christian H, Hofele RV, Urlaub H, Ficner R. Insights into the activation of the helicase Prp43 by biochemical studies and structural mass spectrometry. Nucleic Acids Res 2013; 42:1162-79. [PMID: 24165877 PMCID: PMC3902948 DOI: 10.1093/nar/gkt985] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Splicing of precursor messenger RNA is a hallmark of eukaryotic cells, which is carried out by the spliceosome, a multi-megadalton ribonucleoprotein machinery. The splicing reaction removes non-coding regions (introns) and ligates coding regions (exons). The spliceosome is a highly dynamic ribonucleoprotein complex that undergoes dramatic structural changes during its assembly, the catalysis and its disassembly. The transitions between the different steps during the splicing cycle are promoted by eight conserved DExD/H box ATPases. The DEAH-box protein Prp43 is responsible for the disassembly of the intron-lariat spliceosome and its helicase activity is activated by the G-patch protein Ntr1. Here, we investigate the activation of Prp43 by Ntr1 in the presence and absence of RNA substrate by functional assays and structural proteomics. Residues 51–110 of Ntr1 were identified to be the minimal fragment that induces full activation. We found protein–protein cross-links that indicate that Prp43 interacts with the G-patch motif of Ntr1 through its C-terminal domains. Additionally, we report on functionally important RNA binding residues in both proteins and propose a model for the activation of the helicase.
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Affiliation(s)
- Henning Christian
- Department for Molecular Structural Biology, Institute for Microbiology and Genetics, Georg-August-University Göttingen, D-37077 Göttingen, Germany, Bioanalytical Mass Spectrometry Group, Max-Planck-Institute of Biophysical Chemistry, D-37077 Göttingen, Germany and Bioanalytics, Department of Clinical Chemistry, University Medical Center Göttingen, D-37075 Göttingen, Germany
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63
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Ohrt T, Odenwälder P, Dannenberg J, Prior M, Warkocki Z, Schmitzová J, Karaduman R, Gregor I, Enderlein J, Fabrizio P, Lührmann R. Molecular dissection of step 2 catalysis of yeast pre-mRNA splicing investigated in a purified system. RNA (NEW YORK, N.Y.) 2013; 19:902-15. [PMID: 23685439 PMCID: PMC3683925 DOI: 10.1261/rna.039024.113] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 04/08/2013] [Indexed: 05/04/2023]
Abstract
Step 2 catalysis of pre-mRNA splicing entails the excision of the intron and ligation of the 5' and 3' exons. The tasks of the splicing factors Prp16, Slu7, Prp18, and Prp22 in the formation of the step 2 active site of the spliceosome and in exon ligation, and the timing of their recruitment, remain poorly understood. Using a purified yeast in vitro splicing system, we show that only the DEAH-box ATPase Prp16 is required for formation of a functional step 2 active site and for exon ligation. Efficient docking of the 3' splice site (3'SS) to the active site requires only Slu7/Prp18 but not Prp22. Spliceosome remodeling by Prp16 appears to be subtle as only the step 1 factor Cwc25 is dissociated prior to step 2 catalysis, with its release dependent on docking of the 3'SS to the active site and Prp16 action. We show by fluorescence cross-correlation spectroscopy that Slu7/Prp18 and Prp16 bind early to distinct, low-affinity binding sites on the step-1-activated B* spliceosome, which are subsequently converted into high-affinity sites. Our results shed new light on the factor requirements for step 2 catalysis and the dynamics of step 1 and 2 factors during the catalytic steps of splicing.
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Affiliation(s)
- Thomas Ohrt
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Peter Odenwälder
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Julia Dannenberg
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Mira Prior
- III. Physikalisches Institut (Biophysik), University of Göttingen, 37077 Göttingen, Germany
| | - Zbigniew Warkocki
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Jana Schmitzová
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Ramazan Karaduman
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Ingo Gregor
- III. Physikalisches Institut (Biophysik), University of Göttingen, 37077 Göttingen, Germany
| | - Jörg Enderlein
- III. Physikalisches Institut (Biophysik), University of Göttingen, 37077 Göttingen, Germany
| | - Patrizia Fabrizio
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Reinhard Lührmann
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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64
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Koodathingal P, Staley JP. Splicing fidelity: DEAD/H-box ATPases as molecular clocks. RNA Biol 2013; 10:1073-9. [PMID: 23770752 PMCID: PMC3849154 DOI: 10.4161/rna.25245] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 05/29/2013] [Accepted: 06/01/2013] [Indexed: 12/28/2022] Open
Abstract
The spliceosome discriminates against suboptimal substrates, both during assembly and catalysis, thereby enhancing specificity during pre-mRNA splicing. Central to such fidelity mechanisms are a conserved subset of the DEAD- and DEAH-box ATPases, which belong to a superfamily of proteins that mediate RNP rearrangements in almost all RNA-dependent processes in the cell. Through an investigation of the mechanisms contributing to the specificity of 5' splice site cleavage, two related reports, one from our lab and the other from the Cheng lab, have provided insights into fidelity mechanisms utilized by the spliceosome. In our work, we found evidence for a kinetic proofreading mechanism in splicing in which the DEAH-box ATPase Prp16 discriminates against substrates undergoing slow 5' splice site cleavage. Additionally, our study revealed that discriminated substrates are discarded through a general spliceosome disassembly pathway, mediated by another DEAH-box ATPase Prp43. In their work, Tseng et al. described the underlying molecular events through which Prp16 discriminates against a splicing substrate during 5' splice site cleavage. Here, we present a synthesis of these two studies and, additionally, provide the first biochemical evidence for discrimination of a suboptimal splicing substrate just prior to 5' splice site cleavage. Together, these findings support a general mechanism for a ubiquitous superfamily of ATPases in enhancing specificity during RNA-dependent processes in the cell.
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Affiliation(s)
- Prakash Koodathingal
- Department of Molecular Genetics and Cell Biology; The University of Chicago; Chicago, IL USA
| | - Jonathan P. Staley
- Department of Molecular Genetics and Cell Biology; The University of Chicago; Chicago, IL USA
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Tseng CK, Cheng SC. The spliceosome catalyzes debranching in competition with reverse of the first chemical reaction. RNA (NEW YORK, N.Y.) 2013; 19:971-81. [PMID: 23681507 PMCID: PMC3683931 DOI: 10.1261/rna.038638.113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Splicing of nuclear pre-mRNA occurs via two steps of the transesterification reaction, forming a lariat intermediate and product. The reactions are catalyzed by the spliceosome, a large ribonucleoprotein complex composed of five small nuclear RNAs and numerous protein factors. The spliceosome shares a similar catalytic core structure with that of fungal group II introns, which can self-splice using the same chemical mechanism. Like group II introns, both catalytic steps of pre-mRNA splicing can efficiently reverse on the affinity-purified spliceosome. The spliceosome also catalyzes a hydrolytic spliced-exon reopening reaction as observed in group II introns, indicating a strong link in their evolutionary relationship. We show here that, by arresting splicing after the first catalytic step, the purified spliceosome can catalyze debranching of lariat-intron-exon 2. The debranching reaction, although not observed in group II introns, has similar monovalent cation preferences as those for splicing catalysis of group II introns. The debranching reaction is in competition with the reverse Step 1 reaction influenced by the ionic environment and the structure of components binding near the catalytic center, suggesting that the catalytic center of the spliceosome can switch between different conformations to direct different chemical reactions.
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66
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Single-molecule colocalization FRET evidence that spliceosome activation precedes stable approach of 5' splice site and branch site. Proc Natl Acad Sci U S A 2013; 110:6783-8. [PMID: 23569281 DOI: 10.1073/pnas.1219305110] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Removal of introns from the precursors to messenger RNA (pre-mRNAs) requires close apposition of intron ends by the spliceosome, but when and how apposition occurs is unclear. We investigated the process by which intron ends are brought together using single-molecule fluorescence resonance energy transfer together with colocalization single-molecule spectroscopy, a combination of methods that can directly reveal how conformational transitions in macromolecular machines are coupled to specific assembly and disassembly events. The FRET measurements suggest that the 5' splice site and branch site remain physically separated throughout spliceosome assembly, and only approach one another after the spliceosome is activated for catalysis, at which time the pre-mRNA becomes highly dynamic. Separation of the sites of chemistry until very late in the splicing pathway may be crucial for preventing splicing at incorrect sites.
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67
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Kannan R, Hartnett S, Voelker RB, Berglund JA, Staley JP, Baumann P. Intronic sequence elements impede exon ligation and trigger a discard pathway that yields functional telomerase RNA in fission yeast. Genes Dev 2013; 27:627-38. [PMID: 23468430 DOI: 10.1101/gad.212738.112] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The fission yeast telomerase RNA (TER1) precursor harbors an intron immediately downstream from its mature 3' end. Unlike most introns, which are removed from precursor RNAs by the spliceosome in two sequential but tightly coupled transesterification reactions, TER1 only undergoes the first cleavage reaction during telomerase RNA maturation. The mechanism underlying spliceosome-mediated 3' end processing has remained unclear. We now demonstrate that a strong branch site (BS), a long distance to the 3' splice site (3' SS), and a weak polypyrimidine (Py) tract act synergistically to attenuate the transition from the first to the second step of splicing. The observation that a strong BS antagonizes the second step of splicing in the context of TER1 suggests that the BS-U2 snRNA interaction is disrupted after the first step and thus much earlier than previously thought. The slow transition from first to second step triggers the Prp22 DExD/H-box helicase-dependent rejection of the cleaved products and Prp43-dependent "discard" of the splicing intermediates. Our findings explain how the spliceosome can function in 3' end processing and provide new insights into the mechanism of splicing.
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Affiliation(s)
- Ram Kannan
- Howard Hughes Medical Institute, Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
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68
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Yang F, Wang XY, Zhang ZM, Pu J, Fan YJ, Zhou J, Query CC, Xu YZ. Splicing proofreading at 5' splice sites by ATPase Prp28p. Nucleic Acids Res 2013; 41:4660-70. [PMID: 23462954 PMCID: PMC3632134 DOI: 10.1093/nar/gkt149] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Fidelity and efficiency of pre-mRNA splicing are critical for generating functional mRNAs, but how such accuracy in 5′ splice site (SS) selection is attained is not fully clear. Through a series of yeast genetic screens, we isolated alleles of prp28 that improve splicing of suboptimal 5′SS substrates, demonstrating that WT-Prp28p proofreads, and consequently rejects, poor 5′SS. Prp28p is thought to facilitate the disruption of 5′SS–U1 snRNA pairing to allow for 5′SS–U6 snRNA pairing in the catalytic spliceosome; unexpectedly, 5′SS proofreading by Prp28p is dependent on competition with the stability of the 5′SS:U6 duplex, but not the 5′SS:U1 duplex. E404K, the strongest prp28 allele containing a mutation located in the linker region between adenosine triphosphatase (ATPase) subdomains, exhibited lower RNA-binding activity and enhanced splicing of suboptimal substrates before first-step catalysis, suggesting that decreased Prp28p activity allows longer time for suboptimal 5′SS substrates to pair with U6 snRNA and thereby reduces splicing fidelity. Residue E404 is critical for providing high splicing activity, demonstrated here in both yeast and Drosophila cells. Thus, the subdomain linker in Prp28p plays important roles both in splicing efficiency across species and in proofreading of 5′SS.
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Affiliation(s)
- Fei Yang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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69
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A weak spliceosome-binding domain of Yju2 functions in the first step and bypasses Prp16 in the second step of splicing. Mol Cell Biol 2013; 33:1746-55. [PMID: 23438600 DOI: 10.1128/mcb.00035-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Yju2 is an essential splicing factor required for the first catalytic step after the action of Prp2. We dissected the structure of Yju2 and found that the amino (Yju2-N) and carboxyl (Yju2-C) halves of the protein can be separated and reconstituted for Yju2 function both in vivo and in vitro. Yju2-N has a weak affinity for the spliceosome but functions in promoting the first reaction, with the second reaction being severely impeded. The association of Yju2-N with the spliceosome is stabilized by the presence of Yju2-C at both the precatalytic and postcatalytic stages. Strikingly, Yju2-N supported a low level of the second reaction even in the absence of Prp16. Prp16 is known to mediate destabilization of Yju2 and Cwc25 after the first reaction to allow progression of the second reaction. We propose that in the absence of the C domain, Yju2-N is not stably associated with the spliceosome after lariat formation, and thus bypasses the need for Prp16. We also showed, by UV cross-linking, that Yju2 directly contacts U2 snRNA primarily in the helix II region both pre- and postcatalytically and in the branch-binding region only at the precatalytic stage, suggesting a possible role for Yju2 in positioning the branch point during the first reaction.
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70
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Chang TH, Tung L, Yeh FL, Chen JH, Chang SL. Functions of the DExD/H-box proteins in nuclear pre-mRNA splicing. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:764-74. [PMID: 23454554 DOI: 10.1016/j.bbagrm.2013.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/05/2013] [Accepted: 02/13/2013] [Indexed: 01/09/2023]
Abstract
In eukaryotes, many genes are transcribed as precursor messenger RNAs (pre-mRNAs) that contain exons and introns, the latter of which must be removed and exons ligated to form the mature mRNAs. This process is called pre-mRNA splicing, which occurs in the nucleus. Although the chemistry of pre-mRNA splicing is identical to that of the self-splicing Group II introns, hundreds of proteins and five small nuclear RNAs (snRNAs), U1, U2, U4, U5, and U6, are essential for executing pre-mRNA splicing. Spliceosome, arguably the most complex cellular machine made up of all those proteins and snRNAs, is responsible for carrying out pre-mRNA splicing. In contrast to the transcription and the translation machineries, spliceosome is formed anew onto each pre-mRNA and undergoes a series of highly coordinated reconfigurations to form the catalytic center. This amazing process is orchestrated by a number of DExD/H-proteins that are the focus of this article, which aims to review the field in general and to project the exciting challenges and opportunities ahead. This article is part of a Special Issue entitled: The Biology of RNA helicases - Modulation for life.
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71
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Kim B, Kang S, Kim SJ. Genome-wide pathway analysis reveals different signaling pathways between secreted lactoferrin and intracellular delta-lactoferrin. PLoS One 2013; 8:e55338. [PMID: 23383159 PMCID: PMC3559342 DOI: 10.1371/journal.pone.0055338] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 12/21/2012] [Indexed: 11/27/2022] Open
Abstract
Human lactoferrin (LF) is a multifunctional protein involved in immunomodulation, cellular growth, and differentiation. In addition to its secreted form (sLF), an alternative form (ΔLF) lacking the signal sequence has been found to be downregulated in cancer. Although the signaling pathways mediated by LF have been studied in a few cell models, there have been no relevant systemic approaches. Therefore, this study was carried out to identify and compare signaling networks provoked by the two LF isoforms. For this, the two forms were overexpressed in HEK293 cells using the Flp-In T-Rex system, after which genome-wide expression analysis of 18,367 genes was conducted. Pathway analysis of the genes showing altered expression identified pathways which are responsible for cell survival and apoptosis. In addition, the pathways mediated by the two LF forms were within distantly related networks. GPCR, PI3K complex, and POU5F1, which are involved in receptor-mediated pathways, were centered in the sLF network, whereas RIF1, NOS3, and RNPS1, which are involved in intracellular signaling, were centered in the ΔLF network. These results suggest that structural differences between the LF isoforms, mainly glycosylation, determine the fate of LF signaling. Furthermore, these findings provide information relating to the role of ΔLF which is downregulated during carcinogenesis.
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Affiliation(s)
- Byungtak Kim
- Department of Life Science, Dongguk University-Seoul, Seoul, Korea
| | - Seongeun Kang
- Department of Life Science, Dongguk University-Seoul, Seoul, Korea
| | - Sun Jung Kim
- Department of Life Science, Dongguk University-Seoul, Seoul, Korea
- * E-mail:
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72
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Abstract
In eukaryotic cells, introns are spliced from pre-mRNAs by the spliceosome. Both the composition and the structure of the spliceosome are highly dynamic, and eight DExD/H RNA helicases play essential roles in controlling conformational rearrangements. There is evidence that the various helicases are functionally and physically connected with each other and with many other factors in the spliceosome. Understanding the dynamics of those interactions is essential to comprehend the mechanism and regulation of normal as well as of pathological splicing. This review focuses on recent advances in the characterization of the splicing helicases and their interactions, and highlights the deep integration of splicing helicases in global mRNP biogenesis pathways.
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Affiliation(s)
- Olivier Cordin
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
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73
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Link of NTR-mediated spliceosome disassembly with DEAH-box ATPases Prp2, Prp16, and Prp22. Mol Cell Biol 2012; 33:514-25. [PMID: 23166295 DOI: 10.1128/mcb.01093-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The DEAH-box ATPase Prp43 is required for disassembly of the spliceosome after the completion of splicing or after the discard of the spliceosome due to a splicing defect. Prp43 associates with Ntr1 and Ntr2 to form the NTR complex and is recruited to the spliceosome via the interaction of Ntr2 and U5 component Brr2. Ntr2 alone can bind to U5 and to the spliceosome. To understand how NTR might mediate the disassembly of spliceosome intermediates, we arrested the spliceosome at various stages of the assembly pathway and assessed its susceptibility to disassembly. We found that NTR could catalyze the disassembly of affinity-purified spliceosomes arrested specifically after the ATP-dependent action of DEAH-box ATPase Prp2, Prp16, or Prp22 but not at steps before the action of these ATPases or upon their binding to the spliceosome. These results link spliceosome disassembly to the functioning of splicing ATPases. Analysis of the binding of Ntr2 to each splicing complex has revealed that the presence of Prp16 and Slu7, which also interact with Brr2, has a negative impact on Ntr2 binding. Our study provides insights into the mechanism by which NTR can be recruited to the spliceosome to mediate the disassembly of spliceosome intermediates when the spliceosome pathway is retarded, while disassembly is prevented in normal reactions.
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74
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Abstract
RNA splicing is one of the fundamental processes in gene expression in eukaryotes. Splicing of pre-mRNA is catalysed by a large ribonucleoprotein complex called the spliceosome, which consists of five small nuclear RNAs and numerous protein factors. The spliceosome is a highly dynamic structure, assembled by sequential binding and release of the small nuclear RNAs and protein factors. DExD/H-box RNA helicases are required to mediate structural changes in the spliceosome at various steps in the assembly pathway and have also been implicated in the fidelity control of the splicing reaction. Other proteins also play key roles in mediating the progression of the spliceosome pathway. In this review, we discuss the functional roles of the protein factors involved in the spliceosome pathway primarily from studies in the yeast system.
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75
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The interaction of Prp2 with a defined region of the intron is required for the first splicing reaction. Mol Cell Biol 2012; 32:5056-66. [PMID: 23071087 DOI: 10.1128/mcb.01109-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In Saccharomyces cerevisiae, the 3' splice site is not required for the first catalytic reaction of splicing. We have previously reported that at least 24 nucleotides downstream of the branch point is required for the first reaction to take place, but the precatalytic spliceosome forms efficiently on the truncated pre-mRNA with only 5 nucleotides retained downstream of the branch point. The factors that mediate this length-dependent control of the first catalytic step are not known. We show here that Prp2 can be recruited to the spliceosome without interacting with pre-mRNA when the 3' tail is short. Prp2 interacts with the intron when the 3' tail is extended, which results in destabilization of Prp2 and, consequently, progression of the first reaction. An RNA segment at 23 to 33 nucleotides downstream of the branch point is necessary and sufficient for the ATP-dependent action of Prp2. We also show that Prp2 directly interacts with the carboxyl-terminal fragment of Brr2 by pulldown assays. We propose that Prp2 is recruited to the spliceosome via interaction with Brr2 and is spatially positioned to interact with this specific region of the pre-mRNA, which stimulates the ATPase activity of Prp2 to promote the progression of the first catalytic step.
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76
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Coltri PP, Oliveira CC. Cwc24p is a general Saccharomyces cerevisiae splicing factor required for the stable U2 snRNP binding to primary transcripts. PLoS One 2012; 7:e45678. [PMID: 23029180 PMCID: PMC3454408 DOI: 10.1371/journal.pone.0045678] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/23/2012] [Indexed: 12/31/2022] Open
Abstract
Splicing of primary transcripts is an essential process for the control of gene expression. Specific conserved sequences in premature transcripts are important to recruit the spliceosome machinery. The Saccharomyces cerevisiae catalytic spliceosome is composed of about 60 proteins and 5 snRNAs (U1, U2, U4/U6 and U5). Among these proteins, there are core components and regulatory factors, which might stabilize or facilitate splicing of specific substrates. Assembly of a catalytic complex depends on the dynamics of interactions between these proteins and RNAs. Cwc24p is an essential S. cerevisiae protein, originally identified as a component of the NTC complex, and later shown to affect splicing in vivo. In this work, we show that Cwc24p also affects splicing in vitro. We show that Cwc24p is important for the U2 snRNP binding to primary transcripts, co-migrates with spliceosomes, and that it interacts with Brr2p. Additionally, we show that Cwc24p is important for the stable binding of Prp19p to the spliceosome. We propose a model in which Cwc24p is required for stabilizing the U2 association with primary transcripts, and therefore, especially important for splicing of RNAs containing non-consensus branchpoint sequences.
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Affiliation(s)
- Patricia P. Coltri
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, Brazil
| | - Carla C. Oliveira
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, Brazil
- * E-mail:
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77
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Singh PK, Kanodia S, Dandin CJ, Vijayraghavan U, Malhotra P. Plasmodium falciparum Prp16 homologue and its role in splicing. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:1186-99. [PMID: 22982196 DOI: 10.1016/j.bbagrm.2012.08.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/29/2012] [Accepted: 08/30/2012] [Indexed: 01/25/2023]
Abstract
Large numbers of Plasmodium genes have been predicted to have introns. However, little information exists on the splicing mechanisms in this organism. Here, we describe the DExD/DExH-box containing Pre-mRNA processing proteins (Prps), PfPrp2p, PfPrp5p, PfPrp16p, PfPrp22p, PfPrp28p, PfPrp43p and PfBrr2p, present in the Plasmodium falciparum genome and characterized the role of one of these factors, PfPrp16p. It is a member of DEAH-box protein family with nine collinear sequence motifs, a characteristic of helicase proteins. Experiments with the recombinantly expressed and purified PfPrp16 helicase domain revealed binding to RNA, hydrolysis of ATP as well as catalytic helicase activities. Expression of helicase domain with the C-terminal helicase-associated domain (HA2) reduced these activities considerably, indicating that the helicase-associated domain may regulate the PfPrp16 function. Localization studies with the PfPrp16 GFP transgenic lines suggested a role of its N-terminal domain (1-80 amino acids) in nuclear targeting. Immunodepletion of PfPrp16p, from nuclear extracts of parasite cultures, blocked the second catalytic step of an in vitro constituted splicing reaction suggesting a role for PfPrp16p in splicing catalysis. Further we show by complementation assay in yeast that a chimeric yeast-Plasmodium Prp16 protein, not the full length PfPrp16, can rescue the yeast prp16 temperature-sensitive mutant. These results suggest that although the role of Prp16p in catalytic step II is highly conserved among Plasmodium, human and yeast, subtle differences exist with regards to its associated factors or its assembly with spliceosomes.
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Affiliation(s)
- Prashant Kumar Singh
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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78
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Semlow DR, Staley JP. Staying on message: ensuring fidelity in pre-mRNA splicing. Trends Biochem Sci 2012; 37:263-73. [PMID: 22564363 DOI: 10.1016/j.tibs.2012.04.001] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 02/23/2012] [Accepted: 04/03/2012] [Indexed: 12/28/2022]
Abstract
The faithful expression of genes requires that cellular machinery select substrates with high specificity at each step in gene expression. High specificity is particularly important at the stage of nuclear pre-mRNA splicing, during which the spliceosome selects splice sites and excises intervening introns. With low specificity, the usage of alternative sites would yield insertions, deletions and frame shifts in mRNA. Recently, biochemical, genetic and genome-wide approaches have significantly advanced our understanding of splicing fidelity. In particular, we have learned that DExD/H-box ATPases play a general role in rejecting and discarding suboptimal substrates and that these factors serve as a paradigm for proofreading NTPases in other systems. Recent advances have also defined fundamental questions for future investigations.
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Affiliation(s)
- Daniel R Semlow
- Graduate Program in Cell and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
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79
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Hegele A, Kamburov A, Grossmann A, Sourlis C, Wowro S, Weimann M, Will CL, Pena V, Lührmann R, Stelzl U. Dynamic protein-protein interaction wiring of the human spliceosome. Mol Cell 2012; 45:567-80. [PMID: 22365833 DOI: 10.1016/j.molcel.2011.12.034] [Citation(s) in RCA: 302] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/01/2011] [Accepted: 12/12/2011] [Indexed: 12/12/2022]
Abstract
More than 200 proteins copurify with spliceosomes, the compositionally dynamic RNPs catalyzing pre-mRNA splicing. To better understand protein - protein interactions governing splicing, we systematically investigated interactions between human spliceosomal proteins. A comprehensive Y2H interaction matrix screen generated a protein interaction map comprising 632 interactions between 196 proteins. Among these, 242 interactions were found between spliceosomal core proteins and largely validated by coimmunoprecipitation. To reveal dynamic changes in protein interactions, we integrated spliceosomal complex purification information with our interaction data and performed link clustering. These data, together with interaction competition experiments, suggest that during step 1 of splicing, hPRP8 interactions with SF3b proteins are replaced by hSLU7, positioning this second step factor close to the active site, and that the DEAH-box helicases hPRP2 and hPRP16 cooperate through ordered interactions with GPKOW. Our data provide extensive information about the spliceosomal protein interaction network and its dynamics.
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Affiliation(s)
- Anna Hegele
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics, 14195 Berlin, Germany
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80
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Cordin O, Hahn D, Beggs JD. Structure, function and regulation of spliceosomal RNA helicases. Curr Opin Cell Biol 2012; 24:431-8. [PMID: 22464735 DOI: 10.1016/j.ceb.2012.03.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/12/2012] [Accepted: 03/08/2012] [Indexed: 01/24/2023]
Abstract
Pre-mRNA splicing requires the activities of several ATPases from the DEAH-box, DEAD-box and Ski2-like helicase families to control conformational rearrangements within the spliceosome. Recent findings indicate that several spliceosomal helicases can act at multiple stages of the splicing reaction, and information on how those multiple actions are controlled are emerging. The recently solved crystal structure of the DEAH-box helicase Prp43 provides novel insights into the similarities and differences between the three helicase families. Here we discuss the potential family-specific mechanisms of spliceosomal RNA helicases and their regulation.
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Affiliation(s)
- Olivier Cordin
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh, EH9 3JR, UK
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81
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Horowitz DS. The mechanism of the second step of pre-mRNA splicing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:331-50. [PMID: 22012849 DOI: 10.1002/wrna.112] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The molecular mechanisms of the second step of pre-mRNA splicing in yeast and higher eukaryotes are reviewed. The important elements in the pre-mRNA, the participating proteins, and the proposed secondary structures and roles of the snRNAs are described. The sequence of events in the second step is presented, focusing on the actions of the proteins in setting up and facilitating the second reaction. Mechanisms for avoiding errors in splicing are discussed.
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Affiliation(s)
- David S Horowitz
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
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82
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Tuteja R. Helicases involved in splicing from malaria parasite Plasmodium falciparum. Parasitol Int 2011; 60:335-40. [PMID: 21996352 DOI: 10.1016/j.parint.2011.09.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 09/14/2011] [Accepted: 09/18/2011] [Indexed: 02/06/2023]
Abstract
An interesting element of eukaryotic genomes is the large quantity of non-coding intervening sequences commonly known as introns, which regularly interrupt functional genes and therefore must be removed prior to the use of genetic information by the cell. After splicing, the mature RNA is exported from the nucleus to the cytoplasm. Any error in the process of recognition and removal of introns, or splicing, would lead to change in genetic message and thus has potentially catastrophic consequences. Thus splicing is a highly complex essential step in eukaryotic gene expression. It takes place in spliceosome, which is a dynamic RNA-protein complex made of snRNPs and non-snRNP proteins. The splicing process consists of following sequential steps: spliceosome formation, the first transesterification and second transesterification reactions, release of the mature mRNA and recycling of the snRNPs. The spliceosomal components produce a complex network of RNA-RNA, RNA-protein and protein-protein interactions and spliceosome experience remodeling during each splicing cycle. Helicases are essentially required at almost each step for resolution of RNA-RNA and/or RNA-protein interactions. RNA helicases share a highly conserved helicase domain which includes the motif DExD/H in the single letter amino acid code. This article will focus on members of the DExD/H-box proteins involved specially in splicing in the malaria parasite Plasmodium falciparum.
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Affiliation(s)
- Renu Tuteja
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
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83
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Horowitz DS. The splice is right: guarantors of fidelity in pre-mRNA splicing. RNA (NEW YORK, N.Y.) 2011; 17:551-4. [PMID: 21357751 PMCID: PMC3062167 DOI: 10.1261/rna.2577511] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Two recent papers, one from the Staley laboratory (Koodathingal and colleagues) and the other from the Cheng laboratory (Tseng and colleagues), show that the RNA-dependent ATPase Prp16, which is required for the second step of splicing, acts to reject slowly splicing pre-mRNAs immediately before the first catalytic reaction in pre-mRNA splicing. The results answer long-investigated questions about the actions of Prp16 and provide a wealth of molecular details on the proofreading process in pre-mRNA splicing. The discussion here reviews and integrates the results of the two papers and describes the implications for proofreading in splicing.
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Affiliation(s)
- David S Horowitz
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
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