1
|
Xie J, Wang L, Lin RJ. Variations of intronic branchpoint motif: identification and functional implications in splicing and disease. Commun Biol 2023; 6:1142. [PMID: 37949953 PMCID: PMC10638238 DOI: 10.1038/s42003-023-05513-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 10/26/2023] [Indexed: 11/12/2023] Open
Abstract
The branchpoint (BP) motif is an essential intronic element for spliceosomal pre-mRNA splicing. In mammals, its sequence composition, distance to the downstream exon, and number of BPs per 3´ splice site are highly variable, unlike the GT/AG dinucleotides at the intron ends. These variations appear to provide evolutionary advantages for fostering alternative splicing, satisfying more diverse cellular contexts, and promoting resilience to genetic changes, thus contributing to an extra layer of complexity for gene regulation. Importantly, variants in the BP motif itself or in genes encoding BP-interacting factors cause human genetic diseases or cancers, highlighting the critical function of BP motif and the need to precisely identify functional BPs for faithful interpretation of their roles in splicing. In this perspective, we will succinctly summarize the major findings related to BP motif variations, discuss the relevant issues/challenges, and provide our insights.
Collapse
Affiliation(s)
- Jiuyong Xie
- Department of Physiology & Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
| | - Lili Wang
- Department of Systems Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, 91010, USA.
| | - Ren-Jang Lin
- Center for RNA Biology & Therapeutics, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA, 91010, USA.
| |
Collapse
|
2
|
Li LP, Jin YC, Ren D, Wang JJ, Fang L, Li X, Zhang X, Cui DW, Chen X, Liu XH. Deciphering the photolysis products and biological concerns of triclosan under UVC and UVA. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 258:114998. [PMID: 37167739 DOI: 10.1016/j.ecoenv.2023.114998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/04/2023] [Accepted: 05/08/2023] [Indexed: 05/13/2023]
Abstract
Triclosan (TCS) is omnipresent in the environment and has drawn increasing attention due to its potential adverse effects on human health. Direct photolysis of TCS readily occurs, especially in the surface layers of waters that receive abundant ultraviolet radiation during the daytime. However, biological concerns and the identification of toxic products during TCS photolysis have been explored limitedly. Therefore, in the present work, the structural characterization of the photolysis products by UVC and UVA were performed based on the mass spectra and fragmental ions. The results displayed that TCS was more readily eliminated by UVC than UVA, and the product species were completely different when TCS was degraded by UVC and UVA, respectively. Two products, m/z 235 and m/z 252, were produced via reductive dechlorination and nucleophilic substitution with UVC, while three dioxin-like isomer products were generated by dechlorination, cyclization and hydroxylation. Furthermore, the results of biological concerns suggested that the elimination of TCS did not represent the disappearance of biological risks. Specifically, more hazardous and photolysis products were formed during TCS photolysis with ultraviolets. For instance, the dioxin-like isomer products were highly microtoxic and genotoxic, and mildly antiestrogenic. The positive findings highlighted the biological concerns of TCS photolysis by ultraviolet radiation in the aquatic environment.
Collapse
Affiliation(s)
- Li-Ping Li
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China.
| | - Yan-Chao Jin
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou350007, China; Fujian Key Laboratory of Pollution Control & Resource Reuse, Fuzhou 350007, China
| | - Dong Ren
- College of Environmental Science and Engineering, China West Normal University, Nanchong 637009, China
| | - Jun-Jian Wang
- Guangdong Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China; State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Le Fang
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China
| | - Xia Li
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China
| | - Xin Zhang
- School of Environment, Beijing Normal University, Beijing 100875, China
| | - Ding-Wei Cui
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China
| | - Xi Chen
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China
| | - Xin-Hui Liu
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China; School of Environment, Beijing Normal University, Beijing 100875, China.
| |
Collapse
|
3
|
The Repertoire of RNA Modifications Orchestrates a Plethora of Cellular Responses. Int J Mol Sci 2023; 24:ijms24032387. [PMID: 36768716 PMCID: PMC9916637 DOI: 10.3390/ijms24032387] [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: 12/31/2022] [Revised: 01/21/2023] [Accepted: 01/23/2023] [Indexed: 01/27/2023] Open
Abstract
Although a plethora of DNA modifications have been extensively investigated in the last decade, recent breakthroughs in molecular biology, including high throughput sequencing techniques, have enabled the identification of post-transcriptional marks that decorate RNAs; hence, epitranscriptomics has arisen. This recent scientific field aims to decode the regulatory layer of the transcriptome and set the ground for the detection of modifications in ribose nucleotides. Until now, more than 170 RNA modifications have been reported in diverse types of RNA that contribute to various biological processes, such as RNA biogenesis, stability, and transcriptional and translational accuracy. However, dysfunctions in the RNA-modifying enzymes that regulate their dynamic level can lead to human diseases and cancer. The present review aims to highlight the epitranscriptomic landscape in human RNAs and match the catalytic proteins with the deposition or deletion of a specific mark. In the current review, the most abundant RNA modifications, such as N6-methyladenosine (m6A), N5-methylcytosine (m5C), pseudouridine (Ψ) and inosine (I), are thoroughly described, their functional and regulatory roles are discussed and their contributions to cellular homeostasis are stated. Ultimately, the involvement of the RNA modifications and their writers, erasers, and readers in human diseases and cancer is also discussed.
Collapse
|
4
|
Li LP, Jin YC, Fang L, Zhang C. Direct photolysis of diclofenac under simulated sunlight: Transformation pathway and biological concerns. CHEMOSPHERE 2022; 307:135775. [PMID: 35868525 DOI: 10.1016/j.chemosphere.2022.135775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 07/05/2022] [Accepted: 07/16/2022] [Indexed: 06/15/2023]
Abstract
Topical diclofenac gels are frequently applied on human skin and, consequently are exposed to sunlight during outdoor activities. The degradation of diclofenac (DCF) with sunlight exposure is known to occur but the detailed transformation characteristics and biological concerns have not been comprehensively investigated. In the present work, the transformation products during diclofenac photolysis were identified with the aid of ultra-performance liquid chromatography coupled with triple time-of-flight mass spectrometry (UPLC-TripleTOF). Biological concerns, including microtoxicity, genotoxicity, cytotoxicity and antiestrogenicity were examined with multiple in-vitro bioassays. Spearman correlation analysis was conducted to obtain further insight into the contributions of photolysis products to overall biological concerns. The results demonstrated that diclofenac was readily degraded under sunlight to form five main photolysis products via substitution, dechlorination, dehydroxylation, homodimerization and heterodimerization. Products P1, P2 and P5 were reported previously, while two dimer products (P3 and P4) are innovative products and have not been found in prior studies. A significant elevation in the microtoxicity was found during the photolysis of diclofenac, resulting mainly from the carbazole-containing photolysis products P2, P3, P4 and P5. Genotoxicity and antiestrogenicity declined along with the reduction of diclofenac, indicating that no photolysis products were genotoxic or anti-estrogenic. Modest cytotoxicity to the human skin epidermis cell line was observed and attributed to the formation of intermediate species. This outcome highlighted the biological concerns of diclofenac to human health when exposed to sunlight.
Collapse
Affiliation(s)
- Li-Ping Li
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, 519087, China.
| | - Yan-Chao Jin
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou, 350007, China; Fujian Key Laboratory of Pollution Control & Resource Reuse, Fuzhou, 350007, China
| | - Le Fang
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, 519087, China
| | - Cheng Zhang
- Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, 519087, China
| |
Collapse
|
5
|
Zhang Z, Rigo N, Dybkov O, Fourmann JB, Will CL, Kumar V, Urlaub H, Stark H, Lührmann R. Structural insights into how Prp5 proofreads the pre-mRNA branch site. Nature 2021; 596:296-300. [PMID: 34349264 PMCID: PMC8357632 DOI: 10.1038/s41586-021-03789-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 06/30/2021] [Indexed: 02/07/2023]
Abstract
During the splicing of introns from precursor messenger RNAs (pre-mRNAs), the U2 small nuclear ribonucleoprotein (snRNP) must undergo stable integration into the spliceosomal A complex-a poorly understood, multistep process that is facilitated by the DEAD-box helicase Prp5 (refs. 1-4). During this process, the U2 small nuclear RNA (snRNA) forms an RNA duplex with the pre-mRNA branch site (the U2-BS helix), which is proofread by Prp5 at this stage through an unclear mechanism5. Here, by deleting the branch-site adenosine (BS-A) or mutating the branch-site sequence of an actin pre-mRNA, we stall the assembly of spliceosomes in extracts from the yeast Saccharomyces cerevisiae directly before the A complex is formed. We then determine the three-dimensional structure of this newly identified assembly intermediate by cryo-electron microscopy. Our structure indicates that the U2-BS helix has formed in this pre-A complex, but is not yet clamped by the HEAT domain of the Hsh155 protein (Hsh155HEAT), which exhibits an open conformation. The structure further reveals a large-scale remodelling/repositioning of the U1 and U2 snRNPs during the formation of the A complex that is required to allow subsequent binding of the U4/U6.U5 tri-snRNP, but that this repositioning is blocked in the pre-A complex by the presence of Prp5. Our data suggest that binding of Hsh155HEAT to the bulged BS-A of the U2-BS helix triggers closure of Hsh155HEAT, which in turn destabilizes Prp5 binding. Thus, Prp5 proofreads the branch site indirectly, hindering spliceosome assembly if branch-site mutations prevent the remodelling of Hsh155HEAT. Our data provide structural insights into how a spliceosomal helicase enhances the fidelity of pre-mRNA splicing.
Collapse
Affiliation(s)
- Zhenwei Zhang
- Department of Structural Dynamics, MPI for Biophysical Chemistry, Göttingen, Germany
| | - Norbert Rigo
- Cellular Biochemistry, MPI for Biophysical Chemistry, Göttingen, Germany
| | - Olexandr Dybkov
- Cellular Biochemistry, MPI for Biophysical Chemistry, Göttingen, Germany
| | | | - Cindy L Will
- Cellular Biochemistry, MPI for Biophysical Chemistry, Göttingen, Germany
| | - Vinay Kumar
- Cellular Biochemistry, MPI for Biophysical Chemistry, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry, MPI for Biophysical Chemistry, Göttingen, Germany
- Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Holger Stark
- Department of Structural Dynamics, MPI for Biophysical Chemistry, Göttingen, Germany.
| | - Reinhard Lührmann
- Cellular Biochemistry, MPI for Biophysical Chemistry, Göttingen, Germany.
| |
Collapse
|
6
|
Baptista B, Riscado M, Queiroz J, Pichon C, Sousa F. Non-coding RNAs: Emerging from the discovery to therapeutic applications. Biochem Pharmacol 2021. [DOI: 10.1016/j.bcp.2021.114469 order by 22025--] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
|
7
|
Morais P, Adachi H, Yu YT. Spliceosomal snRNA Epitranscriptomics. Front Genet 2021; 12:652129. [PMID: 33737950 PMCID: PMC7960923 DOI: 10.3389/fgene.2021.652129] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 02/08/2021] [Indexed: 12/15/2022] Open
Abstract
Small nuclear RNAs (snRNAs) are critical components of the spliceosome that catalyze the splicing of pre-mRNA. snRNAs are each complexed with many proteins to form RNA-protein complexes, termed as small nuclear ribonucleoproteins (snRNPs), in the cell nucleus. snRNPs participate in pre-mRNA splicing by recognizing the critical sequence elements present in the introns, thereby forming active spliceosomes. The recognition is achieved primarily by base-pairing interactions (or nucleotide-nucleotide contact) between snRNAs and pre-mRNA. Notably, snRNAs are extensively modified with different RNA modifications, which confer unique properties to the RNAs. Here, we review the current knowledge of the mechanisms and functions of snRNA modifications and their biological relevance in the splicing process.
Collapse
Affiliation(s)
| | - Hironori Adachi
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, Rochester, NY, United States
| | - Yi-Tao Yu
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, Rochester, NY, United States
| |
Collapse
|
8
|
Baptista B, Riscado M, Queiroz JA, Pichon C, Sousa F. Non-coding RNAs: Emerging from the discovery to therapeutic applications. Biochem Pharmacol 2021; 189:114469. [PMID: 33577888 DOI: 10.1016/j.bcp.2021.114469] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/03/2021] [Accepted: 02/04/2021] [Indexed: 02/06/2023]
Abstract
The knowledge about non-coding RNAs (ncRNAs) is rapidly increasing with new data continuously emerging, regarding their diverse types, applications, and roles. Particular attention has been given to ncRNA with regulatory functions, which may have a critical role both in biological and pathological conditions. As a result of the diversity of ncRNAs and their ubiquitous involvement in several biologic processes, ncRNA started to be considered in the biomedical field, with immense potential to be exploited either as biomarkers or as therapeutic agents in certain pathologies. Indeed, ncRNA-based therapeutics have been proposed in many disorders and some even reached clinical trials. However, to prepare an RNA product suitable for pharmacological applications, certain criteria must be fulfilled, and it has to be guaranteed RNA purity, stability, and bioactivity. So, in this review, the different types of ncRNAs are identified and characterized, by describing their biogenesis, functions, and applications. A perspective on the main challenges and innovative approaches for the future and broad therapeutic application of RNA is also presented.
Collapse
Affiliation(s)
- B Baptista
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - M Riscado
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - J A Queiroz
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - C Pichon
- Centre de Biophysique Moléculaire (CBM), UPR 4301 CNRS & University of Orléans Orléans, France
| | - F Sousa
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal.
| |
Collapse
|
9
|
Li L. Toxicity evaluation and by-products identification of triclosan ozonation and chlorination. CHEMOSPHERE 2021; 263:128223. [PMID: 33297179 DOI: 10.1016/j.chemosphere.2020.128223] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 08/29/2020] [Accepted: 08/31/2020] [Indexed: 05/05/2023]
Abstract
Triclosan (TCS) has attracted increasing concern due to its ubiquitous occurrence in aquatic environments as well as its potential adverse effects on human health. This study investigated the toxicity and transformation characteristics of triclosan ozonation and chlorination. The results showed that two hydroxylated by-products were formed via nucleophilic substitution during ozonation, while three chlorinated compounds were generated via electrophilic substitution during chlorination. The toxicity results demonstrated that the parent compound, triclosan, exhibited mild genotoxicity and anti-estrogenic activity. The chlorination of triclosan resulted in a 30-fold increase in anti-estrogenic activity owing to the generation of toxic polychlorinated transformation by-products. In addition, the chlorination by-products were found to be genotoxic like the parent compound. Fortunately, in contrast to chlorination, ozonation could mitigate the genotoxicity and anti-estrogenic activity of triclosan-containing water.
Collapse
Affiliation(s)
- Liping Li
- State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China; Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan, PR China.
| |
Collapse
|
10
|
Borchardt EK, Martinez NM, Gilbert WV. Regulation and Function of RNA Pseudouridylation in Human Cells. Annu Rev Genet 2020; 54:309-336. [PMID: 32870730 DOI: 10.1146/annurev-genet-112618-043830] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent advances in pseudouridine detection reveal a complex pseudouridine landscape that includes messenger RNA and diverse classes of noncoding RNA in human cells. The known molecular functions of pseudouridine, which include stabilizing RNA conformations and destabilizing interactions with varied RNA-binding proteins, suggest that RNA pseudouridylation could have widespread effects on RNA metabolism and gene expression. Here, we emphasize how much remains to be learned about the RNA targets of human pseudouridine synthases, their basis for recognizing distinct RNA sequences, and the mechanisms responsible for regulated RNA pseudouridylation. We also examine the roles of noncoding RNA pseudouridylation in splicing and translation and point out the potential effects of mRNA pseudouridylation on protein production, including in the context of therapeutic mRNAs.
Collapse
Affiliation(s)
- Erin K Borchardt
- Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, Connecticut 06520, USA; , ,
| | - Nicole M Martinez
- Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, Connecticut 06520, USA; , ,
| | - Wendy V Gilbert
- Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, Connecticut 06520, USA; , ,
| |
Collapse
|
11
|
Westhof E. Pseudouridines or how to draw on weak energy differences. Biochem Biophys Res Commun 2020; 520:702-704. [PMID: 31761086 DOI: 10.1016/j.bbrc.2019.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 10/01/2019] [Indexed: 01/28/2023]
Abstract
In many RNA molecules, pseudouridines occur at conserved positions in functional sites. A great diversity of pseudouridine synthases guarantees the insertion of the modified base at precise locations. The accepted structural role of pseudouridines is a reduction of the RNA flexibility around the modification site. However, experiments rarely yield clear-cut evidence. The article "Dynamic stacking of an expected branch point adenosine in duplexes containing pseudouridine-modified or unmodified U2 snRNA sites" published in 2019 in Biochemical and Biophysical Research Communication by Kennedy et al. constitute a provocative case [1]. This example illustrates how a definite conformational state can be selected through small energy differences in a constrained environment.
Collapse
Affiliation(s)
- Eric Westhof
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15 rue René Descartes, 67084, Strasbourg, France.
| |
Collapse
|
12
|
van der Feltz C, Hoskins AA. Structural and functional modularity of the U2 snRNP in pre-mRNA splicing. Crit Rev Biochem Mol Biol 2019; 54:443-465. [PMID: 31744343 DOI: 10.1080/10409238.2019.1691497] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The U2 small nuclear ribonucleoprotein (snRNP) is an essential component of the spliceosome, the cellular machine responsible for removing introns from precursor mRNAs (pre-mRNAs) in all eukaryotes. U2 is an extraordinarily dynamic splicing factor and the most frequently mutated in cancers. Cryo-electron microscopy (cryo-EM) has transformed our structural and functional understanding of the role of U2 in splicing. In this review, we synthesize these and other data with respect to a view of U2 as an assembly of interconnected functional modules. These modules are organized by the U2 small nuclear RNA (snRNA) for roles in spliceosome assembly, intron substrate recognition, and protein scaffolding. We describe new discoveries regarding the structure of U2 components and how the snRNP undergoes numerous conformational and compositional changes during splicing. We specifically highlight large scale movements of U2 modules as the spliceosome creates and rearranges its active site. U2 serves as a compelling example for how cellular machines can exploit the modular organization and structural plasticity of an RNP.
Collapse
Affiliation(s)
| | - Aaron A Hoskins
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| |
Collapse
|
13
|
Structures of SF3b1 reveal a dynamic Achilles heel of spliceosome assembly: Implications for cancer-associated abnormalities and drug discovery. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194440. [PMID: 31707043 DOI: 10.1016/j.bbagrm.2019.194440] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 09/30/2019] [Indexed: 12/11/2022]
Abstract
The pre-mRNA splicing factor SF3b1 exhibits recurrent mutations among hematologic malignancies and cancers, and consequently is a major therapeutic target of clinically-advanced spliceosome inhibitors. In this review, we highlight and rigorously analyze emerging views of SF3b1 conformational transitions, including the human SF3b particle either in isolation or bound to spliceosome inhibitors, and human or yeast spliceosome assemblies. Among spliceosome states characterized to date, an SF3b1 α-helical superhelix significantly closes to surround a U2 small nuclear RNA duplex with the pre-mRNA branch point sequence. The SF3b1 torus is locally unwound at an active site adenosine, whereas protein cofactors appear to stabilize overall closure in the spliceosome. Network analyses demonstrates that the natural SF3b1 dynamics mimic its conformational change in the spliceosome, raising the possibility of conformational selection underpinning spliceosome assembly. These dynamic SF3b1 conformations have consequences for gatekeeping of spliceosome assembly and therapeutic targeting of its cancer-associated dysfunction.
Collapse
|