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Bauer M, Schöbel CM, Wickenhauser C, Seliger B, Jasinski-Bergner S. Deciphering the role of alternative splicing in neoplastic diseases for immune-oncological therapies. Front Immunol 2024; 15:1386993. [PMID: 38736877 PMCID: PMC11082354 DOI: 10.3389/fimmu.2024.1386993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/16/2024] [Indexed: 05/14/2024] Open
Abstract
Alternative splicing (AS) is an important molecular biological mechanism regulated by complex mechanisms involving a plethora of cis and trans-acting elements. Furthermore, AS is tissue specific and altered in various pathologies, including infectious, inflammatory, and neoplastic diseases. Recently developed immuno-oncological therapies include monoclonal antibodies (mAbs) and chimeric antigen receptor (CAR) T cells targeting, among others, immune checkpoint (ICP) molecules. Despite therapeutic successes have been demonstrated, only a limited number of patients showed long-term benefit from these therapies with tumor entity-related differential response rates were observed. Interestingly, splice variants of common immunotherapeutic targets generated by AS are able to completely escape and/or reduce the efficacy of mAb- and/or CAR-based tumor immunotherapies. Therefore, the analyses of splicing patterns of targeted molecules in tumor specimens prior to therapy might help correct stratification, thereby increasing therapy success by antibody panel selection and antibody dosages. In addition, the expression of certain splicing factors has been linked with the patients' outcome, thereby highlighting their putative prognostic potential. Outstanding questions are addressed to translate the findings into clinical application. This review article provides an overview of the role of AS in (tumor) diseases, its molecular mechanisms, clinical relevance, and therapy response.
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Affiliation(s)
- Marcus Bauer
- Institute of Pathology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Chiara-Maria Schöbel
- Institute for Translational Immunology, Brandenburg Medical School (MHB), Theodor Fontane, Brandenburg an der Havel, Germany
| | - Claudia Wickenhauser
- Institute of Pathology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Barbara Seliger
- Institute for Translational Immunology, Brandenburg Medical School (MHB), Theodor Fontane, Brandenburg an der Havel, Germany
- Department of Good Manufacturing Practice (GMP) Development & Advanced Therapy Medicinal Products (ATMP) Design, Fraunhofer Institute for Cell Therapy and Immunology (IZI), Leipzig, Germany
- Institute for Medical Immunology, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Simon Jasinski-Bergner
- Institute for Translational Immunology, Brandenburg Medical School (MHB), Theodor Fontane, Brandenburg an der Havel, Germany
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2
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Aberrant splicing caused by exonic single nucleotide variants positioned 2nd or 3rd to the last nucleotide in the COL4A5 gene. Clin Exp Nephrol 2023; 27:218-226. [PMID: 36371577 PMCID: PMC9950164 DOI: 10.1007/s10157-022-02294-x] [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: 07/27/2022] [Accepted: 10/27/2022] [Indexed: 11/13/2022]
Abstract
BACKGROUND AND OBJECTIVES The evident genotype-phenotype correlation shown by the X-linked Alport syndrome warrants the assessment of the impact of identified gene variants on aberrant splicing. We previously reported that single nucleotide variants (SNVs) in the last nucleotide of exons in COL4A5 cause aberrant splicing. It is known that the nucleotides located 2nd and 3rd to the last nucleotides of exons can also play an essential role in the first step of the splicing process. In this study, we aimed to investigate whether SNVs positioned 2nd or 3rd to the last nucleotide of exons in COL4A5 resulted in aberrant splicing. METHODS We selected eight candidate variants: six from the Human Gene Variant Database Professional and two from our cohort. We performed an in-vitro splicing assay and reverse transcription-polymerase chain reaction (RT-PCR) for messenger RNA obtained from patients, if available. RESULTS The candidate variants were initially classified into the following groups: three nonsense, two missense, and three synonymous variants. Splicing assays and RT-PCR for messenger RNA revealed that six of the eight variants caused aberrant splicing. Four variants, initially classified as non-truncating variants, were found to be truncating ones, which usually show relatively more severe phenotypes. CONCLUSION We revealed that exonic SNVs positioned 2nd or 3rd to the last nucleotide of exons in the COL4A5 were responsible for aberrant splicing. The results of our study suggest that attention should be paid when interpreting the pathogenicity of exonic SNVs near the 5' splice site.
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3
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Zeng Y, Fair BJ, Zeng H, Krishnamohan A, Hou Y, Hall JM, Ruthenburg AJ, Li YI, Staley JP. Profiling lariat intermediates reveals genetic determinants of early and late co-transcriptional splicing. Mol Cell 2022; 82:4681-4699.e8. [PMID: 36435176 PMCID: PMC10448999 DOI: 10.1016/j.molcel.2022.11.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 09/10/2022] [Accepted: 11/02/2022] [Indexed: 11/27/2022]
Abstract
Long introns with short exons in vertebrate genes are thought to require spliceosome assembly across exons (exon definition), rather than introns, thereby requiring transcription of an exon to splice an upstream intron. Here, we developed CoLa-seq (co-transcriptional lariat sequencing) to investigate the timing and determinants of co-transcriptional splicing genome wide. Unexpectedly, 90% of all introns, including long introns, can splice before transcription of a downstream exon, indicating that exon definition is not obligatory for most human introns. Still, splicing timing varies dramatically across introns, and various genetic elements determine this variation. Strong U2AF2 binding to the polypyrimidine tract predicts early splicing, explaining exon definition-independent splicing. Together, our findings question the essentiality of exon definition and reveal features beyond intron and exon length that are determinative for splicing timing.
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Affiliation(s)
- Yi Zeng
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Benjamin J Fair
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA
| | - Huilin Zeng
- 855 Jefferson Ave. Redwood City, CA 94063, USA
| | - Aiswarya Krishnamohan
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Yichen Hou
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Johnathon M Hall
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Alexander J Ruthenburg
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Yang I Li
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA; Department of Human Genetics, University of Chicago, Chicago, IL 60637, USA.
| | - Jonathan P Staley
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
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Abstract
Alternative splicing enables higher eukaryotes to expand mRNA diversity from a finite number of genes through highly combinatorial splice site selection mechanisms that are influenced by the sequence of competing splice sites, cis-regulatory elements binding trans-acting factors, the length of exons and introns harbouring alternative splice sites and RNA secondary structures at putative splice junctions. To test the hypothesis that the intron definition or exon definition modes of splice site recognition direct the selection of alternative splice patterns, we created a database of alternative splice site usage (ALTssDB). When alternative splice sites are embedded within short introns (intron definition), the 5' and 3' splice sites closest to each other across the intron preferentially pair, consistent with previous observations. However, when alternative splice sites are embedded within large flanking introns (exon definition), the 5' and 3' splice sites closest to each other across the exon are preferentially selected. Thus, alternative splicing decisions are influenced by the intron and exon definition modes of splice site recognition. The results demonstrate that the spliceosome pairs splice sites that are closest in proximity within the unit of initial splice site selection.
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Affiliation(s)
- Francisco Carranza
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Hossein Shenasa
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Klemens J Hertel
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
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5
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Hujová P, Souček P, Radová L, Kramárek M, Kováčová T, Freiberger T. Nucleotides in both donor and acceptor splice sites are responsible for choice in NAGNAG tandem splice sites. Cell Mol Life Sci 2021; 78:6979-6993. [PMID: 34596691 PMCID: PMC11072513 DOI: 10.1007/s00018-021-03943-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/08/2021] [Accepted: 09/15/2021] [Indexed: 12/31/2022]
Abstract
Among alternative splicing events in the human transcriptome, tandem NAGNAG acceptor splice sites represent an appreciable proportion. Both proximal and distal NAG can be used to produce two splicing isoforms differing by three nucleotides. In some cases, the upstream exon can be alternatively spliced as well, which further increases the number of possible transcripts. In this study, we showed that NAG choice in tandem splice site depends considerably not only on the concerned acceptor, but also on the upstream donor splice site sequence. Using an extensive set of experiments with systematically modified two-exonic minigene systems of AFAP1L2 or CSTD gene, we recognized the third and fifth intronic upstream donor splice site position and the tandem acceptor splice site region spanning from -10 to +2, including NAGNAG itself, as the main drivers. In addition, competition between different branch points and their composition were also shown to play a significant role in NAG choice. All these nucleotide effects appeared almost additive, which explained the high variability in proximal versus distal NAG usage.
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Affiliation(s)
- Pavla Hujová
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
| | - Přemysl Souček
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic.
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic.
| | - Lenka Radová
- Central European Institute of Technology, Masaryk University, 62500, Brno, Czech Republic
| | - Michal Kramárek
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
| | - Tatiana Kováčová
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
| | - Tomáš Freiberger
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
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Kovalak C, Donovan S, Bicknell AA, Metkar M, Moore MJ. Deep sequencing of pre-translational mRNPs reveals hidden flux through evolutionarily conserved alternative splicing nonsense-mediated decay pathways. Genome Biol 2021; 22:132. [PMID: 33941243 PMCID: PMC8091538 DOI: 10.1186/s13059-021-02309-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 03/02/2021] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Alternative splicing, which generates multiple mRNA isoforms from single genes, is crucial for the regulation of eukaryotic gene expression. The flux through competing splicing pathways cannot be determined by traditional RNA-Seq, however, because different mRNA isoforms can have widely differing decay rates. Indeed, some mRNA isoforms with extremely short half-lives, such as those subject to translation-dependent nonsense-mediated decay (AS-NMD), may be completely overlooked in even the most extensive RNA-Seq analyses. RESULTS RNA immunoprecipitation in tandem (RIPiT) of exon junction complex components allows for purification of post-splicing mRNA-protein particles (mRNPs) not yet subject to translation (pre-translational mRNPs) and, therefore, translation-dependent mRNA decay. Here we compare exon junction complex RIPiT-Seq to whole cell RNA-Seq data from HEK293 cells. Consistent with expectation, the flux through known AS-NMD pathways is substantially higher than that captured by RNA-Seq. Our RIPiT-Seq also definitively demonstrates that the splicing machinery itself has no ability to detect reading frame. We identify thousands of previously unannotated splicing events; while many can be attributed to splicing noise, others are evolutionarily conserved events that produce new AS-NMD isoforms likely involved in maintenance of protein homeostasis. Several of these occur in genes whose overexpression has been linked to poor cancer prognosis. CONCLUSIONS Deep sequencing of RNAs in post-splicing, pre-translational mRNPs provides a means to identify and quantify splicing events without the confounding influence of differential mRNA decay. For many known AS-NMD targets, the nonsense-mediated decay-linked alternative splicing pathway predominates. Exon junction complex RIPiT-Seq also revealed numerous conserved but previously unannotated AS-NMD events.
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Affiliation(s)
- Carrie Kovalak
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, 01605, USA
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605, USA
| | - Scott Donovan
- Present Address: Moderna, 200 Technology Square, Cambridge, MA, 02139, USA
| | - Alicia A Bicknell
- Present Address: Moderna, 200 Technology Square, Cambridge, MA, 02139, USA
| | - Mihir Metkar
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, 01605, USA
- Present Address: Moderna, 200 Technology Square, Cambridge, MA, 02139, USA
| | - Melissa J Moore
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, 01605, USA.
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605, USA.
- Present Address: Moderna, 200 Technology Square, Cambridge, MA, 02139, USA.
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An extended catalogue of tandem alternative splice sites in human tissue transcriptomes. PLoS Comput Biol 2021; 17:e1008329. [PMID: 33826604 PMCID: PMC8055015 DOI: 10.1371/journal.pcbi.1008329] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 04/19/2021] [Accepted: 03/22/2021] [Indexed: 12/18/2022] Open
Abstract
Tandem alternative splice sites (TASS) is a special class of alternative splicing events that are characterized by a close tandem arrangement of splice sites. Most TASS lack functional characterization and are believed to arise from splicing noise. Based on the RNA-seq data from the Genotype Tissue Expression project, we present an extended catalogue of TASS in healthy human tissues and analyze their tissue-specific expression. The expression of TASS is usually dominated by one major splice site (maSS), while the expression of minor splice sites (miSS) is at least an order of magnitude lower. Among 46k miSS with sufficient read support, 9k (20%) are significantly expressed above the expected noise level, and among them 2.5k are expressed tissue-specifically. We found significant correlations between tissue-specific expression of RNA-binding proteins (RBP), tissue-specific expression of miSS, and miSS response to RBP inactivation by shRNA. In combination with RBP profiling by eCLIP, this allowed prediction of novel cases of tissue-specific splicing regulation including a miSS in QKI mRNA that is likely regulated by PTBP1. The analysis of human primary cell transcriptomes suggested that both tissue-specific and cell-type-specific factors contribute to the regulation of miSS expression. More than 20% of tissue-specific miSS affect structured protein regions and may adjust protein-protein interactions or modify the stability of the protein core. The significantly expressed miSS evolve under the same selection pressure as maSS, while other miSS lack signatures of evolutionary selection and conservation. Using mixture models, we estimated that not more than 15% of maSS and not more than 54% of tissue-specific miSS are noisy, while the proportion of noisy splice sites among non-significantly expressed miSS is above 63%. Pre-mRNA splicing is an important step in the processing of the genomic information during gene expression. During splicing, introns are excised from a gene transcript, and the remaining exons are ligated. Our work concerns one its particular subtype, which involves the so-called tandem alternative splice sites, a group of closely located exon borders that are used alternatively. We analyzed RNA-seq measurements of gene expression provided by the Genotype-Tissue Expression (GTEx) project, the largest to-date collection of such measurements in healthy human tissues, and constructed a detailed catalogue of tandem alternative splice sites. Within this catalogue, we characterized patterns of tissue-specific expression, regulation, impact on protein structure, and evolutionary selection acting on tandem alternative splice sites. In a number of genes, we predicted regulatory mechanisms that could be responsible for choosing one of many tandem alternative splice sites. The results of this study provide an invaluable resource for molecular biologists studying alternative splicing.
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8
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Ultra-deep sequencing reveals pre-mRNA splicing as a sequence driven high-fidelity process. PLoS One 2019; 14:e0223132. [PMID: 31581208 PMCID: PMC6776343 DOI: 10.1371/journal.pone.0223132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/13/2019] [Indexed: 11/19/2022] Open
Abstract
Alternative splicing diversifies mRNA transcripts in human cells. While the spliceosome pairs exons with a high degree of accuracy, the rates of rare aberrant and non-canonical pre-mRNA splicing have not been evaluated at the nucleotide level to determine the quantity and identity of these events across splice junctions. Using ultra-deep sequencing the frequency of aberrant and non-canonical splicing events for three splice junctions flanking exon 7 of SMN1 were determined at single nucleotide resolution. After correction for background noise introduced by PCR amplification and sequencing steps, pre-mRNA splicing was shown to maintain a low overall rate of aberrant and non-canonically spliced events. Several previously unannotated splicing events across 3 exon|intron junctions in SMN1 were identified. Mutations within SMN exon 7 were shown to affect splicing fidelity by modulating RNA secondary structures, by altering the binding site of regulatory proteins and by changing the 5’ splice site strength. Mutations also create a truncated SMN1 exon 7 through the introduction of a de novo non-canonical 5’ splice site. The results from the ultra-deep sequencing approach highlight the impressive fidelity of pre-mRNA splicing and demonstrate that the immediate sequence context around splice sites is the main driving force behind non-canonical splice site pairing.
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9
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Ragusa D, Makarov EM, Britten O, Moralli D, Green CM, Tosi S. The RS4;11 cell line as a model for leukaemia with t(4;11)(q21;q23): Revised characterisation of cytogenetic features. Cancer Rep (Hoboken) 2019; 2:e1207. [PMID: 32721124 PMCID: PMC7941496 DOI: 10.1002/cnr2.1207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/03/2019] [Accepted: 06/19/2019] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Haematological malignancies harbouring rearrangements of the KMT2A gene represent a unique subtype of leukaemia, with biphenotypic clinical manifestations, a rapid and aggressive onset, and a generally poor prognosis. Chromosomal translocations involving KMT2A often cause the formation of oncogenic fusion genes, such as the most common translocation t(4;11)(q21;q23) producing the KMT2A-AFF1 chimera. AIM The aim of this study was to confirm and review the cytogenetic and molecular features of the KMT2A-rearranged RS4;11 cell line and put those in context with other reports of cell lines also harbouring a t(4;11) rearrangement. METHODS AND RESULTS The main chromosomal rearrangements t(4;11)(q21;q23) and i(7q), described when the cell line was first established, were confirmed by fluorescence in situ hybridisation (FISH) and 24-colour karyotyping by M-FISH. Additional cytogenetic abnormalities were investigated by further FISH experiments, including the presence of trisomy 18 as a clonal abnormality and the discovery of one chromosome 8 being an i(8q), which indicates a duplication of the oncogene MYC. A homozygous deletion of 9p21 containing the tumour-suppressor genes CDKN2A and CDKN2B was also revealed by FISH. The production of the fusion transcript KMT2A-AFF1 arising from the der(11)t(4;11) was confirmed by RT-PCR, but sequencing of the amplified fragment revealed the presence of multiple isoforms. Two transcript variants, resulting from alternative splicing, were identified differing in one glutamine residue in the translated protein. CONCLUSION As karyotype evolution is a common issue in cell lines, we highlight the need to monitor cell lines in order to re-confirm their characteristics over time. We also reviewed the literature to provide a comparison of key features of several cell lines harbouring a t(4;11). This would guide scientists in selecting the most suitable research model for this particular type of KMT2A-leukaemia.
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Affiliation(s)
- Denise Ragusa
- Division of Biosciences, College of Health and Life Sciences, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK
| | - Evgeny M Makarov
- Division of Biosciences, College of Health and Life Sciences, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK.,Genome Engineering and Maintenance Network, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK
| | - Oliver Britten
- Division of Biosciences, College of Health and Life Sciences, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK
| | - Daniela Moralli
- Chromosome Dynamics, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Catherine M Green
- Chromosome Dynamics, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Sabrina Tosi
- Division of Biosciences, College of Health and Life Sciences, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK.,Genome Engineering and Maintenance Network, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK
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Ling Z, Brockmöller T, Baldwin IT, Xu S. Evolution of Alternative Splicing in Eudicots. FRONTIERS IN PLANT SCIENCE 2019; 10:707. [PMID: 31244865 PMCID: PMC6581728 DOI: 10.3389/fpls.2019.00707] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 05/13/2019] [Indexed: 05/30/2023]
Abstract
Alternative pre-mRNA splicing (AS) is prevalent in plants and is involved in many interactions between plants and environmental stresses. However, the patterns and underlying mechanisms of AS evolution in plants remain unclear. By analyzing the transcriptomes of four eudicot species, we revealed that the divergence of AS is largely due to the gains and losses of AS events among orthologous genes. Furthermore, based on a subset of AS, in which AS can be directly associated with specific transcripts, we found that AS that generates transcripts containing premature termination codons (PTC), are likely more conserved than those that generate non-PTC containing transcripts. This suggests that AS coupled with nonsense-mediated decay (NMD) might play an important role in affecting mRNA levels post-transcriptionally. To understand the mechanisms underlying the divergence of AS, we analyzed the key determinants of AS using a machine learning approach. We found that the presence/absence of alternative splice site (SS) within the junction, the distance between the authentic SS and the nearest alternative SS, the size of exon-exon junctions were the major determinants for both alternative 5' donor site and 3' acceptor site among the studied species, suggesting a relatively conserved AS mechanism. The comparative analysis further demonstrated that variations of the identified AS determinants significantly contributed to the AS divergence among closely related species in both Solanaceae and Brassicaceae taxa. Together, these results provide detailed insights into the evolution of AS in plants.
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Affiliation(s)
- Zhihao Ling
- Max Planck Institute for Chemical Ecology, Jena, Germany
| | | | - Ian T. Baldwin
- Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Shuqing Xu
- Plant Adaptation-in-action Group, Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
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11
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Hujová P, Grodecká L, Souček P, Freiberger T. Impact of acceptor splice site NAGTAG motif on exon recognition. Mol Biol Rep 2019; 46:2877-2884. [PMID: 30840204 DOI: 10.1007/s11033-019-04734-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 02/28/2019] [Indexed: 12/15/2022]
Abstract
Pre-mRNA splicing is an essential step in gene expression, when introns are removed and exons joined by the complex of proteins called spliceosome. Correct splicing requires a precise exon/intron junction definition, which is determined by a consensual donor and acceptor splice site at the 5' and 3' end, respectively. An acceptor splice site (3'ss) consists of highly conserved AG nucleotides in positions E-2 and E-1. These nucleotides can appear in tandem, located 3 bp from each other. Then they are referred to as NAGNAG or tandem 3'ss, which can be alternatively spliced. NAG/TAG 3'ss motif abundance is extremely low and cannot be easily explained by just a nucleotide preference in this position. We tested artificial NAG/TAG motif's potential negative effect on exon recognition using a minigene assay. Introducing the NAG/TAG motif into seven different exons revealed no general negative effect on exon recognition. The only observed effect was the partial use of the newly formed distal 3'ss. We can conclude that this motif's extremely low preference in a natural 3'ss is not a consequence of the NAG/TAG motif's negative effect on exon recognition, but more likely the result of other RNA processing aspects, such as an alternative 3'ss choice, decreased 3'ss strength, or incorporating an amber stop codon.
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Affiliation(s)
- Pavla Hujová
- Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.,Department of Clinical Immunology and Allergology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Lucie Grodecká
- Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic
| | - Přemysl Souček
- Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.
| | - Tomáš Freiberger
- Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.,Department of Clinical Immunology and Allergology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
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12
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Vuillaumier-Barrot S, Schiff M, Mattioli F, Schaefer E, Dupont A, Dancourt J, Dupré T, Couvineau A, de Baulny HO, de Lonlay P, Seta N, Moore S, Chantret I. Wide clinical spectrum in ALG8-CDG: clues from molecular findings suggest an explanation for a milder phenotype in the first-described patient. Pediatr Res 2019; 85:384-389. [PMID: 30420707 DOI: 10.1038/s41390-018-0231-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/24/2018] [Accepted: 10/18/2018] [Indexed: 02/08/2023]
Abstract
BACKGROUND Congenital disorders of glycosylation (CDG) includes ALG8 deficiency, a protein N-glycosylation defect with a broad clinical spectrum. If most of the 15 previously reported patients present an early-onset multisystem severe disease and early death, three patients including the cas princeps, present long-term survival and less severe symptoms. METHODS In order to further characterize ALG8-CDG, two new ALG8 patients are described and mRNA analyses of the ALG8-CDG cas princeps were effected. RESULTS One new patient exhibited a hepato-intestinal and neurological phenotype with two novel variants (c.91A > C p.Thr31Pro; c.139dup p.Thr47Asnfs*12). The other new patient, homozygous for a known variant (c.845C > T p.Ala282Val), presented a neurological phenotype with epilepsy, intellectual disability and retinis pigmentosa. The cas princeps ALG8-CDG patient was reported to have two heterozygous frameshift variants predicted to be without activity. We now described a novel ALG8 transcript variant in this patient and the 3D model of the putative encoded protein reveals no major difference with that of the normal ALG8 protein. CONCLUSION The description of the two new ALG8 patients affirms that ALG8-CDG is a severe disease. In the cas princeps, as the originally described frameshift variants are degraded, the novel variant is promoted and could explain a milder phenotype.
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Affiliation(s)
| | - Manuel Schiff
- APHP, Robert Debré Hospital, Reference Center for Inborn Errors of Metabolism, UMR1141, PROTECT, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Francesca Mattioli
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, INSERM U964, CNRS UMR 7104, Université de Strasbourg, 67400, Illkirch-Graffenstaden, France
| | - Elise Schaefer
- Service de Génétique Médicale, CHU de Hautepierre, avenue Molière, Institut de Génétique Médicale d'Alsace, 67098, Strasbourg, France
| | - Audrey Dupont
- Intensive Care Unit, CHU Lenval, 57 avenue de la Californie, 06200, Nice, France
| | - Julia Dancourt
- INSERM, U1149, Centre de Recherche sur l'Inflammation (CRI) and Université Paris 7 Denis Diderot, BP 416, 75018, Paris, France
| | | | - Alain Couvineau
- INSERM, U1149, Centre de Recherche sur l'Inflammation (CRI) and Université Paris 7 Denis Diderot, BP 416, 75018, Paris, France
| | - Hélène Ogier de Baulny
- APHP, Robert Debré Hospital, Reference Center for Inborn Errors of Metabolism, UMR1141, PROTECT, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Pascale de Lonlay
- AP-HP, Necker-Enfants Malades Hospital, Reference Center for Inborn Errors of Metabolism, metabERN, G2M, IMAGINE Institute, University Paris Descartes-Sorbonne Paris Cité, Paris, France
| | | | - Stuart Moore
- INSERM, U1149, Centre de Recherche sur l'Inflammation (CRI) and Université Paris 7 Denis Diderot, BP 416, 75018, Paris, France
| | - Isabelle Chantret
- INSERM, U1149, Centre de Recherche sur l'Inflammation (CRI) and Université Paris 7 Denis Diderot, BP 416, 75018, Paris, France
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13
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Erkelenz S, Theiss S, Kaisers W, Ptok J, Walotka L, Müller L, Hillebrand F, Brillen AL, Sladek M, Schaal H. Ranking noncanonical 5' splice site usage by genome-wide RNA-seq analysis and splicing reporter assays. Genome Res 2018; 28:1826-1840. [PMID: 30355602 PMCID: PMC6280755 DOI: 10.1101/gr.235861.118] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 10/20/2018] [Indexed: 01/01/2023]
Abstract
Most human pathogenic mutations in 5' splice sites affect the canonical GT in positions +1 and +2, leading to noncanonical dinucleotides. On the other hand, noncanonical dinucleotides are observed under physiological conditions in ∼1% of all human 5'ss. It is therefore a challenging task to understand the pathogenic mutation mechanisms underlying the conditions under which noncanonical 5'ss are used. In this work, we systematically examined noncanonical 5' splice site selection, both experimentally using splicing competition reporters and by analyzing a large RNA-seq data set of 54 fibroblast samples from 27 subjects containing a total of 2.4 billion gapped reads covering 269,375 exon junctions. From both approaches, we consistently derived a noncanonical 5'ss usage ranking GC > TT > AT > GA > GG > CT. In our competition splicing reporter assay, noncanonical splicing was strictly dependent on the presence of upstream or downstream splicing regulatory elements (SREs), and changes in SREs could be compensated by variation of U1 snRNA complementarity in the competing 5'ss. In particular, we could confirm splicing at different positions (i.e., -1, +1, +5) of a splice site for all noncanonical dinucleotides "weaker" than GC. In our comprehensive RNA-seq data set analysis, noncanonical 5'ss were preferentially detected in weakly used exon junctions of highly expressed genes. Among high-confidence splice sites, they were 10-fold overrepresented in clusters with a neighboring, more frequently used 5'ss. Conversely, these more frequently used neighbors contained only the dinucleotides GT, GC, and TT, in accordance with the above ranking.
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Affiliation(s)
- Steffen Erkelenz
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Wolfgang Kaisers
- Center for Biological and Medical Research (BMFZ), Center of Bioinformatics and Biostatistics (CBiBs), Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Johannes Ptok
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Lara Walotka
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Lisa Müller
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Frank Hillebrand
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Anna-Lena Brillen
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Michael Sladek
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Heiner Schaal
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
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14
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Rauschendorf MA, Zimmer AD, Laut A, Demmer P, Rösler B, Happle R, Sartori S, Fischer J. Homozygous intronic MITF mutation causes severe Waardenburg syndrome type 2A. Pigment Cell Melanoma Res 2018; 32:85-91. [PMID: 30117279 DOI: 10.1111/pcmr.12733] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marc-Alexander Rauschendorf
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andreas D Zimmer
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Astrid Laut
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Philipp Demmer
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Bernd Rösler
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Rudolf Happle
- Department of Dermatology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Judith Fischer
- Institute of Human Genetics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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15
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Nguyen H, Das U, Wang B, Xie J. The matrices and constraints of GT/AG splice sites of more than 1000 species/lineages. Gene 2018; 660:92-101. [PMID: 29588184 DOI: 10.1016/j.gene.2018.03.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 03/08/2018] [Accepted: 03/12/2018] [Indexed: 12/11/2022]
Abstract
To provide a resource for the splice sites (SS) of different species, we calculated the matrices of nucleotide compositions of about 38 million splice sites from >1000 species/lineages. The matrices are enriched of aGGTAAGT (5'SS) or (Y)6N(C/t)AG(g/a)t (3'SS) overall; however, they are quite diverse among hundreds of species. The diverse matrices remain prominent even under sequence selection pressures, suggesting the existence of diverse constraints as well as U snRNAs and other spliceosomal factors and/or their interactions with the splice sites. Using an algorithm to measure and compare the splice site constraints across all species, we demonstrate their distinct differences quantitatively. As an example of the resource's application to answering specific questions, we confirm that high constraints of particular positions are significantly associated with transcriptome-wide, increased occurrences of alternative splicing when uncommon nucleotides are present. More interestingly, the abundance of alternative splicing in 16 species correlates with the average constraint index of splice sites in a bell curve. This resource will allow users to assess specific sequences/splice sites against the consensus of every Ensembl-annotated species, and to explore the evolutionary changes or relationship to alternative splicing and transcriptome diversity. Web-search or update features are also included.
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Affiliation(s)
- Hai Nguyen
- Department of Physiology & Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB R3E 0J9, Canada; University of Winnipeg, Winnipeg, MB R3B 2E9, Canada
| | - Urmi Das
- Department of Physiology & Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Benjamin Wang
- Department of Physiology & Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB R3E 0J9, Canada; University of Illinois Urbana-Champaign, IL, USA
| | - Jiuyong Xie
- Department of Physiology & Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.
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16
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The rare nonsense mutation in p53 triggers alternative splicing to produce a protein capable of inducing apoptosis. PLoS One 2017; 12:e0185126. [PMID: 28961258 PMCID: PMC5621691 DOI: 10.1371/journal.pone.0185126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 09/05/2017] [Indexed: 01/17/2023] Open
Abstract
P53 protein is more frequently mutated in human tumours compared with the other proteins. While the majority of the p53 mutations, especially within its DNA-binding domain, lead to the loss of the wild-type function, there are accumulating data demonstrating that the p53 mutants gain tumour promoting activities; the latter triggers a revitalised interest in functional analysis of the p53 mutants. A systematic screening for p53 mutations in surgical materials from patients with glioma revealed a 378C>G mutation that creates a stop codon at the position of amino acid residue 126. The mutation eliminates the recognition site for the restriction endonuclease Sca I that allowed us to carry out RFLP analysis of DNA extracted from the clinical samples and suggests that this mutation is more frequent than is documented in the p53 databases. Both the ECV-304 and EJ cell lines, that probably originate from the bladder carcinoma T24 cell line, were confirmed to contain the homozygous 378C>G mutation but were shown to produce the p53 protein of expected full-length size detected by Western blotting. We provide evidence that the 378C>G mutation generates an alternative 3’ splice site (ss) which is more often used instead of the authentic upstream 3’ ss, driving the production of mRNA encoding the protein with the single amino acid deletion (p53ΔY126). Using endogenous expression, we demonstrated that the p53ΔY126 protein is nearly as active as the wild type protein in inducing the p21/Waf1 expression and apoptosis.
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17
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Ramanouskaya TV, Grinev VV. The determinants of alternative RNA splicing in human cells. Mol Genet Genomics 2017; 292:1175-1195. [PMID: 28707092 DOI: 10.1007/s00438-017-1350-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 07/06/2017] [Indexed: 12/29/2022]
Abstract
Alternative splicing represents an important level of the regulation of gene function in eukaryotic organisms. It plays a critical role in virtually every biological process within an organism, including regulation of cell division and cell death, differentiation of tissues in the embryo and the adult organism, as well as in cellular response to diverse environmental factors. In turn, studies of the last decade have shown that alternative splicing itself is controlled by different mechanisms. Unfortunately, there is no clear understanding of how these diverse mechanisms, or determinants, regulate and constrain the set of alternative RNA species produced from any particular gene in every cell of the human body. Here, we provide a consolidated overview of alternative splicing determinants including RNA-protein interactions, epigenetic regulation via chromatin remodeling, coupling of transcription-to-alternative splicing, effect of secondary structures in pre-RNA, and function of the RNA quality control systems. We also extensively and critically discuss some mechanistic insights on coordinated inclusion/exclusion of exons during the formation of mature RNA molecules. We conclude that the final structure of RNA is pre-determined by a complex interplay between cis- and trans-acting factors. Altogether, currently available empirical data significantly expand our understanding of the functioning of the alternative splicing machinery of cells in normal and pathological conditions. On the other hand, there are still many blind spots that require further deep investigations.
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18
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Ajiro M, Zheng ZM. Vemurafenib-resistant BRAF selects alternative branch points different from its wild-type BRAF in intron 8 for RNA splicing. Cell Biosci 2015; 5:70. [PMID: 26697165 PMCID: PMC4687071 DOI: 10.1186/s13578-015-0061-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 12/14/2015] [Indexed: 12/19/2022] Open
Abstract
One mechanism of resistance of the melanoma-associated BRAF kinase to its small molecule inhibitor vemurafenib is by point mutations in its intron 8 resulting in exons 4–8 skipping. In this report, we carried out in vitro BRAF RNA splicing assays and lariat RT-PCR to map the intron 8 branch points in wild-type and BRAF mutants. We identify multiple branch points (BP) in intron 8 of both wild-type (wt) and vemurafenib-resistant BRAF RNA. In wt BRAF, BPs are located at -29A, -28A and -26A, whereas in a vemurafenib-resistant BRAF splicing mutant, BPs map to -22A, -18A and -15A, proximal to the intron 8 3′ splice site. This finding of a distal-to-proximal shift of the branch point sequence in BRAF splicing in response to point-mutations in intron 8 provides insight into the regulation of BRAF alternative splicing upon vemurafenib resistance.
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Affiliation(s)
- Masahiko Ajiro
- Tumor Virus RNA Biology Section, Gene Regulation and Chromosome Biology Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702 USA
| | - Zhi-Ming Zheng
- Tumor Virus RNA Biology Section, Gene Regulation and Chromosome Biology Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702 USA
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19
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Szafranski K, Kramer M. It's a bit over, is that ok? The subtle surplus from tandem alternative splicing. RNA Biol 2015; 12:115-22. [PMID: 25826565 DOI: 10.1080/15476286.2015.1017210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Tandem alternative splice sites (TASS) form a defined class of alternative splicing and give rise to mRNA insertion/deletion variants with only small size differences. Previous work has confirmed evolutionary conservation of TASS elements while many cases show only low tissue specificity of isoform ratios. We pinpoint stochasticity and noise as important methodological issues for the dissection of TASS isoform patterns. Resolving such uncertainties, a recent report showed regulation in a cell culture system, with shifts of alternative splicing isoform ratios dependent on cell density. This novel type of regulation affects not only multiple TASS isoforms, but also other alternative splicing classes, in a concerted manner. Here, we discuss how specific regulatory network architectures may be realized through the novel regulation type and highlight the role of differential isoform functions as a key step in order to better understand the functional role of TASS.
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Affiliation(s)
- Karol Szafranski
- a Fritz Lipmann Institute - Leibniz Institute on Aging ; Jena , Germany
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20
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Wang M, Zhang P, Shu Y, Yuan F, Zhang Y, Zhou Y, Jiang M, Zhu Y, Hu L, Kong X, Zhang Z. Alternative splicing at GYNNGY 5' splice sites: more noise, less regulation. Nucleic Acids Res 2014; 42:13969-80. [PMID: 25428370 PMCID: PMC4267661 DOI: 10.1093/nar/gku1253] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 10/29/2014] [Accepted: 11/12/2014] [Indexed: 12/28/2022] Open
Abstract
Numerous eukaryotic genes are alternatively spliced. Recently, deep transcriptome sequencing has skyrocketed proportion of alternatively spliced genes; over 95% human multi-exon genes are alternatively spliced. One fundamental question is: are all these alternative splicing (AS) events functional? To look into this issue, we studied the most common form of alternative 5' splice sites-GYNNGYs (Y = C/T), where both GYs can function as splice sites. Global analyses suggest that splicing noise (due to stochasticity of splicing process) can cause AS at GYNNGYs, evidenced by higher AS frequency in non-coding than in coding regions, in non-conserved than in conserved genes and in lowly expressed than in highly expressed genes. However, ∼20% AS GYNNGYs in humans and ∼3% in mice exhibit tissue-dependent regulation. Consistent with being functional, regulated GYNNGYs are more conserved than unregulated ones. And regulated GYNNGYs have distinctive sequence features which may confer regulation. Particularly, each regulated GYNNGY comprises two splice sites more resembling each other than unregulated GYNNGYs, and has more conserved downstream flanking intron. Intriguingly, most regulated GYNNGYs may tune gene expression through coupling with nonsense-mediated mRNA decay, rather than encode different proteins. In summary, AS at GYNNGY 5' splice sites is primarily splicing noise, and secondarily a way of regulation.
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Affiliation(s)
- Meng Wang
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Peiwei Zhang
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yang Shu
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Fei Yuan
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yuchao Zhang
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - You Zhou
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Min Jiang
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yufei Zhu
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Landian Hu
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Xiangyin Kong
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Zhenguo Zhang
- Institute of Molecular Evolutionary Genetics and Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
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21
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Szafranski K, Fritsch C, Schumann F, Siebel L, Sinha R, Hampe J, Hiller M, Englert C, Huse K, Platzer M. Physiological state co-regulates thousands of mammalian mRNA splicing events at tandem splice sites and alternative exons. Nucleic Acids Res 2014; 42:8895-904. [PMID: 25030907 PMCID: PMC4132704 DOI: 10.1093/nar/gku532] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Thousands of tandem alternative splice sites (TASS) give rise to mRNA insertion/deletion variants with small size differences. Recent work has concentrated on the question of biological relevance in general, and the physiological regulation of TASS in particular. We have quantitatively studied 11 representative TASS cases in comparison to one mutually exclusive exon case and two cassette exons (CEs) using a panel of human and mouse tissues, as well as cultured cell lines. Tissues show small but significant differences in TASS isoform ratios, with a variance 4- to 20-fold lower than seen for CEs. Remarkably, in cultured cells, all studied alternative splicing (AS) cases showed a cell-density-dependent shift of isoform ratios with similar time series profiles. A respective genome-wide co-regulation of TASS splicing was shown by next-generation mRNA sequencing data. Moreover, data from human and mouse organs indicate that this co-regulation of TASS occurs in vivo, with brain showing the strongest difference to other organs. Together, the results indicate a physiological AS regulation mechanism that functions almost independently from the splice site context and sequence.
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Affiliation(s)
- Karol Szafranski
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
| | - Claudia Fritsch
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany Department of General Internal Medicine, Christian-Albrechts-University, Schittenhelmstrasse 12, 24105 Kiel, Germany
| | - Frank Schumann
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany Department of General Internal Medicine, Christian-Albrechts-University, Schittenhelmstrasse 12, 24105 Kiel, Germany
| | - Lisa Siebel
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
| | - Rileen Sinha
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
| | - Jochen Hampe
- Medical Department I, University Hospital, Technical University Dresden, Fetscherstr. 74, 01307 Dresden, Germany
| | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics & Max Planck Institute for the Physics of Complex Systems, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Christoph Englert
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
| | - Klaus Huse
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
| | - Matthias Platzer
- Fritz Lipmann Institute-Institute for Age Research, Beutenbergstr. 11, 07745 Jena, Germany
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22
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A subtle alternative splicing event gives rise to a widely expressed human RNase k isoform. PLoS One 2014; 9:e96557. [PMID: 24797913 PMCID: PMC4010519 DOI: 10.1371/journal.pone.0096557] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Accepted: 04/09/2014] [Indexed: 12/30/2022] Open
Abstract
Subtle alternative splicing leads to the formation of RNA variants lacking or including a small number of nucleotides. To date, the impact of subtle alternative splicing phenomena on protein biosynthesis has been studied in frame-preserving incidents. On the contrary, mRNA isoforms derived from frame-shifting events were poorly studied and generally characterized as non-coding. This work provides evidence for a frame-shifting subtle alternative splicing event which results in the production of a novel protein isoform. We applied a combined molecular approach for the cloning and expression analysis of a human RNase κ transcript (RNase κ-02) which lacks four consecutive bases compared to the previously isolated RNase κ isoform. RNase κ-02 mRNA is expressed in all human cell lines tested end encodes the synthesis of a 134-amino-acid protein by utilizing an alternative initiation codon. The expression of RNase κ-02 in the cytoplasm of human cells was verified by Western blot and immunofluorescence analysis using a specific polyclonal antibody developed on the basis of the amino-acid sequence difference between the two protein isoforms. The results presented here show that subtle changes during mRNA splicing can lead to the expression of significantly altered protein isoforms.
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23
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Alternative splicing of mutually exclusive exons—A review. Biosystems 2013; 114:31-8. [DOI: 10.1016/j.biosystems.2013.07.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 07/03/2013] [Indexed: 12/16/2022]
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24
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Abstract
HEXEvent (http://hexevent.mmg.uci.edu) is a new database that permits the user to compile genome-wide exon data sets of human internal exons showing selected splicing events. User queries can be customized based on the type and the frequency of alternative splicing events. For each splicing version of an exon, an ESTs count is given, specifying the frequency of the event. A user-specific definition of constitutive exons can be entered to designate an exon exclusion level still acceptable for an exon to be considered as constitutive. Similarly, the user has the option to define a maximum inclusion level for an exon to be called an alternatively spliced exon. Unlike other existing splicing databases, HEXEvent permits the user to easily extract alternative splicing information for individual, multiple or genome-wide human internal exons. Importantly, the generated data sets are downloadable for further analysis.
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Affiliation(s)
- Anke Busch
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
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25
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Alternative splicing of RNA triplets is often regulated and accelerates proteome evolution. PLoS Biol 2012; 10:e1001229. [PMID: 22235189 PMCID: PMC3250501 DOI: 10.1371/journal.pbio.1001229] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 11/18/2011] [Indexed: 11/19/2022] Open
Abstract
Thousands of human genes contain introns ending in NAGNAG (N any nucleotide), where both NAGs can function as 3' splice sites, yielding isoforms that differ by inclusion/exclusion of three bases. However, few models exist for how such splicing might be regulated, and some studies have concluded that NAGNAG splicing is purely stochastic and nonfunctional. Here, we used deep RNA-Seq data from 16 human and eight mouse tissues to analyze the regulation and evolution of NAGNAG splicing. Using both biological and technical replicates to estimate false discovery rates, we estimate that at least 25% of alternatively spliced NAGNAGs undergo tissue-specific regulation in mammals, and alternative splicing of strongly tissue-specific NAGNAGs was 10 times as likely to be conserved between species as was splicing of non-tissue-specific events, implying selective maintenance. Preferential use of the distal NAG was associated with distinct sequence features, including a more distal location of the branch point and presence of a pyrimidine immediately before the first NAG, and alteration of these features in a splicing reporter shifted splicing away from the distal site. Strikingly, alignments of orthologous exons revealed a ∼15-fold increase in the frequency of three base pair gaps at 3' splice sites relative to nearby exon positions in both mammals and in Drosophila. Alternative splicing of NAGNAGs in human was associated with dramatically increased frequency of exon length changes at orthologous exon boundaries in rodents, and a model involving point mutations that create, destroy, or alter NAGNAGs can explain both the increased frequency and biased codon composition of gained/lost sequence observed at the beginnings of exons. This study shows that NAGNAG alternative splicing generates widespread differences between the proteomes of mammalian tissues, and suggests that the evolutionary trajectories of mammalian proteins are strongly biased by the locations and phases of the introns that interrupt coding sequences.
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26
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Kralovicova J, Hwang G, Asplund AC, Churbanov A, Smith CIE, Vorechovsky I. Compensatory signals associated with the activation of human GC 5' splice sites. Nucleic Acids Res 2011; 39:7077-91. [PMID: 21609956 PMCID: PMC3167603 DOI: 10.1093/nar/gkr306] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
GC 5′ splice sites (5′ss) are present in ∼1% of human introns, but factors promoting their efficient selection are poorly understood. Here, we describe a case of X-linked agammaglobulinemia resulting from a GC 5′ss activated by a mutation in BTK intron 3. This GC 5′ss was intrinsically weak, yet it was selected in >90% primary transcripts in the presence of a strong and intact natural GT counterpart. We show that efficient selection of this GC 5′ss required a high density of GAA/CAA-containing splicing enhancers in the exonized segment and was promoted by SR proteins 9G8, Tra2β and SC35. The GC 5′ss was efficiently inhibited by splice-switching oligonucleotides targeting either the GC 5′ss itself or the enhancer. Comprehensive analysis of natural GC-AG introns and previously reported pathogenic GC 5′ss showed that their efficient activation was facilitated by higher densities of splicing enhancers and lower densities of silencers than their GT 5′ss equivalents. Removal of the GC-AG introns was promoted to a minor extent by the splice-site strength of adjacent exons and inhibited by flanking Alu repeats, with the first downstream Alus located on average at a longer distance from the GC 5′ss than other transposable elements. These results provide new insights into the splicing code that governs selection of noncanonical splice sites.
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Affiliation(s)
- Jana Kralovicova
- University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK
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Pickrell JK, Pai AA, Gilad Y, Pritchard JK. Noisy splicing drives mRNA isoform diversity in human cells. PLoS Genet 2010; 6:e1001236. [PMID: 21151575 PMCID: PMC3000347 DOI: 10.1371/journal.pgen.1001236] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2010] [Accepted: 11/03/2010] [Indexed: 11/18/2022] Open
Abstract
While the majority of multiexonic human genes show some evidence of alternative splicing, it is unclear what fraction of observed splice forms is functionally relevant. In this study, we examine the extent of alternative splicing in human cells using deep RNA sequencing and de novo identification of splice junctions. We demonstrate the existence of a large class of low abundance isoforms, encompassing approximately 150,000 previously unannotated splice junctions in our data. Newly-identified splice sites show little evidence of evolutionary conservation, suggesting that the majority are due to erroneous splice site choice. We show that sequence motifs involved in the recognition of exons are enriched in the vicinity of unconserved splice sites. We estimate that the average intron has a splicing error rate of approximately 0.7% and show that introns in highly expressed genes are spliced more accurately, likely due to their shorter length. These results implicate noisy splicing as an important property of genome evolution. Most human genes are split into pieces, such that the protein-coding parts (exons) are separated in the genome by large tracts of non-coding DNA (introns) that must be transcribed and spliced out to create a functional transcript. Variation in splicing reactions can create multiple transcripts from the same gene, yet the function for many of these alternative transcripts is unknown. In this study, we show that many of these transcripts are due to splicing errors which are not preserved over evolutionary time. We estimate that the error rate in the splicing of an intron is about 0.7% and demonstrate that there are two major types of splicing error: errors in the recognition of exons and errors in the precise choice of splice site. These results raise the possibility that variation in levels of alternative splicing across species may in part be to variation in splicing error rate.
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Affiliation(s)
- Joseph K. Pickrell
- Department of Human Genetics, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (JK Pickrell); (AA Pai); (Y Gilad); (JK Pritchard)
| | - Athma A. Pai
- Department of Human Genetics, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (JK Pickrell); (AA Pai); (Y Gilad); (JK Pritchard)
| | - Yoav Gilad
- Department of Human Genetics, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (JK Pickrell); (AA Pai); (Y Gilad); (JK Pritchard)
| | - Jonathan K. Pritchard
- Department of Human Genetics, The University of Chicago, Chicago, Illinois, United States of America
- Howard Hughes Medical Institute, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (JK Pickrell); (AA Pai); (Y Gilad); (JK Pritchard)
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Tandem alternative splicing of zebrafish connexin45.6. Genomics 2010; 96:112-8. [PMID: 20466054 DOI: 10.1016/j.ygeno.2010.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 04/19/2010] [Accepted: 05/04/2010] [Indexed: 11/24/2022]
Abstract
Early studies suggested that most connexin genes share a relatively simple structure with a single intron of variable length interrupting the 5' untranslated region (UTR). Here we report that zebrafish cx45.6 shows six isoforms of alternative 5'UTRs which are generated from multiple promoter usage and alternative pre-mRNA splicing. Interestingly, cx45.6 undergoes tandem alternative splicing, which produces transcripts only differing by 3 nucleotides. This is the first study that has demonstrated tandem alternative pre-mRNA splicing in the connexin gene family. Expression patterns of cx45.6 alternative transcripts were demonstrated by real-time RT-PCR during zebrafish embryonic development and in adult tissues. The complexity of 5'UTR diversity suggests complicated regulatory mechanisms for cx45.6 gene expression at both transcriptional and post-transcriptional levels, and we propose that tandem alternative splicing in cx45.6 5'UTRs could play a role in translational control. These results lay groundwork for further investigations on the regulation and function of cx45.6 gene expression.
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Tsai KW, Chan WC, Hsu CN, Lin WC. Sequence features involved in the mechanism of 3' splice junction wobbling. BMC Mol Biol 2010; 11:34. [PMID: 20459675 PMCID: PMC2875228 DOI: 10.1186/1471-2199-11-34] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 05/07/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Alternative splicing is an important mechanism mediating the diversified functions of genes in multicellular organisms, and such event occurs in around 40-60% of human genes. Recently, a new splice-junction wobbling mechanism was proposed that subtle modifications exist in mRNA maturation by alternatively choosing at 5'- GTNGT and 3'- NAGNAG, which created single amino acid insertion and deletion isoforms. RESULTS By browsing the Alternative Splicing Database information, we observed that most 3' alternative splice site choices occur within six nucleotides of the dominant splice site and the incidence significantly decreases further away from the dominant acceptor site. Although a lower frequency of alternative splicing occurs within the intronic region (alternative splicing at the proximal AG) than in the exonic region (alternative splicing at the distal AG), alternative AG sites located within the intronic region show stronger potential as the acceptor. These observations revealed that the choice of 3' splice sites during 3' splicing junction wobbling could depend on the distance between the duplicated AG and the branch point site (BPS). Further mutagenesis experiments demonstrated that the distance of AG-to-AG and BPS-to-AG can greatly influence 3' splice site selection. Knocking down a known alternative splicing regulator, hSlu7, failed to affect wobble splicing choices. CONCLUSION Our results implied that nucleotide distance between proximal and distal AG sites has an important regulatory function. In this study, we showed that occurrence of 3' wobble splicing occurs in a distance-dependent manner and that most of this wobble splicing is probably caused by steric hindrance from a factor bound at the neighboring tandem motif sequence.
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Affiliation(s)
- Kuo-Wang Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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Sinha R, Lenser T, Jahn N, Gausmann U, Friedel S, Szafranski K, Huse K, Rosenstiel P, Hampe J, Schuster S, Hiller M, Backofen R, Platzer M. TassDB2 - A comprehensive database of subtle alternative splicing events. BMC Bioinformatics 2010; 11:216. [PMID: 20429909 PMCID: PMC2878309 DOI: 10.1186/1471-2105-11-216] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 04/29/2010] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Subtle alternative splicing events involving tandem splice sites separated by a short (2-12 nucleotides) distance are frequent and evolutionarily widespread in eukaryotes, and a major contributor to the complexity of transcriptomes and proteomes. However, these events have been either omitted altogether in databases on alternative splicing, or only the cases of experimentally confirmed alternative splicing have been reported. Thus, a database which covers all confirmed cases of subtle alternative splicing as well as the numerous putative tandem splice sites (which might be confirmed once more transcript data becomes available), and allows to search for tandem splice sites with specific features and download the results, is a valuable resource for targeted experimental studies and large-scale bioinformatics analyses of tandem splice sites. Towards this goal we recently set up TassDB (Tandem Splice Site DataBase, version 1), which stores data about alternative splicing events at tandem splice sites separated by 3 nt in eight species. DESCRIPTION We have substantially revised and extended TassDB. The currently available version 2 contains extensive information about tandem splice sites separated by 2-12 nt for the human and mouse transcriptomes including data on the conservation of the tandem motifs in five vertebrates. TassDB2 offers a user-friendly interface to search for specific genes or for genes containing tandem splice sites with specific features as well as the possibility to download result datasets. For example, users can search for cases of alternative splicing where the proportion of EST/mRNA evidence supporting the minor isoform exceeds a specific threshold, or where the difference in splice site scores is specified by the user. The predicted impact of each event on the protein is also reported, along with information about being a putative target for the nonsense-mediated decay (NMD) pathway. Links are provided to the UCSC genome browser and other external resources. CONCLUSION TassDB2, available via http://www.tassdb.info, provides comprehensive resources for researchers interested in both targeted experimental studies and large-scale bioinformatics analyses of short distance tandem splice sites.
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Affiliation(s)
- Rileen Sinha
- Bioinformatics group, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Thorsten Lenser
- Bio Systems Analysis Group, Friedrich Schiller University Jena, Ernst-Abbe-Platz 1-4, D-07743 Jena, Germany
| | - Niels Jahn
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Ulrike Gausmann
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Swetlana Friedel
- Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Systems Biology/Bioinformatics, Beutenbergstrasse. 11a, 07745 Jena, Germany
| | - Karol Szafranski
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Klaus Huse
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Philip Rosenstiel
- Institute of Clinical Molecular Biology, Christian-Albrechts-University Kiel, Schittenhelmstrasse, 12, 24105 Kiel, Germany
| | - Jochen Hampe
- Department of General Internal Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Schittenhelmstrasse, 12, 24105 Kiel, Germany
| | - Stefan Schuster
- Department of Bioinformatics, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany
| | - Michael Hiller
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | - Rolf Backofen
- Bioinformatics group, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany
- Freiburg Initiative for Systems Biology (FRISYS), University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany
| | - Matthias Platzer
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
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Sinha R, Zimmer AD, Bolte K, Lang D, Reski R, Platzer M, Rensing SA, Backofen R. Identification and characterization of NAGNAG alternative splicing in the moss Physcomitrella patens. BMC PLANT BIOLOGY 2010; 10:76. [PMID: 20426810 PMCID: PMC3095350 DOI: 10.1186/1471-2229-10-76] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 04/28/2010] [Indexed: 05/05/2023]
Abstract
BACKGROUND Alternative splicing (AS) involving tandem acceptors that are separated by three nucleotides (NAGNAG) is an evolutionarily widespread class of AS, which is well studied in Homo sapiens (human) and Mus musculus (mouse). It has also been shown to be common in the model seed plants Arabidopsis thaliana and Oryza sativa (rice). In one of the first studies involving sequence-based prediction of AS in plants, we performed a genome-wide identification and characterization of NAGNAG AS in the model plant Physcomitrella patens, a moss. RESULTS Using Sanger data, we found 295 alternatively used NAGNAG acceptors in P. patens. Using 31 features and training and test datasets of constitutive and alternative NAGNAGs, we trained a classifier to predict the splicing outcome at NAGNAG tandem splice sites (alternative splicing, constitutive at the first acceptor, or constitutive at the second acceptor). Our classifier achieved a balanced specificity and sensitivity of >or= 89%. Subsequently, a classifier trained exclusively on data well supported by transcript evidence was used to make genome-wide predictions of NAGNAG splicing outcomes. By generation of more transcript evidence from a next-generation sequencing platform (Roche 454), we found additional evidence for NAGNAG AS, with altogether 664 alternative NAGNAGs being detected in P. patens using all currently available transcript evidence. The 454 data also enabled us to validate the predictions of the classifier, with 64% (80/125) of the well-supported cases of AS being predicted correctly. CONCLUSION NAGNAG AS is just as common in the moss P. patens as it is in the seed plants A. thaliana and O. sativa (but not conserved on the level of orthologous introns), and can be predicted with high accuracy. The most informative features are the nucleotides in the NAGNAG and in its immediate vicinity, along with the splice sites scores, as found earlier for NAGNAG AS in animals. Our results suggest that the mechanism behind NAGNAG AS in plants is similar to that in animals and is largely dependent on the splice site and its immediate neighborhood.
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Affiliation(s)
- Rileen Sinha
- Bioinformatics group, University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany
- Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany
| | - Andreas D Zimmer
- Faculty of Biology, University of Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
| | - Kathrin Bolte
- Faculty of Biology, University of Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- Freiburg Initiative for Systems Biology (FRISYS), University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Philipps-Universität Marburg, Laboratorium für Zellbiologie, Karl-von-Frisch Str., 35032 Marburg, Germany
| | - Daniel Lang
- Faculty of Biology, University of Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
| | - Ralf Reski
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Freiburg Initiative for Systems Biology (FRISYS), University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany
| | - Matthias Platzer
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
| | - Stefan A Rensing
- Faculty of Biology, University of Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany
- Freiburg Initiative for Systems Biology (FRISYS), University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany
| | - Rolf Backofen
- Bioinformatics group, University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany
- Freiburg Initiative for Systems Biology (FRISYS), University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
- Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany
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Matsumoto J, Dewar K, Wasserscheid J, Wiley GB, Macmil SL, Roe BA, Zeller RW, Satou Y, Hastings KEM. High-throughput sequence analysis of Ciona intestinalis SL trans-spliced mRNAs: alternative expression modes and gene function correlates. Genome Res 2010; 20:636-45. [PMID: 20212022 DOI: 10.1101/gr.100271.109] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Pre-mRNA 5' spliced-leader (SL) trans-splicing occurs in some metazoan groups but not in others. Genome-wide characterization of the trans-spliced mRNA subpopulation has not yet been reported for any metazoan. We carried out a high-throughput analysis of the SL trans-spliced mRNA population of the ascidian tunicate Ciona intestinalis by 454 Life Sciences (Roche) pyrosequencing of SL-PCR-amplified random-primed reverse transcripts of tailbud embryo RNA. We obtained approximately 250,000 high-quality reads corresponding to 8790 genes, approximately 58% of the Ciona total gene number. The great depth of this data revealed new aspects of trans-splicing, including the existence of a significant class of "infrequently trans-spliced" genes, accounting for approximately 28% of represented genes, that generate largely non-trans-spliced mRNAs, but also produce trans-spliced mRNAs, in part through alternative promoter use. Thus, the conventional qualitative dichotomy of trans-spliced versus non-trans-spliced genes should be supplanted by a more accurate quantitative view recognizing frequently and infrequently trans-spliced gene categories. Our data include reads representing approximately 80% of Ciona frequently trans-spliced genes. Our analysis also revealed significant use of closely spaced alternative trans-splice acceptor sites which further underscores the mechanistic similarity of cis- and trans-splicing and indicates that the prevalence of +/-3-nt alternative splicing events at tandem acceptor sites, NAGNAG, is driven by spliceosomal mechanisms, and not nonsense-mediated decay, or selection at the protein level. The breadth of gene representation data enabled us to find new correlations between trans-splicing status and gene function, namely the overrepresentation in the frequently trans-spliced gene class of genes associated with plasma/endomembrane system, Ca(2+) homeostasis, and actin cytoskeleton.
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Affiliation(s)
- Jun Matsumoto
- Department of Neurology & Neurosurgery, McGill University, Montreal Neurological Institute, Montréal, Québec H3A 2B4, Canada
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Schindler S, Heiner M, Platzer M, Szafranski K. Comparison of methods for quantification of subtle splice variants. Electrophoresis 2010; 30:3674-81. [PMID: 19862747 DOI: 10.1002/elps.200900292] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Alternative splicing is capable of generating multiple mRNA variants from a single gene and is hence a key mediator of molecular diversity generated at the transcript level. Consequently, delivering quantitative information on the fractions of splice variants is essential for the understanding of their biological roles. Here we compare techniques for subtle splice variant quantification that are able to resolve length differences as small as one nucleotide: PAGE with ethidium-bromide densitometry, pyrosequencing, and CE-LIF. We give comprehensive descriptions of assay designs and calibration procedures and present an evaluation of these methods in terms of accuracy, reproducibility and applicability. We also examined template concentrations and reverse transcription-coupled PCR conditions as potential cause of biased results as they were observed for extreme low template concentrations and/or PCR amplicons with size differences of 195 nt. As proof of concept, we determine the splice ratios of variants differing by 3 and 12 nt in five human tissues. We demonstrate that CE-LIF is the most precise and also the most labor- and time-efficient method.
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Schirmeyer J, Szafranski K, Leipold E, Mawrin C, Platzer M, Heinemann SH. A subtle alternative splicing event of the Na(V)1.8 voltage-gated sodium channel is conserved in human, rat, and mouse. J Mol Neurosci 2009; 41:310-4. [PMID: 19953341 DOI: 10.1007/s12031-009-9315-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 11/12/2009] [Indexed: 11/25/2022]
Abstract
The voltage-gated sodium channel subtype Na(V)1.8 (SCN10A) is exclusively expressed in dorsal root ganglia (DRG) and plays a critical role in pain perception. We isolated mRNA from human, rat, and mouse DRGs and screened for alternatively spliced isoforms of the SCN10A mRNA using 454 sequencing. In all three species, we found an event of subtle alternative splicing at a NAGNAG tandem acceptor that results in isoforms including or lacking glutamine 1030 (Na(V)1.8+Q and Na(V)1.8-Q, respectively) within the cytoplasmic loop between domains II and III. The relative amount of Na(V)1.8-Q mRNA in adult DRG was measured with 14.1 +/- 0.1% in humans and 11.2 +/- 0.2% in rats. This is in contrast to an abundance of 64.3 +/- 0.3% in mouse DRG. Thus, the NAGNAG tandem acceptor in SCN10A is conserved among rodents and humans but its alternative usage apparently occurs with species-specific abundance. Analysis of human Na(V)1.8+Q and -Q isoforms in whole-cell patch-clamp experiments after heterologous expression in the neuroblastoma cell line Neuro-2A revealed no obvious impact of the splicing event on channel function.
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Affiliation(s)
- Jana Schirmeyer
- Department of Biophysics, Center for Molecular Biomedicine, University of Jena, Jena, Germany
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Tanner G, Glaus E, Barthelmes D, Ader M, Fleischhauer J, Pagani F, Berger W, Neidhardt J. Therapeutic strategy to rescue mutation-induced exon skipping in rhodopsin by adaptation of U1 snRNA. Hum Mutat 2009; 30:255-63. [DOI: 10.1002/humu.20861] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Sinha R, Hiller M, Pudimat R, Gausmann U, Platzer M, Backofen R. Improved identification of conserved cassette exons using Bayesian networks. BMC Bioinformatics 2008; 9:477. [PMID: 19014490 PMCID: PMC2621368 DOI: 10.1186/1471-2105-9-477] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 11/12/2008] [Indexed: 12/14/2022] Open
Abstract
Background Alternative splicing is a major contributor to the diversity of eukaryotic transcriptomes and proteomes. Currently, large scale detection of alternative splicing using expressed sequence tags (ESTs) or microarrays does not capture all alternative splicing events. Moreover, for many species genomic data is being produced at a far greater rate than corresponding transcript data, hence in silico methods of predicting alternative splicing have to be improved. Results Here, we show that the use of Bayesian networks (BNs) allows accurate prediction of evolutionary conserved exon skipping events. At a stringent false positive rate of 0.5%, our BN achieves an improved true positive rate of 61%, compared to a previously reported 50% on the same dataset using support vector machines (SVMs). Incorporating several novel discriminative features such as intronic splicing regulatory elements leads to the improvement. Features related to mRNA secondary structure increase the prediction performance, corroborating previous findings that secondary structures are important for exon recognition. Random labelling tests rule out overfitting. Cross-validation on another dataset confirms the increased performance. When using the same dataset and the same set of features, the BN matches the performance of an SVM in earlier literature. Remarkably, we could show that about half of the exons which are labelled constitutive but receive a high probability of being alternative by the BN, are in fact alternative exons according to the latest EST data. Finally, we predict exon skipping without using conservation-based features, and achieve a true positive rate of 29% at a false positive rate of 0.5%. Conclusion BNs can be used to achieve accurate identification of alternative exons and provide clues about possible dependencies between relevant features. The near-identical performance of the BN and SVM when using the same features shows that good classification depends more on features than on the choice of classifier. Conservation based features continue to be the most informative, and hence distinguishing alternative exons from constitutive ones without using conservation based features remains a challenging problem.
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Affiliation(s)
- Rileen Sinha
- Genome Analysis, Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany.
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Bortfeldt R, Schindler S, Szafranski K, Schuster S, Holste D. Comparative analysis of sequence features involved in the recognition of tandem splice sites. BMC Genomics 2008; 9:202. [PMID: 18447903 PMCID: PMC2423196 DOI: 10.1186/1471-2164-9-202] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 04/30/2008] [Indexed: 01/05/2023] Open
Abstract
Background The splicing of pre-mRNAs is conspicuously often variable and produces multiple alternatively spliced (AS) isoforms that encode different messages from one gene locus. Computational studies uncovered a class of highly similar isoforms, which were related to tandem 5'-splice sites (5'ss) and 3'-splice sites (3'ss), yet with very sparse anecdotal evidence in experimental studies. To compare the types and levels of alternative tandem splice site exons occurring in different human organ systems and cell types, and to study known sequence features involved in the recognition and distinction of neighboring splice sites, we performed large-scale, stringent alignments of cDNA sequences and ESTs to the human and mouse genomes, followed by experimental validation. Results We analyzed alternative 5'ss exons (A5Es) and alternative 3'ss exons (A3Es), derived from transcript sequences that were aligned to assembled genome sequences to infer patterns of AS occurring in several thousands of genes. Comparing the levels of overlapping (tandem) and non-overlapping (competitive) A5Es and A3Es, a clear preference of isoforms was seen for tandem acceptors and donors, with four nucleotides and three to six nucleotides long exon extensions, respectively. A subset of inferred A5E tandem exons was selected and experimentally validated. With the focus on A5Es, we investigated their transcript coverage, sequence conservation and base-paring to U1 snRNA, proximal and distal splice site classification, candidate motifs for cis-regulatory activity, and compared A5Es with A3Es, constitutive and pseudo-exons, in H. sapiens and M. musculus. The results reveal a small but authentic enriched set of tandem splice site preference, with specific distances between proximal and distal 5'ss (3'ss), which showed a marked dichotomy between the levels of in- and out-of-frame splicing for A5Es and A3Es, respectively, identified a number of candidate NMD targets, and allowed a rough estimation of a number of undetected tandem donors based on splice site information. Conclusion This comparative study distinguishes tandem 5'ss and 3'ss, with three to six nucleotides long extensions, as having unusually high proportions of AS, experimentally validates tandem donors in a panel of different human tissues, highlights the dichotomy in the types of AS occurring at tandem splice sites, and elucidates that human alternative exons spliced at overlapping 5'ss posses features of typical splice variants that could well be beneficial for the cell.
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Affiliation(s)
- Ralf Bortfeldt
- Department of Bioinformatics, Friedrich-Schiller University, Ernst-Abbe-Platz 2, D-07743 Jena, Germany.
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Alternative splicing at NAGNAG acceptors in Arabidopsis thaliana SR and SR-related protein-coding genes. BMC Genomics 2008; 9:159. [PMID: 18402682 PMCID: PMC2375911 DOI: 10.1186/1471-2164-9-159] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Accepted: 04/10/2008] [Indexed: 11/10/2022] Open
Abstract
Background Several recent studies indicate that alternative splicing in Arabidopsis and other plants is a common mechanism for post-transcriptional modulation of gene expression. However, few analyses have been done so far to elucidate the functional relevance of alternative splicing in higher plants. Representing a frequent and universal subtle alternative splicing event among eukaryotes, alternative splicing at NAGNAG acceptors contributes to transcriptome diversity and therefore, proteome plasticity. Alternatively spliced NAGNAG acceptors are overrepresented in genes coding for proteins with RNA-recognition motifs (RRMs). As SR proteins, a family of RRM-containing important splicing factors, are known to be extensively alternatively spliced in Arabidopsis, we analyzed alternative splicing at NAGNAG acceptors in SR and SR-related genes. Results In a comprehensive analysis of the Arabidopsis thaliana genome, we identified 6,772 introns that exhibit a NAGNAG acceptor motif. Alternative splicing at these acceptors was assessed using available EST data, complemented by a sequence-based prediction method. Of the 36 identified introns within 30 SR and SR-related protein-coding genes that have a NAGNAG acceptor, we selected 15 candidates for an experimental analysis of alternative splicing under several conditions. We provide experimental evidence for 8 of these candidates being alternatively spliced. Quantifying the ratio of NAGNAG-derived splice variants under several conditions, we found organ-specific splicing ratios in adult plants and changes in seedlings of different ages. Splicing ratio changes were observed in response to heat shock and most strikingly, cold shock. Interestingly, the patterns of differential splicing ratios are similar for all analyzed genes. Conclusion NAGNAG acceptors frequently occur in the Arabidopsis genome and are particularly prevalent in SR and SR-related protein-coding genes. A lack of extensive EST coverage can be compensated by using the proposed sequence-based method to predict alternative splicing at these acceptors. Our findings indicate that the differential effects on NAGNAG alternative splicing in SR and SR-related genes are organ- and condition-specific rather than gene-specific.
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Hiller M, Platzer M. Widespread and subtle: alternative splicing at short-distance tandem sites. Trends Genet 2008; 24:246-55. [PMID: 18394746 DOI: 10.1016/j.tig.2008.03.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 03/05/2008] [Accepted: 03/06/2008] [Indexed: 12/11/2022]
Abstract
Alternative splicing at donor or acceptor sites located just a few nucleotides apart is widespread in many species. It results in subtle changes in the transcripts and often in the encoded proteins. Several of these tandem splice events contribute to the repertoire of functionally different proteins, whereas many are neutral or deleterious. Remarkably, some of the functional events are differentially spliced in tissues or developmental stages, whereas others exhibit constant splicing ratios, indicating that function is not always associated with differential splicing. Stochastic splice site selection seems to play a major role in these processes. Here, we review recent progress in understanding functional and evolutionary aspects as well as the mechanism of splicing at short-distance tandem sites.
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Affiliation(s)
- Michael Hiller
- Bioinformatics Group, Albert-Ludwigs-University Freiburg, 79110 Freiburg, Germany.
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Hiller M, Szafranski K, Sinha R, Huse K, Nikolajewa S, Rosenstiel P, Schreiber S, Backofen R, Platzer M. Assessing the fraction of short-distance tandem splice sites under purifying selection. RNA (NEW YORK, N.Y.) 2008; 14:616-29. [PMID: 18268022 PMCID: PMC2271360 DOI: 10.1261/rna.883908] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Many alternative splice events result in subtle mRNA changes, and most of them occur at short-distance tandem donor and acceptor sites. The splicing mechanism of such tandem sites likely involves the stochastic selection of either splice site. While tandem splice events are frequent, it is unknown how many are functionally important. Here, we use phylogenetic conservation to address this question, focusing on tandems with a distance of 3-9 nucleotides. We show that previous contradicting results on whether alternative or constitutive tandem motifs are more conserved between species can be explained by a statistical paradox (Simpson's paradox). Applying methods that take biases into account, we found higher conservation of alternative tandems in mouse, dog, and even chicken, zebrafish, and Fugu genomes. We estimated a lower bound for the number of alternative sites that are under purifying (negative) selection. While the absolute number of conserved tandem motifs decreases with the evolutionary distance, the fraction under selection increases. Interestingly, a number of frameshifting tandems are under selection, suggesting a role in regulating mRNA and protein levels via nonsense-mediated decay (NMD). An analysis of the intronic flanks shows that purifying selection also acts on the intronic sequence. We propose that stochastic splice site selection can be an advantageous mechanism that allows constant splice variant ratios in situations where a deviation in this ratio is deleterious.
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Affiliation(s)
- Michael Hiller
- Bioinformatics Group, Albert-Ludwigs-University Freiburg, 79110 Freiburg, Germany.
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Hiller M, Szafranski K, Huse K, Backofen R, Platzer M. Selection against tandem splice sites affecting structured protein regions. BMC Evol Biol 2008; 8:89. [PMID: 18366714 PMCID: PMC2279118 DOI: 10.1186/1471-2148-8-89] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Accepted: 03/21/2008] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Alternative selection of splice sites in tandem donors and acceptors is a major mode of alternative splicing. Here, we analyzed whether in-frame tandem sites leading to subtle mRNA insertions/deletions of 3, 6, or 9 nucleotides are under natural selection. RESULTS We found multiple lines of evidence that the human protein coding sequences are under selection against such in-frame tandem splice events, indicating that these events are often deleterious. The strength of selection is not homogeneous within the coding sequence as protein regions that fold into a fixed 3D structure (intrinsically ordered) are under stronger selection, especially against sites with a strong minor splice site. Investigating structures of functional protein domains, we found that tandem acceptors are preferentially located at the domain surface and outside structural elements such as helices and sheets. Using three-species comparisons, we estimate that more than half of all mutations that create NAGNAG acceptors in the coding region have been eliminated by selection. CONCLUSION We estimate that ~2,400 introns are under selection against possessing a tandem site.
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Affiliation(s)
- Michael Hiller
- Bioinformatics Group, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany.
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Sela N, Mersch B, Gal-Mark N, Lev-Maor G, Hotz-Wagenblatt A, Ast G. Comparative analysis of transposed element insertion within human and mouse genomes reveals Alu's unique role in shaping the human transcriptome. Genome Biol 2008; 8:R127. [PMID: 17594509 PMCID: PMC2394776 DOI: 10.1186/gb-2007-8-6-r127] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 06/07/2007] [Accepted: 06/27/2007] [Indexed: 01/31/2023] Open
Abstract
Analysis of transposed elements in the human and mouse genomes reveals many effects on the transcriptomes, including a higher level of exonization of Alu elements than other elements. Background Transposed elements (TEs) have a substantial impact on mammalian evolution and are involved in numerous genetic diseases. We compared the impact of TEs on the human transcriptome and the mouse transcriptome. Results We compiled a dataset of all TEs in the human and mouse genomes, identifying 3,932,058 and 3,122,416 TEs, respectively. We than extracted TEs located within human and mouse genes and, surprisingly, we found that 60% of TEs in both human and mouse are located in intronic sequences, even though introns comprise only 24% of the human genome. All TE families in both human and mouse can exonize. TE families that are shared between human and mouse exhibit the same percentage of TE exonization in the two species, but the exonization level of Alu, a primate-specific retroelement, is significantly greater than that of other TEs within the human genome, leading to a higher level of TE exonization in human than in mouse (1,824 exons compared with 506 exons, respectively). We detected a primate-specific mechanism for intron gain, in which Alu insertion into an exon creates a new intron located in the 3' untranslated region (termed 'intronization'). Finally, the insertion of TEs into the first and last exons of a gene is more frequent in human than in mouse, leading to longer exons in human. Conclusion Our findings reveal many effects of TEs on these two transcriptomes. These effects are substantially greater in human than in mouse, which is due to the presence of Alu elements in human.
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Affiliation(s)
- Noa Sela
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Britta Mersch
- HUSAR Bioinformatics Lab, Department of Molecular Biophysics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld, D-69120 Heidelberg, Germany
| | - Nurit Gal-Mark
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Galit Lev-Maor
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Agnes Hotz-Wagenblatt
- HUSAR Bioinformatics Lab, Department of Molecular Biophysics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld, D-69120 Heidelberg, Germany
| | - Gil Ast
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
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Akerman M, Mandel-Gutfreund Y. Does distance matter? Variations in alternative 3' splicing regulation. Nucleic Acids Res 2007; 35:5487-98. [PMID: 17704130 PMCID: PMC2018619 DOI: 10.1093/nar/gkm603] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Alternative splicing constitutes a major mechanism creating protein diversity in humans. This diversity can result from the alternative skipping of entire exons or by alternative selection of the 5' or 3' splice sites that define the exon boundaries. In this study, we analyze the sequence and evolutionary characteristics of alternative 3' splice sites conserved between human and mouse genomes for distances ranging from 3 to 100 nucleotides. We show that alternative splicing events can be distinguished from constitutive splicing by a combination of properties which vary depending on the distance between the splice sites. Among the unique features of alternative 3' splice sites, we observed an unexpectedly high occurrence of events in which a polypyrimidine tract was found to overlap the upstream splice site. By applying a machine-learning approach, we show that we can successfully discriminate true alternative 3' splice sites from constitutive 3' splice sites. Finally, we propose that the unique features of the intron flanking alternative splice sites are indicative of a regulatory mechanism that is involved in splice site selection. We postulate that the process of splice site selection is influenced by the distance between the competitive splice sites.
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Koren E, Lev-Maor G, Ast G. The emergence of alternative 3' and 5' splice site exons from constitutive exons. PLoS Comput Biol 2007; 3:e95. [PMID: 17530917 PMCID: PMC1876488 DOI: 10.1371/journal.pcbi.0030095] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 04/10/2007] [Indexed: 11/19/2022] Open
Abstract
Alternative 3' and 5' splice site (ss) events constitute a significant part of all alternative splicing events. These events were also found to be related to several aberrant splicing diseases. However, only few of the characteristics that distinguish these events from alternative cassette exons are known currently. In this study, we compared the characteristics of constitutive exons, alternative cassette exons, and alternative 3'ss and 5'ss exons. The results revealed that alternative 3'ss and 5'ss exons are an intermediate state between constitutive and alternative cassette exons, where the constitutive side resembles constitutive exons, and the alternative side resembles alternative cassette exons. The results also show that alternative 3'ss and 5'ss exons exhibit low levels of symmetry (frame-preserving), similar to constitutive exons, whereas the sequence between the two alternative splice sites shows high symmetry levels, similar to alternative cassette exons. In addition, flanking intronic conservation analysis revealed that exons whose alternative splice sites are at least nine nucleotides apart show a high conservation level, indicating intronic participation in the regulation of their splicing, whereas exons whose alternative splice sites are fewer than nine nucleotides apart show a low conservation level. Further examination of these exons, spanning seven vertebrate species, suggests an evolutionary model in which the alternative state is a derivative of an ancestral constitutive exon, where a mutation inside the exon or along the flanking intron resulted in the creation of a new splice site that competes with the original one, leading to alternative splice site selection. This model was validated experimentally on four exons, showing that they indeed originated from constitutive exons that acquired a new competing splice site during evolution.
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Affiliation(s)
- Eli Koren
- Department of Human Molecular Genetics, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Galit Lev-Maor
- Department of Human Molecular Genetics, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Gil Ast
- Department of Human Molecular Genetics, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- * To whom correspondence should be addressed. E-mail:
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Buratti E, Chivers M, Královičová J, Romano M, Baralle M, Krainer AR, Vořechovský I. Aberrant 5' splice sites in human disease genes: mutation pattern, nucleotide structure and comparison of computational tools that predict their utilization. Nucleic Acids Res 2007; 35:4250-63. [PMID: 17576681 PMCID: PMC1934990 DOI: 10.1093/nar/gkm402] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Despite a growing number of splicing mutations found in hereditary diseases, utilization of aberrant splice sites and their effects on gene expression remain challenging to predict. We compiled sequences of 346 aberrant 5′splice sites (5′ss) that were activated by mutations in 166 human disease genes. Mutations within the 5′ss consensus accounted for 254 cryptic 5′ss and mutations elsewhere activated 92 de novo 5′ss. Point mutations leading to cryptic 5′ss activation were most common in the first intron nucleotide, followed by the fifth nucleotide. Substitutions at position +5 were exclusively G>A transitions, which was largely attributable to high mutability rates of C/G>T/A. However, the frequency of point mutations at position +5 was significantly higher than that observed in the Human Gene Mutation Database, suggesting that alterations of this position are particularly prone to aberrant splicing, possibly due to a requirement for sequential interactions with U1 and U6 snRNAs. Cryptic 5′ss were best predicted by computational algorithms that accommodate nucleotide dependencies and not by weight-matrix models. Discrimination of intronic 5′ss from their authentic counterparts was less effective than for exonic sites, as the former were intrinsically stronger than the latter. Computational prediction of exonic de novo 5′ss was poor, suggesting that their activation critically depends on exonic splicing enhancers or silencers. The authentic counterparts of aberrant 5′ss were significantly weaker than the average human 5′ss. The development of an online database of aberrant 5′ss will be useful for studying basic mechanisms of splice-site selection, identifying splicing mutations and optimizing splice-site prediction algorithms.
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Affiliation(s)
- Emanuele Buratti
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Martin Chivers
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Jana Královičová
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Maurizio Romano
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Marco Baralle
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Adrian R. Krainer
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Igor Vořechovský
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy, University of Southampton School of Medicine, Division of Human Genetics, Southampton SO16 6YD, UK and Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
- *To whom correspondence should be addressed. +44 2380 796425+44 2380 794264
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Davis CA, Brown MPS, Singh U. Functional characterization of spliceosomal introns and identification of U2, U4, and U5 snRNAs in the deep-branching eukaryote Entamoeba histolytica. EUKARYOTIC CELL 2007; 6:940-8. [PMID: 17468393 PMCID: PMC1951529 DOI: 10.1128/ec.00059-07] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Pre-mRNA splicing is essential to ensure accurate expression of many genes in eukaryotic organisms. In Entamoeba histolytica, a deep-branching eukaryote, approximately 30% of the annotated genes are predicted to contain introns; however, the accuracy of these predictions has not been tested. In this study, we mined an expressed sequence tag (EST) library representing 7% of amoebic genes and found evidence supporting splicing of 60% of the testable intron predictions, the majority of which contain a GUUUGU 5' splice site and a UAG 3' splice site. Additionally, we identified several splice site misannotations, evidence for the existence of 30 novel introns in previously annotated genes, and identified novel genes through uncovering their spliced ESTs. Finally, we provided molecular evidence for the E. histolytica U2, U4, and U5 snRNAs. These data lay the foundation for further dissection of the role of RNA processing in E. histolytica gene expression.
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Affiliation(s)
- Carrie A Davis
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, USA
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