1
|
Burgardt R, Lambert D, Heuwieser C, Sack M, Wagner G, Weinberg Z, Wachter A. Positioning of pyrimidine motifs around cassette exons defines their PTB-dependent splicing in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:2202-2218. [PMID: 38578875 DOI: 10.1111/tpj.16739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 03/14/2024] [Indexed: 04/07/2024]
Abstract
Alternative splicing (AS) is a complex process that generates transcript variants from a single pre-mRNA and is involved in numerous biological functions. Many RNA-binding proteins are known to regulate AS; however, little is known about the underlying mechanisms, especially outside the mammalian clade. Here, we show that polypyrimidine tract binding proteins (PTBs) from Arabidopsis thaliana regulate AS of cassette exons via pyrimidine (Py)-rich motifs close to the alternative splice sites. Mutational studies on three PTB-dependent cassette exon events revealed that only some of the Py motifs in this region are critical for AS. Moreover, in vitro binding of PTBs did not reflect a motif's impact on AS in vivo. Our mutational studies and bioinformatic investigation of all known PTB-regulated cassette exons from A. thaliana and human suggested that the binding position of PTBs relative to a cassette exon defines whether its inclusion or skipping is induced. Accordingly, exon skipping is associated with a higher frequency of Py stretches within the cassette exon, and in human also upstream of it, whereas exon inclusion is characterized by increased Py motif occurrence downstream of said exon. Enrichment of Py motifs downstream of PTB-activated 5' splice sites is also seen for PTB-dependent intron removal and alternative 5' splice site events from A. thaliana, suggesting this is a common step of exon definition. In conclusion, the position-dependent AS regulatory mechanism by PTB homologs has been conserved during the separate evolution of plants and mammals, while other critical features, in particular intron length, have considerably changed.
Collapse
Affiliation(s)
- Rica Burgardt
- Institute for Molecular Physiology (imP), University of Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128, Mainz, Germany
| | - Dorothee Lambert
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Christina Heuwieser
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Maximilian Sack
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107, Leipzig, Germany
| | - Gabriele Wagner
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Zasha Weinberg
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107, Leipzig, Germany
| | - Andreas Wachter
- Institute for Molecular Physiology (imP), University of Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128, Mainz, Germany
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| |
Collapse
|
2
|
Hamid FM, Makeyev EV. A mechanism underlying position-specific regulation of alternative splicing. Nucleic Acids Res 2019; 45:12455-12468. [PMID: 30053257 PMCID: PMC5716086 DOI: 10.1093/nar/gkx901] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/26/2017] [Indexed: 01/01/2023] Open
Abstract
Many RNA-binding proteins including a master regulator of splicing in developing brain and muscle, polypyrimidine tract-binding protein 1 (PTBP1), can either activate or repress alternative exons depending on the pre-mRNA recruitment position. When bound upstream or within regulated exons PTBP1 tends to promote their skipping, whereas binding to downstream sites often stimulates inclusion. How this switch is orchestrated at the molecular level is poorly understood. Using bioinformatics and biochemical approaches we show that interaction of PTBP1 with downstream intronic sequences can activate natural cassette exons by promoting productive docking of the spliceosomal U1 snRNP to a suboptimal 5' splice site. Strikingly, introducing upstream PTBP1 sites to this circuitry leads to a potent splicing repression accompanied by the assembly of an exonic ribonucleoprotein complex with a tightly bound U1 but not U2 snRNP. Our data suggest a molecular mechanism underlying the transition between a better-known repressive function of PTBP1 and its role as a bona fide splicing activator. More generally, we argue that the functional outcome of individual RNA contacts made by an RNA-binding protein is subject to extensive context-specific modulation.
Collapse
Affiliation(s)
- Fursham M Hamid
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK.,School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Eugene V Makeyev
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
| |
Collapse
|
3
|
Xie R, Chen X, Chen Z, Huang M, Dong W, Gu P, Zhang J, Zhou Q, Dong W, Han J, Wang X, Li H, Huang J, Lin T. Polypyrimidine tract binding protein 1 promotes lymphatic metastasis and proliferation of bladder cancer via alternative splicing of MEIS2 and PKM. Cancer Lett 2019; 449:31-44. [PMID: 30742945 DOI: 10.1016/j.canlet.2019.01.041] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/27/2019] [Accepted: 01/30/2019] [Indexed: 12/24/2022]
Abstract
Lymph node (LN) metastasis is the leading cause of bladder cancer-related mortality. Splicing factors facilitate cancer progression by modulating oncogenic variants, but it is unclear whether and how splicing factors regulate bladder cancer LN metastasis. In this study, Polypyrimidine tract binding protein 1 (PTBP1) expression was found to relate to bladder cancer LN metastasis, and was positively correlated with LN metastasis status, tumor stage, histological grade, and poor patient prognosis. Functional assays demonstrated that PTBP1 promoted bladder cancer cell migration, invasion, and proliferation in vitro, as well as LN metastasis and tumor growth in vivo. Mechanistic investigations revealed that PTBP1 upregulated MEIS2-L variant to promote metastasis and increased expression of PKM2 variant to enhance proliferation by modulating alternative mRNA splicing. Moreover, overexpression of MEIS2-L or PKM2 could rescue the oncogenic abilities of bladder cancer cells and the expression of MMP9 or CCND1 respectively after PTBP1 knockdown. In conclusion, our data demonstrate that PTBP1 induces bladder cancer LN metastasis and proliferation through an alternative splicing mechanism. PTBP1 may serve as a novel prognostic marker and therapeutic target for LN-metastatic bladder cancer.
Collapse
Affiliation(s)
- Ruihui Xie
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Xu Chen
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
| | - Ziyue Chen
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China; Department of Pediatric Surgery, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, China
| | - Ming Huang
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Wen Dong
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Peng Gu
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Jingtong Zhang
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Qianghua Zhou
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Wei Dong
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Jinli Han
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Xisheng Wang
- Department of Urology, Shenzhen Longhua District Central Hospital, Shenzhen, China.
| | - Hui Li
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
| | - Jian Huang
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
| | - Tianxin Lin
- Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
| |
Collapse
|
4
|
Bielli P, Bordi M, Di Biasio V, Sette C. Regulation of BCL-X splicing reveals a role for the polypyrimidine tract binding protein (PTBP1/hnRNP I) in alternative 5' splice site selection. Nucleic Acids Res 2014; 42:12070-81. [PMID: 25294838 PMCID: PMC4231771 DOI: 10.1093/nar/gku922] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/18/2014] [Accepted: 09/22/2014] [Indexed: 02/06/2023] Open
Abstract
Alternative splicing (AS) modulates many physiological and pathological processes. For instance, AS of the BCL-X gene balances cell survival and apoptosis in development and cancer. Herein, we identified the polypyrimidine tract binding protein (PTBP1) as a direct regulator of BCL-X AS. Overexpression of PTBP1 promotes selection of the distal 5' splice site in BCL-X exon 2, generating the pro-apoptotic BCL-Xs splice variant. Conversely, depletion of PTBP1 enhanced splicing of the anti-apoptotic BCL-XL variant. In vivo cross-linking experiments and site-directed mutagenesis restricted the PTBP1 binding site to a polypyrimidine tract located between the two alternative 5' splice sites. Binding of PTBP1 to this site was required for its effect on splicing. Notably, a similar function of PTBP1 in the selection of alternative 5' splice sites was confirmed using the USP5 gene as additional model. Mechanistically, PTBP1 displaces SRSF1 binding from the proximal 5' splice site, thus repressing its selection. Our study provides a novel mechanism of alternative 5' splice site selection by PTBP1 and indicates that the presence of a PTBP1 binding site between two alternative 5' splice sites promotes selection of the distal one, while repressing the proximal site by competing for binding of a positive regulator.
Collapse
Affiliation(s)
- Pamela Bielli
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Matteo Bordi
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Valentina Di Biasio
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Claudio Sette
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome, Italy Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| |
Collapse
|
5
|
Mickleburgh I, Kafasla P, Cherny D, Llorian M, Curry S, Jackson RJ, Smith CWJ. The organization of RNA contacts by PTB for regulation of FAS splicing. Nucleic Acids Res 2014; 42:8605-20. [PMID: 24957602 PMCID: PMC4117754 DOI: 10.1093/nar/gku519] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Post-transcriptional steps of gene expression are regulated by RNA binding proteins. Major progress has been made in characterizing RNA-protein interactions, from high resolution structures to transcriptome-wide profiling. Due to the inherent technical challenges, less attention has been paid to the way in which proteins with multiple RNA binding domains engage with target RNAs. We have investigated how the four RNA recognition motif (RRM) domains of Polypyrimidine tract binding (PTB) protein, a major splicing regulator, interact with FAS pre-mRNA under conditions in which PTB represses FAS exon 6 splicing. A combination of tethered hydroxyl radical probing, targeted inactivation of individual RRMs and single molecule analyses revealed an unequal division of labour between the four RRMs of PTB. RNA binding by RRM4 is the most important for function despite the low intrinsic binding specificity and the complete lack of effect of disrupting individual RRM4 contact points on the RNA. The ordered RRM3-4 di-domain packing provides an extended binding surface for RNA interacting at RRM4, via basic residues in the preceding linker. Our results illustrate how multiple alternative low-specificity binding configurations of RRM4 are consistent with repressor function as long as the overall ribonucleoprotein architecture provided by appropriate di-domain packing is maintained.
Collapse
Affiliation(s)
- Ian Mickleburgh
- Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Panagiota Kafasla
- Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Dmitry Cherny
- Department of Biochemistry, Henry Wellcome Building, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Miriam Llorian
- Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Stephen Curry
- Division of Cell and Molecular Biology, Imperial College, Exhibition Road, London SW7 2AZ, UK
| | - Richard J Jackson
- Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Christopher W J Smith
- Department of Biochemistry, University of Cambridge, Downing Site, Tennis Court Road, Cambridge, CB2 1QW, UK
| |
Collapse
|