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Martin RM, de Almeida MR, Gameiro E, de Almeida SF. Live-cell imaging unveils distinct R-loop populations with heterogeneous dynamics. Nucleic Acids Res 2023; 51:11010-11023. [PMID: 37819055 PMCID: PMC10639055 DOI: 10.1093/nar/gkad812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 09/08/2023] [Accepted: 09/20/2023] [Indexed: 10/13/2023] Open
Abstract
We have developed RHINO, a genetically encoded sensor that selectively binds RNA:DNA hybrids enabling live-cell imaging of cellular R-loops. RHINO comprises a tandem array of three copies of the RNA:DNA hybrid binding domain of human RNase H1 connected by optimized linker segments and fused to a fluorescent protein. This tool allows the measurement of R-loop abundance and dynamics in live cells with high specificity and sensitivity. Using RHINO, we provide a kinetic framework for R-loops at nucleoli, telomeres and protein-coding genes. Our findings demonstrate that R-loop dynamics vary significantly across these regions, potentially reflecting the distinct roles R-loops play in different chromosomal contexts. RHINO is a powerful tool for investigating the role of R-loops in cellular processes and their contribution to disease development and progression.
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Affiliation(s)
- Robert M Martin
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Madalena R de Almeida
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Eduardo Gameiro
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Sérgio F de Almeida
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
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Moreira GG, Gomes CM. Tau liquid-liquid phase separation is modulated by the Ca 2+ -switched chaperone activity of the S100B protein. J Neurochem 2023; 166:76-86. [PMID: 36621842 DOI: 10.1111/jnc.15756] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 12/03/2022] [Accepted: 12/19/2022] [Indexed: 01/10/2023]
Abstract
Aggregation of the microtubule-associated protein tau is implicated in several neurodegenerative tauopathies including Alzheimer's disease (AD). Recent studies evidenced tau liquid-liquid phase separation (LLPS) into droplets as an early event in tau pathogenesis with the potential to enhance aggregation. Tauopathies like AD are accompanied by sustained neuroinflammation and the release of alarmins at early stages of inflammatory responses encompass protective functions. The Ca2+ -binding S100B protein is an alarmin augmented in AD that was recently implicated as a proteostasis regulator acting as a chaperone-type protein, inhibiting aggregation and toxicity through interactions of amyloidogenic clients with a regulatory surface exposed upon Ca2+ -binding. Here we expand the regulatory functions of S100B over protein condensation phenomena by reporting its Ca2+ -dependent activity as a modulator of tau LLPS induced by crowding agents (PEG) and metal ions (Zn2+ ). We observe that apo S100B has a negligible effect on PEG-induced tau demixing but that Ca2+ -bound S100B prevents demixing, resulting in a shift of the phase diagram boundary to higher crowding concentrations. Also, while incubation with apo S100B does not compromise tau LLPS, addition of Ca2+ results in a sharp decrease in turbidity, indicating that interactions with S100B-Ca2+ promote transition of tau to the mixed phase. Further, electrophoretic analysis and FLIM-FRET studies revealed that S100B incorporates into tau liquid droplets, suggesting an important stabilizing and chaperoning role contributing to minimize toxic tau aggregates. Resorting to Alexa488-labeled tau we observed that S100B-Ca2+ reduces the formation of tau fluorescent droplets, without compromising liquid-like behavior and droplet fusion events. The Zn2+ -binding properties of S100B also contribute to regulate Zn2+ -promoted tau LLPS as droplets are decreased by Zn2+ buffering by S100B, in addition to the Ca2+ -triggered interactions with tau. Altogether this work uncovers the versatility of S100B as a proteostasis regulator acting on protein condensation phenomena of relevance across the neurodegeneration continuum.
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Affiliation(s)
- Guilherme G Moreira
- BioISI-Instituto de Biosistemas e Ciências Integrativas, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Cláudio M Gomes
- BioISI-Instituto de Biosistemas e Ciências Integrativas, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
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Cao H, Wang Y, Zhang N, Xia S, Tian P, Lu L, Du J, Du Y. Progress of CRISPR-Cas13 Mediated Live-Cell RNA Imaging and Detection of RNA-Protein Interactions. Front Cell Dev Biol 2022; 10:866820. [PMID: 35356276 PMCID: PMC8959342 DOI: 10.3389/fcell.2022.866820] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 02/21/2022] [Indexed: 12/26/2022] Open
Abstract
Ribonucleic acid (RNA) and proteins play critical roles in gene expression and regulation. The relevant study increases the understanding of various life processes and contributes to the diagnosis and treatment of different diseases. RNA imaging and mapping RNA-protein interactions expand the understanding of RNA biology. However, the existing methods have some limitations. Recently, precise RNA targeting of CRISPR-Cas13 in cells has been reported, which is considered a new promising platform for RNA imaging in living cells and recognition of RNA-protein interactions. In this review, we first described the current findings on Cas13. Furthermore, we introduced current tools of RNA real-time imaging and mapping RNA-protein interactions and highlighted the latest advances in Cas13-mediated tools. Finally, we discussed the advantages and disadvantages of Cas13-based methods, providing a set of new ideas for the optimization of Cas13-mediated methods.
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Affiliation(s)
- Huake Cao
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- First School of Clinical Medicine, Anhui Medical University, Hefei, China
| | - Yuechen Wang
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- Second School of Clinical Medicine, Anhui Medical University, Hefei, China
| | - Ning Zhang
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- First School of Clinical Medicine, Anhui Medical University, Hefei, China
- First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Siyuan Xia
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- Second School of Clinical Medicine, Anhui Medical University, Hefei, China
| | - Pengfei Tian
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- First School of Clinical Medicine, Anhui Medical University, Hefei, China
- First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Li Lu
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Juan Du
- School of Medicine, The Chinese University of Hong Kong, Shenzhen, China
- Longgang District People’s Hospital of Shenzhen & The Second Affiliated Hospital, The Chinese University of Hong Kong, Shenzhen, China
- *Correspondence: Yinan Du, ; Juan Du,
| | - Yinan Du
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- *Correspondence: Yinan Du, ; Juan Du,
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Wachutka L, Caizzi L, Gagneur J, Cramer P. Global donor and acceptor splicing site kinetics in human cells. eLife 2019; 8:45056. [PMID: 31025937 PMCID: PMC6548502 DOI: 10.7554/elife.45056] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 04/25/2019] [Indexed: 11/13/2022] Open
Abstract
RNA splicing is an essential part of eukaryotic gene expression. Although the mechanism of splicing has been extensively studied in vitro, in vivo kinetics for the two-step splicing reaction remain poorly understood. Here, we combine transient transcriptome sequencing (TT-seq) and mathematical modeling to quantify RNA metabolic rates at donor and acceptor splice sites across the human genome. Splicing occurs in the range of minutes and is limited by the speed of RNA polymerase elongation. Splicing kinetics strongly depends on the position and nature of nucleotides flanking splice sites, and on structural interactions between unspliced RNA and small nuclear RNAs in spliceosomal intermediates. Finally, we introduce the 'yield' of splicing as the efficiency of converting unspliced to spliced RNA and show that it is highest for mRNAs and independent of splicing kinetics. These results lead to quantitative models describing how splicing rates and yield are encoded in the human genome.
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Affiliation(s)
- Leonhard Wachutka
- Department of Informatics, Technical University of Munich, Garching, Germany
| | - Livia Caizzi
- Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Julien Gagneur
- Department of Informatics, Technical University of Munich, Garching, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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Kretzschmar A, Schülke JP, Masana M, Dürre K, Müller MB, Bausch AR, Rein T. The Stress-Inducible Protein DRR1 Exerts Distinct Effects on Actin Dynamics. Int J Mol Sci 2018; 19:ijms19123993. [PMID: 30545002 PMCID: PMC6321462 DOI: 10.3390/ijms19123993] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 12/07/2018] [Accepted: 12/10/2018] [Indexed: 12/13/2022] Open
Abstract
Cytoskeletal dynamics are pivotal to memory, learning, and stress physiology, and thus psychiatric diseases. Downregulated in renal cell carcinoma 1 (DRR1) protein was characterized as the link between stress, actin dynamics, neuronal function, and cognition. To elucidate the underlying molecular mechanisms, we undertook a domain analysis of DRR1 and probed the effects on actin binding, polymerization, and bundling, as well as on actin-dependent cellular processes. Methods: DRR1 domains were cloned and expressed as recombinant proteins to perform in vitro analysis of actin dynamics (binding, bundling, polymerization, and nucleation). Cellular actin-dependent processes were analyzed in transfected HeLa cells with fluorescence recovery after photobleaching (FRAP) and confocal microscopy. Results: DRR1 features an actin binding site at each terminus, separated by a coiled coil domain. DRR1 enhances actin bundling, the cellular F-actin content, and serum response factor (SRF)-dependent transcription, while it diminishes actin filament elongation, cell spreading, and actin treadmilling. We also provide evidence for a nucleation effect of DRR1. Blocking of pointed end elongation by addition of profilin indicates DRR1 as a novel barbed end capping factor. Conclusions: DRR1 impacts actin dynamics in several ways with implications for cytoskeletal dynamics in stress physiology and pathophysiology.
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Affiliation(s)
- Anja Kretzschmar
- Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80805 München, Germany.
| | - Jan-Philip Schülke
- Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80805 München, Germany.
| | - Mercè Masana
- Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80805 München, Germany.
- Department of Psychiatry and Psychotherapy & Focus Program Translational Neuroscience, Johannes Gutenberg Universität Medical Center, 55131 Mainz, Germany.
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Barcelona, IDIBAPS, CIBERNED, Casanova, 143, 08036 Barcelona, Spain.
| | - Katharina Dürre
- Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.
| | - Marianne B Müller
- Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80805 München, Germany.
- Department of Psychiatry and Psychotherapy & Focus Program Translational Neuroscience, Johannes Gutenberg Universität Medical Center, 55131 Mainz, Germany.
| | - Andreas R Bausch
- Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.
| | - Theo Rein
- Max Planck Institute of Psychiatry, Kraepelinstraße 2-10, 80805 München, Germany.
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Abstract
When in the lampbrush configuration, chromosomes display thousands of visible DNA loops that are transcribed at exceptionally high rates by RNA polymerase II (pol II). These transcription loops provide unique opportunities to investigate not only the detailed architecture of pol II transcription sites but also the structural dynamics of chromosome looping, which is receiving fresh attention as the organizational principle underpinning the higher-order structure of all chromosome states. The approach described here allows for extended imaging of individual transcription loops and transcription units under conditions in which loop RNA synthesis continues. In intact nuclei from lampbrush-stage Xenopus oocytes isolated under mineral oil, highly specific targeting of fluorescent fusions of the RNA-binding protein CELF1 to nascent transcripts allowed functional transcription loops to be observed and their longevity assessed over time. Some individual loops remained extended and essentially static structures over time courses of up to an hour. However, others were less stable and shrank markedly over periods of 30-60 min in a manner that suggested that loop extension requires continued dense coverage with nascent transcripts. In stable loops and loop-derived structures, the molecular dynamics of the visible nascent RNP component were addressed using photokinetic approaches. The results suggested that CELF1 exchanges freely between the accumulated nascent RNP and the surrounding nucleoplasm, and that it exits RNP with similar kinetics to its entrance. Overall, it appears that on transcription loops, nascent transcripts contribute to a dynamic self-organizing structure that exemplifies a phase-separated nuclear compartment.
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Affiliation(s)
- Garry T Morgan
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
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Abstract
RNA plays an important role in life processes. Imaging of messenger RNAs (mRNAs) and micro-RNAs (miRNAs) not only allows us to learn the formation and transcription of mRNAs and the biogenesis of miRNAs involved in various life processes, but also helps in detecting cancer. High-performance RNA imaging probes greatly expand our view of life processes and enhance the cancer detection accuracy. In this review, we summarize the state-of-the-art high-performance RNA imaging probes, including exogenous probes that can image RNA sequences with special modification and endogeneous probes that can directly image endogenous RNAs without special treatment. For each probe, we review its structure and imaging principle in detail. Finally, we summarize the application of mRNA and miRNA imaging probes in studying life processes as well as in detecting cancer. By correlating the structures and principles of various probes with their practical uses, we compare different RNA imaging probes and offer guidance for better utilization of the current imaging probes and the future design of higher-performance RNA imaging probes.
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Affiliation(s)
- Yuqiong Xia
- Engineering Research Center of Molecular-imaging and Neuro-imaging of Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710126, China.
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Powrie EA, Ciocanel V, Kreiling JA, Gagnon JA, Sandstede B, Mowry KL. Using in vivo imaging to measure RNA mobility in Xenopus laevis oocytes. Methods 2015; 98:60-65. [PMID: 26546269 DOI: 10.1016/j.ymeth.2015.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 11/01/2015] [Accepted: 11/03/2015] [Indexed: 01/05/2023] Open
Abstract
RNA localization in the Xenopus oocyte is responsible for the establishment of polarity during oogenesis as well as the specification of germ layers during embryogenesis. However, the inability to monitor mRNA localization in live vertebrate oocytes has posed a major barrier to understanding the mechanisms driving directional transport. Here we describe a method for imaging MS2 tagged RNA in live Xenopus oocytes to study the dynamics of RNA localization. We also focus on methods for implementing and analyzing FRAP data. This protocol is optimized for imaging of the RNAs in stage II oocytes but it can be adapted to study dynamics of other molecules during oogenesis. Using this approach, mobility can be measured in different regions of the oocyte, enabling the direct observation of molecular dynamics throughout the oocyte.
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Affiliation(s)
- Erin A Powrie
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Veronica Ciocanel
- Department of Applied Mathematics, Brown University, Providence, RI 02912, USA
| | - Jill A Kreiling
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - James A Gagnon
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Bjӧrn Sandstede
- Department of Applied Mathematics, Brown University, Providence, RI 02912, USA
| | - Kimberly L Mowry
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.
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Ule J. Gene regulation via protein–RNA interactions. Methods 2014. [DOI: 10.1016/j.ymeth.2014.02.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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