51
|
Budzak J, Rudenko G. Pedal to the Metal: Nuclear Splicing Bodies Turbo-Charge VSG mRNA Production in African Trypanosomes. Front Cell Dev Biol 2022; 10:876701. [PMID: 35517511 PMCID: PMC9065277 DOI: 10.3389/fcell.2022.876701] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 03/18/2022] [Indexed: 11/18/2022] Open
Abstract
The African trypanosome Trypanosoma brucei is a parasite of the mammalian bloodstream and tissues, where an antigenically variable Variant Surface Glycoprotein (VSG) coat protects it from immune attack. This dense layer comprised of ∼107 VSG proteins, makes VSG by far the most abundant mRNA (7-10% total) and protein (∼10% total) in the bloodstream form trypanosome. How can such prodigious amounts of VSG be produced from a single VSG gene? Extremely high levels of RNA polymerase I (Pol I) transcription of the active VSG provide part of the explanation. However, recent discoveries highlight the role of pre-mRNA processing, both in maintaining high levels of VSG transcription, as well as its monoallelic expression. Trypanosome mRNAs are matured through trans-splicing a spliced leader (SL) RNA to the 5' end of precursor transcripts, meaning abundant SL RNA is required throughout the nucleus. However, requirement for SL RNA in the vicinity of the active VSG gene is so intense, that the cell reconfigures its chromatin architecture to facilitate interaction between the SL RNA genes and the active VSG. This presumably ensures that sufficient localised SL RNA is available, and not limiting for VSG mRNA expression. Recently, novel nuclear splicing bodies which appear to provide essential trans-splicing components, have been identified associating with the active VSG. These observations highlight the underappreciated role of pre-mRNA processing in modulating gene expression in trypanosomes. Dissecting the function of these nuclear RNA processing bodies should help us elucidate the mechanisms of both VSG expression and monoallelic exclusion in T. brucei.
Collapse
Affiliation(s)
| | - Gloria Rudenko
- Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, London, United Kingdom
| |
Collapse
|
52
|
Tammer L, Hameiri O, Keydar I, Roy VR, Ashkenazy-Titelman A, Custódio N, Sason I, Shayevitch R, Rodríguez-Vaello V, Rino J, Lev Maor G, Leader Y, Khair D, Aiden EL, Elkon R, Irimia M, Sharan R, Shav-Tal Y, Carmo-Fonseca M, Ast G. Gene architecture directs splicing outcome in separate nuclear spatial regions. Mol Cell 2022; 82:1021-1034.e8. [PMID: 35182478 DOI: 10.1016/j.molcel.2022.02.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 01/31/2022] [Accepted: 01/31/2022] [Indexed: 12/13/2022]
Abstract
How the splicing machinery defines exons or introns as the spliced unit has remained a puzzle for 30 years. Here, we demonstrate that peripheral and central regions of the nucleus harbor genes with two distinct exon-intron GC content architectures that differ in the splicing outcome. Genes with low GC content exons, flanked by long introns with lower GC content, are localized in the periphery, and the exons are defined as the spliced unit. Alternative splicing of these genes results in exon skipping. In contrast, the nuclear center contains genes with a high GC content in the exons and short flanking introns. Most splicing of these genes occurs via intron definition, and aberrant splicing leads to intron retention. We demonstrate that the nuclear periphery and center generate different environments for the regulation of alternative splicing and that two sets of splicing factors form discrete regulatory subnetworks for the two gene architectures. Our study connects 3D genome organization and splicing, thus demonstrating that exon and intron definition modes of splicing occur in different nuclear regions.
Collapse
Affiliation(s)
- Luna Tammer
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Ofir Hameiri
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Ifat Keydar
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Vanessa Rachel Roy
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Asaf Ashkenazy-Titelman
- The Mina & Everard Goodman Faculty of Life Sciences and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Noélia Custódio
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Itay Sason
- Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ronna Shayevitch
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Victoria Rodríguez-Vaello
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain, ICREA, Barcelona, Spain
| | - José Rino
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Galit Lev Maor
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Yodfat Leader
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Doha Khair
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Erez Lieberman Aiden
- The Center for Genome Architecture, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ran Elkon
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Manuel Irimia
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain, ICREA, Barcelona, Spain
| | - Roded Sharan
- Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yaron Shav-Tal
- The Mina & Everard Goodman Faculty of Life Sciences and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Gil Ast
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel.
| |
Collapse
|
53
|
Uchino S, Ito Y, Sato Y, Handa T, Ohkawa Y, Tokunaga M, Kimura H. Live imaging of transcription sites using an elongating RNA polymerase II-specific probe. J Cell Biol 2022; 221:212888. [PMID: 34854870 PMCID: PMC8647360 DOI: 10.1083/jcb.202104134] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 10/12/2021] [Accepted: 11/10/2021] [Indexed: 12/15/2022] Open
Abstract
In eukaryotic nuclei, most genes are transcribed by RNA polymerase II (RNAP2), whose regulation is a key to understanding the genome and cell function. RNAP2 has a long heptapeptide repeat (Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7), and Ser2 is phosphorylated on an elongation form. To detect RNAP2 Ser2 phosphorylation (RNAP2 Ser2ph) in living cells, we developed a genetically encoded modification-specific intracellular antibody (mintbody) probe. The RNAP2 Ser2ph-mintbody exhibited numerous foci, possibly representing transcription “factories,” and foci were diminished during mitosis and in a Ser2 kinase inhibitor. An in vitro binding assay using phosphopeptides confirmed the mintbody’s specificity. RNAP2 Ser2ph-mintbody foci were colocalized with proteins associated with elongating RNAP2 compared with factors involved in the initiation. These results support the view that mintbody localization represents the sites of RNAP2 Ser2ph in living cells. RNAP2 Ser2ph-mintbody foci showed constrained diffusional motion like chromatin, but they were more mobile than DNA replication domains and p300-enriched foci, suggesting that the elongating RNAP2 complexes are separated from more confined chromatin domains.
Collapse
Affiliation(s)
- Satoshi Uchino
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Yuma Ito
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Yuko Sato
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.,Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Tetsuya Handa
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Yasuyuki Ohkawa
- Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Makio Tokunaga
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Hiroshi Kimura
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.,Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| |
Collapse
|
54
|
Kimura H, Sato Y. Imaging transcription elongation dynamics by new technologies unveils the organization of initiation and elongation in transcription factories. Curr Opin Cell Biol 2022; 74:71-79. [DOI: 10.1016/j.ceb.2022.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 01/05/2022] [Accepted: 01/10/2022] [Indexed: 11/27/2022]
|
55
|
Abstract
In eukaryotic cells, protein and RNA factors involved in genome activities like transcription, RNA processing, DNA replication, and repair accumulate in self-organizing membraneless chromatin subcompartments. These structures contribute to efficiently conduct chromatin-mediated reactions and to establish specific cellular programs. However, the underlying mechanisms for their formation are only partly understood. Recent studies invoke liquid-liquid phase separation (LLPS) of proteins and RNAs in the establishment of chromatin activity patterns. At the same time, the folding of chromatin in the nucleus can drive genome partitioning into spatially distinct domains. Here, the interplay between chromatin organization, chromatin binding, and LLPS is discussed by comparing and contrasting three prototypical chromatin subcompartments: the nucleolus, clusters of active RNA polymerase II, and pericentric heterochromatin domains. It is discussed how the different ways of chromatin compartmentalization are linked to transcription regulation, the targeting of soluble factors to certain parts of the genome, and to disease-causing genetic aberrations.
Collapse
Affiliation(s)
- Karsten Rippe
- Division of Chromatin Networks, German Cancer Research Center (DKFZ) and Bioquant, 69120 Heidelberg, Germany
| |
Collapse
|
56
|
Palacio M, Taatjes DJ. Merging Established Mechanisms with New Insights: Condensates, Hubs, and the Regulation of RNA Polymerase II Transcription. J Mol Biol 2022; 434:167216. [PMID: 34474085 PMCID: PMC8748285 DOI: 10.1016/j.jmb.2021.167216] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 01/17/2023]
Abstract
The regulation of RNA polymerase II (pol II) transcription requires a complex and context-specific array of proteins and protein complexes, as well as nucleic acids and metabolites. Every major physiological process requires coordinated transcription of specific sets of genes at the appropriate time, and a breakdown in this regulation is a hallmark of human disease. A proliferation of recent studies has revealed that many general transcription components, including sequence-specific, DNA-binding transcription factors, Mediator, and pol II itself, are capable of liquid-liquid phase separation, to form condensates that partition these factors away from the bulk aqueous phase. These findings hold great promise for next-level understanding of pol II transcription; however, many mechanistic aspects align with more conventional models, and whether phase separation per se regulates pol II activity in cells remains controversial. In this review, we describe the conventional and condensate-dependent models, and why their similarities and differences are important. We also compare and contrast these models in the context of genome organization and pol II transcription (initiation, elongation, and termination), and highlight the central role of RNA in these processes. Finally, we discuss mutations that disrupt normal partitioning of transcription factors, and how this may contribute to disease.
Collapse
Affiliation(s)
- Megan Palacio
- Dept. of Biochemistry, University of Colorado, Boulder, CO, USA
| | - Dylan J. Taatjes
- Dept. of Biochemistry, University of Colorado, Boulder, CO, USA,corresponding author;
| |
Collapse
|
57
|
Cawte AD, Iino H, Unrau PJ, Rueda DS. Single-Molecule RNA Imaging Using Mango II Arrays. Methods Mol Biol 2022; 2404:267-280. [PMID: 34694614 DOI: 10.1007/978-1-0716-1851-6_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In recent years, fluorogenic RNA aptamers, such as Spinach, Broccoli, Corn, Mango, Coral, and Pepper have gathered traction as an efficient alternative labeling strategy for background-free imaging of cellular RNAs. However, their application has been somewhat limited by relatively inefficient folding and fluorescent stability. With the recent advent of novel RNA-Mango variants which are improved in both fluorescence intensity and folding stability in tandem arrays, it is now possible to image RNAs with single-molecule sensitivity. Here we discuss the protocol for imaging Mango II tagged RNAs in both fixed and live cells.
Collapse
Affiliation(s)
- Adam D Cawte
- Single Molecule Imaging Group, MRC London Institute of Medical Sciences, London, UK
- Section of Virology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
- Developmental Epigenetics, Department of Biochemistry, University of Oxford, Oxford, UK
| | - Haruki Iino
- Single Molecule Imaging Group, MRC London Institute of Medical Sciences, London, UK
- Section of Virology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
| | - Peter J Unrau
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.
| | - David S Rueda
- Single Molecule Imaging Group, MRC London Institute of Medical Sciences, London, UK.
- Section of Virology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK.
| |
Collapse
|
58
|
Shao W, Bi X, Pan Y, Gao B, Wu J, Yin Y, Liu Z, Peng M, Zhang W, Jiang X, Ren W, Xu Y, Wu Z, Wang K, Zhan G, Lu JY, Han X, Li T, Wang J, Li G, Deng H, Li B, Shen X. Phase separation of RNA-binding protein promotes polymerase binding and transcription. Nat Chem Biol 2022; 18:70-80. [PMID: 34916619 DOI: 10.1038/s41589-021-00904-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 09/22/2021] [Indexed: 01/27/2023]
Abstract
An RNA-involved phase-separation model has been proposed for transcription control. However, the molecular links that connect RNA to the transcription machinery remain missing. Here we find that RNA-binding proteins (RBPs) constitute half of the chromatin proteome in embryonic stem cells (ESCs), some being colocalized with RNA polymerase (Pol) II at promoters and enhancers. Biochemical analyses of representative RBPs show that the paraspeckle protein PSPC1 inhibits the RNA-induced premature release of Pol II, and makes use of RNA as multivalent molecules to enhance the formation of transcription condensates and subsequent phosphorylation and release of Pol II. This synergistic interplay enhances polymerase engagement and activity via the RNA-binding and phase-separation activities of PSPC1. In ESCs, auxin-induced acute degradation of PSPC1 leads to genome-wide defects in Pol II binding and nascent transcription. We propose that promoter-associated RNAs and their binding proteins synergize the phase separation of polymerase condensates to promote active transcription.
Collapse
Affiliation(s)
- Wen Shao
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Xianju Bi
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Yixuan Pan
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Boyang Gao
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Jun Wu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yafei Yin
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Zhimin Liu
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Mengyuan Peng
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wenhao Zhang
- Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xu Jiang
- Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China
| | - Wenlin Ren
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Yanhui Xu
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Zhongyang Wu
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Kaili Wang
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Ge Zhan
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - J Yuyang Lu
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Xue Han
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Tong Li
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Jianlong Wang
- Department of Medicine, Columbia Center for Human Development, Columbia University Irving Medical Center, New York, NY, USA
| | - Guohong Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Haiteng Deng
- Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China
| | - Bing Li
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Xiaohua Shen
- School of Medicine and School of Life Sciences, Tsinghua University; Tsinghua-Peking Joint Center for Life Sciences, Beijing, China.
| |
Collapse
|
59
|
Akhlaghpour H. An RNA-Based Theory of Natural Universal Computation. J Theor Biol 2021; 537:110984. [PMID: 34979104 DOI: 10.1016/j.jtbi.2021.110984] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 09/30/2021] [Accepted: 12/07/2021] [Indexed: 12/15/2022]
Abstract
Life is confronted with computation problems in a variety of domains including animal behavior, single-cell behavior, and embryonic development. Yet we currently do not know of a naturally existing biological system that is capable of universal computation, i.e., Turing-equivalent in scope. Generic finite-dimensional dynamical systems (which encompass most models of neural networks, intracellular signaling cascades, and gene regulatory networks) fall short of universal computation, but are assumed to be capable of explaining cognition and development. I present a class of models that bridge two concepts from distant fields: combinatory logic (or, equivalently, lambda calculus) and RNA molecular biology. A set of basic RNA editing rules can make it possible to compute any computable function with identical algorithmic complexity to that of Turing machines. The models do not assume extraordinarily complex molecular machinery or any processes that radically differ from what we already know to occur in cells. Distinct independent enzymes can mediate each of the rules and RNA molecules solve the problem of parenthesis matching through their secondary structure. In the most plausible of these models all of the editing rules can be implemented with merely cleavage and ligation operations at fixed positions relative to predefined motifs. This demonstrates that universal computation is well within the reach of molecular biology. It is therefore reasonable to assume that life has evolved - or possibly began with - a universal computer that yet remains to be discovered. The variety of seemingly unrelated computational problems across many scales can potentially be solved using the same RNA-based computation system. Experimental validation of this theory may immensely impact our understanding of memory, cognition, development, disease, evolution, and the early stages of life.
Collapse
Affiliation(s)
- Hessameddin Akhlaghpour
- Laboratory of Integrative Brain Function, The Rockefeller University, New York, NY, 10065, USA
| |
Collapse
|
60
|
Castells-Garcia A, Ed-Daoui I, González-Almela E, Vicario C, Ottestrom J, Lakadamyali M, Neguembor MV, Cosma MP. Super resolution microscopy reveals how elongating RNA polymerase II and nascent RNA interact with nucleosome clutches. Nucleic Acids Res 2021; 50:175-190. [PMID: 34929735 PMCID: PMC8754629 DOI: 10.1093/nar/gkab1215] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 10/13/2021] [Accepted: 11/26/2021] [Indexed: 11/17/2022] Open
Abstract
Transcription and genome architecture are interdependent, but it is still unclear how nucleosomes in the chromatin fiber interact with nascent RNA, and which is the relative nuclear distribution of these RNAs and elongating RNA polymerase II (RNAP II). Using super-resolution (SR) microscopy, we visualized the nascent transcriptome, in both nucleoplasm and nucleolus, with nanoscale resolution. We found that nascent RNAs organize in structures we termed RNA nanodomains, whose characteristics are independent of the number of transcripts produced over time. Dual-color SR imaging of nascent RNAs, together with elongating RNAP II and H2B, shows the physical relation between nucleosome clutches, RNAP II, and RNA nanodomains. The distance between nucleosome clutches and RNA nanodomains is larger than the distance measured between elongating RNAP II and RNA nanodomains. Elongating RNAP II stands between nascent RNAs and the small, transcriptionally active, nucleosome clutches. Moreover, RNA factories are small and largely formed by few RNAP II. Finally, we describe a novel approach to quantify the transcriptional activity at an individual gene locus. By measuring local nascent RNA accumulation upon transcriptional activation at single alleles, we confirm the measurements made at the global nuclear level.
Collapse
Affiliation(s)
- Alvaro Castells-Garcia
- Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, China
| | - Ilyas Ed-Daoui
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Esther González-Almela
- Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, China
| | - Chiara Vicario
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Jason Ottestrom
- ICFO-Institute of Photonic Sciences, The Barcelona Institute of Science and Technology, Barcelona, 08860, Spain
| | - Melike Lakadamyali
- Perelman School of Medicine, Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, USA.,Perelman School of Medicine, Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Maria Victoria Neguembor
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Maria Pia Cosma
- Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, China.,CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain.,ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Dr Aiguader 88, 08003 Barcelona, Spain
| |
Collapse
|
61
|
Wang Z, Deng W. Dynamic transcription regulation at the single-molecule level. Dev Biol 2021; 482:67-81. [PMID: 34896367 DOI: 10.1016/j.ydbio.2021.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 11/14/2021] [Accepted: 11/15/2021] [Indexed: 02/07/2023]
Abstract
Cell fate changes during development, differentiation, and reprogramming are largely controlled at the transcription level. The DNA-binding transcription factors (TFs) often act in a combinatorial fashion to alter chromatin states and drive cell type-specific gene expression. Recent advances in fluorescent microscopy technologies have enabled direct visualization of biomolecules involved in the process of transcription and its regulatory events at the single-molecule level in living cells. Remarkably, imaging and tracking individual TF molecules at high temporal and spatial resolution revealed that they are highly dynamic in searching and binding cognate targets, rather than static and binding constantly. In combination with investigation using techniques from biochemistry, structure biology, genetics, and genomics, a more well-rounded view of transcription regulation is emerging. In this review, we briefly cover the technical aspects of live-cell single-molecule imaging and focus on the biological relevance and interpretation of the single-molecule dynamic features of transcription regulatory events observed in the native chromatin environment of living eukaryotic cells. We also discuss how these dynamic features might shed light on mechanistic understanding of transcription regulation.
Collapse
Affiliation(s)
- Zuhui Wang
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Wulan Deng
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China; Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing, 100871, China; Peking-Tsinghua Center for Life Sciences (CLS), Peking University, Beijing, 100871, China; School of Life Sciences, Peking University, Beijing, 100871, China.
| |
Collapse
|
62
|
Goelzer M, Goelzer J, Ferguson ML, Neu CP, Uzer G. Nuclear envelope mechanobiology: linking the nuclear structure and function. Nucleus 2021; 12:90-114. [PMID: 34455929 PMCID: PMC8432354 DOI: 10.1080/19491034.2021.1962610] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/26/2021] [Accepted: 07/27/2021] [Indexed: 01/10/2023] Open
Abstract
The nucleus, central to cellular activity, relies on both direct mechanical input as well as its molecular transducers to sense external stimuli and respond by regulating intra-nuclear chromatin organization that determines cell function and fate. In mesenchymal stem cells of musculoskeletal tissues, changes in nuclear structures are emerging as a key modulator of their differentiation and proliferation programs. In this review we will first introduce the structural elements of the nucleoskeleton and discuss the current literature on how nuclear structure and signaling are altered in relation to environmental and tissue level mechanical cues. We will focus on state-of-the-art techniques to apply mechanical force and methods to measure nuclear mechanics in conjunction with DNA, RNA, and protein visualization in living cells. Ultimately, combining real-time nuclear deformations and chromatin dynamics can be a powerful tool to study mechanisms of how forces affect the dynamics of genome function.
Collapse
Affiliation(s)
- Matthew Goelzer
- Materials Science and Engineering, Boise State University, Boise, ID, US
| | | | - Matthew L. Ferguson
- Biomolecular Science, Boise State University, Boise, ID, US
- Physics, Boise State University, Boise, ID, US
| | - Corey P. Neu
- Paul M. Rady Department of Mechanical Engineering, University of Colorado, Boulder, CO, US
| | - Gunes Uzer
- Mechanical and Biomedical Engineering, Boise State University, Boise, ID, US
| |
Collapse
|
63
|
Biswas J, Li W, Singer RH, Coleman RA. Imaging Organization of RNA Processing within the Nucleus. Cold Spring Harb Perspect Biol 2021; 13:a039453. [PMID: 34127450 PMCID: PMC8635003 DOI: 10.1101/cshperspect.a039453] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Within the nucleus, messenger RNA is generated and processed in a highly organized and regulated manner. Messenger RNA processing begins during transcription initiation and continues until the RNA is translated and degraded. Processes such as 5' capping, alternative splicing, and 3' end processing have been studied extensively with biochemical methods and more recently with single-molecule imaging approaches. In this review, we highlight how imaging has helped understand the highly dynamic process of RNA processing. We conclude with open questions and new technological developments that may further our understanding of RNA processing.
Collapse
Affiliation(s)
- Jeetayu Biswas
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Weihan Li
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robert H Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robert A Coleman
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| |
Collapse
|
64
|
Abstract
To predict transcription, one needs a mechanistic understanding of how the numerous required transcription factors (TFs) explore the nuclear space to find their target genes, assemble, cooperate, and compete with one another. Advances in fluorescence microscopy have made it possible to visualize real-time TF dynamics in living cells, leading to two intriguing observations: first, most TFs contact chromatin only transiently; and second, TFs can assemble into clusters through their intrinsically disordered regions. These findings suggest that highly dynamic events and spatially structured nuclear microenvironments might play key roles in transcription regulation that are not yet fully understood. The emerging model is that while some promoters directly convert TF-binding events into on/off cycles of transcription, many others apply complex regulatory layers that ultimately lead to diverse phenotypic outputs. Cracking this kinetic code is an ongoing and challenging task that is made possible by combining innovative imaging approaches with biophysical models.
Collapse
Affiliation(s)
- Feiyue Lu
- Institute for Systems Genetics and Cell Biology Department, NYU School of Medicine, New York, New York 10016, USA
| | - Timothée Lionnet
- Institute for Systems Genetics and Cell Biology Department, NYU School of Medicine, New York, New York 10016, USA
| |
Collapse
|
65
|
Grün JT, Schwalbe H. Folding dynamics of polymorphic G-quadruplex structures. Biopolymers 2021; 113:e23477. [PMID: 34664713 DOI: 10.1002/bip.23477] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 12/14/2022]
Abstract
G-quadruplexes (G4), found in numerous places within the human genome, are involved in essential processes of cell regulation. Chromosomal DNA G4s are involved for example, in replication and transcription as first steps of gene expression. Hence, they influence a plethora of downstream processes. G4s possess an intricate structure that differs from canonical B-form DNA. Identical DNA G4 sequences can adopt multiple long-lived conformations, a phenomenon known as G4 polymorphism. A detailed understanding of the molecular mechanisms that drive G4 folding is essential to understand their ambivalent regulatory roles. Disentangling the inherent dynamic and polymorphic nature of G4 structures thus is key to unravel their biological functions and make them amenable as molecular targets in novel therapeutic approaches. We here review recent experimental approaches to monitor G4 folding and discuss structural aspects for possible folding pathways. Substantial progress in the understanding of G4 folding within the recent years now allows drawing comprehensive models of the complex folding energy landscape of G4s that we herein evaluate based on computational and experimental evidence.
Collapse
Affiliation(s)
- J Tassilo Grün
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University, Frankfurt/M, Germany.,Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Frankfurt/M, Germany
| |
Collapse
|
66
|
Boka AP, Mukherjee A, Mir M. Single-molecule tracking technologies for quantifying the dynamics of gene regulation in cells, tissue and embryos. Development 2021; 148:272071. [PMID: 34490887 DOI: 10.1242/dev.199744] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
For decades, we have relied on population and time-averaged snapshots of dynamic molecular scale events to understand how genes are regulated during development and beyond. The advent of techniques to observe single-molecule kinetics in increasingly endogenous contexts, progressing from in vitro studies to living embryos, has revealed how much we have missed. Here, we provide an accessible overview of the rapidly expanding family of technologies for single-molecule tracking (SMT), with the goal of enabling the reader to critically analyse single-molecule studies, as well as to inspire the application of SMT to their own work. We start by overviewing the basics of and motivation for SMT experiments, and the trade-offs involved when optimizing parameters. We then cover key technologies, including fluorescent labelling, excitation and detection optics, localization and tracking algorithms, and data analysis. Finally, we provide a summary of selected recent applications of SMT to study the dynamics of gene regulation.
Collapse
Affiliation(s)
- Alan P Boka
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Apratim Mukherjee
- Center for Computational and Genomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Mustafa Mir
- Center for Computational and Genomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.,Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| |
Collapse
|
67
|
Basyuk E, Rage F, Bertrand E. RNA transport from transcription to localized translation: a single molecule perspective. RNA Biol 2021; 18:1221-1237. [PMID: 33111627 PMCID: PMC8354613 DOI: 10.1080/15476286.2020.1842631] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 10/21/2020] [Accepted: 10/22/2020] [Indexed: 12/21/2022] Open
Abstract
Transport of mRNAs is an important step of gene expression, which brings the genetic message from the DNA in the nucleus to a precise cytoplasmic location in a regulated fashion. Perturbation of this process can lead to pathologies such as developmental and neurological disorders. In this review, we discuss recent advances in the field of mRNA transport made using single molecule fluorescent imaging approaches. We present an overview of these approaches in fixed and live cells and their input in understanding the key steps of mRNA journey: transport across the nucleoplasm, export through the nuclear pores and delivery to its final cytoplasmic location. This review puts a particular emphasis on the coupling of mRNA transport with translation, such as localization-dependent translational regulation and translation-dependent mRNA localization. We also highlight the recently discovered translation factories, and how cellular and viral RNAs can hijack membrane transport systems to travel in the cytoplasm.
Collapse
Affiliation(s)
- Eugenia Basyuk
- Institut de Génétique Humaine, CNRS-UMR9002, Univ Montpellier, Montpellier, France
- Present address: Laboratoire de Microbiologie Fondamentale et Pathogénicité, CNRS-UMR 5234, Université de Bordeaux, Bordeaux, France
| | - Florence Rage
- Institut de Génétique Moléculaire de Montpellier, CNRS-UMR5535, Univ Montpellier, Montpellier, France
| | - Edouard Bertrand
- Institut de Génétique Humaine, CNRS-UMR9002, Univ Montpellier, Montpellier, France
- Institut de Génétique Moléculaire de Montpellier, CNRS-UMR5535, Univ Montpellier, Montpellier, France
- Equipe Labélisée Ligue Nationale Contre Le Cancer, Montpellier, France
| |
Collapse
|
68
|
Pancholi A, Klingberg T, Zhang W, Prizak R, Mamontova I, Noa A, Sobucki M, Kobitski AY, Nienhaus GU, Zaburdaev V, Hilbert L. RNA polymerase II clusters form in line with surface condensation on regulatory chromatin. Mol Syst Biol 2021; 17:e10272. [PMID: 34569155 PMCID: PMC8474054 DOI: 10.15252/msb.202110272] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 08/26/2021] [Accepted: 09/10/2021] [Indexed: 12/15/2022] Open
Abstract
It is essential for cells to control which genes are transcribed into RNA. In eukaryotes, two major control points are recruitment of RNA polymerase II (Pol II) into a paused state, and subsequent pause release toward transcription. Pol II recruitment and pause release occur in association with macromolecular clusters, which were proposed to be formed by a liquid-liquid phase separation mechanism. How such a phase separation mechanism relates to the interaction of Pol II with DNA during recruitment and transcription, however, remains poorly understood. Here, we use live and super-resolution microscopy in zebrafish embryos to reveal Pol II clusters with a large variety of shapes, which can be explained by a theoretical model in which regulatory chromatin regions provide surfaces for liquid-phase condensation at concentrations that are too low for canonical liquid-liquid phase separation. Model simulations and chemical perturbation experiments indicate that recruited Pol II contributes to the formation of these surface-associated condensates, whereas elongating Pol II is excluded from these condensates and thereby drives their unfolding.
Collapse
Affiliation(s)
- Agnieszka Pancholi
- Zoological InstituteDepartment of Systems Biology and BioinformaticsKarlsruhe Institute of TechnologyKarlsruheGermany
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Tim Klingberg
- Department of BiologyFriedrich‐Alexander‐Universität Erlangen‐NürnbergErlangenGermany
- Max‐Planck‐Zentrum für Physik und MedizinErlangenGermany
| | - Weichun Zhang
- Institute of Applied PhysicsKarlsruhe Institute of TechnologyKarlsruheGermany
- Institute of NanotechnologyKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Roshan Prizak
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Irina Mamontova
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Amra Noa
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Marcel Sobucki
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| | - Andrei Yu Kobitski
- Institute of Applied PhysicsKarlsruhe Institute of TechnologyKarlsruheGermany
| | - Gerd Ulrich Nienhaus
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
- Institute of Applied PhysicsKarlsruhe Institute of TechnologyKarlsruheGermany
- Institute of NanotechnologyKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
- Department of PhysicsUniversity of Illinois at Urbana‐ChampaignUrbanaILUSA
| | - Vasily Zaburdaev
- Department of BiologyFriedrich‐Alexander‐Universität Erlangen‐NürnbergErlangenGermany
- Max‐Planck‐Zentrum für Physik und MedizinErlangenGermany
| | - Lennart Hilbert
- Zoological InstituteDepartment of Systems Biology and BioinformaticsKarlsruhe Institute of TechnologyKarlsruheGermany
- Institute of Biological and Chemical Systems—Biological Information ProcessingKarlsruhe Institute of TechnologyEggenstein‐LeopoldshafenGermany
| |
Collapse
|
69
|
Alamos S, Reimer A, Niyogi KK, Garcia HG. Quantitative imaging of RNA polymerase II activity in plants reveals the single-cell basis of tissue-wide transcriptional dynamics. NATURE PLANTS 2021; 7:1037-1049. [PMID: 34373604 PMCID: PMC8616715 DOI: 10.1038/s41477-021-00976-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 06/22/2021] [Indexed: 05/18/2023]
Abstract
The responses of plants to their environment are often dependent on the spatiotemporal dynamics of transcriptional regulation. While live-imaging tools have been used extensively to quantitatively capture rapid transcriptional dynamics in living animal cells, the lack of implementation of these technologies in plants has limited concomitant quantitative studies in this kingdom. Here, we applied the PP7 and MS2 RNA-labelling technologies for the quantitative imaging of RNA polymerase II activity dynamics in single cells of living plants as they respond to experimental treatments. Using this technology, we counted nascent RNA transcripts in real time in Nicotiana benthamiana (tobacco) and Arabidopsis thaliana. Examination of heat shock reporters revealed that plant tissues respond to external signals by modulating the proportion of cells that switch from an undetectable basal state to a high-transcription state, instead of modulating the rate of transcription across all cells in a graded fashion. This switch-like behaviour, combined with cell-to-cell variability in transcription rate, results in mRNA production variability spanning three orders of magnitude. We determined that cellular heterogeneity stems mainly from stochasticity intrinsic to individual alleles instead of variability in cellular composition. Together, our results demonstrate that it is now possible to quantitatively study the dynamics of transcriptional programs in single cells of living plants.
Collapse
Affiliation(s)
- Simon Alamos
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA
| | - Armando Reimer
- Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA
| | - Krishna K Niyogi
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA.
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Hernan G Garcia
- Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA.
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA.
- Department of Physics, University of California Berkeley, Berkeley, CA, USA.
- Institute for Quantitative Biosciences-QB3, University of California Berkeley, Berkeley, CA, USA.
| |
Collapse
|
70
|
Muniz L, Nicolas E, Trouche D. RNA polymerase II speed: a key player in controlling and adapting transcriptome composition. EMBO J 2021; 40:e105740. [PMID: 34254686 PMCID: PMC8327950 DOI: 10.15252/embj.2020105740] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 05/01/2021] [Accepted: 05/10/2021] [Indexed: 12/19/2022] Open
Abstract
RNA polymerase II (RNA Pol II) speed or elongation rate, i.e., the number of nucleotides synthesized per unit of time, is a major determinant of transcriptome composition. It controls co‐transcriptional processes such as splicing, polyadenylation, and transcription termination, thus regulating the production of alternative splice variants, circular RNAs, alternatively polyadenylated transcripts, or read‐through transcripts. RNA Pol II speed itself is regulated in response to intra‐ and extra‐cellular stimuli and can in turn affect the transcriptome composition in response to these stimuli. Evidence points to a potentially important role of transcriptome composition modification through RNA Pol II speed regulation for adaptation of cells to a changing environment, thus pointing to a function of RNA Pol II speed regulation in cellular physiology. Analyzing RNA Pol II speed dynamics may therefore be central to fully understand the regulation of physiological processes, such as the development of multicellular organisms. Recent findings also raise the possibility that RNA Pol II speed deregulation can be detrimental and participate in disease progression. Here, we review initial and current approaches to measure RNA Pol II speed, as well as providing an overview of the factors controlling speed and the co‐transcriptional processes which are affected. Finally, we discuss the role of RNA Pol II speed regulation in cell physiology.
Collapse
Affiliation(s)
- Lisa Muniz
- MCD, Centre de Biologie Integrative (CBI), CNRS, UPS, University of Toulouse, Toulouse, France
| | - Estelle Nicolas
- MCD, Centre de Biologie Integrative (CBI), CNRS, UPS, University of Toulouse, Toulouse, France
| | - Didier Trouche
- MCD, Centre de Biologie Integrative (CBI), CNRS, UPS, University of Toulouse, Toulouse, France
| |
Collapse
|
71
|
Patange S, Ball DA, Karpova TS, Larson DR. Towards a 'Spot On' Understanding of Transcription in the Nucleus. J Mol Biol 2021; 433:167016. [PMID: 33951451 PMCID: PMC8184600 DOI: 10.1016/j.jmb.2021.167016] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 04/16/2021] [Accepted: 04/22/2021] [Indexed: 11/29/2022]
Abstract
Regulation of transcription by RNA Polymerase II (RNAPII) is a rapidly evolving area of research. Technological developments in microscopy have revealed insight into the dynamics, structure, and localization of transcription components within single cells. A frequent observation in many studies is the appearance of 'spots' in cell nuclei associated with the transcription process. In this review we highlight studies that characterize the temporal and spatial characteristics of these spots, examine possible pitfalls in interpreting these kind of imaging data, and outline directions where single-cell imaging may advance in ways to further our understanding of transcription regulation.
Collapse
Affiliation(s)
- Simona Patange
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - David A Ball
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Tatiana S Karpova
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Daniel R Larson
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States.
| |
Collapse
|
72
|
Escobar EE, Venkat Ramani MK, Zhang Y, Brodbelt JS. Evaluating Spatiotemporal Dynamics of Phosphorylation of RNA Polymerase II Carboxy-Terminal Domain by Ultraviolet Photodissociation Mass Spectrometry. J Am Chem Soc 2021; 143:8488-8498. [PMID: 34053220 DOI: 10.1021/jacs.1c03321] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The critical role of site-specific phosphorylation in eukaryotic transcription has motivated efforts to decipher the complex phosphorylation patterns exhibited by the carboxyl-terminal domain (CTD) of RNA polymerase II. Phosphorylation remains a challenging post-translational modification to characterize by mass spectrometry owing to the labile phosphate ester linkage and low stoichiometric prevalence, two features that complicate analysis by high-throughput MS/MS methods. Identifying phosphorylation sites represents one significant hurdle in decrypting the CTD phosphorylation, a problem exaggerated by a large number of potential phosphorylation sites. An even greater obstacle is decoding the dynamic phosphorylation pattern along the length of the periodic CTD sequence. Ultraviolet photodissociation (UVPD) is a high-energy ion activation method that provides ample backbone cleavages of peptides while preserving labile post-translational modifications that facilitate their confident localization. Herein, we report a quantitative parallel reaction monitoring (PRM) method developed to monitor spatiotemporal changes in site-specific Ser5 phosphorylation of the CTD by cyclin-dependent kinase 7 (CDK7) using UVPD for sequence identification, phosphosite localization, and differentiation of phosphopeptide isomers. We capitalize on the series of phospho-retaining fragment ions produced by UVPD to create unique transition lists that are pivotal for distinguishing the array of phosphopeptides generated from the CTD.
Collapse
|
73
|
Live-cell imaging reveals the spatiotemporal organization of endogenous RNA polymerase II phosphorylation at a single gene. Nat Commun 2021; 12:3158. [PMID: 34039974 PMCID: PMC8155019 DOI: 10.1038/s41467-021-23417-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 04/16/2021] [Indexed: 02/07/2023] Open
Abstract
The carboxyl-terminal domain of RNA polymerase II (RNAP2) is phosphorylated during transcription in eukaryotic cells. While residue-specific phosphorylation has been mapped with exquisite spatial resolution along the 1D genome in a population of fixed cells using immunoprecipitation-based assays, the timing, kinetics, and spatial organization of phosphorylation along a single-copy gene have not yet been measured in living cells. Here, we achieve this by combining multi-color, single-molecule microscopy with fluorescent antibody-based probes that specifically bind to different phosphorylated forms of endogenous RNAP2 in living cells. Applying this methodology to a single-copy HIV-1 reporter gene provides live-cell evidence for heterogeneity in the distribution of RNAP2 along the length of the gene as well as Serine 5 phosphorylated RNAP2 clusters that remain separated in both space and time from nascent mRNA synthesis. Computational models determine that 5 to 40 RNAP2 cluster around the promoter during a typical transcriptional burst, with most phosphorylated at Serine 5 within 6 seconds of arrival and roughly half escaping the promoter in ~1.5 minutes. Taken together, our data provide live-cell support for the notion of efficient transcription clusters that transiently form around promoters and contain high concentrations of RNAP2 phosphorylated at Serine 5.
Collapse
|
74
|
Liu J, Hansen D, Eck E, Kim YJ, Turner M, Alamos S, Garcia HG. Real-time single-cell characterization of the eukaryotic transcription cycle reveals correlations between RNA initiation, elongation, and cleavage. PLoS Comput Biol 2021; 17:e1008999. [PMID: 34003867 PMCID: PMC8162642 DOI: 10.1371/journal.pcbi.1008999] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 05/28/2021] [Accepted: 04/23/2021] [Indexed: 12/23/2022] Open
Abstract
The eukaryotic transcription cycle consists of three main steps: initiation, elongation, and cleavage of the nascent RNA transcript. Although each of these steps can be regulated as well as coupled with each other, their in vivo dissection has remained challenging because available experimental readouts lack sufficient spatiotemporal resolution to separate the contributions from each of these steps. Here, we describe a novel application of Bayesian inference techniques to simultaneously infer the effective parameters of the transcription cycle in real time and at the single-cell level using a two-color MS2/PP7 reporter gene and the developing fruit fly embryo as a case study. Our method enables detailed investigations into cell-to-cell variability in transcription-cycle parameters as well as single-cell correlations between these parameters. These measurements, combined with theoretical modeling, suggest a substantial variability in the elongation rate of individual RNA polymerase molecules. We further illustrate the power of this technique by uncovering a novel mechanistic connection between RNA polymerase density and nascent RNA cleavage efficiency. Thus, our approach makes it possible to shed light on the regulatory mechanisms in play during each step of the transcription cycle in individual, living cells at high spatiotemporal resolution.
Collapse
Affiliation(s)
- Jonathan Liu
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
| | - Donald Hansen
- Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, Heidelberg, Germany
| | - Elizabeth Eck
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Yang Joon Kim
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Meghan Turner
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Simon Alamos
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Hernan G. Garcia
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, United States of America
- Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, California, United States of America
| |
Collapse
|
75
|
Liu K, Patteson AE, Banigan EJ, Schwarz JM. Dynamic Nuclear Structure Emerges from Chromatin Cross-Links and Motors. PHYSICAL REVIEW LETTERS 2021; 126:158101. [PMID: 33929233 DOI: 10.1103/physrevlett.126.158101] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 02/22/2021] [Indexed: 06/12/2023]
Abstract
The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin protein filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, cross-linked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity and cross-links. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, cross-linking, and chromosome-lamina binding. Therefore, complex chromosome dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.
Collapse
Affiliation(s)
- Kuang Liu
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
| | - Alison E Patteson
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
| | - Edward J Banigan
- Institute for Medical Engineering and Science and Department of Physics, MIT, Cambridge, Massachusetts 02139, USA
| | - J M Schwarz
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
- Indian Creek Farm, Ithaca, New York 14850, USA
| |
Collapse
|
76
|
Pipkin ME. Runx proteins and transcriptional mechanisms that govern memory CD8 T cell development. Immunol Rev 2021; 300:100-124. [PMID: 33682165 DOI: 10.1111/imr.12954] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/23/2020] [Accepted: 12/28/2020] [Indexed: 12/14/2022]
Abstract
Adaptive immunity to intracellular pathogens and tumors is mediated by antigen-experienced CD8 T cells. Individual naive CD8 T cells have the potential to differentiate into a diverse array of antigen-experienced subsets that exhibit distinct effector functions, life spans, anatomic positioning, and potential for regenerating an entirely new immune response during iterative pathogenic exposures. The developmental process by which activated naive cells undergo diversification involves regulation of chromatin structure and transcription but is not entirely understood. This review examines how alterations in chromatin structure, transcription factor binding, extracellular signals, and single-cell gene expression explain the differential development of distinct effector (TEFF ) and memory (TMEM ) CD8 T cell subsets. Special emphasis is placed on how Runx proteins function with additional transcription factors to pioneer changes in chromatin accessibility and drive transcriptional programs that establish the core attributes of cytotoxic T lymphocytes, subdivide circulating and non-circulating TMEM cell subsets, and govern terminal differentiation. The discussion integrates the roles of specific cytokine signals, transcriptional circuits and how regulation of individual nucleosomes and RNA polymerase II activity can contribute to the process of differentiation. A model that integrates many of these features is discussed to conceptualize how activated CD8 T cells arrive at their fates.
Collapse
Affiliation(s)
- Matthew E Pipkin
- Department of Immunology and Microbiology, The Scripps Research Institute - FL, Jupiter, FL, USA
| |
Collapse
|
77
|
Ohnuki H, Venzon DJ, Lobanov A, Tosato G. Iterative epigenomic analyses in the same single cell. Genome Res 2021; 31:1819-1830. [PMID: 33627472 DOI: 10.1101/gr.269068.120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 01/14/2021] [Indexed: 11/24/2022]
Abstract
Gene expression in individual cells is epigenetically regulated by DNA modifications, histone modifications, transcription factors, and other DNA-binding proteins. It has been shown that multiple histone modifications can predict gene expression and reflect future responses of bulk cells to extracellular cues. However, the predictive ability of epigenomic analysis is still limited for mechanistic research at a single cell level. To overcome this limitation, it would be useful to acquire reliable signals from multiple epigenetic marks in the same single cell. Here, we propose a new approach and a new method for analysis of several components of the epigenome in the same single cell. The new method allows reanalysis of the same single cell. We found that reanalysis of the same single cell is feasible, provides confirmation of the epigenetic signals, and allows application of statistical analysis to identify reproduced reads using data sets generated only from the single cell. Reanalysis of the same single cell is also useful to acquire multiple epigenetic marks from the same single cells. The method can acquire at least five epigenetic marks: H3K27ac, H3K27me3, mediator complex subunit 1, a DNA modification, and a DNA-interacting protein. We can predict active signaling pathways in K562 single cells using the epigenetic data and confirm that the predicted results strongly correlate with actual active signaling pathways identified by RNA-seq results. These results suggest that the new method provides mechanistic insights for cellular phenotypes through multilayered epigenome analysis in the same single cells.
Collapse
Affiliation(s)
- Hidetaka Ohnuki
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - David J Venzon
- Biostatistics and Data Management Section, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Rockville, Maryland 20850, USA
| | - Alexei Lobanov
- CCR Collaborative Bioinformatics Resource (CCBR), Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.,Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research sponsored by the National Cancer Institute, Frederick, Maryland 21702, USA
| | - Giovanna Tosato
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| |
Collapse
|
78
|
Cuba Samaniego C, Franco E. Ultrasensitive molecular controllers for quasi-integral feedback. Cell Syst 2021; 12:272-288.e3. [PMID: 33539724 DOI: 10.1016/j.cels.2021.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 09/22/2020] [Accepted: 01/11/2021] [Indexed: 12/24/2022]
Abstract
Feedback control has enabled the success of automated technologies by mitigating the effects of variability, unknown disturbances, and noise. While it is known that biological feedback loops reduce the impact of noise and help shape kinetic responses, many questions remain about how to design molecular integral controllers. Here, we propose a modular strategy to build molecular quasi-integral feedback controllers, which involves following two design principles. The first principle is to utilize an ultrasensitive response, which determines the gain of the controller and influences the steady-state error. The second is to use a tunable threshold of the ultrasensitive response, which determines the equilibrium point of the system. We describe a reaction network, named brink controller, that satisfies these conditions by combining molecular sequestration and an activation/deactivation cycle. With computational models, we examine potential biological implementations of brink controllers, and we illustrate different example applications.
Collapse
Affiliation(s)
- Christian Cuba Samaniego
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Elisa Franco
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California at Los Angeles, Los Angeles, CA 90095, USA; Bioengineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Mechanical Engineering, University of California at Riverside, Riverside, CA 92521, USA.
| |
Collapse
|
79
|
Badjatia N, Rossi MJ, Bataille AR, Mittal C, Lai WKM, Pugh BF. Acute stress drives global repression through two independent RNA polymerase II stalling events in Saccharomyces. Cell Rep 2021; 34:108640. [PMID: 33472084 PMCID: PMC7879390 DOI: 10.1016/j.celrep.2020.108640] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/23/2020] [Accepted: 12/21/2020] [Indexed: 11/30/2022] Open
Abstract
In multicellular eukaryotes, RNA polymerase (Pol) II pauses transcription ~30-50 bp after initiation. While the budding yeast Saccharomyces has its transcription mechanisms mostly conserved with other eukaryotes, it appears to lack this fundamental promoter-proximal pausing. However, we now report that nearly all yeast genes, including constitutive and inducible genes, manifest two distinct transcriptional stall sites that are brought on by acute environmental signaling (e.g., peroxide stress). Pol II first stalls at the pre-initiation stage before promoter clearance, but after DNA melting and factor acquisition, and may involve inhibited dephosphorylation. The second stall occurs at the +2 nucleosome. It acquires most, but not all, elongation factor interactions. Its regulation may include Bur1/Spt4/5. Our results suggest that a double Pol II stall is a mechanism to downregulate essentially all genes in concert.
Collapse
Affiliation(s)
- Nitika Badjatia
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Matthew J Rossi
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Alain R Bataille
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Chitvan Mittal
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - William K M Lai
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - B Franklin Pugh
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
| |
Collapse
|
80
|
Li Y, Eshein A, Virk RKA, Eid A, Wu W, Frederick J, VanDerway D, Gladstein S, Huang K, Shim AR, Anthony NM, Bauer GM, Zhou X, Agrawal V, Pujadas EM, Jain S, Esteve G, Chandler JE, Nguyen TQ, Bleher R, de Pablo JJ, Szleifer I, Dravid VP, Almassalha LM, Backman V. Nanoscale chromatin imaging and analysis platform bridges 4D chromatin organization with molecular function. SCIENCE ADVANCES 2021; 7:eabe4310. [PMID: 33523864 PMCID: PMC7775763 DOI: 10.1126/sciadv.abe4310] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 11/09/2020] [Indexed: 05/10/2023]
Abstract
Extending across multiple length scales, dynamic chromatin structure is linked to transcription through the regulation of genome organization. However, no individual technique can fully elucidate this structure and its relation to molecular function at all length and time scales at both a single-cell level and a population level. Here, we present a multitechnique nanoscale chromatin imaging and analysis (nano-ChIA) platform that consolidates electron tomography of the primary chromatin fiber, optical super-resolution imaging of transcription processes, and label-free nano-sensing of chromatin packing and its dynamics in live cells. Using nano-ChIA, we observed that chromatin is localized into spatially separable packing domains, with an average diameter of around 200 nanometers, sub-megabase genomic size, and an internal fractal structure. The chromatin packing behavior of these domains exhibits a complex bidirectional relationship with active gene transcription. Furthermore, we found that properties of PDs are correlated among progenitor and progeny cells across cell division.
Collapse
Affiliation(s)
- Yue Li
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Adam Eshein
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Ranya K A Virk
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Aya Eid
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Wenli Wu
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Jane Frederick
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - David VanDerway
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Scott Gladstein
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Kai Huang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China
| | - Anne R Shim
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Nicholas M Anthony
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Greta M Bauer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Xiang Zhou
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Vasundhara Agrawal
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Emily M Pujadas
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Surbhi Jain
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - George Esteve
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - John E Chandler
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - The-Quyen Nguyen
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Reiner Bleher
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Vinayak P Dravid
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA
| | - Luay M Almassalha
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
| |
Collapse
|
81
|
Price RM, Budzyński MA, Kundra S, Teves SS. Advances in visualizing transcription factor - DNA interactions. Genome 2020; 64:449-466. [PMID: 33113335 DOI: 10.1139/gen-2020-0086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
At the heart of the transcription process is the specific interaction between transcription factors (TFs) and their target DNA sequences. Decades of molecular biology research have led to unprecedented insights into how TFs access the genome to regulate transcription. In the last 20 years, advances in microscopy have enabled scientists to add imaging as a powerful tool in probing two specific aspects of TF-DNA interactions: structure and dynamics. In this review, we examine how applications of diverse imaging technologies can provide structural and dynamic information that complements insights gained from molecular biology assays. As a case study, we discuss how applications of advanced imaging techniques have reshaped our understanding of TF behavior across the cell cycle, leading to a rethinking in the field of mitotic bookmarking.
Collapse
Affiliation(s)
- Rachel M Price
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.,Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Marek A Budzyński
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.,Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Shivani Kundra
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.,Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Sheila S Teves
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.,Department of Biochemistry and Molecular Biology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| |
Collapse
|
82
|
Robinson-Thiewes S, McCloskey J, Kimble J. Two classes of active transcription sites and their roles in developmental regulation. Proc Natl Acad Sci U S A 2020; 117:26812-26821. [PMID: 33033228 PMCID: PMC7604424 DOI: 10.1073/pnas.2013163117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The expression of genes encoding powerful developmental regulators is exquisitely controlled, often at multiple levels. Here, we investigate developmental expression of three conserved genes, Caenorhabditis elegans mpk-1, lag-1, and lag-3/sel-8, which encode homologs of ERK/MAPK and core components of the Notch-dependent transcription complex, respectively. We use single-molecule FISH (smFISH) and MATLAB to visualize and quantify nuclear nascent transcripts and cytoplasmic mRNAs as a function of position along the germline developmental axis. Using differentially labeled probes, one spanning an exceptionally long first intron and the other spanning exons, we identify two classes of active transcription sites (ATS). The iATS class, for "incomplete" ATS, harbors only partial nascent transcripts; the cATS class, for "complete" ATS, harbors full-length nascent transcripts. Remarkably, the frequencies of iATS and cATS are patterned along the germline axis. For example, most mpk-1 ATS are iATS in hermaphrodite germline stem cells, but most are cATS in differentiating stem cell daughters. Thus, mpk-1 ATS class frequencies switch in a graded manner as stem cell daughters begin differentiation. Importantly, the patterns of ATS class frequency are gene-, stage-, and sex-specific, and cATS frequency strongly correlates with transcriptional output. Although the molecular mechanism underlying ATS classes is not understood, their primary difference is the extent of transcriptional progression. To generate only partial nascent transcripts in iATS, progression must be slowed, paused, or aborted midway through the gene. We propose that regulation of ATS class can be a critical mode of developmental gene regulation.
Collapse
Affiliation(s)
| | - John McCloskey
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| |
Collapse
|
83
|
Miura M, Chen H. CUT&RUN detects distinct DNA footprints of RNA polymerase II near the transcription start sites. Chromosome Res 2020; 28:381-393. [PMID: 33070289 PMCID: PMC7691310 DOI: 10.1007/s10577-020-09643-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 11/30/2022]
Abstract
CUT&RUN is a powerful tool to study protein-DNA interactions in vivo. DNA fragments cleaved by the targeted micrococcal nuclease identify the footprints of DNA-binding proteins on the chromatin. We performed CUT&RUN on human lung carcinoma cell line A549 maintained in a multi-well cell culture plate to profile RNA polymerase II. Long (> 270 bp) DNA fragments released by CUT&RUN corresponded to the bimodal peak around the transcription start sites, as previously seen with chromatin immunoprecipitation. However, we found that short (< 120 bp) fragments identify a well-defined peak localised at the transcription start sites. This distinct DNA footprint of short fragments, which constituted only about 5% of the total reads, suggests the transient positioning of RNA polymerase II before promoter-proximal pausing, which has not been detected in the physiological settings by standard chromatin immunoprecipitation. We showed that the positioning of the large-size-class DNA footprints around the short-fragment peak was associated with the directionality of transcription, demonstrating the biological significance of distinct CUT&RUN footprints of RNA polymerase II.
Collapse
Affiliation(s)
- Michi Miura
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.
| | - Honglin Chen
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China
| |
Collapse
|
84
|
Zidovska A. The rich inner life of the cell nucleus: dynamic organization, active flows, and emergent rheology. Biophys Rev 2020; 12:1093-1106. [PMID: 33064286 PMCID: PMC7575674 DOI: 10.1007/s12551-020-00761-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/03/2020] [Accepted: 09/14/2020] [Indexed: 02/07/2023] Open
Abstract
The cell nucleus stores the genetic material essential for life, and provides the environment for transcription, maintenance, and replication of the genome. Moreover, the nucleoplasm is filled with subnuclear bodies such as nucleoli that are responsible for other vital functions. Overall, the nucleus presents a highly heterogeneous and dynamic environment with diverse functionality. Here, we propose that its biophysical complexity can be organized around three inter-related and interactive facets: heterogeneity, activity, and rheology. Most nuclear constituents are sites of active, ATP-dependent processes and are thus inherently dynamic: The genome undergoes constant rearrangement, the nuclear envelope flickers and fluctuates, nucleoli migrate and coalesce, and many of these events are mediated by nucleoplasmic flows and interactions. And yet there is spatiotemporal organization in terms of hierarchical structure of the genome, its coherently moving regions and membrane-less compartmentalization via phase-separated nucleoplasmic constituents. Moreover, the non-equilibrium or activity-driven nature of the nucleus gives rise to emergent rheology and material properties that impact all cellular processes via the central dogma of molecular biology. New biophysical insights into the cell nucleus can come from appreciating this rich inner life.
Collapse
Affiliation(s)
- Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY, USA.
| |
Collapse
|
85
|
Schieweck R, Ninkovic J, Kiebler MA. RNA-binding proteins balance brain function in health and disease. Physiol Rev 2020; 101:1309-1370. [PMID: 33000986 DOI: 10.1152/physrev.00047.2019] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Posttranscriptional gene expression including splicing, RNA transport, translation, and RNA decay provides an important regulatory layer in many if not all molecular pathways. Research in the last decades has positioned RNA-binding proteins (RBPs) right in the center of posttranscriptional gene regulation. Here, we propose interdependent networks of RBPs to regulate complex pathways within the central nervous system (CNS). These are involved in multiple aspects of neuronal development and functioning, including higher cognition. Therefore, it is not sufficient to unravel the individual contribution of a single RBP and its consequences but rather to study and understand the tight interplay between different RBPs. In this review, we summarize recent findings in the field of RBP biology and discuss the complex interplay between different RBPs. Second, we emphasize the underlying dynamics within an RBP network and how this might regulate key processes such as neurogenesis, synaptic transmission, and synaptic plasticity. Importantly, we envision that dysfunction of specific RBPs could lead to perturbation within the RBP network. This would have direct and indirect (compensatory) effects in mRNA binding and translational control leading to global changes in cellular expression programs in general and in synaptic plasticity in particular. Therefore, we focus on RBP dysfunction and how this might cause neuropsychiatric and neurodegenerative disorders. Based on recent findings, we propose that alterations in the entire regulatory RBP network might account for phenotypic dysfunctions observed in complex diseases including neurodegeneration, epilepsy, and autism spectrum disorders.
Collapse
Affiliation(s)
- Rico Schieweck
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Jovica Ninkovic
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Michael A Kiebler
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| |
Collapse
|
86
|
Luse DS, Parida M, Spector BM, Nilson KA, Price DH. A unified view of the sequence and functional organization of the human RNA polymerase II promoter. Nucleic Acids Res 2020; 48:7767-7785. [PMID: 32597978 PMCID: PMC7641323 DOI: 10.1093/nar/gkaa531] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/31/2020] [Accepted: 06/24/2020] [Indexed: 12/20/2022] Open
Abstract
To better understand human RNA polymerase II (Pol II) promoters in the context of promoter-proximal pausing and local chromatin organization, 5′ and 3′ ends of nascent capped transcripts and the locations of nearby nucleosomes were accurately identified through sequencing at exceptional depth. High-quality visualization tools revealed a preferred sequence that defines over 177 000 core promoters with strengths varying by >10 000-fold. This sequence signature encompasses and better defines the binding site for TFIID and is surprisingly invariant over a wide range of promoter strength. We identified a sequence motif associated with promoter-proximal pausing and demonstrated that cap methylation only begins once transcripts are about 30 nt long. Mapping also revealed a ∼150 bp periodic downstream sequence element (PDE) following the typical pause location, strongly suggestive of a +1 nucleosome positioning element. A nuclear run-off assay utilizing the unique properties of the DNA fragmentation factor (DFF) coupled with sequencing of DFF protected fragments demonstrated that a +1 nucleosome is present downstream of paused Pol II. Our data more clearly define the human Pol II promoter: a TFIID binding site with built-in downstream information directing ubiquitous promoter-proximal pausing and downstream nucleosome location.
Collapse
Affiliation(s)
- Donal S Luse
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Mrutyunjaya Parida
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA
| | - Benjamin M Spector
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA
| | - Kyle A Nilson
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA
| | - David H Price
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA
| |
Collapse
|
87
|
Saha K, England W, Fernandez MM, Biswas T, Spitale RC, Ghosh G. Structural disruption of exonic stem-loops immediately upstream of the intron regulates mammalian splicing. Nucleic Acids Res 2020; 48:6294-6309. [PMID: 32402057 PMCID: PMC7293017 DOI: 10.1093/nar/gkaa358] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 04/20/2020] [Accepted: 04/27/2020] [Indexed: 12/31/2022] Open
Abstract
Recognition of highly degenerate mammalian splice sites by the core spliceosomal machinery is regulated by several protein factors that predominantly bind exonic splicing motifs. These are postulated to be single-stranded in order to be functional, yet knowledge of secondary structural features that regulate the exposure of exonic splicing motifs across the transcriptome is not currently available. Using transcriptome-wide RNA structural information we show that retained introns in mouse are commonly flanked by a short (≲70 nucleotide), highly base-paired segment upstream and a predominantly single-stranded exonic segment downstream. Splicing assays with select pre-mRNA substrates demonstrate that loops immediately upstream of the introns contain pre-mRNA-specific splicing enhancers, the substitution or hybridization of which impedes splicing. Additionally, the exonic segments flanking the retained introns appeared to be more enriched in a previously identified set of hexameric exonic splicing enhancer (ESE) sequences compared to their spliced counterparts, suggesting that base-pairing in the exonic segments upstream of retained introns could be a means for occlusion of ESEs. The upstream exonic loops of the test substrate promoted recruitment of splicing factors and consequent pre-mRNA structural remodeling, leading up to assembly of the early spliceosome. These results suggest that disruption of exonic stem-loop structures immediately upstream (but not downstream) of the introns regulate alternative splicing events, likely through modulating accessibility of splicing factors.
Collapse
Affiliation(s)
- Kaushik Saha
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0375, USA
| | - Whitney England
- Department of Pharmaceutical Sciences, University of California Irvine, 147 Bison Modular, Building 515, Irvine, CA 92697, USA
| | - Mike Minh Fernandez
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0375, USA
| | - Tapan Biswas
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0375, USA
| | - Robert C Spitale
- Department of Pharmaceutical Sciences, University of California Irvine, 147 Bison Modular, Building 515, Irvine, CA 92697, USA
| | - Gourisankar Ghosh
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0375, USA
| |
Collapse
|
88
|
Slobodin B, Dikstein R. So close, no matter how far: multiple paths connecting transcription to mRNA translation in eukaryotes. EMBO Rep 2020; 21:e50799. [PMID: 32803873 PMCID: PMC7507372 DOI: 10.15252/embr.202050799] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/22/2020] [Accepted: 07/23/2020] [Indexed: 12/15/2022] Open
Abstract
Transcription of DNA into mRNA and translation of mRNA into proteins are two major processes underlying gene expression. Due to the distinct molecular mechanisms, timings, and locales of action, these processes are mainly considered to be independent. During the last two decades, however, multiple factors and elements were shown to coordinate transcription and translation, suggesting an intricate level of synchronization. This review discusses the molecular mechanisms that impact both processes in eukaryotic cells of different origins. The emerging global picture suggests evolutionarily conserved regulation and coordination between transcription and mRNA translation, indicating the importance of this phenomenon for the fine-tuning of gene expression and the adjustment to constantly changing conditions.
Collapse
Affiliation(s)
- Boris Slobodin
- Department of Biomolecular SciencesThe Weizmann Institute of ScienceRehovotIsrael
| | - Rivka Dikstein
- Department of Biomolecular SciencesThe Weizmann Institute of ScienceRehovotIsrael
| |
Collapse
|
89
|
Gene Transcription as a Limiting Factor in Protein Production and Cell Growth. G3-GENES GENOMES GENETICS 2020; 10:3229-3242. [PMID: 32694199 PMCID: PMC7466996 DOI: 10.1534/g3.120.401303] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cell growth is driven by the synthesis of proteins, genes, and other cellular components. Defining processes that limit biosynthesis rates is fundamental for understanding the determinants of cell physiology. Here, we analyze the consequences of engineering cells to express extremely high levels of mCherry proteins, as a tool to define limiting processes that fail to adapt upon increasing biosynthetic demands. Protein-burdened cells were transcriptionally and phenotypically similar to mutants of the Mediator, a transcription coactivator complex. However, our binding data suggest that the Mediator was not depleted from endogenous promoters. Burdened cells showed an overall increase in the abundance of the majority of endogenous transcripts, except for highly expressed genes. Our results, supported by mathematical modeling, suggest that wild-type cells transcribe highly expressed genes at the maximal possible rate, as defined by the transcription machinery’s physical properties. We discuss the possible cellular benefit of maximal transcription rates to allow a coordinated optimization of cell size and cell growth.
Collapse
|
90
|
Tellier M, Maudlin I, Murphy S. Transcription and splicing: A two-way street. WILEY INTERDISCIPLINARY REVIEWS. RNA 2020; 11:e1593. [PMID: 32128990 DOI: 10.1002/wrna.1593] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 12/18/2019] [Accepted: 02/12/2020] [Indexed: 12/11/2022]
Abstract
RNA synthesis by RNA polymerase II and RNA processing are closely coupled during the transcription cycle of protein-coding genes. This coupling affords opportunities for quality control and regulation of gene expression and the effects can go in both directions. For example, polymerase speed can affect splice site selection and splicing can increase transcription and affect the chromatin landscape. Here we review the many ways that transcription and splicing influence one another, including how splicing "talks back" to transcription. We will also place the connections between transcription and splicing in the context of other RNA processing events that define the exons that will make up the final mRNA. This article is categorized under: RNA Processing > Splicing Mechanisms RNA Processing > Splicing Regulation/Alternative Splicing.
Collapse
Affiliation(s)
- Michael Tellier
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Isabella Maudlin
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Shona Murphy
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| |
Collapse
|
91
|
Linking transcription, RNA polymerase II elongation and alternative splicing. Biochem J 2020; 477:3091-3104. [DOI: 10.1042/bcj20200475] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/31/2020] [Accepted: 08/04/2020] [Indexed: 12/21/2022]
Abstract
Gene expression is an intricately regulated process that is at the basis of cell differentiation, the maintenance of cell identity and the cellular responses to environmental changes. Alternative splicing, the process by which multiple functionally distinct transcripts are generated from a single gene, is one of the main mechanisms that contribute to expand the coding capacity of genomes and help explain the level of complexity achieved by higher organisms. Eukaryotic transcription is subject to multiple layers of regulation both intrinsic — such as promoter structure — and dynamic, allowing the cell to respond to internal and external signals. Similarly, alternative splicing choices are affected by all of these aspects, mainly through the regulation of transcription elongation, making it a regulatory knob on a par with the regulation of gene expression levels. This review aims to recapitulate some of the history and stepping-stones that led to the paradigms held today about transcription and splicing regulation, with major focus on transcription elongation and its effect on alternative splicing.
Collapse
|
92
|
Alkalay E, Gam Ze Letova Refael C, Shoval I, Kinor N, Sarid R, Shav-Tal Y. The Sub-Nuclear Localization of RNA-Binding Proteins in KSHV-Infected Cells. Cells 2020; 9:cells9091958. [PMID: 32854341 PMCID: PMC7564026 DOI: 10.3390/cells9091958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 08/21/2020] [Indexed: 12/13/2022] Open
Abstract
RNA-binding proteins, particularly splicing factors, localize to sub-nuclear domains termed nuclear speckles. During certain viral infections, as the nucleus fills up with replicating virus compartments, host cell chromatin distribution changes, ending up condensed at the nuclear periphery. In this study we wished to determine the fate of nucleoplasmic RNA-binding proteins and nuclear speckles during the lytic cycle of the Kaposi's sarcoma associated herpesvirus (KSHV). We found that nuclear speckles became fewer and dramatically larger, localizing at the nuclear periphery, adjacent to the marginalized chromatin. Enlarged nuclear speckles contained splicing factors, whereas other proteins were nucleoplasmically dispersed. Polyadenylated RNA, typically found in nuclear speckles under regular conditions, was also found in foci separated from nuclear speckles in infected cells. Poly(A) foci did not contain lncRNAs known to colocalize with nuclear speckles but contained the poly(A)-binding protein PABPN1. Examination of the localization of spliced viral RNAs revealed that some spliced transcripts could be detected within the nuclear speckles. Since splicing is required for the maturation of certain KSHV transcripts, we suggest that the infected cell does not dismantle nuclear speckles but rearranges their components at the nuclear periphery to possibly serve in splicing and transport of viral RNAs into the cytoplasm.
Collapse
|
93
|
Ramani MKV, Escobar EE, Irani S, Mayfield JE, Moreno RY, Butalewicz JP, Cotham VC, Wu H, Tadros M, Brodbelt JS, Zhang YJ. Structural Motifs for CTD Kinase Specificity on RNA Polymerase II during Eukaryotic Transcription. ACS Chem Biol 2020; 15:2259-2272. [PMID: 32568517 DOI: 10.1021/acschembio.0c00474] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The phosphorylation states of RNA polymerase II coordinate the process of eukaryotic transcription by recruitment of transcription regulators. The individual residues of the repetitive heptad of the C-terminal domain (CTD) of the biggest subunit of RNA polymerase II are phosphorylated temporally at different stages of transcription. Intriguingly, despite similar flanking residues, phosphorylation of Ser2 and Ser5 in CTD heptads play dramatically different roles. The mechanism of how the kinases place phosphorylation on the correct serine is not well understood. In this paper, we use biochemical assays, mass spectrometry, molecular modeling, and structural analysis to understand the structural elements determining which serine of the CTD heptad is subject to phosphorylation. We identified three motifs in the activation/P+1 loops differentiating the intrinsic specificity of CTD in various CTD kinases. We characterized the enzyme specificity of the CTD kinases-CDK7 as Ser5-specific, Erk2 with dual specificity for Ser2 and Ser5, and Dyrk1a as a Ser2-specific kinase. We also show that the specificities of kinases are malleable and can be modified by incorporating mutations in their activation/P+1 loops that alter the interactions of the three motifs. Our results provide an important clue to the understanding of post-translational modification of RNA polymerase II temporally during active transcription.
Collapse
|
94
|
Braselmann E, Rathbun C, Richards EM, Palmer AE. Illuminating RNA Biology: Tools for Imaging RNA in Live Mammalian Cells. Cell Chem Biol 2020; 27:891-903. [PMID: 32640188 PMCID: PMC7595133 DOI: 10.1016/j.chembiol.2020.06.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/30/2020] [Accepted: 06/15/2020] [Indexed: 01/06/2023]
Abstract
The central dogma teaches us that DNA makes RNA, which in turn makes proteins, the main building blocks of the cell. But this over simplified linear transmission of information overlooks the vast majority of the genome produces RNAs that do not encode proteins and the myriad ways that RNA regulates cellular functions. Historically, one of the challenges in illuminating RNA biology has been the lack of tools for visualizing RNA in live cells. But clever approaches for exploiting RNA binding proteins, in vitro RNA evolution, and chemical biology have resulted in significant advances in RNA visualization tools in recent years. This review provides an overview of current tools for tagging RNA with fluorescent probes and tracking their dynamics, localization andfunction in live mammalian cells.
Collapse
Affiliation(s)
- Esther Braselmann
- Department of Biochemistry, BioFrontiers Institute, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, CO 80309, USA
| | - Colin Rathbun
- Department of Biochemistry, BioFrontiers Institute, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, CO 80309, USA
| | - Erin M Richards
- Department of Biochemistry, BioFrontiers Institute, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, CO 80309, USA
| | - Amy E Palmer
- Department of Biochemistry, BioFrontiers Institute, University of Colorado Boulder, 3415 Colorado Avenue, Boulder, CO 80309, USA.
| |
Collapse
|
95
|
Buccitelli C, Selbach M. mRNAs, proteins and the emerging principles of gene expression control. Nat Rev Genet 2020; 21:630-644. [PMID: 32709985 DOI: 10.1038/s41576-020-0258-4] [Citation(s) in RCA: 473] [Impact Index Per Article: 118.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2020] [Indexed: 12/15/2022]
Abstract
Gene expression involves transcription, translation and the turnover of mRNAs and proteins. The degree to which protein abundances scale with mRNA levels and the implications in cases where this dependency breaks down remain an intensely debated topic. Here we review recent mRNA-protein correlation studies in the light of the quantitative parameters of the gene expression pathway, contextual confounders and buffering mechanisms. Although protein and mRNA levels typically show reasonable correlation, we describe how transcriptomics and proteomics provide useful non-redundant readouts. Integrating both types of data can reveal exciting biology and is an essential step in refining our understanding of the principles of gene expression control.
Collapse
Affiliation(s)
| | - Matthias Selbach
- Proteome Dynamics, Max Delbrück Center for Molecular Medicine, Berlin, Germany. .,Charité - Universitätsmedizin Berlin, Berlin, Germany.
| |
Collapse
|
96
|
Stochastic allelic expression as trigger for contractile imbalance in hypertrophic cardiomyopathy. Biophys Rev 2020; 12:1055-1064. [PMID: 32661905 PMCID: PMC7429642 DOI: 10.1007/s12551-020-00719-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 07/02/2020] [Indexed: 12/17/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM), the most common inherited cardiac disease, is caused by several mostly heterozygous mutations in sarcomeric genes. Hallmarks of HCM are cardiomyocyte and myofibrillar disarray and hypertrophy and fibrosis of the septum and the left ventricle. To date, a pathomechanism common to all mutations remains elusive. We have proposed that contractile imbalance, an unequal force generation of neighboring cardiomyocytes, may contribute to development of HCM hallmarks. At the same calcium concentration, we found substantial differences in force generation between individual cardiomyocytes from HCM patients with mutations in β-MyHC (β-myosin heavy chain). Variability among cardiomyocytes was significantly larger in HCM patients as compared with donor controls. We assume that this heterogeneity in force generation among cardiomyocytes may lead to myocardial disarray and trigger hypertrophy and fibrosis. We provided evidence that burst-like transcription of the MYH7-gene, encoding for β-MyHC, is associated with unequal fractions of mutant per wild-type mRNA from cell to cell (cell-to-cell allelic imbalance). This will presumably lead to unequal fractions of mutant per wild-type protein from cell to cell which may underlie contractile imbalance. In this review, we discuss molecular mechanisms of burst-like transcription with regard to contractile imbalance and disease development in HCM.
Collapse
|
97
|
Abstract
Transcription in several organisms from certain bacteria to humans has been observed to be stochastic in nature: toggling between active and inactive states. Periods of active nascent RNA synthesis known as bursts represent individual gene activation events in which multiple polymerases are initiated. Therefore, bursting is the single locus illustration of both gene activation and repression. Although transcriptional bursting was originally observed decades ago, only recently have technological advances enabled the field to begin elucidating gene regulation at the single-locus level. In this review, we focus on how biochemical, genomic, and single-cell data describe the regulatory steps of transcriptional bursts.
Collapse
Affiliation(s)
- Joseph Rodriguez
- National Institute of Environmental Health Sciences, Durham, North Carolina 27709, USA
| | - Daniel R. Larson
- Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
| |
Collapse
|
98
|
Markey FB, Parashar V, Batish M. Methods for spatial and temporal imaging of the different steps involved in RNA processing at single-molecule resolution. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1608. [PMID: 32543077 DOI: 10.1002/wrna.1608] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 12/26/2022]
Abstract
RNA plays a quintessential role as a messenger of information from genotype (DNA) to phenotype (proteins), as well as acts as a regulatory molecule (noncoding RNAs). All steps in the journey of RNA from synthesis (transcription), splicing, transport, localization, translation, to its eventual degradation, comprise important steps in gene expression, thereby controlling the fate of the cell. This lifecycle refers to the majority of RNAs (primarily mRNAs), but not other RNAs such as tRNAs. Imaging these processes in fixed cells and in live cells has been an important tool in developing an understanding of the regulatory steps in RNAs journey. Single-cell and single-molecule imaging techniques enable a much deeper understanding of cellular biology, which is not possible with bulk studies involving RNA isolated from a large pool of cells. Classic techniques, such as fluorescence in situ hybridization (FISH), as well as more recent aptamer-based approaches, have provided detailed insights into RNA localization, and have helped to predict the functions carried out by many RNA species. However, there are still certain processing steps that await high-resolution imaging, which is an exciting and upcoming area of research. In this review, we will discuss the methods that have revolutionized single-molecule resolution imaging in general, the steps of RNA processing in which these methods have been used, and new emerging technologies. This article is categorized under: RNA Export and Localization > RNA Localization RNA Methods > RNA Analyses in Cells RNA Interactions with Proteins and Other Molecules > Small Molecule-RNA Interactions.
Collapse
Affiliation(s)
- Fatu Badiane Markey
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Vijay Parashar
- Department of Medical and Molecular Sciences, University of Delaware, Newark, Delaware, USA
| | - Mona Batish
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA.,Department of Medical and Molecular Sciences, University of Delaware, Newark, Delaware, USA
| |
Collapse
|
99
|
Fischer J, Song YS, Yosef N, di Iulio J, Churchman LS, Choder M. The yeast exoribonuclease Xrn1 and associated factors modulate RNA polymerase II processivity in 5' and 3' gene regions. J Biol Chem 2020; 295:11435-11454. [PMID: 32518159 DOI: 10.1074/jbc.ra120.013426] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 06/05/2020] [Indexed: 11/06/2022] Open
Abstract
mRNA levels are determined by the balance between mRNA synthesis and decay. Protein factors that mediate both processes, including the 5'-3' exonuclease Xrn1, are responsible for a cross-talk between the two processes that buffers steady-state mRNA levels. However, the roles of these proteins in transcription remain elusive and controversial. Applying native elongating transcript sequencing (NET-seq) to yeast cells, we show that Xrn1 functions mainly as a transcriptional activator and that its disruption manifests as a reduction of RNA polymerase II (Pol II) occupancy downstream of transcription start sites. By combining our sequencing data and mathematical modeling of transcription, we found that Xrn1 modulates transcription initiation and elongation of its target genes. Furthermore, Pol II occupancy markedly increased near cleavage and polyadenylation sites in xrn1Δ cells, whereas its activity decreased, a characteristic feature of backtracked Pol II. We also provide indirect evidence that Xrn1 is involved in transcription termination downstream of polyadenylation sites. We noted that two additional decay factors, Dhh1 and Lsm1, seem to function similarly to Xrn1 in transcription, perhaps as a complex, and that the decay factors Ccr4 and Rpb4 also perturb transcription in other ways. Interestingly, the decay factors could differentiate between SAGA- and TFIID-dominated promoters. These two classes of genes responded differently to XRN1 deletion in mRNA synthesis and were differentially regulated by mRNA decay pathways, raising the possibility that one distinction between these two gene classes lies in the mechanisms that balance mRNA synthesis with mRNA decay.
Collapse
Affiliation(s)
- Jonathan Fischer
- Computer Science Division, University of California, Berkeley, California, USA.,Department of Statistics, University of California, Berkeley, California, USA
| | - Yun S Song
- Computer Science Division, University of California, Berkeley, California, USA.,Department of Statistics, University of California, Berkeley, California, USA.,Chan Zuckerberg BioHub, San Francisco, California, USA
| | - Nir Yosef
- Chan Zuckerberg BioHub, San Francisco, California, USA.,Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, USA.,Ragon Institute of MGH, MIT, and Harvard, Cambridge, Massachusetts, USA
| | - Julia di Iulio
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Mordechai Choder
- Department of Molecular Microbiology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| |
Collapse
|
100
|
Zidovska A. The self-stirred genome: large-scale chromatin dynamics, its biophysical origins and implications. Curr Opin Genet Dev 2020; 61:83-90. [PMID: 32497955 DOI: 10.1016/j.gde.2020.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 01/02/2023]
Abstract
The organization and dynamics of human genome govern all cellular processes - directly impacting the central dogma of biology - yet are poorly understood, especially at large length scales. Chromatin, the functional form of DNA in cells, undergoes frequent local remodeling and rearrangements to accommodate processes such as transcription, replication and DNA repair. How these local activities contribute to nucleus-wide coherent chromatin motion, where micron-scale regions of chromatin move together over several seconds, remains unclear. Activity of nuclear enzymes was found to drive the coherent chromatin dynamics, however, its biological nature and physical mechanism remain to be revealed. The coherent dynamics leads to a perpetual stirring of the genome, leading to collective gene dynamics over microns and seconds, thus likely contributing to local and global gene-expression patterns. Hence, a possible biological role of chromatin coherence may involve gene regulation.
Collapse
Affiliation(s)
- Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY, 10003, USA.
| |
Collapse
|