1
|
Kelly SL, Strobel EJ. Systematic analysis of cotranscriptional RNA folding using transcription elongation complex display. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.22.573115. [PMID: 38187752 PMCID: PMC10769408 DOI: 10.1101/2023.12.22.573115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
RNA can fold into structures that mediate diverse cellular functions. Understanding how RNA primary sequence directs the formation of functional structures requires methods that can comprehensively assess how changes in an RNA sequence affect its structure and function. Here we have developed a platform for performing high-throughput cotranscriptional RNA biochemical assays, called Transcription Elongation Complex display (TECdisplay). TECdisplay measures RNA function by fractionating a TEC library based on the activity of cotranscriptionally displayed nascent RNA. In this way, RNA function is measured as the distribution of template DNA molecules between fractions of the transcription reaction. This approach circumvents typical RNA sequencing library preparation steps that can cause technical bias. We used TECdisplay to characterize the transcription antitermination activity of 32,768 variants of the Clostridium beijerinckii pfl ZTP riboswitch designed to perturb steps within its cotranscriptional folding pathway. Our findings establish TECdisplay as an accessible platform for high-throughput RNA biochemical assays.
Collapse
Affiliation(s)
- Skyler L. Kelly
- Department of Biological Sciences, The University at Buffalo, Buffalo, NY 14260, USA
| | - Eric J. Strobel
- Department of Biological Sciences, The University at Buffalo, Buffalo, NY 14260, USA
| |
Collapse
|
2
|
Jensen D, Ruiz Manzano A, Rector M, Tomko E, Record M, Galburt E. High-throughput, fluorescent-aptamer-based measurements of steady-state transcription rates for the Mycobacterium tuberculosis RNA polymerase. Nucleic Acids Res 2023; 51:e99. [PMID: 37739412 PMCID: PMC10602862 DOI: 10.1093/nar/gkad761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 08/04/2023] [Accepted: 09/11/2023] [Indexed: 09/24/2023] Open
Abstract
The first step in gene expression is the transcription of DNA sequences into RNA. Regulation at the level of transcription leads to changes in steady-state concentrations of RNA transcripts, affecting the flux of downstream functions and ultimately cellular phenotypes. Changes in transcript levels are routinely followed in cellular contexts via genome-wide sequencing techniques. However, in vitro mechanistic studies of transcription have lagged with respect to throughput. Here, we describe the use of a real-time, fluorescent-aptamer-based method to quantitate steady-state transcription rates of the Mycobacterium tuberculosis RNA polymerase. We present clear controls to show that the assay specifically reports on promoter-dependent, full-length RNA transcription rates that are in good agreement with the kinetics determined by gel-resolved, α-32P NTP incorporation experiments. We illustrate how the time-dependent changes in fluorescence can be used to measure regulatory effects of nucleotide concentrations and identity, RNAP and DNA concentrations, transcription factors, and antibiotics. Our data showcase the ability to easily perform hundreds of parallel steady-state measurements across varying conditions with high precision and reproducibility to facilitate the study of the molecular mechanisms of bacterial transcription.
Collapse
Affiliation(s)
- Drake Jensen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63108, USA
| | - Ana Ruiz Manzano
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63108, USA
| | - Maxwell Rector
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Eric J Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63108, USA
| | - M Thomas Record
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Eric A Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63108, USA
| |
Collapse
|
3
|
Wang L, Watters JW, Ju X, Lu G, Liu S. Head-on and co-directional RNA polymerase collisions orchestrate bidirectional transcription termination. Mol Cell 2023; 83:1153-1164.e4. [PMID: 36917983 PMCID: PMC10081963 DOI: 10.1016/j.molcel.2023.02.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 01/03/2023] [Accepted: 02/15/2023] [Indexed: 03/14/2023]
Abstract
Genomic DNA is a crowded track where motor proteins frequently collide. It remains underexplored whether these collisions carry physiological function. In this work, we develop a single-molecule assay to visualize the trafficking of individual E. coli RNA polymerases (RNAPs) on DNA. Based on transcriptomic data, we hypothesize that RNAP collisions drive bidirectional transcription termination of convergent gene pairs. Single-molecule results show that the head-on collision between two converging RNAPs is necessary to prevent transcriptional readthrough but insufficient to release the RNAPs from the DNA. Remarkably, co-directional collision of a trailing RNAP into the head-on collided complex dramatically increases the termination efficiency. Furthermore, stem-loop structures formed in the nascent RNA are required for collisions to occur at well-defined positions between convergent genes. These findings suggest that physical collisions between RNAPs furnish a mechanism for transcription termination and that programmed genomic conflicts can be exploited to co-regulate the expression of multiple genes.
Collapse
Affiliation(s)
- Ling Wang
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA.
| | - John W Watters
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Xiangwu Ju
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Genzhe Lu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Shixin Liu
- Laboratory of Nanoscale Biophysics and Biochemistry, The Rockefeller University, New York, NY, USA.
| |
Collapse
|
4
|
Jensen D, Manzano AR, Rector M, Tomko EJ, Record MT, Galburt EA. High-throughput, fluorescent-aptamer-based measurements of steady-state transcription rates for Mycobacterium tuberculosis RNA polymerase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.13.532464. [PMID: 36993414 PMCID: PMC10054983 DOI: 10.1101/2023.03.13.532464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The first step in gene expression is the transcription of DNA sequences into RNA. Regulation at the level of transcription leads to changes in steady-state concentrations of RNA transcripts, affecting the flux of downstream functions and ultimately cellular phenotypes. Changes in transcript levels are routinely followed in cellular contexts via genome-wide sequencing techniques. However, in vitro mechanistic studies of transcription have lagged with respect to throughput. Here, we describe the use of a real-time, fluorescent-aptamer-based method to quantitate steady-state transcription rates of the Mycobacterium tuberculosis RNA polymerase. We present clear controls to show that the assay specifically reports on promoter-dependent, full-length RNA transcription rates that are in good agreement with the kinetics determined by gel-resolved, α- 32 P NTP incorporation experiments. We illustrate how the time-dependent changes in fluorescence can be used to measure regulatory effects of nucleotide concentrations and identity, RNAP and DNA concentrations, transcription factors, and antibiotics. Our data showcase the ability to easily perform hundreds of parallel steady-state measurements across varying conditions with high precision and reproducibility to facilitate the study of the molecular mechanisms of bacterial transcription. Significance Statement RNA polymerase transcription mechanisms have largely been determined from in vitro kinetic and structural biology methods. In contrast to the limited throughput of these approaches, in vivo RNA sequencing provides genome-wide measurements but lacks the ability to dissect direct biochemical from indirect genetic mechanisms. Here, we present a method that bridges this gap, permitting high-throughput fluorescence-based measurements of in vitro steady-state transcription kinetics. We illustrate how an RNA-aptamer-based detection system can be used to generate quantitative information on direct mechanisms of transcriptional regulation and discuss the far-reaching implications for future applications.
Collapse
Affiliation(s)
- Drake Jensen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| | - Ana Ruiz Manzano
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| | - Maxwell Rector
- Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA
| | - Eric J. Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| | - M. Thomas Record
- Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA
| | - Eric A. Galburt
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| |
Collapse
|
5
|
Ribosome reactivates transcription by physically pushing RNA polymerase out of transcription arrest. Proc Natl Acad Sci U S A 2020; 117:8462-8467. [PMID: 32238560 PMCID: PMC7165469 DOI: 10.1073/pnas.1919985117] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In bacteria, the first two steps of gene expression-transcription and translation-are spatially and temporally coupled. Uncoupling may lead to the arrest of transcription through RNA polymerase backtracking, which interferes with replication forks, leading to DNA double-stranded breaks and genomic instability. How transcription-translation coupling mitigates these conflicts is unknown. Here we show that, unlike replication, translation is not inhibited by arrested transcription elongation complexes. Instead, the translating ribosome actively pushes RNA polymerase out of the backtracked state, thereby reactivating transcription. We show that the distance between the two machineries upon their contact on mRNA is smaller than previously thought, suggesting intimate interactions between them. However, this does not lead to the formation of a stable functional complex between the enzymes, as was once proposed. Our results reveal an active, energy-driven mechanism that reactivates backtracked elongation complexes and thus helps suppress their interference with replication.
Collapse
|
6
|
Prajapati RK, Rosenqvist P, Palmu K, Mäkinen JJ, Malinen AM, Virta P, Metsä-Ketelä M, Belogurov GA. Oxazinomycin arrests RNA polymerase at the polythymidine sequences. Nucleic Acids Res 2019; 47:10296-10312. [PMID: 31495891 PMCID: PMC6821320 DOI: 10.1093/nar/gkz782] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 08/13/2019] [Accepted: 08/31/2019] [Indexed: 02/06/2023] Open
Abstract
Oxazinomycin is a C-nucleoside antibiotic that is produced by Streptomyces hygroscopicus and closely resembles uridine. Here, we show that the oxazinomycin triphosphate is a good substrate for bacterial and eukaryotic RNA polymerases (RNAPs) and that a single incorporated oxazinomycin is rapidly extended by the next nucleotide. However, the incorporation of several successive oxazinomycins or a single oxazinomycin in a certain sequence context arrested a fraction of the transcribing RNAP. The addition of Gre RNA cleavage factors eliminated the transcriptional arrest at a single oxazinomycin and shortened the nascent RNAs arrested at the polythymidine sequences suggesting that the transcriptional arrest was caused by backtracking of RNAP along the DNA template. We further demonstrate that the ubiquitous C-nucleoside pseudouridine is also a good substrate for RNA polymerases in a triphosphorylated form but does not inhibit transcription of the polythymidine sequences. Our results collectively suggest that oxazinomycin functions as a Trojan horse substrate and its inhibitory effect is attributable to the oxygen atom in the position corresponding to carbon five of the uracil ring.
Collapse
Affiliation(s)
- Ranjit K Prajapati
- Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland
| | - Petja Rosenqvist
- Department of Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Kaisa Palmu
- Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland
| | - Janne J Mäkinen
- Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland
| | - Anssi M Malinen
- Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland
| | - Pasi Virta
- Department of Chemistry, University of Turku, FIN-20014 Turku, Finland
| | - Mikko Metsä-Ketelä
- Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland
| | | |
Collapse
|
7
|
Turtola M, Belogurov GA. NusG inhibits RNA polymerase backtracking by stabilizing the minimal transcription bubble. eLife 2016; 5. [PMID: 27697152 PMCID: PMC5100998 DOI: 10.7554/elife.18096] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 10/03/2016] [Indexed: 12/25/2022] Open
Abstract
Universally conserved factors from NusG family bind at the upstream fork junction of transcription elongation complexes and modulate RNA synthesis in response to translation, processing, and folding of the nascent RNA. Escherichia coli NusG enhances transcription elongation in vitro by a poorly understood mechanism. Here we report that E. coli NusG slows Gre factor-stimulated cleavage of the nascent RNA, but does not measurably change the rates of single nucleotide addition and translocation by a non-paused RNA polymerase. We demonstrate that NusG slows RNA cleavage by inhibiting backtracking. This activity is abolished by mismatches in the upstream DNA and is independent of the gate and rudder loops, but is partially dependent on the lid loop. Our comprehensive mapping of the upstream fork junction by base analogue fluorescence and nucleic acids crosslinking suggests that NusG inhibits backtracking by stabilizing the minimal transcription bubble. DOI:http://dx.doi.org/10.7554/eLife.18096.001 Cells decode genes in two steps. First, they synthesize a molecule similar to DNA, called RNA, which is a complementary copy of the gene. This process, known as transcription, creates an intermediate RNA molecule that is turned into protein in the second step. RNA polymerase is an enzyme that carries out transcription; it separates the two strands of the DNA helix so that the RNA can be synthesized from the DNA template. By opening up the DNA downstream of where active copying is taking place, and re-annealing it upstream, RNA polymerase maintains a structure called a "transcription bubble". RNA polymerases do not copy continuously but oscillate back and forth along the DNA. Sometimes larger backwards oscillations, known as backtracking, temporarily block the production of the RNA molecule and slow down the transcription process. A protein called NusG helps to couple transcription to the other related processes that happen at the same time. One end of the protein, the N-terminal domain, anchors it to RNA polymerase and stimulates transcription elongation. The other end, the C-terminal domain, interacts with other proteins involved in the related processes and can positively or negatively control transcription elongation. Nevertheless it was poorly understood how NusG carries out these roles. Turtola and Belogurov investigated how NusG from the bacterium Escherichia coli affects the individual steps of transcription elongation. A simple experimental system was used, consisting of short pieces of DNA and RNA, an RNA polymerase and NusG. A transcription bubble resembles an opening in a zipper with two sliders; and rather than affecting the synthesis of RNA, NusG affected the part that corresponds to the “slider” located at the rear edge of the bubble. NusG helped this slider-like element to bring the DNA strands at this edge of the bubble back together and modified it so that it behaved as a ratchet that inhibited RNA polymerase from backtracking. This did not affect the smaller backwards and forwards oscillations of RNA polymerase. Turtola and Belogurov suggest that these newly discovered effects play a key role in regulating transcription; NusG’s N-terminal domain makes the RNA polymerase more efficient, whilst the C-terminal domain makes it amenable to control by other proteins. Future studies will investigate whether these effects are seen in more complex experimental systems, which include proteins that interact with NusG. DOI:http://dx.doi.org/10.7554/eLife.18096.002
Collapse
Affiliation(s)
- Matti Turtola
- Department of Biochemistry, University of Turku, Turku, Finland
| | | |
Collapse
|
8
|
Maddalena LLD, Niederholtmeyer H, Turtola M, Swank ZN, Belogurov GA, Maerkl SJ. GreA and GreB Enhance Expression of Escherichia coli RNA Polymerase Promoters in a Reconstituted Transcription-Translation System. ACS Synth Biol 2016; 5:929-35. [PMID: 27186988 DOI: 10.1021/acssynbio.6b00017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cell-free environments are becoming viable alternatives for implementing biological networks in synthetic biology. The reconstituted cell-free expression system (PURE) allows characterization of genetic networks under defined conditions but its applicability to native bacterial promoters and endogenous genetic networks is limited due to the poor transcription rate of Escherichia coli RNA polymerase in this minimal system. We found that addition of transcription elongation factors GreA and GreB to the PURE system increased transcription rates of E. coli RNA polymerase from sigma factor 70 promoters up to 6-fold and enhanced the performance of a genetic network. Furthermore, we reconstituted activation of natural E. coli promoters controlling flagella biosynthesis by the transcriptional activator FlhDC and sigma factor 28. Addition of GreA/GreB to the PURE system allows efficient expression from natural and synthetic E. coli promoters and characterization of their regulation in minimal and defined reaction conditions, making the PURE system more broadly applicable to study genetic networks and bottom-up synthetic biology.
Collapse
Affiliation(s)
- Lea L. de Maddalena
- Institute
of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Henrike Niederholtmeyer
- Institute
of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Matti Turtola
- Department
of Biochemistry, University of Turku, FI-20014 Turku, Finland
| | - Zoe N. Swank
- Institute
of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | | | - Sebastian J. Maerkl
- Institute
of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| |
Collapse
|
9
|
Strobel EJ, Roberts JW. Two transcription pause elements underlie a σ70-dependent pause cycle. Proc Natl Acad Sci U S A 2015; 112:E4374-80. [PMID: 26216999 PMCID: PMC4538648 DOI: 10.1073/pnas.1512986112] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The movement of RNA polymerase (RNAP) during transcription elongation is modulated by DNA-encoded elements that cause the elongation complex to pause. One of the best-characterized pause sequences is a binding site for the σ(70) initiation factor that induces pausing at a site near lambdoid phage late-gene promoters. An essential component of this σ(70)-dependent pause is the elemental pause site (EPS), a sequence that itself induces transcription pausing throughout the Escherichia coli genome and underlies other complex regulatory pause elements, such as the ops and his operon pauses. Here, we identify and provide a detailed kinetic analysis of a transcription cycle analogous to abortive cycling that underlies the σ(70)-dependent pause. We show that, in σ(70)-dependent pausing, the elemental pause acts primarily to modulate the rate at which complexes attempt to disengage the σ(70):DNA interaction. Our findings establish the σ(70)-dependent pause-encoding region as a multipartite element in which several pause-inducing components make distinct mechanistic contributions to the induction and maintenance of a regulatory transcription pause.
Collapse
Affiliation(s)
- Eric J Strobel
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
| | - Jeffrey W Roberts
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853
| |
Collapse
|
10
|
Strobel EJ, Roberts JW. Regulation of promoter-proximal transcription elongation: enhanced DNA scrunching drives λQ antiterminator-dependent escape from a σ70-dependent pause. Nucleic Acids Res 2014; 42:5097-108. [PMID: 24550164 PMCID: PMC4005639 DOI: 10.1093/nar/gku147] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
During initial transcription, RNA polymerase remains bound at the promoter and synthesizes RNA without movement along the DNA template, drawing downstream DNA into itself in a process called scrunching and thereby storing energy to sever the bonds that hold the enzyme at the promoter. We show that DNA scrunching also is the driving force behind the escape of RNA polymerase from a regulatory pause of the late gene operon of bacteriophage λ, and that this process is enhanced by the activity of the Q(λ) antiterminator. Furthermore, we show that failure of transcription complexes to escape the pause results in backtracking and arrest in a process analogous to abortive initiation. We identify a sequence element that modulates both abortive synthesis and the formation of arrested elongation complexes.
Collapse
Affiliation(s)
- Eric J Strobel
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | | |
Collapse
|
11
|
Vassylyeva MN, Svetlov V, Dearborn AD, Klyuyev S, Artsimovitch I, Vassylyev DG. The carboxy-terminal coiled-coil of the RNA polymerase beta'-subunit is the main binding site for Gre factors. EMBO Rep 2007; 8:1038-43. [PMID: 17917675 DOI: 10.1038/sj.embor.7401079] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Revised: 08/09/2007] [Accepted: 08/22/2007] [Indexed: 11/09/2022] Open
Abstract
Bacterial Gre transcript cleavage factors stimulate the intrinsic endonucleolytic activity of RNA polymerase (RNAP) to rescue stalled transcription complexes. They bind to RNAP and extend their coiled-coil (CC) domains to the catalytic centre through the secondary channel. Three existing models for the Gre-RNAP complex postulate congruent mechanisms of Gre-assisted catalysis, while offering conflicting views of the Gre-RNAP interactions. Here, we report the GreB structure of Escherichia coli. The GreB monomers form a triangle with the tip of the amino-terminal CC of one molecule trapped within the hydrophobic cavity of the carboxy-terminal domain of a second molecule. This arrangement suggests an analogous model for recruitment to RNAP. Indeed, the beta'-subunit CC located at the rim of the secondary channel has conserved hydrophobic residues at its tip. We show that substitutions of these residues and those in the GreB C-terminal domain cavity confer defects in GreB activity and binding to RNAP, and present a plausible model for the RNAP-GreB complex.
Collapse
Affiliation(s)
- Marina N Vassylyeva
- Department of Biochemistry and Molecular Genetics, Schools of Medicine and Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | | | | | | | | | | |
Collapse
|