51
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Simms CL, Thomas EN, Zaher HS. Ribosome-based quality control of mRNA and nascent peptides. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 8. [PMID: 27193249 DOI: 10.1002/wrna.1366] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/25/2016] [Accepted: 04/26/2016] [Indexed: 11/06/2022]
Abstract
Quality control processes are widespread and play essential roles in detecting defective molecules and removing them in order to maintain organismal fitness. Aberrant messenger RNA (mRNA) molecules, unless properly managed, pose a significant hurdle to cellular proteostasis. Often mRNAs harbor premature stop codons, possess structures that present a block to the translational machinery, or lack stop codons entirely. In eukaryotes, the three cytoplasmic mRNA-surveillance processes, nonsense-mediated decay (NMD), no-go decay (NGD), and nonstop decay (NSD), evolved to cope with these aberrant mRNAs, respectively. Nonstop mRNAs and mRNAs that inhibit translation elongation are especially problematic as they sequester valuable ribosomes from the translating ribosome pool. As a result, in addition to RNA degradation, NSD and NGD are intimately coupled to ribosome rescue in all domains of life. Furthermore, protein products produced from all three classes of defective mRNAs are more likely to malfunction. It is not surprising then that these truncated nascent protein products are subject to degradation. Over the past few years, many studies have begun to document a central role for the ribosome in initiating the RNA and protein quality control processes. The ribosome appears to be responsible for recognizing the target mRNAs as well as for recruiting the factors required to carry out the processes of ribosome rescue and nascent protein decay. WIREs RNA 2017, 8:e1366. doi: 10.1002/wrna.1366 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Carrie L Simms
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - Erica N Thomas
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - Hani S Zaher
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
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52
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Bridge helix bending promotes RNA polymerase II backtracking through a critical and conserved threonine residue. Nat Commun 2016; 7:11244. [PMID: 27091704 PMCID: PMC4838855 DOI: 10.1038/ncomms11244] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 03/03/2016] [Indexed: 12/19/2022] Open
Abstract
The dynamics of the RNA polymerase II (Pol II) backtracking process is poorly understood. We built a Markov State Model from extensive molecular dynamics simulations to identify metastable intermediate states and the dynamics of backtracking at atomistic detail. Our results reveal that Pol II backtracking occurs in a stepwise mode where two intermediate states are involved. We find that the continuous bending motion of the Bridge helix (BH) serves as a critical checkpoint, using the highly conserved BH residue T831 as a sensing probe for the 3′-terminal base paring of RNA:DNA hybrid. If the base pair is mismatched, BH bending can promote the RNA 3′-end nucleotide into a frayed state that further leads to the backtracked state. These computational observations are validated by site-directed mutagenesis and transcript cleavage assays, and provide insights into the key factors that regulate the preferences of the backward translocation. RNA Polymerase II can detect and cleave mis-incorporated nucleotides by a proofreading mechanism that requires backtracking of the enzyme. Here the authors show that Pol II backtracking occurs in a stepwise mode that involves two intermediate states where the fraying of the terminal RNA nucleotide is a prerequisite.
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53
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Appling FD, Lucius AL, Schneider DA. Transient-State Kinetic Analysis of the RNA Polymerase I Nucleotide Incorporation Mechanism. Biophys J 2015; 109:2382-93. [PMID: 26636949 PMCID: PMC4675888 DOI: 10.1016/j.bpj.2015.10.037] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/15/2015] [Accepted: 10/28/2015] [Indexed: 10/22/2022] Open
Abstract
Eukaryotes express three or more multisubunit nuclear RNA polymerases (Pols) referred to as Pols I, II, and III, each of which synthesizes a specific subset of RNAs. Consistent with the diversity of their target genes, eukaryotic cells have evolved divergent cohorts of transcription factors and enzymatic properties for each RNA polymerase system. Over the years, many trans-acting factors that orchestrate transcription by the individual Pols have been described; however, little effort has been devoted to characterizing the molecular mechanisms of Pol I activity. To begin to address this gap in our understanding of eukaryotic gene expression, here we establish transient-state kinetic approaches to characterize the nucleotide incorporation mechanism of Pol I. We collected time courses for single turnover nucleotide incorporation reactions over a range of substrate ATP concentrations that provide information on both Pol I's nucleotide addition and nuclease activities. The data were analyzed by model-independent and model-dependent approaches, resulting in, to our knowledge, the first minimal model for the nucleotide addition pathway for Pol I. Using a grid searching approach we provide rigorous bounds on estimated values of the individual elementary rate constants within the proposed model. This work reports the most detailed analysis of Pol I mechanism to date. Furthermore, in addition to their use in transient state kinetic analyses, the computational approaches applied here are broadly applicable to global optimization problems.
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Affiliation(s)
- Francis D Appling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama.
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama.
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54
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Esyunina DM, Kulbachinskiy AV. Purification and characterization of recombinant Deinococcus radiodurans RNA Polymerase. BIOCHEMISTRY (MOSCOW) 2015; 80:1271-8. [DOI: 10.1134/s0006297915100077] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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55
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Duan B, Wu S, Da LT, Yu J. A critical residue selectively recruits nucleotides for t7 RNA polymerase transcription fidelity control. Biophys J 2015; 107:2130-40. [PMID: 25418098 PMCID: PMC4223216 DOI: 10.1016/j.bpj.2014.09.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 09/23/2014] [Accepted: 09/30/2014] [Indexed: 01/21/2023] Open
Abstract
Nucleotide selection is essential for fidelity control in gene replication and transcription. Recent work on T7 RNA polymerase suggested that a small posttranslocation free energy bias stabilizes Tyr(639) in the active site to aid nucleotide selection. However, it was not clear exactly how Tyr(639) assists the selection. Here we report a molecular-dynamics simulation study revealing atomistic detail of this critical selectivity. The study shows first that Tyr(639) blocks the active site at posttranslocation by marginally stacking to the end basepair of the DNA-RNA hybrid. The study then demonstrates that at the nucleotide preinsertion state, a cognate RNA nucleotide does not affect the local Tyr(639) stabilization, whereas a noncognate nucleotide substantially stabilizes Tyr(639) so that Tyr(639) keeps blocking the active site. As a result, further nucleotide insertion into the active site, which requires moving Tyr(639) out of the site, would be hindered for the noncognate nucleotide, but not for the cognate nucleotide. In particular, we note that water molecules assist the ribose recognition in the RNA nucleotide preinsertion, and help Tyr(639) stacking to the end basepair in the case of a DNA nucleotide. It was also seen that a base-mismatched nucleotide at preinsertion directly grabs Tyr(639) for the active site stabilization. We also find that in a mutant polymerase Y639F the strong stabilization of residue 639 in the active site cannot establish upon the DNA nucleotide preinsertion. The finding explains the reduced differentiation between ribo- and deoxyribonucleotides that has been recorded experimentally for the mutant polymerase.
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Affiliation(s)
- Baogen Duan
- Beijing Computational Science Research Center, Beijing, P. R. China
| | - Shaogui Wu
- Beijing Computational Science Research Center, Beijing, P. R. China
| | - Lin-Tai Da
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Jin Yu
- Beijing Computational Science Research Center, Beijing, P. R. China.
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56
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Structural basis and functional analysis of the SARS coronavirus nsp14-nsp10 complex. Proc Natl Acad Sci U S A 2015; 112:9436-41. [PMID: 26159422 DOI: 10.1073/pnas.1508686112] [Citation(s) in RCA: 331] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nonstructural protein 14 (nsp14) of coronaviruses (CoV) is important for viral replication and transcription. The N-terminal exoribonuclease (ExoN) domain plays a proofreading role for prevention of lethal mutagenesis, and the C-terminal domain functions as a (guanine-N7) methyl transferase (N7-MTase) for mRNA capping. The molecular basis of both these functions is unknown. Here, we describe crystal structures of severe acute respiratory syndrome (SARS)-CoV nsp14 in complex with its activator nonstructural protein10 (nsp10) and functional ligands. One molecule of nsp10 interacts with ExoN of nsp14 to stabilize it and stimulate its activity. Although the catalytic core of nsp14 ExoN is reminiscent of proofreading exonucleases, the presence of two zinc fingers sets it apart from homologs. Mutagenesis studies indicate that both these zinc fingers are essential for the function of nsp14. We show that a DEEDh (the five catalytic amino acids) motif drives nucleotide excision. The N7-MTase domain exhibits a noncanonical MTase fold with a rare β-sheet insertion and a peripheral zinc finger. The cap-precursor guanosine-P3-adenosine-5',5'-triphosphate and S-adenosyl methionine bind in proximity in a highly constricted pocket between two β-sheets to accomplish methyl transfer. Our studies provide the first glimpses, to our knowledge, into the architecture of the nsp14-nsp10 complex involved in RNA viral proofreading.
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57
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Dunkle JA, Dunham CM. Mechanisms of mRNA frame maintenance and its subversion during translation of the genetic code. Biochimie 2015; 114:90-6. [PMID: 25708857 PMCID: PMC4458409 DOI: 10.1016/j.biochi.2015.02.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 02/11/2015] [Indexed: 01/26/2023]
Abstract
Important viral and cellular gene products are regulated by stop codon readthrough and mRNA frameshifting, processes whereby the ribosome detours from the reading frame defined by three nucleotide codons after initiation of translation. In the last few years, rapid progress has been made in mechanistically characterizing both processes and also revealing that trans-acting factors play important regulatory roles in frameshifting. Here, we review recent biophysical studies that bring new molecular insights to stop codon readthrough and frameshifting. Lastly, we consider whether there may be common mechanistic themes in -1 and +1 frameshifting based on recent X-ray crystal structures of +1 frameshift-prone tRNAs bound to the ribosome.
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Affiliation(s)
- Jack A Dunkle
- Emory University School of Medicine, Department of Biochemistry, 1510 Clifton Road NE, Suite G223, Atlanta, GA 30322, USA
| | - Christine M Dunham
- Emory University School of Medicine, Department of Biochemistry, 1510 Clifton Road NE, Suite G223, Atlanta, GA 30322, USA.
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58
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59
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Abstract
The plasma membrane (PM) and endocytic protein quality control (QC) in conjunction with the endosomal sorting machinery either repairs or targets conformationally damaged membrane proteins for lysosomal/vacuolar degradation. Here, we provide an overview of emerging aspects of the underlying mechanisms of PM QC that fulfill a critical role in preserving cellular protein homeostasis in health and diseases.
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Affiliation(s)
- Pirjo M Apaja
- Department of Physiology and Research Group Focused on Protein Structure (GRASP), McGill University, Montreal, Quebec, Canada; and
| | - Gergely L Lukacs
- Department of Physiology and Research Group Focused on Protein Structure (GRASP), McGill University, Montreal, Quebec, Canada; and Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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60
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Smith JE, Baker KE. Nonsense-mediated RNA decay--a switch and dial for regulating gene expression. Bioessays 2015; 37:612-23. [PMID: 25820233 DOI: 10.1002/bies.201500007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Nonsense-mediated RNA decay (NMD) represents an established quality control checkpoint for gene expression that protects cells from consequences of gene mutations and errors during RNA biogenesis that lead to premature termination during translation. Characterization of NMD-sensitive transcriptomes has revealed, however, that NMD targets not only aberrant transcripts but also a broad array of mRNA isoforms expressed from many endogenous genes. NMD is thus emerging as a master regulator that drives both fine and coarse adjustments in steady-state RNA levels in the cell. Importantly, while NMD activity is subject to autoregulation as a means to maintain homeostasis, modulation of the pathway by external cues provides a means to reprogram gene expression and drive important biological processes. Finally, the unanticipated observation that transcripts predicted to lack protein-coding capacity are also sensitive to this translation-dependent surveillance mechanism implicates NMD in regulating RNA function in new and diverse ways.
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Affiliation(s)
- Jenna E Smith
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Kristian E Baker
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
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61
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Abstract
RNA polymerase (RNAP) loses activity during transcription as it stalls at various inactive states due to erratic translocation. Reactivation of these stalled RNAPs is essential for efficient RNA synthesis. Here we report a 4.7-Å resolution crystal structure of the Escherichia coli RNAP core enzyme in complex with ATPase RapA that is involved in reactivating stalled RNAPs. The structure reveals that RapA binds at the RNA exit channel of the RNAP and makes the channel unable to accommodate the formation of an RNA hairpin. The orientation of RapA on the RNAP core complex suggests that RapA uses its ATPase activity to propel backward translocation of RNAP along the DNA template in an elongation complex. This structure provides insights into the reactivation of stalled RNA polymerases and helps support ATP-driven backward translocation as a general mechanism for transcriptional regulation.
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62
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Kuhn CD, Wilusz JE, Zheng Y, Beal PA, Joshua-Tor L. On-enzyme refolding permits small RNA and tRNA surveillance by the CCA-adding enzyme. Cell 2015; 160:644-658. [PMID: 25640237 PMCID: PMC4329729 DOI: 10.1016/j.cell.2015.01.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 11/07/2014] [Accepted: 12/31/2014] [Indexed: 11/16/2022]
Abstract
Transcription in eukaryotes produces a number of long noncoding RNAs (lncRNAs). Two of these, MALAT1 and Menβ, generate a tRNA-like small RNA in addition to the mature lncRNA. The stability of these tRNA-like small RNAs and bona fide tRNAs is monitored by the CCA-adding enzyme. Whereas CCA is added to stable tRNAs and tRNA-like transcripts, a second CCA repeat is added to certain unstable transcripts to initiate their degradation. Here, we characterize how these two scenarios are distinguished. Following the first CCA addition cycle, nucleotide binding to the active site triggers a clockwise screw motion, producing torque on the RNA. This ejects stable RNAs, whereas unstable RNAs are refolded while bound to the enzyme and subjected to a second CCA catalytic cycle. Intriguingly, with the CCA-adding enzyme acting as a molecular vise, the RNAs proofread themselves through differential responses to its interrogation between stable and unstable substrates.
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Affiliation(s)
- Claus-D Kuhn
- W.M. Keck Structural Biology Laboratory, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Jeremy E Wilusz
- Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Yuxuan Zheng
- Department of Chemistry, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Peter A Beal
- Department of Chemistry, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Leemor Joshua-Tor
- W.M. Keck Structural Biology Laboratory, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
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63
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Mejia YX, Nudler E, Bustamante C. Trigger loop folding determines transcription rate of Escherichia coli's RNA polymerase. Proc Natl Acad Sci U S A 2015; 112:743-8. [PMID: 25552559 PMCID: PMC4311812 DOI: 10.1073/pnas.1421067112] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Two components of the RNA polymerase (RNAP) catalytic center, the bridge helix and the trigger loop (TL), have been linked with changes in elongation rate and pausing. Here, single molecule experiments with the WT and two TL-tip mutants of the Escherichia coli enzyme reveal that tip mutations modulate RNAP's pause-free velocity, identifying TL conformational changes as one of two rate-determining steps in elongation. Consistent with this observation, we find a direct correlation between helix propensity of the modified amino acid and pause-free velocity. Moreover, nucleotide analogs affect transcription rate, suggesting that their binding energy also influences TL folding. A kinetic model in which elongation occurs in two steps, TL folding on nucleoside triphosphate (NTP) binding followed by NTP incorporation/pyrophosphate release, quantitatively accounts for these results. The TL plays no role in pause recovery remaining unfolded during a pause. This model suggests a finely tuned mechanism that balances transcription speed and fidelity.
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Affiliation(s)
- Yara X Mejia
- Jason L. Choy Laboratory of Single-Molecule Biophysics, the California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology and Howard Hughes Medical Institute, New York University School of Medicine, New York, NY 10016
| | - Carlos Bustamante
- Jason L. Choy Laboratory of Single-Molecule Biophysics, the California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720; Department of Molecular and Cell Biology, Department of Physics, Department of Chemistry, Biophysics Graduate Group and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; and Kavli Energy Nanosciences Institute at Berkeley, Berkeley, CA 94720
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64
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Wang X, Li C, Gao X, Wang J, Liang X. Preparation of Small RNAs Using Rolling Circle Transcription and Site-Specific RNA Disconnection. MOLECULAR THERAPY-NUCLEIC ACIDS 2015; 4:e215. [PMID: 25584899 PMCID: PMC4272408 DOI: 10.1038/mtna.2014.66] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 10/17/2014] [Indexed: 01/22/2023]
Abstract
A facile and robust RNA preparation protocol was developed by combining rolling circle transcription (RCT) with RNA cleavage by RNase H. Circular DNA with a complementary sequence was used as the template for promoter-free transcription. With the aid of a 2′-O-methylated DNA, the RCT-generated tandem repeats of the desired RNA sequence were disconnected at the exact end-to-end position to harvest the desired RNA oligomers. Compared with the template DNA, more than 4 × 103 times the amount of small RNA products were obtained when modest cleavage was carried out during transcription. Large amounts of RNA oligomers could easily be obtained by simply increasing the reaction volume.
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Affiliation(s)
- Xingyu Wang
- College of Food Science and Engineering, Ocean University of China, Shandong, China
| | - Can Li
- College of Food Science and Engineering, Ocean University of China, Shandong, China
| | - Xiaomeng Gao
- College of Food Science and Engineering, Ocean University of China, Shandong, China
| | - Jing Wang
- College of Food Science and Engineering, Ocean University of China, Shandong, China
| | - Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Shandong, China
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65
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Borisov OV, Alvarez M, Carroll JA, Brown PW. Sequence Variants and Sequence Variant Analysis in Biotherapeutic Proteins. ACS SYMPOSIUM SERIES 2015. [DOI: 10.1021/bk-2015-1201.ch002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Oleg V. Borisov
- Novavax, Inc., Gaithersburg, Maryland 20878, United States
- Roche Group Member, Genentech, Inc., South San Francisco, California 94080, United States
- Pfizer Worldwide Research & Development, Chesterfield, Missouri 63017, United States
| | - Melissa Alvarez
- Novavax, Inc., Gaithersburg, Maryland 20878, United States
- Roche Group Member, Genentech, Inc., South San Francisco, California 94080, United States
- Pfizer Worldwide Research & Development, Chesterfield, Missouri 63017, United States
| | - James A. Carroll
- Novavax, Inc., Gaithersburg, Maryland 20878, United States
- Roche Group Member, Genentech, Inc., South San Francisco, California 94080, United States
- Pfizer Worldwide Research & Development, Chesterfield, Missouri 63017, United States
| | - Paul W. Brown
- Novavax, Inc., Gaithersburg, Maryland 20878, United States
- Roche Group Member, Genentech, Inc., South San Francisco, California 94080, United States
- Pfizer Worldwide Research & Development, Chesterfield, Missouri 63017, United States
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66
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Wang B, Opron K, Burton ZF, Cukier RI, Feig M. Five checkpoints maintaining the fidelity of transcription by RNA polymerases in structural and energetic details. Nucleic Acids Res 2014; 43:1133-46. [PMID: 25550432 PMCID: PMC4333413 DOI: 10.1093/nar/gku1370] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Transcriptional fidelity, which prevents the misincorporation of incorrect nucleoside monophosphates in RNA, is essential for life. Results from molecular dynamics (MD) simulations of eukaryotic RNA polymerase (RNAP) II and bacterial RNAP with experimental data suggest that fidelity may involve as many as five checkpoints. Using MD simulations, the effects of different active site NTPs in both open and closed trigger loop (TL) structures of RNAPs are compared. Unfavorable initial binding of mismatched substrates in the active site with an open TL is proposed to be the first fidelity checkpoint. The leaving of an incorrect substrate is much easier than a correct one energetically from the umbrella sampling simulations. Then, the closing motion of the TL, required for catalysis, is hindered by the presence of mismatched NTPs. Mismatched NTPs also lead to conformational changes in the active site, which perturb the coordination of magnesium ions and likely affect the ability to proceed with catalysis. This step appears to be the most important checkpoint for deoxy-NTP discrimination. Finally, structural perturbations in the template DNA and the nascent RNA in the presence of mismatches likely hinder nucleotide addition and provide the structural foundation for backtracking followed by removing erroneously incorporated nucleotides during proofreading.
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Affiliation(s)
- Beibei Wang
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Kristopher Opron
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Zachary F Burton
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Robert I Cukier
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Michael Feig
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
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67
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Abstract
Accurate folding, assembly, localization, and maturation of newly synthesized proteins are essential to all cells and require high fidelity in the protein biogenesis machineries that mediate these processes. Here, we review our current understanding of how high fidelity is achieved in one of these processes, the cotranslational targeting of nascent membrane and secretory proteins by the signal recognition particle (SRP). Recent biochemical, biophysical, and structural studies have elucidated how the correct substrates drive a series of elaborate conformational rearrangements in the SRP and SRP receptor GTPases; these rearrangements provide effective fidelity checkpoints to reject incorrect substrates and enhance the fidelity of this essential cellular pathway. The mechanisms used by SRP to ensure fidelity share important conceptual analogies with those used by cellular machineries involved in DNA replication, transcription, and translation, and these mechanisms likely represent general principles for other complex cellular pathways.
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Affiliation(s)
- Xin Zhang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125;
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68
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Westhof E, Yusupov M, Yusupova G. Recognition of Watson-Crick base pairs: constraints and limits due to geometric selection and tautomerism. F1000PRIME REPORTS 2014; 6:19. [PMID: 24765524 PMCID: PMC3974571 DOI: 10.12703/p6-19] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The natural bases of nucleic acids have a strong preference for one tautomer form, guaranteeing fidelity in their hydrogen bonding potential. However, base pairs observed in recent crystal structures of polymerases and ribosomes are best explained by an alternative base tautomer, leading to the formation of base pairs with Watson-Crick-like geometries. These observations set limits to geometric selection in molecular recognition of complementary Watson-Crick pairs for fidelity in replication and translation processes.
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Affiliation(s)
- Eric Westhof
- Architecture et Réactivité de l’ARN, Université de Strasbourg, Institut de Biologie Moléculaire et CellulaireCNRS, 15 rue René Descartes, F-67084 Strasbourg CedexFrance
| | - Marat Yusupov
- Département de Biologie et de Génomique Structurales, Institut de Génétique et de Biologie Moléculaire et CellulaireCNRS, INSERM, Université de Strasbourg, F-67400 IllkirchFrance
| | - Gulnara Yusupova
- Département de Biologie et de Génomique Structurales, Institut de Génétique et de Biologie Moléculaire et CellulaireCNRS, INSERM, Université de Strasbourg, F-67400 IllkirchFrance
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69
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Knippa K, Peterson DO. Fidelity of RNA Polymerase II Transcription: Role of Rbp9 in Error Detection and Proofreading. Biochemistry 2013; 52:7807-17. [DOI: 10.1021/bi4009566] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Kevin Knippa
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, United States
| | - David O. Peterson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, United States
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70
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Intermittent Transcription Dynamics for the Rapid Production of Long Transcripts of High Fidelity. Cell Rep 2013; 5:521-30. [DOI: 10.1016/j.celrep.2013.09.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 02/01/2013] [Accepted: 09/05/2013] [Indexed: 11/23/2022] Open
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71
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Affiliation(s)
- Jens Michaelis
- Biophysics
Institute, Faculty of Natural Sciences, Ulm University, Albert-Einstein-Allee
11, 89081 Ulm, Germany
- Center
for Integrated Protein Science Munich (CIPSM), Department
of Chemistry and Biochemistry, Munich University, Butenandtstrasse 5-13, 81377 München, Germany
| | - Barbara Treutlein
- Department
of Bioengineering, Stanford University, James H. Clark Center, E-300, 318
Campus Drive, Stanford, California 94305-5432, United States
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72
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Sahoo M, Klumpp S. Backtracking dynamics of RNA polymerase: pausing and error correction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:374104. [PMID: 23945272 DOI: 10.1088/0953-8984/25/37/374104] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Transcription by RNA polymerases is frequently interrupted by pauses. One mechanism of such pauses is backtracking, where the RNA polymerase translocates backward with respect to both the DNA template and the RNA transcript, without shortening the transcript. Backtracked RNA polymerases move in a diffusive fashion and can return to active transcription either by diffusive return to the position where backtracking was initiated or by cleaving the transcript. The latter process also provides a mechanism for proofreading. Here we present some exact results for a kinetic model of backtracking and analyse its impact on the speed and the accuracy of transcription. We show that proofreading through backtracking is different from the classical (Hopfield-Ninio) scheme of kinetic proofreading. Our analysis also suggests that, in addition to contributing to the accuracy of transcription, backtracking may have a second effect: it attenuates the slow down of transcription that arises as a side effect of discriminating between correct and incorrect nucleotides based on the stepping rates.
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Affiliation(s)
- Mamata Sahoo
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, D-14424 Potsdam, Germany
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73
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Viktorovskaya OV, Engel KL, French SL, Cui P, Vandeventer PJ, Pavlovic EM, Beyer AL, Kaplan CD, Schneider DA. Divergent contributions of conserved active site residues to transcription by eukaryotic RNA polymerases I and II. Cell Rep 2013; 4:974-84. [PMID: 23994471 DOI: 10.1016/j.celrep.2013.07.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/10/2013] [Accepted: 07/30/2013] [Indexed: 12/29/2022] Open
Abstract
Multisubunit RNA polymerases (msRNAPs) exhibit high sequence and structural homology, especially within their active sites, which is generally thought to result in msRNAP functional conservation. However, we show that mutations in the trigger loop (TL) in the largest subunit of RNA polymerase I (Pol I) yield phenotypes unexpected from studies of Pol II. For example, a well-characterized gain-of-function mutation in Pol II results in loss of function in Pol I (Pol II: rpb1- E1103G; Pol I: rpa190-E1224G). Studies of chimeric Pol II enzymes hosting Pol I or Pol III TLs suggest that consequences of mutations that alter TL dynamics are dictated by the greater enzymatic context and not solely the TL sequence. Although the rpa190-E1224G mutation diminishes polymerase activity, when combined with mutations that perturb Pol I catalysis, it enhances polymerase function, similar to the analogous Pol II mutation. These results suggest that Pol I and Pol II have different rate-limiting steps.
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Affiliation(s)
- Olga V Viktorovskaya
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294-0024, USA
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74
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Fouqueau T, Zeller ME, Cheung AC, Cramer P, Thomm M. The RNA polymerase trigger loop functions in all three phases of the transcription cycle. Nucleic Acids Res 2013; 41:7048-59. [PMID: 23737452 PMCID: PMC3737540 DOI: 10.1093/nar/gkt433] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The trigger loop (TL) forms a conserved element in the RNA polymerase active centre that functions in the elongation phase of transcription. Here, we show that the TL also functions in transcription initiation and termination. Using recombinant variants of RNA polymerase from Pyrococcus furiosus and a reconstituted transcription system, we demonstrate that the TL is essential for initial RNA synthesis until a complete DNA–RNA hybrid is formed. The archaeal TL is further important for transcription fidelity during nucleotide incorporation, but not for RNA cleavage during proofreading. A conserved glutamine residue in the TL binds the 2’-OH group of the nucleoside triphosphate (NTP) to discriminate NTPs from dNTPs. The TL also prevents aberrant transcription termination at non-terminator sites.
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Affiliation(s)
- Thomas Fouqueau
- Institut of Microbiology and Archaea Center, Universität Regensburg, 93053 Regensburg, Germany
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75
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Reorganization of an intersubunit bridge induced by disparate 16S ribosomal ambiguity mutations mimics an EF-Tu-bound state. Proc Natl Acad Sci U S A 2013; 110:9716-21. [PMID: 23630274 DOI: 10.1073/pnas.1301585110] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
After four decades of research aimed at understanding tRNA selection on the ribosome, the mechanism by which ribosomal ambiguity (ram) mutations promote miscoding remains unclear. Here, we present two X-ray crystal structures of the Thermus thermophilus 70S ribosome containing 16S rRNA ram mutations, G347U and G299A. Each of these mutations causes miscoding in vivo and stimulates elongation factor thermo unstable (EF-Tu)-dependent GTP hydrolysis in vitro. Mutation G299A is located near the interface of ribosomal proteins S4 and S5 on the solvent side of the subunit, whereas G347U is located 77 Å distant, at intersubunit bridge B8, close to where EF-Tu engages the ribosome. Despite these disparate locations, both mutations induce almost identical structural rearrangements that disrupt the B8 bridge--namely, the interaction of h8/h14 with L14 and L19. This conformation most closely resembles that seen upon EF-Tu-GTP-aminoacyl-tRNA binding to the 70S ribosome. These data provide evidence that disruption and/or distortion of B8 is an important aspect of GTPase activation. We propose that, by destabilizing B8, G299A and G347U reduce the energetic cost of attaining the GTPase-activated state and thereby decrease the stringency of decoding. This previously unappreciated role for B8 in controlling the decoding process may hold relevance for many other ribosomal mutations known to influence translational fidelity.
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76
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Da LT, Pardo Avila F, Wang D, Huang X. A two-state model for the dynamics of the pyrophosphate ion release in bacterial RNA polymerase. PLoS Comput Biol 2013; 9:e1003020. [PMID: 23592966 PMCID: PMC3617016 DOI: 10.1371/journal.pcbi.1003020] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 02/19/2013] [Indexed: 01/10/2023] Open
Abstract
The dynamics of the PPi release during the transcription elongation of bacterial RNA polymerase and its effects on the Trigger Loop (TL) opening motion are still elusive. Here, we built a Markov State Model (MSM) from extensive all-atom molecular dynamics (MD) simulations to investigate the mechanism of the PPi release. Our MSM has identified a simple two-state mechanism for the PPi release instead of a more complex four-state mechanism observed in RNA polymerase II (Pol II). We observed that the PPi release in bacterial RNA polymerase occurs at sub-microsecond timescale, which is ∼3-fold faster than that in Pol II. After escaping from the active site, the (Mg-PPi)(2-) group passes through a single elongated metastable region where several positively charged residues on the secondary channel provide favorable interactions. Surprisingly, we found that the PPi release is not coupled with the TL unfolding but correlates tightly with the side-chain rotation of the TL residue R1239. Our work sheds light on the dynamics underlying the transcription elongation of the bacterial RNA polymerase.
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Affiliation(s)
- Lin-Tai Da
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Fátima Pardo Avila
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Dong Wang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Xuhui Huang
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- Center of Systems Biology and Human Health, Institute for Advance Study and School of Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- * E-mail:
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77
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SHARMA AJEETK, CHOWDHURY DEBASHISH. TEMPLATE-DIRECTED BIOPOLYMERIZATION: TAPE-COPYING TURING MACHINES. ACTA ACUST UNITED AC 2013. [DOI: 10.1142/s1793048012300083] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
DNA, RNA and proteins are among the most important macromolecules in a living cell. These molecules are polymerized by molecular machines. These natural nano-machines polymerize such macromolecules, adding one monomer at a time, using another linear polymer as the corresponding template. The machine utilizes input chemical energy to move along the template which also serves as a track for the movements of the machine. In the Alan Turing year 2012, it is worth pointing out that these machines are "tape-copying Turing machines". We review the operational mechanisms of the polymerizer machines and their collective behavior from the perspective of statistical physics, emphasizing their common features in spite of the crucial differences in their biological functions. We also draw the attention of the physics community to another class of modular machines that carry out a different type of template-directed polymerization. We hope this review will inspire new kinetic models for these modular machines.
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Affiliation(s)
- AJEET K. SHARMA
- Department of Physics, Indian Institute of Technology, Kanpur 208016, India
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78
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Rodrigo-Brenni MC, Hegde RS. Design principles of protein biosynthesis-coupled quality control. Dev Cell 2013; 23:896-907. [PMID: 23153486 DOI: 10.1016/j.devcel.2012.10.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The protein biosynthetic machinery, composed of ribosomes, chaperones, and localization factors, is increasingly found to interact directly with factors dedicated to protein degradation. The coupling of these two opposing processes facilitates quality control of nascent polypeptides at each stage of their maturation. Sequential checkpoints maximize the overall fidelity of protein maturation, minimize the exposure of defective products to the bulk cellular environment, and protect organisms from protein misfolding diseases.
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79
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Xie Z. PROG BIOCHEM BIOPHYS 2013; 39:1174-1177. [DOI: 10.3724/sp.j.1206.2012.00226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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80
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Bittner L, Gobet A, Audic S, Romac S, Egge ES, Santini S, Ogata H, Probert I, Edvardsen B, de Vargas C. Diversity patterns of uncultured Haptophytes unravelled by pyrosequencing in Naples Bay. Mol Ecol 2012; 22:87-101. [PMID: 23163508 DOI: 10.1111/mec.12108] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 09/13/2012] [Accepted: 09/20/2012] [Indexed: 11/30/2022]
Abstract
Haptophytes are a key phylum of marine protists, including ~300 described morphospecies and 80 morphogenera. We used 454 pyrosequencing on large subunit ribosomal DNA (LSU rDNA) fragments to assess the diversity from size-fractioned plankton samples collected in the Bay of Naples. One group-specific primer set targeting the LSU rDNA D1/D2 region was designed to amplify Haptophyte sequences from nucleic acid extracts (total DNA or RNA) of two size fractions (0.8-3 or 3-20 μm) and two sampling depths [subsurface, at 1 m, or deep chlorophyll maximum (DCM) at 23 m]. 454 reads were identified using a database covering the entire Haptophyta diversity currently sequenced. Our data set revealed several hundreds of Haptophyte clusters. However, most of these clusters could not be linked to taxonomically known sequences: considering OTUs(97%) (clusters build at a sequence identity level of 97%) on our global data set, less than 1% of the reads clustered with sequences from cultures, and less than 12% clustered with reference sequences obtained previously from cloning and Sanger sequencing of environmental samples. Thus, we highlighted a large uncharacterized environmental genetic diversity, which clearly shows that currently cultivated species poorly reflect the actual diversity present in the natural environment. Haptophyte community appeared to be significantly structured according to the depth. The highest diversity and evenness were obtained in samples from the DCM, and samples from the large size fraction (3-20 μm) taken at the DCM shared a lower proportion of common OTUs(97%) with the other samples. Reads from the species Chrysoculter romboideus were notably found at the DCM, while they could be detected at the subsurface. The highest proportion of totally unknown OTUs(97%) was collected at the DCM in the smallest size fraction (0.8-3 μm). Overall, this study emphasized several technical and theoretical barriers inherent to the exploration of the large and largely unknown diversity of unicellular eukaryotes.
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Affiliation(s)
- Lucie Bittner
- CNRS, UMR7144 & Université Pierre et Marie Curie, Team EPPO, Station biologique de Roscoff, Place Georges Tessier, Roscoff, France.
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81
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Bianchetti L, Kieffer D, Féderkeil R, Poch O. Increased frequency of single base substitutions in a population of transcripts expressed in cancer cells. BMC Cancer 2012; 12:509. [PMID: 23137041 PMCID: PMC3522053 DOI: 10.1186/1471-2407-12-509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 10/09/2012] [Indexed: 12/03/2022] Open
Abstract
Background Single Base Substitutions (SBS) that alter transcripts expressed in cancer originate from somatic mutations. However, recent studies report SBS in transcripts that are not supported by the genomic DNA of tumor cells. Methods We used sequence based whole genome expression profiling, namely Long-SAGE (L-SAGE) and Tag-seq (a combination of L-SAGE and deep sequencing), and computational methods to identify transcripts with greater SBS frequencies in cancer. Millions of tags produced by 40 healthy and 47 cancer L-SAGE experiments were compared to 1,959 Reference Tags (RT), i.e. tags matching the human genome exactly once. Similarly, tens of millions of tags produced by 7 healthy and 8 cancer Tag-seq experiments were compared to 8,572 RT. For each transcript, SBS frequencies in healthy and cancer cells were statistically tested for equality. Results In the L-SAGE and Tag-seq experiments, 372 and 4,289 transcripts respectively, showed greater SBS frequencies in cancer. Increased SBS frequencies could not be attributed to known Single Nucleotide Polymorphisms (SNP), catalogued somatic mutations or RNA-editing enzymes. Hypothesizing that Single Tags (ST), i.e. tags sequenced only once, were indicators of SBS, we observed that ST proportions were heterogeneously distributed across Embryonic Stem Cells (ESC), healthy differentiated and cancer cells. ESC had the lowest ST proportions, whereas cancer cells had the greatest. Finally, in a series of experiments carried out on a single patient at 1 healthy and 3 consecutive tumor stages, we could show that SBS frequencies increased during cancer progression. Conclusion If the mechanisms generating the base substitutions could be known, increased SBS frequency in transcripts would be a new useful biomarker of cancer. With the reduction of sequencing cost, sequence based whole genome expression profiling could be used to characterize increased SBS frequency in patient’s tumor and aid diagnostic.
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Affiliation(s)
- Laurent Bianchetti
- Plate-forme Bioinformatique de Strasbourg (BIPS), Institut de Génétique et de Biologie Moléculaire et Cellulaire (CNRS/INSERM/ULP), Illkirch, Cedex, France.
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82
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Bolotin DA, Mamedov IZ, Britanova OV, Zvyagin IV, Shagin D, Ustyugova SV, Turchaninova MA, Lukyanov S, Lebedev YB, Chudakov DM. Next generation sequencing for TCR repertoire profiling: Platform-specific features and correction algorithms. Eur J Immunol 2012; 42:3073-83. [DOI: 10.1002/eji.201242517] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 06/14/2012] [Accepted: 07/10/2012] [Indexed: 01/17/2023]
Affiliation(s)
- Dmitry A. Bolotin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
| | - Ilgar Z. Mamedov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
| | - Olga V. Britanova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
| | - Ivan V. Zvyagin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
| | - Dmitriy Shagin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
- Evrogen JSC; Moscow Russia
| | | | | | - Sergey Lukyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
| | - Yury B. Lebedev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS; Moscow Russia
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83
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Martinez-Rucobo FW, Cramer P. Structural basis of transcription elongation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:9-19. [PMID: 22982352 DOI: 10.1016/j.bbagrm.2012.09.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 01/13/2023]
Abstract
For transcription elongation, all cellular RNA polymerases form a stable elongation complex (EC) with the DNA template and the RNA transcript. Since the millennium, a wealth of structural information and complementary functional studies provided a detailed three-dimensional picture of the EC and many of its functional states. Here we summarize these studies that elucidated EC structure and maintenance, nucleotide selection and addition, translocation, elongation inhibition, pausing and proofreading, backtracking, arrest and reactivation, processivity, DNA lesion-induced stalling, lesion bypass, and transcriptional mutagenesis. In the future, additional structural and functional studies of elongation factors that control the EC and their possible allosteric modes of action should result in a more complete understanding of the dynamic molecular mechanisms underlying transcription elongation. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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84
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Basic mechanism of transcription by RNA polymerase II. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:20-8. [PMID: 22982365 DOI: 10.1016/j.bbagrm.2012.08.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 07/23/2012] [Accepted: 08/29/2012] [Indexed: 11/21/2022]
Abstract
RNA polymerase II-like enzymes carry out transcription of genomes in Eukaryota, Archaea, and some viruses. They also exhibit fundamental similarity to RNA polymerases from bacteria, chloroplasts, and mitochondria. In this review we take an inventory of recent studies illuminating different steps of basic transcription mechanism, likely common for most multi-subunit RNA polymerases. Through the amalgamation of structural and computational chemistry data we attempt to highlight the most feasible reaction pathway for the two-metal nucleotidyl transfer mechanism, and to evaluate the way catalysis can be linked to translocation in the mechano-chemical cycle catalyzed by RNA polymerase II. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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85
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Abstract
We provide here a molecular movie that captures key aspects of RNA polymerase II initiation and elongation. To create the movie, we combined structural snapshots of the initiation-elongation transition and of elongation, including nucleotide addition, translocation, pausing, proofreading, backtracking, arrest, reactivation, and inhibition. The movie reveals open questions about the mechanism of transcription and provides a useful teaching tool.
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Affiliation(s)
- Alan C M Cheung
- Gene Center and Department of Biochemistry, Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität München, Munich, Germany
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86
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Smith EC, Denison MR. Implications of altered replication fidelity on the evolution and pathogenesis of coronaviruses. Curr Opin Virol 2012; 2:519-24. [PMID: 22857992 PMCID: PMC7102773 DOI: 10.1016/j.coviro.2012.07.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 07/12/2012] [Accepted: 07/16/2012] [Indexed: 01/09/2023]
Abstract
RNA virus evolution results from viral replication fidelity and mutational robustness in combination with selection. Recent studies have confirmed the impact of increased fidelity on RNA virus replication and pathogenesis; however, the impact of decreased fidelity is less defined. Coronaviruses have the largest RNA genomes, and encode an exoribonuclease activity that is required for high-fidelity replication. Genetically stable exoribonuclease mutants will allow direct testing of viral mutational tolerance to RNA mutagens and other selective pressures. Recent studies support the hypothesis that coronavirus replication fidelity may result from a multi-protein complex, suggesting multiple pathways to disrupt or alter virus fidelity and diversity, and attenuate pathogenesis.
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Affiliation(s)
- Everett C Smith
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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87
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Abstract
Transcription by RNA polymerase II is the process that copies DNA into RNA leading to the expression of a specific gene. Averaged estimates of polymerase elongation rates in mammalian cells have been shown to vary between 1 and 4 kilobases per minute. However, recent advances in live cell imaging allowed direct measurements of RNA biogenesis from a single gene exceeded 50 kb·min(-1) . This unexpected finding opens novel and intriguing perspectives on the control of metazoan transcription.
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Affiliation(s)
- Alessandro Marcello
- Laboratory of Molecular Virology, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
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88
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RNA 3'-end mismatch excision by the severe acute respiratory syndrome coronavirus nonstructural protein nsp10/nsp14 exoribonuclease complex. Proc Natl Acad Sci U S A 2012; 109:9372-7. [PMID: 22635272 DOI: 10.1073/pnas.1201130109] [Citation(s) in RCA: 246] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The replication/transcription complex of severe acute respiratory syndrome coronavirus is composed of at least 16 nonstructural proteins (nsp1-16) encoded by the ORF-1a/1b. This complex includes replication enzymes commonly found in positive-strand RNA viruses, but also a set of RNA-processing activities unique to some nidoviruses. The nsp14 protein carries both exoribonuclease (ExoN) and (guanine-N7)-methyltransferase (N7-MTase) activities. The nsp14 ExoN activity ensures a yet-uncharacterized function in the virus life cycle and must be regulated to avoid nonspecific RNA degradation. In this work, we show that the association of nsp10 with nsp14 stimulates >35-fold the ExoN activity of the latter while playing no effect on N7-MTase activity. Nsp10 mutants unable to interact with nsp14 are not proficient for ExoN activation. The nsp10/nsp14 complex hydrolyzes double-stranded RNA in a 3' to 5' direction as well as a single mismatched nucleotide at the 3'-end mimicking an erroneous replication product. In contrast, di-, tri-, and longer unpaired ribonucleotide stretches, as well as 3'-modified RNAs, resist nsp10/nsp14-mediated excision. In addition to the activation of nsp16-mediated 2'-O-MTase activity, nsp10 also activates nsp14 in an RNA processing function potentially connected to a replicative mismatch repair mechanism.
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89
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Voliotis M, Cohen N, Molina-París C, Liverpool TB. Proofreading of misincorporated nucleotides in DNA transcription. Phys Biol 2012; 9:036002. [PMID: 22551978 DOI: 10.1088/1478-3975/9/3/036002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The accuracy of DNA transcription is crucial for the proper functioning of the cell. Although RNA polymerases demonstrate selectivity for correct nucleotides, additional active mechanisms of transcriptional error correction are required to achieve observed levels of fidelity. Recent experimental findings have shed light on a particular mechanism of transcriptional error correction involving: (i) diffusive translocation of the RNA polymerase along the DNA (backtracking) and (ii) irreversible RNA cleavage. This mechanism achieves preferential cleavage of misincorporated nucleotides by biasing the local rates of translocation. Here, we study how misincorporated nucleotides affect backtracking dynamics and how this effect determines the level of transcriptional fidelity. We consider backtracking as a diffusive process in a periodic, one-dimensional energy landscape, which at a coarse-grained level gives rise to a hopping process between neighbouring local minima. We propose a model for how misincorporated nucleotides deform this energy landscape and hence affect the hopping rates. In particular, we show that this model can be used to derive both the theoretical limit on the fidelity (i.e. the minimum fraction of misincorporated nucleotides) and the actual fidelity relative to this optimum, achieved for specific combinations of the cleavage and polymerization rates. Finally, we study how external factors influencing backtracking dynamics affect transcriptional fidelity. We show that biologically relevant loads, similar to those exerted by nucleosomes or other transcriptional barriers, increase error correction.
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Affiliation(s)
- Margaritis Voliotis
- School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, UK.
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90
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Arnold JJ, Smidansky ED, Moustafa IM, Cameron CE. Human mitochondrial RNA polymerase: structure-function, mechanism and inhibition. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:948-60. [PMID: 22551784 DOI: 10.1016/j.bbagrm.2012.04.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 04/09/2012] [Accepted: 04/11/2012] [Indexed: 11/29/2022]
Abstract
Transcription of the human mitochondrial genome is required for the expression of 13 subunits of the respiratory chain complexes involved in oxidative phosphorylation, which is responsible for meeting the cells' energy demands in the form of ATP. Also transcribed are the two rRNAs and 22 tRNAs required for mitochondrial translation. This process is accomplished, with the help of several accessory proteins, by the human mitochondrial RNA polymerase (POLRMT, also known as h-mtRNAP), a nuclear-encoded single-subunit DNA-dependent RNA polymerase (DdRp or RNAP) that is distantly related to the bacteriophage T7 class of single-subunit RNAPs. In addition to its role in transcription, POLRMT serves as the primase for mitochondrial DNA replication. Therefore, this enzyme is of fundamental importance for both expression and replication of the human mitochondrial genome. Over the past several years rapid progress has occurred in understanding POLRMT and elucidating the molecular mechanisms of mitochondrial transcription. Important accomplishments include development of recombinant systems that reconstitute human mitochondrial transcription in vitro, determination of the X-ray crystal structure of POLRMT, identification of distinct mechanisms for promoter recognition and transcription initiation, elucidation of the kinetic mechanism for POLRMT-catalyzed nucleotide incorporation and discovery of unique mechanisms of mitochondrial transcription inhibition including the realization that POLRMT is an off target for antiviral ribonucleoside analogs. This review summarizes the current understanding of POLRMT structure-function, mechanism and inhibition. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Jamie J Arnold
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
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91
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Gao F, Lin Y, Zhang RR. RNA-DNA differences are rarer in proto-oncogenes than in tumor suppressor genes. Sci Rep 2012; 2:245. [PMID: 22355757 PMCID: PMC3270091 DOI: 10.1038/srep00245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 01/16/2012] [Indexed: 11/09/2022] Open
Abstract
It has long been assumed that DNA sequences and corresponding RNA transcripts are almost identical; a recent discovery, however, revealed widespread RNA-DNA differences (RDDs), which represent a largely unexplored aspect of human genome variation. It has been speculated that RDDs can affect disease susceptibility and manifestations; however, almost nothing is known about how RDDs are related to disease. Here, we show that RDDs are rarer in proto-oncogenes than in tumor suppressor genes; the number of RDDs in coding exons, but not in 3′UTR and 5′UTR, is significantly lower in the former than the latter, and this trend is especially pronounced in non-synonymous RDDs, i.e., those cause amino acid changes. A potential mechanism is that, unlike proto-oncogenes, the requirement of tumor suppressor genes to have both alleles affected to cause tumor ‘buffers' these genes to tolerate more RDDs.
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Affiliation(s)
- Feng Gao
- Department of Physics, Tianjin University, Tianjin 300072, China
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92
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Da LT, Wang D, Huang X. Dynamics of pyrophosphate ion release and its coupled trigger loop motion from closed to open state in RNA polymerase II. J Am Chem Soc 2012; 134:2399-406. [PMID: 22206270 PMCID: PMC3273452 DOI: 10.1021/ja210656k] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pyrophosphate ion (PP(i)) release after nucleotide incorporation is a necessary step for RNA polymerase II (pol II) to enter the next nucleotide addition cycle during transcription elongation. However, the role of pol II residues in PP(i) release and the mechanistic relationship between PP(i) release and the conformational change of the trigger loop remain unclear. In this study, we constructed a Markov state model (MSM) from extensive all-atom molecular dynamics (MD) simulations in the explicit solvent to simulate the PP(i) release process along the pol II secondary channel. Our results show that the trigger loop has significantly larger intrinsic motion after catalysis and formation of PP(i), which in turn aids PP(i) release mainly through the hydrogen bonding between the trigger loop residue H1085 and the (Mg-PP(i))(2-) group. Once PP(i) leaves the active site, it adopts a hopping model through several highly conserved positively charged residues such as K752 and K619 to release from the pol II pore region of the secondary channel. These positive hopping sites form favorable interactions with PP(i) and generate four kinetically metastable states as identified by our MSM. Furthermore, our single-mutant simulations suggest that H1085 and K752 aid PP(i) exit from the active site after catalysis, whereas K619 facilitates its passage through the secondary channel. Finally, we suggest that PP(i) release could help the opening motion of the trigger loop, even though PP(i) release precedes full opening of the trigger loop due to faster PP(i) dynamics. Our simulations provide predictions to guide future experimental tests.
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Affiliation(s)
- Lin-Tai Da
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Dong Wang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093-0625, USA
| | - Xuhui Huang
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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93
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Abstract
Bidirectional transport of intracellular cargo along microtubule tracks is the subject of intense debate in the motility field. In the present review, we provide an overview of the models describing the possible mechanisms driving intracellular saltatory transport, taking into account current experimental results that may at first seem contradictory. We examine the phenomenon of saltatory motion, in an attempt to interpret the mechanistic debate in terms of the utility of saltatory motion.
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94
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Swapna LS, Rekha N, Srinivasan N. Accommodation of profound sequence differences at the interfaces of eubacterial RNA polymerase multi-protein assembly. Bioinformation 2012; 8:6-12. [PMID: 22359428 PMCID: PMC3282269 DOI: 10.6026/97320630008006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Accepted: 12/17/2011] [Indexed: 11/23/2022] Open
Abstract
Evolutionarily divergent proteins have been shown to change their interacting partners. RNA polymerase assembly is one of the rare cases which retain its component proteins in the course of evolution. This ubiquitous molecular assembly, involved in transcription, consists of four core subunits (alpha, beta, betaprime, and omega), which assemble to form the core enzyme. Remarkably, the orientation of the four subunits in the complex is conserved from prokaryotes to eukaryotes although their sequence similarity is low. We have studied how the sequence divergence of the core subunits of RNA polymerase is accommodated in the formation of the multi-molecular assembly, with special reference to eubacterial species. Analysis of domain composition and order of the core subunits in >85 eubacterial species indicates complete conservation. However, sequence analysis indicates that interface residues of alpha and omega subunits are more divergent than those of beta, betaprime, and sigma70 subunits. Although beta and betaprime are generally well-conserved, residues involved in interaction with divergent subunits are not conserved. Insertions/deletions are also observed near interacting regions even in case of the most conserved subunits, beta and betaprime. Homology modelling of three divergent RNA polymerase complexes, from Helicobacter pylori, Mycoplasma pulmonis and Onion yellows phytoplasma, indicates that insertions/deletions can be accommodated near the interface as they generally occur at the periphery. Evaluation of the modeled interfaces indicates that they are physico-chemically similar to that of the template interfaces in Thermus thermophilus, indicating that nature has evolved to retain the obligate complex in spite of substantial substitutions and insertions/deletions.
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Affiliation(s)
| | - Nambudiry Rekha
- Biobase Databases India Pvt Ltd, Langford Town, Bangalore 560025, India
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95
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Smith BA, Jackman JE. Kinetic analysis of 3'-5' nucleotide addition catalyzed by eukaryotic tRNA(His) guanylyltransferase. Biochemistry 2011; 51:453-65. [PMID: 22136300 DOI: 10.1021/bi201397f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The tRNA(His) guanylyltransferase (Thg1) catalyzes the incorporation of a single guanosine residue at the -1 position (G(-1)) of tRNA(His), using an unusual 3'-5' nucleotidyl transfer reaction. Thg1 and Thg1 orthologs known as Thg1-like proteins (TLPs), which catalyze tRNA repair and editing, are the only known enzymes that add nucleotides in the 3'-5' direction. Thg1 enzymes share no identifiable sequence similarity with any other known enzyme family that could be used to suggest the mechanism for catalysis of the unusual 3'-5' addition reaction. The high-resolution crystal structure of human Thg1 revealed remarkable structural similarity between canonical DNA/RNA polymerases and eukaryotic Thg1; nevertheless, questions regarding the molecular mechanism of 3'-5' nucleotide addition remain. Here, we use transient kinetics to measure the pseudo-first-order forward rate constants for the three steps of the G(-1) addition reaction catalyzed by yeast Thg1: adenylylation of the 5' end of the tRNA (k(aden)), nucleotidyl transfer (k(ntrans)), and removal of pyrophosphate from the G(-1)-containing tRNA (k(ppase)). This kinetic framework, in conjunction with the crystal structure of nucleotide-bound Thg1, suggests a likely role for two-metal ion chemistry in all three chemical steps of the G(-1) addition reaction. Furthermore, we have identified additional residues (K44 and N161) involved in adenylylation and three positively charged residues (R27, K96, and R133) that participate primarily in the nucleotidyl transfer step of the reaction. These data provide a foundation for understanding the mechanism of 3'-5' nucleotide addition in tRNA(His) maturation.
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Affiliation(s)
- Brian A Smith
- Department of Biochemistry, Center for RNA Biology and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, United States
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96
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Ulrich S, Kool ET. Importance of steric effects on the efficiency and fidelity of transcription by T7 RNA polymerase. Biochemistry 2011; 50:10343-9. [PMID: 22044042 DOI: 10.1021/bi2011465] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
DNA-dependent RNA polymerases such as T7 RNA polymerase (T7 RNAP) perform the transcription of DNA into mRNA with high efficiency and high fidelity. Although structural studies have provided a detailed account of the molecular basis of transcription, the relative importance of factors like hydrogen bonds and steric effects remains poorly understood. We report herein the first study aimed at systematically probing the importance of steric and electrostatic effects on the efficiency and fidelity of DNA transcription by T7 RNAP. We used synthetic nonpolar analogues of thymine with sizes varying in subangstrom increments to probe the steric requirements of T7 RNAP during the elongation mode of transcription. Enzymatic assays with internal radiolabeling were performed to compare the efficiency of transcription of modified DNA templates with a natural template containing thymine as a reference. Furthermore, we analyzed effects on the fidelity by measuring the composition of RNA transcripts by enzymatic digestion followed by two-dimensional thin layer chromatography separation. Our results demonstrate that hydrogen bonds play an important role in the efficiency of transcription but, interestingly, do not appear to be required for faithful transcription. Steric effects (size and shape variations) are found to be significant both in insertion of a new RNA base and in extension beyond it.
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Affiliation(s)
- Sébastien Ulrich
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
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97
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98
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Li M, Wang IX, Li Y, Bruzel A, Richards AL, Toung JM, Cheung VG. Widespread RNA and DNA sequence differences in the human transcriptome. Science 2011; 333:53-8. [PMID: 21596952 PMCID: PMC3204392 DOI: 10.1126/science.1207018] [Citation(s) in RCA: 315] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The transmission of information from DNA to RNA is a critical process. We compared RNA sequences from human B cells of 27 individuals to the corresponding DNA sequences from the same individuals and uncovered more than 10,000 exonic sites where the RNA sequences do not match that of the DNA. All 12 possible categories of discordances were observed. These differences were nonrandom as many sites were found in multiple individuals and in different cell types, including primary skin cells and brain tissues. Using mass spectrometry, we detected peptides that are translated from the discordant RNA sequences and thus do not correspond exactly to the DNA sequences. These widespread RNA-DNA differences in the human transcriptome provide a yet unexplored aspect of genome variation.
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Affiliation(s)
- Mingyao Li
- Departments of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Isabel X. Wang
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Yun Li
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
- Department of Biostatistics, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Alan Bruzel
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Allison L. Richards
- Cell and Molecular Biology Graduate Program, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Jonathan M. Toung
- Genomics and Computational Biology Graduate Program, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Vivian G. Cheung
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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99
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Smidansky ED, Arnold JJ, Reynolds SL, Cameron CE. Human mitochondrial RNA polymerase: evaluation of the single-nucleotide-addition cycle on synthetic RNA/DNA scaffolds. Biochemistry 2011; 50:5016-32. [PMID: 21548588 PMCID: PMC3698222 DOI: 10.1021/bi200350d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The human mitochondrial RNA polymerase (h-mtRNAP) serves as both the transcriptase for expression and the primase for replication of mitochondrial DNA. As such, the enzyme is of fundamental importance to cellular energy metabolism, and defects in its function may be related to human disease states. Here we describe in vitro analysis of the h-mtRNAP kinetic mechanism for single, correct nucleotide incorporation. This was made possible by the development of efficient methods for expression and purification of h-mtRNAP using a bacterial system and by utilization of assays that rely on simple, synthetic RNA/DNA scaffolds without the need for mitochondrial transcription accessory proteins. We find that h-mtRNAP accomplishes single-nucleotide incorporation by using the same core steps, including conformational change steps before and after chemistry, that are prototypical for most types of nucleic acid polymerases. The polymerase binds to scaffolds via a two-step mechanism consisting of a fast initial-encounter step followed by a much slower isomerization that leads to catalytic competence. A substantial solvent deuterium kinetic isotope effect was observed for the forward reaction, but none was detectable for the reverse reaction, suggesting that chemistry is at least partially rate-limiting in the forward direction but not in the reverse. h-mtRNAP appears to exercise much more stringent surveillance over base than over sugar in determining the correctness of a nucleotide. The utility of developing the robust in vitro assays described here and of establishing a baseline of kinetic performance for the wild-type enzyme is that biological questions concerning h-mtRNAP may now begin to be addressed.
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Affiliation(s)
- Eric D. Smidansky
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jamie J. Arnold
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Shelley L. Reynolds
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Craig E. Cameron
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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100
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Abstract
Based on their extremely high mutation rates, RNA viruses have been traditionally considered as the fastest evolving entities in nature. However, recent work has revealed that, despite their greater replication fidelity, single-stranded (ss) DNA viruses can evolve fast in a similar way. To further investigate this issue, we have compared the rates of adaptation and molecular evolution of ssRNA and ssDNA viruses under highly controlled laboratory conditions using the bacteriophages ΦX174, G4, f1, Qβ, SP, and MS2 as model systems. Our results indicate that ssRNA phages evolve faster than ssDNA phages under strong selective pressure, and that their extremely high mutation rates appear to be optimal for this kind of scenario. However, their performance becomes similar to that of ssDNA phages over the longer term or when the population is moderately well-adapted. Interestingly, the roughly 100-fold difference between the mutation rates of ssRNA and ssDNA phages yields less than a fivefold difference in adaptation and nucleotide substitution rates. The results are therefore consistent with the observation that, despite their lower mutation rates, ssDNA viruses can sometimes match the evolvability of RNA viruses.
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Affiliation(s)
- Pilar Domingo-Calap
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Spain Departament de Genètica, Universitat de València, Spain Unidad Mixta de Investigación en Genómica y Salud, Centro Superior de Investigación en Salud Pública (CSISP), Valencia, Spain E-mail:
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