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Aseev LV, Koledinskaya LS, Boni IV. Extraribosomal Functions of Bacterial Ribosomal Proteins-An Update, 2023. Int J Mol Sci 2024; 25:2957. [PMID: 38474204 DOI: 10.3390/ijms25052957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 02/19/2024] [Accepted: 02/21/2024] [Indexed: 03/14/2024] Open
Abstract
Ribosomal proteins (r-proteins) are abundant, highly conserved, and multifaceted cellular proteins in all domains of life. Most r-proteins have RNA-binding properties and can form protein-protein contacts. Bacterial r-proteins govern the co-transcriptional rRNA folding during ribosome assembly and participate in the formation of the ribosome functional sites, such as the mRNA-binding site, tRNA-binding sites, the peptidyl transferase center, and the protein exit tunnel. In addition to their primary role in a cell as integral components of the protein synthesis machinery, many r-proteins can function beyond the ribosome (the phenomenon known as moonlighting), acting either as individual regulatory proteins or in complexes with various cellular components. The extraribosomal activities of r-proteins have been studied over the decades. In the past decade, our understanding of r-protein functions has advanced significantly due to intensive studies on ribosomes and gene expression mechanisms not only in model bacteria like Escherichia coli or Bacillus subtilis but also in little-explored bacterial species from various phyla. The aim of this review is to update information on the multiple functions of r-proteins in bacteria.
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Affiliation(s)
- Leonid V Aseev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, 117997 Moscow, Russia
| | | | - Irina V Boni
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, 117997 Moscow, Russia
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Mikhaylina AO, Nikonova EY, Kostareva OS, Tishchenko SV. Regulation of Ribosomal Protein Synthesis in Prokaryotes. Mol Biol 2021. [DOI: 10.1134/s0026893321010118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
The rRNA is the largest and most abundant RNA in bacterial and archaeal cells. It is also one of the best-characterized RNAs in terms of its structural motifs and sequence variation. Production of ribosome components including >50 ribosomal proteins (r-proteins) consumes significant cellular resources. Thus, RNA cis-regulatory structures that interact with r-proteins to repress further r-protein synthesis play an important role in maintaining appropriate stoichiometry between r-proteins and rRNA. Classically, such mRNA structures were thought to directly mimic the rRNA. However, more than 30 years of research has demonstrated that a variety of different recognition and regulatory paradigms are present. This review will demonstrate how structural mimicry between the rRNA and mRNA cis-regulatory structures may take many different forms. The collection of mRNA structures that interact with r-proteins to regulate r-protein operons are best characterized in Escherichia coli, but are increasingly found within species from nearly all phyla of bacteria and several archaea. Furthermore, they represent a unique opportunity to assess the plasticity of RNA structure in the context of RNA-protein interactions. The binding determinants imposed by r-proteins to allow regulation can be fulfilled in many ways. Some r-protein-interacting mRNAs are immediately obvious as rRNA mimics from primary sequence similarity, others are identifiable only after secondary or tertiary structure determination, and some show no obvious similarity. In addition, across different bacterial species a host of different mechanisms of action have been characterized, showing that there is no simple one-size-fits-all solution.
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Rahim MMA, Vigneault F, Zerges W. The RNA Structure of cis-acting Translational Elements of the Chloroplast psbC mRNA in Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2016; 7:828. [PMID: 27379123 PMCID: PMC4906055 DOI: 10.3389/fpls.2016.00828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 05/26/2016] [Indexed: 05/08/2023]
Abstract
Photosystem II is the first of two light-driven oxidoreductase complexes in oxygenic photosynthesis. The biogenesis of photosystem II requires the synthesis of polypeptide subunits encoded by the genomes in the chloroplast and the nucleus. In the chloroplast of the green alga Chlamydomonas reinhardtii, the synthesis of each subunit requires interactions between the 5' UTR of the mRNA encoding it and gene-specific translation factors. Here, we analyze the sequences and structures in the 5' UTR of the psbC mRNA, which are known to be required to promote translation and genetic interaction with TBC1, a nuclear gene required specifically for psbC translation. Results of enzymatic probing in vitro and chemical probing in vivo and in vitro support three secondary structures and reveal that one participates in a pseudoknot structure. Analyses of the effects of mutations affecting pseudoknot sequences, by structural mapping and thermal gradient gel electrophoresis, reveal that flexibility at the base of the major stem-loop is required for translation and higher order RNA conformation, and suggest that this conformation is stabilized by TBC1. This RNA pseudoknot tertiary structure is analogous to the internal ribosome entry sites that promote translation of certain viruses and cellular mRNAs in the nuclear-cytoplasmic systems of eukaryotes.
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Affiliation(s)
- Mir Munir A. Rahim
- Department of Microbiology and Immunology, Dalhousie University, HalifaxNS, Canada
| | - Frederic Vigneault
- Synthetic Biology Platform, Wyss Institute for Biologically Inspired Engineering, Harvard University, BostonMA, USA
| | - William Zerges
- Biology Department and Centre for Structural and Functional Genomics, Concordia University, MontrealQC, Canada
- *Correspondence: William Zerges,
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Jiang N, Hu L, Liu C, Gao X, Zheng S. 60S ribosomal protein L35 regulates β-casein translational elongation and secretion in bovine mammary epithelial cells. Arch Biochem Biophys 2015; 583:130-9. [PMID: 26297660 DOI: 10.1016/j.abb.2015.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 08/13/2015] [Accepted: 08/16/2015] [Indexed: 11/18/2022]
Abstract
60S ribosomal protein L35 (RPL35) is an important component of the 60S ribosomal subunit and has a role in protein translation and endoplasmic reticulum (ER) docking. However, few studies have investigated RPL35 in eukaryotes and much remains to be learned. Here, we analyzed the function of RPL35 in β-casein (CSN2) synthesis and secretion in bovine mammary epithelial cells (BMECs). We found that methionine (Met) could promote the expressions of CSN2 and RPL35. Analysis of overexpression and inhibition of RPL35 confirmed that it could mediate the Met signal and regulate CSN2 expression. The mechanism of CSN2 regulation by RPL35 was analyzed by coimmunoprecipitation (Co-IP), colocalization, fluorescence resonance energy transfer (FRET) and gene mutation. We found that RPL35 could control ribosome translational elongation during synthesis of CSN2 by interacting with eukaryotic translational elongation factor 2 (eEF2), and that eEF2 was the signaling molecule downstream of RPL35 controlling this process. RPL35 could also control the secretion of CSN2 by locating it to the ER. Taken together, these results revealed that, RPL35 was an important positive regulatory factor involving in the Met-mediated regulation of CSN2 translational elongation and secretion.
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Affiliation(s)
- Nan Jiang
- College of Life Science and Technology, Dalian University, Dalian Economic Technological Development Zone, Liaoning, 116622, China; The Laboratory of Pathophysiology in College of Veterinary Medicine, Northeast Agricultura University, Xiangfang District, Harbin, 150030, China.
| | - Lijun Hu
- The Laboratory of Pathophysiology in College of Veterinary Medicine, Northeast Agricultura University, Xiangfang District, Harbin, 150030, China.
| | - Chaonan Liu
- The Laboratory of Pathophysiology in College of Veterinary Medicine, Northeast Agricultura University, Xiangfang District, Harbin, 150030, China.
| | - Xueli Gao
- The Laboratory of Pathophysiology in College of Veterinary Medicine, Northeast Agricultura University, Xiangfang District, Harbin, 150030, China.
| | - Shimin Zheng
- The Laboratory of Pathophysiology in College of Veterinary Medicine, Northeast Agricultura University, Xiangfang District, Harbin, 150030, China.
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Benjamin JAM, Massé E. The iron-sensing aconitase B binds its own mRNA to prevent sRNA-induced mRNA cleavage. Nucleic Acids Res 2014; 42:10023-36. [PMID: 25092924 PMCID: PMC4150767 DOI: 10.1093/nar/gku649] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Aconitase is an iron–sulfur protein and a major enzyme of the TCA cycle that catalyzes the conversion of citrate to isocitrate under iron-rich conditions. In Escherichia coli, aconitase B (AcnB) is a typical moonlighting protein that can switch to its apo form (apo-AcnB) which favors binding its own mRNA 3′UTR and stabilize it when intracellular iron become scarce. The small regulatory RNA (sRNA) RyhB has previously been shown to promote RNase E-dependent degradation of acnB mRNA when it was expressed from an ectopic arabinose-dependent promoter, independently of intracellular iron levels. In marked contrast, we report here that expression of RyhB under low-iron conditions did not result in acnB mRNA degradation even when RyhB was bound to acnB ribosome binding site (RBS). Genetic and biochemical evidence suggested that, under low-iron conditions, apo-AcnB bound to acnB 3′UTR close to a RNase E cleavage site that is essential for RyhB-induced acnB mRNA degradation. Whereas RyhB can block acnB translation initiation, RNase E-dependent degradation of acnB was prevented by apo-AcnB binding close to the cleavage site. This previously uncharacterized regulation suggests an intricate post-transcriptional mechanism that represses protein expression while insuring mRNA stability.
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Affiliation(s)
- Julie-Anna M Benjamin
- Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada
| | - Eric Massé
- Department of Biochemistry, RNA Group, University of Sherbrooke, 3201 Jean Mignault Street, Sherbrooke, Quebec J1E 4K8, Canada
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Peselis A, Serganov A. Structure and function of pseudoknots involved in gene expression control. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 5:803-22. [PMID: 25044223 DOI: 10.1002/wrna.1247] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 05/09/2014] [Accepted: 05/21/2014] [Indexed: 11/08/2022]
Abstract
Natural RNA molecules can have a high degree of structural complexity but even the most complexly folded RNAs are assembled from simple structural building blocks. Among the simplest RNA elements are double-stranded helices that participate in the formation of different folding topologies and constitute the major fraction of RNA structures. One common folding motif of RNA is a pseudoknot, defined as a bipartite helical structure formed by base-pairing of the apical loop in the stem-loop structure with an outside sequence. Pseudoknots constitute integral parts of the RNA structures essential for various cellular activities. Among many functions of pseudoknotted RNAs is feedback regulation of gene expression, carried out through specific recognition of various molecules. Pseudoknotted RNAs autoregulate ribosomal and phage protein genes in response to downstream encoded proteins, while many metabolic and transport genes are controlled by cellular metabolites interacting with pseudoknotted RNA elements from the riboswitch family. Modulation of some genes also depends on metabolite-induced messenger RNA (mRNA) cleavage performed by pseudoknotted ribozymes. Several regulatory pseudoknots have been characterized biochemically and structurally in great detail. These studies have demonstrated a plethora of pseudoknot-based folds and have begun uncovering diverse molecular principles of the ligand-dependent gene expression control. The pseudoknot-mediated mechanisms of gene control and many unexpected and interesting features of the regulatory pseudoknots have significantly advanced our understanding of the genetic circuits and laid the foundation for modulation of their outcomes.
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Affiliation(s)
- Alla Peselis
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
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Transcriptome dynamics-based operon prediction in prokaryotes. BMC Bioinformatics 2014; 15:145. [PMID: 24884724 PMCID: PMC4235196 DOI: 10.1186/1471-2105-15-145] [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] [Received: 04/26/2013] [Accepted: 04/22/2014] [Indexed: 11/21/2022] Open
Abstract
Background Inferring operon maps is crucial to understanding the regulatory networks of prokaryotic genomes. Recently, RNA-seq based transcriptome studies revealed that in many bacterial species the operon structure vary with the change of environmental conditions. Therefore, new computational solutions that use both static and dynamic data are necessary to create condition specific operon predictions. Results In this work, we propose a novel classification method that integrates RNA-seq based transcriptome profiles with genomic sequence features to accurately identify the operons that are expressed under a measured condition. The classifiers are trained on a small set of confirmed operons and then used to classify the remaining gene pairs of the organism studied. Finally, by linking consecutive gene pairs classified as operons, our computational approach produces condition-dependent operon maps. We evaluated our approach on various RNA-seq expression profiles of the bacteria Haemophilus somni, Porphyromonas gingivalis, Escherichia coli and Salmonella enterica. Our results demonstrate that, using features depending on both transcriptome dynamics and genome sequence characteristics, we can identify operon pairs with high accuracy. Moreover, the combination of DNA sequence and expression data results in more accurate predictions than each one alone. Conclusion We present a computational strategy for the comprehensive analysis of condition-dependent operon maps in prokaryotes. Our method can be used to generate condition specific operon maps of many bacterial organisms for which high-resolution transcriptome data is available.
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Bos J, Duverger Y, Thouvenot B, Chiaruttini C, Branlant C, Springer M, Charpentier B, Barras F. The sRNA RyhB regulates the synthesis of the Escherichia coli methionine sulfoxide reductase MsrB but not MsrA. PLoS One 2013; 8:e63647. [PMID: 23671689 PMCID: PMC3650055 DOI: 10.1371/journal.pone.0063647] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 04/04/2013] [Indexed: 11/18/2022] Open
Abstract
Controlling iron homeostasis is crucial for all aerobically grown living cells that are exposed to oxidative damage by reactive oxygen species (ROS), as free iron increases the production of ROS. Methionine sulfoxide reductases (Msr) are key enzymes in repairing ROS-mediated damage to proteins, as they reduce oxidized methionine (MetSO) residues to methionine. E. coli synthesizes two Msr, A and B, which exhibit substrate diastereospecificity. The bacterial iron-responsive small RNA (sRNA) RyhB controls iron metabolism by modulating intracellular iron usage. We show in this paper that RyhB is a direct regulator of the msrB gene that encodes the MsrB enzyme. RyhB down-regulates msrB transcripts along with Hfq and RNaseE proteins since mutations in the ryhB, fur, hfq, or RNaseE-encoded genes resulted in iron-insensitive expression of msrB. Our results show that RyhB binds to two sequences within the short 5'UTR of msrB mRNA as identified by reverse transcriptase and RNase and lead (II) protection assays. Toeprinting analysis shows that RyhB pairing to msrB mRNA prevents efficient ribosome binding and thereby inhibits translation initiation. In vivo site directed-mutagenesis experiments in the msrB 5'UTR region indicate that both RyhB-pairing sites are required to decrease msrB expression. Thus, this study suggests a novel mechanism of translational regulation where a same sRNA can basepair to two different locations within the same mRNA species. In contrast, expression of msrA is not influenced by changes in iron levels.
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MESH Headings
- 5' Untranslated Regions/genetics
- Base Sequence
- Binding Sites/genetics
- Binding, Competitive
- Blotting, Northern
- Blotting, Western
- Down-Regulation
- Escherichia coli/enzymology
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/metabolism
- Gene Expression Regulation, Bacterial
- Gene Expression Regulation, Enzymologic
- Iron/metabolism
- Methionine Sulfoxide Reductases/genetics
- Methionine Sulfoxide Reductases/metabolism
- Mutation
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Untranslated/genetics
- RNA, Small Untranslated/metabolism
- Ribosomes/metabolism
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Affiliation(s)
- Julia Bos
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique-Aix Marseille Université, Unité Mixte de Recherche, Marseille, France
| | - Yohann Duverger
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique-Aix Marseille Université, Unité Mixte de Recherche, Marseille, France
| | - Benoît Thouvenot
- Centre National de la Recherche Scientifique-Université de Lorraine, Unité Mixte de Recherche, Biopôle de l’Université de Lorraine, Campus Biologie Santé, Vandœuvre-lès-Nancy, France
| | - Claude Chiaruttini
- Unité Propre de Recherche du Centre National de la Recherche Scientifique, Université Denis Diderot, Paris VII, Institut de Biologie Physico-chimique, Paris, France
| | - Christiane Branlant
- Centre National de la Recherche Scientifique-Université de Lorraine, Unité Mixte de Recherche, Biopôle de l’Université de Lorraine, Campus Biologie Santé, Vandœuvre-lès-Nancy, France
| | - Mathias Springer
- Unité Propre de Recherche du Centre National de la Recherche Scientifique, Université Denis Diderot, Paris VII, Institut de Biologie Physico-chimique, Paris, France
| | - Bruno Charpentier
- Centre National de la Recherche Scientifique-Université de Lorraine, Unité Mixte de Recherche, Biopôle de l’Université de Lorraine, Campus Biologie Santé, Vandœuvre-lès-Nancy, France
| | - Frédéric Barras
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique-Aix Marseille Université, Unité Mixte de Recherche, Marseille, France
- * E-mail:
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10
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Abstract
Ribosomal (r-) RNA adopts a well-defined structure within the ribosome, but the role of r-proteins in stabilizing this structure is poorly understood. To address this issue, we use optical tweezers to unfold RNA fragments in the presence or absence of r-proteins. Here, we focus on Escherichia coli r-protein L20, whose globular C-terminal domain (L20C) recognizes an irregular stem in domain II of 23S rRNA. L20C also binds its own mRNA and represses its translation; binding occurs at two different sites--i.e., a pseudoknot and an irregular stem. We find that L20C makes rRNA and mRNA fragments encompassing its binding sites more resistant to mechanical unfolding. The regions of increased resistance correspond within two base pairs to the binding sites identified by conventional methods. While stabilizing specific RNA structures, L20C does not accelerate their formation from alternate conformations--i.e., it acts as a clamp but not as a chaperone. In the ribosome, L20C contacts only one side of its target stem but interacts with both strands, explaining its clamping effect. Other r-proteins bind rRNA similarly, suggesting that several rRNA structures are stabilized by "one-side" clamping.
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12
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Tai V, Poon AFY, Paulsen IT, Palenik B. Selection in coastal Synechococcus (cyanobacteria) populations evaluated from environmental metagenomes. PLoS One 2011; 6:e24249. [PMID: 21931665 PMCID: PMC3170327 DOI: 10.1371/journal.pone.0024249] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 08/05/2011] [Indexed: 11/19/2022] Open
Abstract
Environmental metagenomics provides snippets of genomic sequences from all organisms in an environmental sample and are an unprecedented resource of information for investigating microbial population genetics. Current analytical methods, however, are poorly equipped to handle metagenomic data, particularly of short, unlinked sequences. A custom analytical pipeline was developed to calculate dN/dS ratios, a common metric to evaluate the role of selection in the evolution of a gene, from environmental metagenomes sequenced using 454 technology of flow-sorted populations of marine Synechococcus, the dominant cyanobacteria in coastal environments. The large majority of genes (98%) have evolved under purifying selection (dN/dS<1). The metagenome sequence coverage of the reference genomes was not uniform and genes that were highly represented in the environment (i.e. high read coverage) tended to be more evolutionarily conserved. Of the genes that may have evolved under positive selection (dN/dS>1), 77 out of 83 (93%) were hypothetical. Notable among annotated genes, ribosomal protein L35 appears to be under positive selection in one Synechococcus population. Other annotated genes, in particular a possible porin, a large-conductance mechanosensitive channel, an ATP binding component of an ABC transporter, and a homologue of a pilus retraction protein had regions of the gene with elevated dN/dS. With the increasing use of next-generation sequencing in metagenomic investigations of microbial diversity and ecology, analytical methods need to accommodate the peculiarities of these data streams. By developing a means to analyze population diversity data from these environmental metagenomes, we have provided the first insight into the role of selection in the evolution of Synechococcus, a globally significant primary producer.
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Affiliation(s)
- Vera Tai
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States of America
| | - Art F. Y. Poon
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Ian T. Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Brian Palenik
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States of America
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Jayant L, Priano C, Mills DR. In polycistronic Qbeta RNA, single-strandedness at one ribosome binding site directly affects translational initiations at a distal upstream cistron. Nucleic Acids Res 2010; 38:7199-210. [PMID: 20581118 PMCID: PMC2978339 DOI: 10.1093/nar/gkq541] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In Qβ RNA, sequestering the coat gene ribosome binding site in a putatively strong hairpin stem structure eliminated synthesis of coat protein and activated protein synthesis from the much weaker maturation gene initiation site, located 1300 nucleotides upstream. As the stability of a hairpin stem comprising the coat gene Shine-Dalgarno site was incrementally increased, there was a corresponding increase in translation of maturation protein. The effect of the downstream coat gene ribosome binding sequence on maturation gene expression appeared to have occurred only in cis and did not require an AUG start codon or initiation of coat protein synthesis. In all cases, no structural reorganization was predicted to occur within Qβ RNA. Our results suggest that protein synthesis from a relatively weak translational initiation site is greatly influenced by the presence or absence of a stronger ribosome binding site located elsewhere on the same RNA molecule. The data are consistent with a mechanism in which multiple ribosome binding sites compete in cis for translational initiations as a means of regulating protein synthesis on a polycistronic messenger RNA.
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Affiliation(s)
- Lalitha Jayant
- Science Department, Borough of Manhattan Community College, City University of New York, New York, NY 10007, USA.
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14
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Abstract
RNA binding proteins are capable of regulating translation initiation by a variety of mechanisms. Although the vast majority of these regulatory mechanisms involve translational repression, one example of translational activation has been characterized in detail. The RNA recognition targets of these regulatory proteins exhibit a wide range in structural complexity, with some proteins recognizing complex pseudoknot structures and others binding to simple RNA hairpins and/or short repeated single-stranded sequences. In some instances the bound protein directly competes with ribosome binding, and in other instances the bound protein promotes formation of an RNA structure that inhibits ribosome binding. Examples also exist in which the bound protein traps the ribosome in a complex that is incapable of initiating translation.
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Affiliation(s)
- Paul Babitzke
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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15
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Pradhan P, Li W, Kaur P. Translational coupling controls expression and function of the DrrAB drug efflux pump. J Mol Biol 2008; 385:831-42. [PMID: 19063901 DOI: 10.1016/j.jmb.2008.11.027] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Revised: 11/17/2008] [Accepted: 11/18/2008] [Indexed: 11/26/2022]
Abstract
This study investigates the role of translational coupling in the expression and function of DrrA and DrrB proteins, which form an efflux pump for the export of anticancer drugs doxorubicin and daunorubicin in the producer organism Streptomyces peucetius. Interest in studying the role of translational coupling came from the initial observation that DrrA and DrrB proteins confer doxorubicin resistance only when they are expressed in cis. Because of the presence of overlapping stop and start codons in the intergenic region between drrA and drrB, it has been assumed that the translation of drrB is coupled to the translation of the upstream gene drrA even though direct evidence for coupling has been lacking. In this study, we show that the expression of drrB is indeed coupled to translation of drrA. We also show that the introduction of non-coding sequences between the stop codon of drrA and the start of drrB prevents formation of a functional complex, although both proteins are still produced at normal levels, thus suggesting that translational coupling also plays a crucial role in proper assembly. Interestingly, replacement of drrA with an unrelated gene was found to result in very high drrB expression, which becomes severely growth inhibitory. This indicates that an additional mechanism within drrA may optimize expression of drrB. Based on the observations reported here, it is proposed that the production and assembly of DrrA and DrrB are tightly linked. Furthermore, we propose that the key to assembly of the DrrAB complex lies in co-folding of the two proteins, which requires that the genes be maintained in cis in a translationally coupled manner.
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Affiliation(s)
- Prajakta Pradhan
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA
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16
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Abstract
RNA pseudoknots are structural elements found in almost all classes of RNA. Pseudoknots form when a single-stranded region in the loop of a hairpin base-pairs with a stretch of complementary nucleotides elsewhere in the RNA chain. This simple folding strategy is capable of generating a large number of stable three-dimensional folds that display a diverse range of highly specific functions in a variety of biological processes. The present review focuses on pseudoknots that act in the regulation of protein synthesis using cellular and viral examples to illustrate their versatility. Emphasis is placed on structurally well-defined pseudoknots that play a role in internal ribosome entry, autoregulation of initiation, ribosomal frameshifting during elongation and trans-translation.
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17
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Peil L, Virumäe K, Remme J. Ribosome assembly in Escherichia coli strains lacking the RNA helicase DeaD/CsdA or DbpA. FEBS J 2008; 275:3772-82. [PMID: 18565105 DOI: 10.1111/j.1742-4658.2008.06523.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Ribosome subunit assembly in bacteria is a fast and efficient process. Among the nonribosomal proteins involved in ribosome biogenesis are RNA helicases. We describe ribosome biogenesis in Escherichia coli strains lacking RNA helicase DeaD (CsdA) or DbpA. Ribosome large subunit assembly intermediate particles (40S) accumulate at 25 degrees C and at 37 degrees C in the absence of DeaD but not without DbpA. 23S rRNA is incompletely processed in the 40S and 50S particles of the DeaD(-) strain. Pulse labeling showed that the 40S particles are converted nearly completely into functional ribosomes. The rate of large ribosomal subunit assembly was reduced about four times in DeaD-deficient cells. Functional activity tests of the ribosomal particles demonstrated that the final step of 50S assembly, the activation step, was affected when DeaD was not present. The results are compatible with the model that predicts multiple DeaD-catalyzed structural transitions of the ribosome large subunit assembly.
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Affiliation(s)
- Lauri Peil
- Institute of Molecular and Cell Biology, University of Tartu, Estonia
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