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Mezhyrova J, Martin J, Börnsen C, Dötsch V, Frangakis AS, Morgner N, Bernhard F. In vitro characterization of the phage lysis protein MS2-L. MICROBIOME RESEARCH REPORTS 2023; 2:28. [PMID: 38045926 PMCID: PMC10688784 DOI: 10.20517/mrr.2023.28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 06/29/2023] [Accepted: 07/10/2023] [Indexed: 12/05/2023]
Abstract
Background: The peptide MS2-L represents toxins of the ssRNA Leviviridae phage family and consists of a predicted N-terminal soluble domain followed by a transmembrane domain. MS2-L mediates bacterial cell lysis through the formation of large lesions in the cell envelope, but further details of this mechanism as a prerequisite for applied bioengineering studies are lacking. The chaperone DnaJ is proposed to modulate MS2-L activity, whereas other cellular targets of MS2-L are unknown. Methods: Here, we provide a combined in vitro and in vivo overexpression approach to reveal molecular insights into MS2-L action and its interaction with DnaJ. Full-length MS2-L and truncated derivatives were synthesized cell-free and co-translationally inserted into nanodiscs or solubilized in detergent micelles. By native liquid bead ion desorption mass spectrometry, we demonstrate that MS2-L assembles into high oligomeric states after membrane insertion. Results: Oligomerization is directed by the transmembrane domain and is impaired in detergent environments. Studies with truncated MS2-L derivatives provide evidence that the soluble domain acts as a modulator of oligomer formation. DnaJ strongly interacts with MS2-L in membranes as well as in detergent environments. However, this interaction affects neither the MS2-L membrane insertion efficiency nor its oligomerization in nanodisc membranes. In accordance with the in vitro data, the assembly of MS2-L derivatives into large membrane located clusters was monitored by overexpression of corresponding fusions with fluorescent monitors in E. coli cells. Analysis by cryo-electron microscopy indicates that lesion formation is initiated in the outer membrane, followed by disruption of the peptidoglycan layer and disintegration of the inner membrane. Conclusion: MS2-L forms oligomeric complexes similar to the related phage toxin ΦX174-E. The oligomeric interface of both peptides is located within their transmembrane domains. We propose a potential function of the higher-order assembly of small phage toxins in membrane disintegration and cell lysis.
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Affiliation(s)
- Julija Mezhyrova
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main 60438, Germany
| | - Janosch Martin
- Institute of Physical and Theoretical Chemistry, Goethe University, Frankfurt am Main 60438, Germany
| | - Clara Börnsen
- Buchmann Institute for Molecular Life Sciences & Institute of Biophysics, Goethe University, Frankfurt am Main 60438, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main 60438, Germany
| | - Achilleas Stefanos Frangakis
- Buchmann Institute for Molecular Life Sciences & Institute of Biophysics, Goethe University, Frankfurt am Main 60438, Germany
| | - Nina Morgner
- Institute of Physical and Theoretical Chemistry, Goethe University, Frankfurt am Main 60438, Germany
| | - Frank Bernhard
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main 60438, Germany
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2
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Abstract
The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads rapidly and harbors many mutations in the spike protein, but the origin of this virus variant remains unclear. We address the role of unusual virus evolution mechanisms such as hypermutation, out-of-frame reading, and recombination. Rather, regular Darwinian evolution, that is, the repeated selection of beneficial spike mutations, seems to have led to the appearance of the grossly altered spike protein of the Omicron variant.
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3
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Meir M, Harel N, Miller D, Gelbart M, Eldar A, Gophna U, Stern A. Competition between social cheater viruses is driven by mechanistically different cheating strategies. SCIENCE ADVANCES 2020; 6:eabb7990. [PMID: 32937370 PMCID: PMC7442481 DOI: 10.1126/sciadv.abb7990] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/09/2020] [Indexed: 05/09/2023]
Abstract
Cheater viruses, also known as defective interfering viruses, cannot replicate on their own yet replicate faster than the wild type upon coinfection. While there is growing interest in using cheaters as antiviral therapeutics, the mechanisms underlying cheating have been rarely explored. During experimental evolution of MS2 phage, we observed the parallel emergence of two independent cheater mutants. The first, a point deletion mutant, lacked polymerase activity but was advantageous in viral packaging. The second synonymous mutant cheater displayed a completely different cheating mechanism, involving an altered RNA structure. Continued evolution revealed the demise of the deletion cheater and rise of the synonymous cheater. A mathematical model inferred that while a single cheater is expected to reach an equilibrium with the wild type, cheater demise arises from antagonistic interactions between coinfecting cheaters. These findings highlight layers of parasitism: viruses parasitizing cells, cheaters parasitizing intact viruses, and cheaters may parasitize other cheaters.
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Affiliation(s)
- Moran Meir
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Noam Harel
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Danielle Miller
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Maoz Gelbart
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Avigdor Eldar
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Uri Gophna
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
| | - Adi Stern
- School of Molecular Cell Biology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
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4
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Sterk M, Romilly C, Wagner EGH. Unstructured 5'-tails act through ribosome standby to override inhibitory structure at ribosome binding sites. Nucleic Acids Res 2019; 46:4188-4199. [PMID: 29420821 PMCID: PMC5934652 DOI: 10.1093/nar/gky073] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 01/26/2018] [Indexed: 11/13/2022] Open
Abstract
Initiation is the rate-limiting step in translation. It is well-known that stable structure at a ribosome binding site (RBS) impedes initiation. The ribosome standby model of de Smit and van Duin, based on studies of the MS2 phage coat cistron, proposed how high translation rates can be reconciled with stable, inhibitory structures at an RBS. Here, we revisited the coat protein system and assessed the translation efficiency from its sequestered RBS by introducing standby mutations. Further experiments with gfp reporter constructs assessed the effects of 5′-tails—as standby sites—with respect to length and sequence contributions. In particular, combining in vivo and in vitro assays, we can show that tails of CA-dinucleotide repeats—and to a lesser extent, AU-repeats—dramatically increase translation rates. Tails of increasing length reach maximal rate-enhancing effects at 16–18 nucleotides. These standby tails are single-stranded and do not exert their effect by structure changes in the neighboring RBS stem–loop. In vitro translation and toeprinting assays furthermore demonstrate that standby effects are exerted at the level of translation initiation. Finally, as expected, destabilizing mutations within the coat RBS indicate an interplay with the effects of standby tails.
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Affiliation(s)
- Maaike Sterk
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, S-75124 Uppsala, Sweden
| | - Cédric Romilly
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, S-75124 Uppsala, Sweden
| | - E Gerhart H Wagner
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, S-75124 Uppsala, Sweden
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5
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Callanan J, Stockdale SR, Shkoporov A, Draper LA, Ross RP, Hill C. RNA Phage Biology in a Metagenomic Era. Viruses 2018; 10:E386. [PMID: 30037084 PMCID: PMC6071253 DOI: 10.3390/v10070386] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/22/2022] Open
Abstract
The number of novel bacteriophage sequences has expanded significantly as a result of many metagenomic studies of phage populations in diverse environments. Most of these novel sequences bear little or no homology to existing databases (referred to as the "viral dark matter"). Also, these sequences are primarily derived from DNA-encoded bacteriophages (phages) with few RNA phages included. Despite the rapid advancements in high-throughput sequencing, few studies enrich for RNA viruses, i.e., target viral rather than cellular fraction and/or RNA rather than DNA via a reverse transcriptase step, in an attempt to capture the RNA viruses present in a microbial communities. It is timely to compile existing and relevant information about RNA phages to provide an insight into many of their important biological features, which should aid in sequence-based discovery and in their subsequent annotation. Without comprehensive studies, the biological significance of RNA phages has been largely ignored. Future bacteriophage studies should be adapted to ensure they are properly represented in phageomic studies.
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Affiliation(s)
- Julie Callanan
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
- School of Microbiology, University College Cork, Cork, T12 YN60, Ireland.
| | - Stephen R Stockdale
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
- Teagasc Food Research Centre, Moorepark, Fermoy, Cork, P61 C996, Ireland.
| | - Andrey Shkoporov
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
| | - Lorraine A Draper
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
- School of Microbiology, University College Cork, Cork, T12 YN60, Ireland.
| | - R Paul Ross
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
- School of Microbiology, University College Cork, Cork, T12 YN60, Ireland.
- Teagasc Food Research Centre, Moorepark, Fermoy, Cork, P61 C996, Ireland.
| | - Colin Hill
- APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
- School of Microbiology, University College Cork, Cork, T12 YN60, Ireland.
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6
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MS2 Lysis of Escherichia coli Depends on Host Chaperone DnaJ. J Bacteriol 2017; 199:JB.00058-17. [PMID: 28396351 DOI: 10.1128/jb.00058-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/03/2017] [Indexed: 11/20/2022] Open
Abstract
The L protein of the single-stranded RNA phage MS2 causes lysis of Escherichia coli without inducing bacteriolytic activity or inhibiting net peptidoglycan (PG) synthesis. To find host genes required for L-mediated lysis, spontaneous Ill (insensitivity to Llysis) mutants were selected as survivors of L expression and shown to have a missense change of the highly conserved proline (P330Q) in the C-terminal domain of DnaJ. In the dnaJP330Q mutant host, L-mediated lysis is completely blocked at 30°C without affecting the intracellular levels of L. At higher temperatures (37°C and 42°C), both lysis and L accumulation are delayed. The lysis block at 30°C in the dnaJP330Q mutant was recessive and could be suppressed by Lovercomes dnaJ (Lodj ) alleles selected for restoration of lysis. All three Lodj alleles lack the highly basic N-terminal half of the lysis protein and cause lysis ∼20 min earlier than full-length L. DnaJ was found to form a complex with full-length L. This complex was abrogated by the P330Q mutation and was absent with the Lodj truncations. These results suggest that, in the absence of interaction with DnaJ, the N-terminal domain of L interferes with its ability to bind to its unknown target. The lysis retardation and DnaJ chaperone dependency conferred by the nonessential, highly basic N-terminal domain of L resembles the SlyD chaperone dependency conferred by the highly basic C-terminal domain of the E lysis protein of ϕX174, suggesting a common theme where single-gene lysis can be modulated by host factors influenced by physiological conditions.IMPORTANCE Small single-stranded nucleic acid lytic phages (Microviridae and Leviviridae) lyse their host by expressing a single "protein antibiotic." The protein antibiotics from two out of three prototypic small lytic viruses have been shown to inhibit two different steps in the conserved PG biosynthesis pathway. However, the molecular basis of lysis caused by L, the lysis protein of the third prototypic virus, MS2, is unknown. The significance of our research lies in the identification of DnaJ as a chaperone in the MS2 L lysis pathway and the identification of the minimal lytic domain of MS2 L. Additionally, our research highlights the importance of the highly conserved P330 residue in the C-terminal domain of DnaJ for specific protein interactions.
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7
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In situ structures of the genome and genome-delivery apparatus in a single-stranded RNA virus. Nature 2016; 541:112-116. [PMID: 27992877 PMCID: PMC5701785 DOI: 10.1038/nature20589] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/26/2016] [Indexed: 12/11/2022]
Abstract
Genome packaging into a protein capsid and its subsequent delivery into a host cell are two fundamental processes in the life cycle of a virus. Unlike dsDNA viruses which pump their genome into a preformed capsid1-3, ssRNA viruses, such as bacteriophage MS2, co-assemble their capsid with genome4-7; however, the structural basis of this co-assembly is poorly understood. MS2 infects Escherichia coli via host “sex” pilus (F-pilus)8 and is the first fully-sequenced organism9 and a model system for studies of gene translational regulations10,11, RNA-protein interactions12-14, and RNA virus assembly15-17. Its positive-sense ssRNA genome of 3569 bases is enclosed in a capsid with one maturation protein (MP) monomer and 89 coat protein (CP) dimers arranged in a T=3 icosahedral lattice18,19. MP is responsible for attaching the virus to an F-pilus and delivering the viral genome into the host during infection8, but how the genome is organized and delivered are not known. Here we show the MS2 structure at 3.6Å resolution determined by electron-counting cryo electron microscopy (cryoEM) and asymmetric reconstruction. We traced ~80% backbone of the viral genome, built atomic models for 16 RNA stem-loops, and identified three conserved motifs of RNA-CP interactions among 15 of these stem-loops with diverse sequences. The stem-loop at 3’ end of the genome interacts extensively with the MP, which, with just a six-helix bundle and a six-stranded β-sheet, forms a genome-delivery apparatus, and joins 89 CP-dimers to form a capsid. This first atomic description of genome-capsid interactions in a spherical ssRNA virus provides insights into genome delivery via host “sex” pilus and mechanisms underlying ssRNA-capsid co-assembly, and inspires imaginations about links between nucleoprotein complexes and the origin of viruses.
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8
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Abstract
An RNA secondary structure model for the complete HIV-1 genome has recently been published based on SHAPE technology. Several well-known RNA motifs such as TAR and RRE were confirmed and numerous new structured motifs were described that may play important roles in virus replication. The 9 kb viral RNA genome is densely packed with many RNA hairpin motifs and the collective fold may play an important role in HIV-1 biology. We initially focused on 16 RNA hairpin motifs scattered along the viral genome. We considered conservation of these structures, despite sequence variation among virus isolates, as a first indication for a significant function. Four relatively small hairpins exhibited considerable structural conservation and were selected for experimental validation in virus replication assays. Mutations were introduced into the HIV-1 RNA genome to destabilize individual RNA structures without affecting the protein-coding properties (silent codon changes). No major virus replication defects were scored, suggesting that these four hairpin structures do not play essential roles in HIV-1 replication.
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Affiliation(s)
- Stefanie A Knoepfel
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center; University of Amsterdam, Amsterdam, the Netherlands
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9
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Borodavka A, Tuma R, Stockley PG. A two-stage mechanism of viral RNA compaction revealed by single molecule fluorescence. RNA Biol 2013; 10:481-9. [PMID: 23422316 PMCID: PMC3710354 DOI: 10.4161/rna.23838] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Long RNAs often exist as multiple conformers in equilibrium. For the genomes of single-stranded RNA viruses, one of these conformers must include a compacted state allowing the RNA to be confined within the virion. We have used single molecule fluorescence correlation spectroscopy to monitor the conformations of viral genomes and sub-fragments in the absence and presence of coat proteins. Cognate RNA-coat protein interactions in two model viruses cause a rapid collapse in the hydrodynamic radii of their respective RNAs. This is caused by protein binding at multiple sites on the RNA that facilitate additional protein-protein contacts. The collapsed species recruit further coat proteins to complete capsid assembly with great efficiency and fidelity. The specificity in RNA-coat protein interactions seen at single-molecule concentrations reflects the packaging selectivity seen for such viruses in vivo. This contrasts with many in vitro reassembly measurements performed at much higher concentrations. RNA compaction by coat protein or polycation binding are distinct processes, implying that defined RNA-coat protein contacts are required for assembly.
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Affiliation(s)
- Alexander Borodavka
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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10
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Genomewide patterns of substitution in adaptively evolving populations of the RNA bacteriophage MS2. Genetics 2009; 181:1535-44. [PMID: 19189959 DOI: 10.1534/genetics.107.085837] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Experimental evolution of bacteriophage provides a powerful means of studying the genetics of adaptation, as every substitution contributing to adaptation can be identified and characterized. Here, I use experimental evolution of MS2, an RNA bacteriophage, to study its adaptive response to a novel environment. To this end, three lines of MS2 were adapted to rapid growth and lysis at cold temperature for a minimum of 50 phage generations and subjected to whole-genome sequencing. Using this system, I identified adaptive substitutions, monitored changes in frequency of adaptive mutations through the course of the experiment, and measured the effect on phage growth rate of each substitution. All three lines showed a substantial increase in fitness (a two- to threefold increase in growth rate) due to a modest number of substitutions (three to four). The data show some evidence that the substitutions occurring early in the experiment have larger beneficial effects than later ones, in accordance with the expected diminishing returns relationship between the fitness effects of a mutation and its order of substitution. Patterns of molecular evolution seen here--primarily a paucity of hitchhiking mutations--suggest an abundant supply of beneficial mutations in this system. Nevertheless, some beneficial mutations appear to have been lost, possibly due to accumulation of beneficial mutations on other genetic backgrounds, clonal interference, and negatively epistatic interactions with other beneficial mutations.
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11
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Parallel genetic evolution within and between bacteriophage species of varying degrees of divergence. Genetics 2008; 181:225-34. [PMID: 19001294 DOI: 10.1534/genetics.107.085225] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Parallel evolution is the acquisition of identical adaptive traits in independently evolving populations. Understanding whether the genetic changes underlying adaptation to a common selective environment are parallel within and between species is interesting because it sheds light on the degree of evolutionary constraints. If parallel evolution is perfect, then the implication is that forces such as functional constraints, epistasis, and pleiotropy play an important role in shaping the outcomes of adaptive evolution. In addition, population genetic theory predicts that the probability of parallel evolution will decline with an increase in the number of adaptive solutions-if a single adaptive solution exists, then parallel evolution will be observed among highly divergent species. For this reason, it is predicted that close relatives-which likely overlap more in the details of their adaptive solutions-will show more parallel evolution. By adapting three related bacteriophage species to a novel environment we find (1) a high rate of parallel genetic evolution at orthologous nucleotide and amino acid residues within species, (2) parallel beneficial mutations do not occur in a common order in which they fix or appear in an evolving population, (3) low rates of parallel evolution and convergent evolution between species, and (4) the probability of parallel and convergent evolution between species is strongly effected by divergence.
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12
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Bollback JP, Huelsenbeck JP. Clonal interference is alleviated by high mutation rates in large populations. Mol Biol Evol 2007; 24:1397-406. [PMID: 17379621 DOI: 10.1093/molbev/msm056] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
When a beneficial mutation is fixed in a population that lacks recombination, the genetic background linked to that mutation is fixed. As a result, beneficial mutations on different backgrounds experience competition, or "clonal interference," that can cause asexual populations to evolve more slowly than their sexual counterparts. Factors such as a large population size (N) and high mutation rates (mu) increase the number of competing beneficial mutations, and hence are expected to increase the intensity of clonal interference. However, recent theory suggests that, with very large values of Nmu, the severity of clonal interference may instead decline. The reason is that, with large Nmu, genomes including both beneficial mutations are rapidly created by recurrent mutation, obviating the need for recombination. Here, we analyze data from experimentally evolved asexual populations of a bacteriophage and find that, in these nonrecombining populations with very large Nmu, recurrent mutation does appear to ameliorate this cost of asexuality.
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13
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Praszkier J, Pittard AJ. Control of replication in I-complex plasmids. Plasmid 2005; 53:97-112. [PMID: 15737397 DOI: 10.1016/j.plasmid.2004.12.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Revised: 12/17/2004] [Accepted: 12/22/2004] [Indexed: 11/18/2022]
Abstract
The closely related plasmids that make up the I-complex group and the more distantly related IncL/M plasmids regulate the frequency of initiation of their replication by controlling the efficiency of translation of the rate limiting replication initiator protein, RepA. Translation initiation of repA is dependent on the formation of a pseudoknot immediately upstream of its Shine-Dalgarno sequence. Formation of this pseudoknot involves base pairing between two complementary sequences in the repA mRNA and requires that the secondary structure sequestering the distal sequence be disrupted by movement of the ribosome translating and terminating a leader peptide, whose coding sequence precedes and overlaps that of repA. Expression of repA is controlled by a small antisense RNA, RNAI, which on binding to its complementary target in the repA mRNA not only pre-empts formation of the pseudoknot, but also inhibits translation of the leader peptide. The requirement that translation of the leader peptide be completed for the pseudoknot to form increases the time available for the inhibitory interaction of RNAI with its target, so that at high copy number the frequency of pseudoknot formation is lowered, reducing the proportion of repA mRNA that are translated. At low copy number, when concentration of RNAI is low, repA is translated with increased frequency, leading to increased frequency of plasmid replication.
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Affiliation(s)
- Judy Praszkier
- Department of Microbiology and Immunology, The University of Melbourne, Vic. 3010, Australia.
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14
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Saini M, Vrati S. High-level synthesis of Johnson grass mosaic virus coat protein in Escherichia coli and its auto-assembly to form virus-like particles. Protein Expr Purif 2003; 28:86-92. [PMID: 12651111 DOI: 10.1016/s1046-5928(02)00647-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The coat protein (CP) of Johnson grass mosaic virus (JGMV) auto-assembles to form virus-like particles (VLPs) and hence could be useful for presenting small peptides to the immune system. We are therefore attempting to synthesize JGMV CP in large amounts in Escherichia coli. The JGMV CP-encoding DNA, cloned under the bacteriophage T7 promoter, showed only low levels of CP synthesis in E. coli. The predicted secondary structure of the CP mRNA showed that its translational initiation codon was part of a stable hairpin-loop structure. The initiation codon could be relieved of the hairpin-loop structure by substitution of three neighboring nucleotides. This resulted in a single amino acid change at the N-terminus of the protein. The modified RNA translated very efficiently, resulting in at least 16-fold higher CP accumulation in E. coli. The N-terminal amino acid substitution did not affect CP folding, as it auto-assembled in E. coli to form VLPs.
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Affiliation(s)
- Manisha Saini
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, New Delhi 110 067, India
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15
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Praszkier J, Pittard AJ. Pseudoknot-dependent translational coupling in repBA genes of the IncB plasmid pMU720 involves reinitiation. J Bacteriol 2002; 184:5772-80. [PMID: 12270836 PMCID: PMC139621 DOI: 10.1128/jb.184.20.5772-5780.2002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Replication of the IncB miniplasmid pMU720 requires synthesis of the replication initiator protein, RepA, whose translation is coupled to that of a leader peptide, RepB. The unusual feature of this system is that translational coupling in repBA has to be activated by the formation of a pseudoknot immediately upstream of the repA Shine-Dalgarno sequence. A small antisense RNA, RNAI, controls replication of pMU720 by interacting with repBA mRNA to inhibit expression of repA both directly, by preventing formation of the pseudoknot, and indirectly, by inhibiting translation of repB. The mechanism of translational coupling in repBA was investigated using the specialized ribosome system, which directs a subpopulation of ribosomes that carry an altered anti-Shine-Dalgarno sequence to translate mRNA molecules whose Shine-Dalgarno sequences have been altered to be complementary to the mutant anti-Shine-Dalgarno sequence. Our data indicate that translation of repA involves reinitiation by the ribosome that has terminated translation of repB. The role of the pseudoknot in this process and its effect on the control of copy number in pMU720 are discussed.
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Affiliation(s)
- J Praszkier
- Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.
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16
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Abstract
Bacteriophages must destroy the bacterial cell wall to lyse their host and release their progeny into the environment. There are at least two distinct mechanisms by which phages destroy the cell wall. Bacteriophages with large genomes use a holin-endolysin system, while bacteriophages with small genomes encode a single lysis protein. Three unrelated single protein lysis systems are known and these proteins will be the focus of the review. Recent results indicate that at least two of these proteins inhibit cell wall synthesis and are thus the phage analogs of antibiotics like penicillin.
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Affiliation(s)
- Thomas G Bernhardt
- Department of Molecular Biology and Microbiology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA
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17
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Inokuchi Y, Hirashima A, Sekine Y, Janosi L, Kaji A. Role of ribosome recycling factor (RRF) in translational coupling. EMBO J 2000; 19:3788-98. [PMID: 10899132 PMCID: PMC313962 DOI: 10.1093/emboj/19.14.3788] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
RNA phage GA coat and lysis protein expression are translationally coupled through an overlapping termination and initiation codon UAAUG. Essential for this coupling are the proximity of the termination codon of the upstream coat gene to the initiation codon of the lysis gene (either a <3 nucleotide separation or physical closeness through a possible hairpin structure) but not the Shine-Dalgarno sequence. This suggests that the ribosomes completing the coat gene translation are exclusively responsible for translation of the lysis gene. Inactivation of ribosome recycling factor (RRF), which normally releases ribosomes at the termination codon, did not influence the expression of the reporter gene fused to the lysis gene. This suggests the possibility that RRF may not release ribosomes from the junction UAAUG. However, RRF is essential for correct ribosomal recognition of the AUG codon as the initiation site for the lysis gene.
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MESH Headings
- Amino Acid Sequence
- Bacteriophages/genetics
- Bacteriophages/metabolism
- Base Sequence
- Capsid/biosynthesis
- Capsid/genetics
- Codon, Initiator/genetics
- Codon, Terminator/genetics
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Escherichia coli/virology
- Gene Expression Regulation, Viral
- Genes, Reporter/genetics
- Genes, Viral/genetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Biosynthesis
- Proteins/genetics
- Proteins/metabolism
- RNA Viruses/genetics
- RNA Viruses/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Ribosomal Proteins
- Ribosomes/genetics
- Ribosomes/metabolism
- Sequence Analysis, Protein
- Sequence Deletion
- Substrate Specificity
- Viral Proteins/biosynthesis
- Viral Proteins/genetics
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Affiliation(s)
- Y Inokuchi
- Department of Bioscience, Teikyo University, Utsunomiya 320-8551, Yakult Pharmaceutical Inc. Co. Tokyo, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan
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18
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Tedin K, Moll I, Grill S, Resch A, Graschopf A, Gualerzi CO, Bläsi U. Translation initiation factor 3 antagonizes authentic start codon selection on leaderless mRNAs. Mol Microbiol 1999; 31:67-77. [PMID: 9987111 DOI: 10.1046/j.1365-2958.1999.01147.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this study, we have examined the influence of initiation factors on translation initiation of leaderless mRNAs whose 5'-terminal residues are the A of the AUG initiating codon. A 1:1 ratio of initiation factors to ribosomes abolished ternary complex formation at the authentic start codon of different leaderless mRNAs. Supporting this observation, in vitro translation assays using limiting ribosome concentrations with competing leaderless lambda cl and Escherichia coli ompA mRNAs, the latter containing a canonical ribosome binding site, revealed reduced cl synthesis relative to OmpA in the presence of added initiation factors. Using in vitro toeprinting and in vitro translation assays, we show that this effect can be attributed to IF3. Moreover, in vivo studies revealed that the translational efficiency of a leaderless reporter gene is decreased with increased IF3 levels. These studies are corroborated by the observed increased translational efficiency of a leaderless reporter construct in an infC mutant strain unable to discriminate against non-standard start codons. These results suggest that, in the absence of a leader or a Shine-Dalgarno sequence, the function(s) of IF3 limits stable 30S ternary complex formation.
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Affiliation(s)
- K Tedin
- Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Austria
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19
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Licis N, van Duin J, Balklava Z, Berzins V. Long-range translational coupling in single-stranded RNA bacteriophages: an evolutionary analysis. Nucleic Acids Res 1998; 26:3242-6. [PMID: 9628925 PMCID: PMC147662 DOI: 10.1093/nar/26.13.3242] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In coliphage MS2 RNA a long-distance interaction (LDI) between an internal segment of the upstream coat gene and the start region of the replicase gene prevents initiation of replicase synthesis in the absence of coat gene translation. Elongating ribosomes break up the repressor LDI and thus activate the hidden initiation site. Expression studies on partial MS2 cDNA clones identified base pairing between 1427-1433 and 1738-1744, the so-called Min Jou (MJ) interaction, as the molecular basis for the long-range coupling mechanism. Here, we examine the biological significance of this interaction for the control of replicase gene translation. The LDI was disrupted by mutations in the 3'-side and the evolutionary adaptation was monitored upon phage passaging. Two categories of pseudorevertants emerged. The first type had restored the MJ interaction but not necessarily the native sequence. The pseudorevertants of the second type acquired a compensatory substitution some 80 nt downstream of the MJ interaction that stabilizes an adjacent LDI. In one examined case we confirmed that the second site mutations had restored coat-replicase translational coupling. Our results show the importance of translational control for fitness of the phage. They also reveal that the structure that buries the replicase start extends to structure elements bordering the MJ interaction.
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Affiliation(s)
- N Licis
- Biomedical Research and Study Centre, University of Latvia, Ratsupites 1, LV1067 Riga, Latvia.
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20
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Madison-Antenucci S, Steege DA. Translation limits synthesis of an assembly-initiating coat protein of filamentous phage IKe. J Bacteriol 1998; 180:464-72. [PMID: 9457845 PMCID: PMC106909 DOI: 10.1128/jb.180.3.464-472.1998] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Translation is shown to be downregulated sharply between genes V and VII of IKe, a filamentous bacteriophage classed with the Ff group (phages f1, M13, and fd) but having only 55% DNA sequence identity to it. Genes V and VII encode the following proteins which are used in very different amounts: pV, used to coat the large number of viral DNA molecules prior to assembly, and pVII, used to serve as a cap with pIX in 3 to 5 copies on the end of the phage particle that emerges first from Escherichia coli. The genes are immediately adjacent to each other and are represented in the same amounts on the Ff and IKe mRNAs. Ff gene VII has an initiation site that lacks detectable intrinsic activity yet through coupling is translated at a level 10-fold lower than that of upstream gene V. The experiments reported reveal that by contrast, the IKe gene VII initiation site had detectable activity but was coupled only marginally to upstream translation. The IKe gene V and VII initiation sites both showed higher activities than the Ff sites, but the drop in translation at the IKe V-VII junction was unexpectedly severe, approximately 75-fold. As a result, gene VII is translated at similarly low levels in IKe- and Ff-infected hosts, suggesting that selection to limit its expression has occurred.
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Affiliation(s)
- S Madison-Antenucci
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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21
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Satchidanandam V, Shivashankar Y. Availability of a second upstream AUG can completely overcome inhibition of protein synthesis initiation engendered by mRNA secondary structure encompassing the start codon. Gene X 1997; 196:231-7. [PMID: 9322762 DOI: 10.1016/s0378-1119(97)00232-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Secondary structure analysis of the mRNA from a nonproductive construct carrying the nonstructural gene 3 (NS3) of Japanese Encephalitis Virus revealed the presence of a potential 28 nucleotide long stem and loop beginning with the guanine of the initiation codon AUG that had a calculated stabilization energy of -13 kcal/mol (delta Gfzero). Provision of an additional AUG along with three codons upstream resulted in complete relief of inhibition. N-terminal amino acid sequence of the recombinant protein was consistent with initiation of protein synthesis having occurred from the upstream AUG. Similar levels of NS3 specific RNA in E. coli cells carrying the expressing and nonexpressing constructs and restoration of recombinant protein expression following deletion of segments beginning with the stem and loop confirmed the role of this structure in blocking expression at the level of translation initiation. Our approach exploits the ability of a ribosome in motion to open up downstream secondary structural elements of considerable stability and represents a novel and widely applicable strategy to overcome a block in translation initiation caused by mRNA secondary structure around the translation start site.
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Affiliation(s)
- V Satchidanandam
- Centre for Genetic Engineering, Indian Institute of Science, Bangalore, India.
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22
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Govantes F, Molina-López JA, Santero E. Mechanism of coordinated synthesis of the antagonistic regulatory proteins NifL and NifA of Klebsiella pneumoniae. J Bacteriol 1996; 178:6817-23. [PMID: 8955302 PMCID: PMC178581 DOI: 10.1128/jb.178.23.6817-6823.1996] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nifLA operon of Klebsiella pneumoniae codes for the two antagonistic regulatory proteins which control expression of all other nitrogen fixation genes. NifA is a transcriptional activator, and NifL inhibits NifA. The importance of a correct NifL-NifA stoichiometry for efficient regulation of nitrogen fixation genes has been investigated by constructing a strain with an altered nifL-nifA gene dosage ratio, resulting from the integration of an extra copy of nifA. Results showed that a balanced synthesis of both gene products is essential for correct regulation. Effects of mutations provoking translation termination of nifL upstream or downstream of its natural stop codon, combined with overproduction of both proteins when the genes are transcribed and translated from signals of the phi10 gene of the phage T7, showed that, in addition to the previously reported transcriptional polarity, there is translational coupling between nifL and nifA. In spite of the apparently efficient ribosome binding site of nifA, its rate of independent translation is very low. This is due to a secondary structure masking the Shine-Dalgarno sequence of nifA, which could be melted by ribosomes translating nifL. Mutational analysis confirmed the functional significance of the secondary structure in preventing independent translation of nifA. Translational coupling between the two cistrons is proposed as an efficient mechanism to prevent production of an excess of NifA, which would affect the normal regulation of nitrogen fixation genes.
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Affiliation(s)
- F Govantes
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Spain
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23
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Ishida M, Oshima T. A leader open reading frame is essential for the expression in Escherichia coli of GC-rich leuB gene of an extreme thermophile, Thermus thermophilus. FEMS Microbiol Lett 1996; 135:137-42. [PMID: 8598270 DOI: 10.1111/j.1574-6968.1996.tb07978.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To improve expression efficiency of the leuB gene of an extreme thermophile. Thermus thermophilus, in Escherichia coli, the gene was placed under a potent promoter, tac. However, the expression was hardly improved, despite increased transcription. The expression under tac promoter was significantly improved by introducing a leader open reading frame in front of the gene. Similar improvement under a weak promoter, tet, with a leader open reading frame had been described previously. The present results provide evidence that the major limiting step in the expression of a GC-rich thermophile gene in E. coli is translation, and that the addition of a leader open reading frame is more crucial for high level expression of the gene than the use of a potent promoter.
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Affiliation(s)
- M Ishida
- Laboratory of Biochemistry of Marine Resources, Tokyo University of Fisheries, Japan
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24
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Ruiz-Echevarría MJ, de la Cueva G, Díaz-Orejas R. Translational coupling and limited degradation of a polycistronic messenger modulate differential gene expression in the parD stability system of plasmid R1. MOLECULAR & GENERAL GENETICS : MGG 1995; 248:599-609. [PMID: 7476860 DOI: 10.1007/bf02423456] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The parD stability system of plasmid R1 is an auto-regulated operon containing two genes, kis and kid, that code, respectively, for a killer protein (Kid) and for an antagonist of Kid action (Kis protein). A polycistronic transcript and a shorter mRNA, coding only for Kis and ending in a stem-loop sequence, have been identified as the main parD transcripts in cells carrying a derepressed parD operon. In this communication we show that both parD mRNAs have a half-life close to 1 min and are present in similar amounts. Using an assay based on cell-free extracts of Escherichia coli, we demonstrate that the short kis mRNA originates from limited degradation of the bicistronic parD transcript and that the stem-loop structure within the 5' end of the kid gene is specifically required for the formation of this short transcript. In vivo experiments show that synthesis of Kis is required for efficient synthesis of Kid. These data indicate that RNA processing and translational coupling are important mechanisms that modulate the differential expression of the two genes, kis and kid, in the bicistronic parD operon.
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25
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Abstract
Bacteriophage lysis involves at least two fundamentally different strategies. Most phages elaborate at least two proteins, one of which is a murein hydrolase, or lysin, and the other is a membrane protein, which is given the designation holin in this review. The function of the holin is to create a lesion in the cytoplasmic membrane through which the murein hydrolase passes to gain access to the murein layer. This is necessary because phage-encoded lysins never have secretory signal sequences and are thus incapable of unassisted escape from the cytoplasm. The holins, whose prototype is the lambda S protein, share a common organization in terms of the arrangement of charged and hydrophobic residues, and they may all contain at least two transmembrane helical domains. The available evidence suggests that holins oligomerize to form nonspecific holes and that this hole-forming step is the regulated step in phage lysis. The correct scheduling of the lysis event is as much an essential feature of holin function as is the hole formation itself. In the second strategy of lysis, used by the small single-stranded DNA phage phi X174 and the single-stranded RNA phage MS2, no murein hydrolase activity is synthesized. Instead, there is a single species of small membrane protein, unlike the holins in primary structure, which somehow causes disruption of the envelope. These lysis proteins function by activation of cellular autolysins. A host locus is required for the lytic function of the phi X174 lysis gene E.
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Affiliation(s)
- R Young
- Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843
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26
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Ringquist S, Shinedling S, Barrick D, Green L, Binkley J, Stormo GD, Gold L. Translation initiation in Escherichia coli: sequences within the ribosome-binding site. Mol Microbiol 1992; 6:1219-29. [PMID: 1375310 DOI: 10.1111/j.1365-2958.1992.tb01561.x] [Citation(s) in RCA: 246] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The translational roles of the Shine-Dalgarno sequence, the initiation codon, the space between them, and the second codon have been studied. The Shine-Dalgarno sequence UAAGGAGG initiated translation roughly four times more efficiently than did the shorter AAGGA sequence. Each Shine-Dalgarno sequence required a minimum distance to the initiation codon in order to drive translation; spacing, however, could be rather long. Initiation at AUG was more efficient than at GUG or UUG at each spacing examined; initiation at GUG was only slightly better than UUG. Translation was also affected by residues 3' to the initiation codon. The second codon can influence the rate of initiation, with the magnitude depending on the initiation codon. The data are consistent with a simple kinetic model in which a variety of rate constants contribute to the process of translation initiation.
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Affiliation(s)
- S Ringquist
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309
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27
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Matteson RJ, Biswas SJ, Steege DA. Distinctive patterns of translational reinitiation in the lac repressor mRNA: bridging of long distances by out-of-frame translation and RNA secondary structure, effects of primary sequence. Nucleic Acids Res 1991; 19:3499-506. [PMID: 1906601 PMCID: PMC328371 DOI: 10.1093/nar/19.13.3499] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In the early region of the Escherichia coli lac repressor mRNA, translational reinitiation events triggered by nonsense codons occur over long distances and in a distinctive pattern not explained by simple use of the next available initiator triplet. Defined fusions of the restart sites to the lacZ coding region have been used to explore the basis for these reinitiation patterns and to ask whether the sites can function in independent initiation at the 5' end of an mRNA. The results obtained confirm earlier indications that the restart sites may have little or no inherent capacity for binding free 30S ribosomes. The data also add to growing evidence that primary sequence elements are important determinants of reinitiation efficiency. On the basis of the reinitiation activities for nonsense sites throughout the early region of the mRNA, we suggest that out-of-frame restarts and RNA secondary structure bridge long distances between the point of termination and downstream restart codons. Such bridging mechanisms could serve more generally as a means of propagating translational activity across long polycistronic mRNAs.
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Affiliation(s)
- R J Matteson
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
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28
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Spielmann-Ryser J, Moser M, Kast P, Weber H. Factors determining the frequency of plasmid cointegrate formation mediated by insertion sequence IS3 from Escherichia coli. MOLECULAR & GENERAL GENETICS : MGG 1991; 226:441-8. [PMID: 1645443 DOI: 10.1007/bf00260657] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Transposition events mediated by plasmidborne copies of the insertion sequence IS3 of Escherichia coli are difficult to detect because of a low frequency of cointegrate formation. We found that cointegration activity could be strongly enhanced by using plasmid constructions in which a second IS3 element, disabled by a large deletion, was placed adjacent to an intact IS3 copy. Attempts to construct plasmids containing two adjacent intact IS3 copies were unsuccessful, probably because of instability. Transpositional hyperactivity of tandemly duplicated IS sequences was previously described for spontaneous duplications of IS21 and IS30 and may well be a more general phenomenon. The frequency of cointegration events was also strongly increased in an E. coli strain deficient in Dam methylation, suggesting that IS3, like some other Dam site-containing IS elements, is regulated by the Dam methylation system. Insertion sites were strongly clustered within the target lambda repressor gene: however no sequence specificity determinants could be identified. All insertions analyzed carried the IS element in the same orientation; target sequence duplications were mostly 3 bp, but in some cases 4 bp long. To obtain information about the roles of the open reading frames (ORFs) in IS3, we constructed plasmid-borne mutant elements in which potentially functional reading frames were inactivated by site-directed mutations; the mutants were introduced into partial tandem constructions and tested in cointegration assays. Mutations inactivating the putative initiation condons of ORF I and II in the intact element reduced insertion activity to less than 4% of the wild type, whereas the introduction of a termination codon into ORF IV had no effect on cointegration frequency.(ABSTRACT TRUNCATED AT 250 WORDS)
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29
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Velázquez L, Camarena L, Reyes JL, Bastarrachea F. Mutations affecting the Shine-Dalgarno sequences of the untranslated region of the Escherichia coli gltBDF operon. J Bacteriol 1991; 173:3261-4. [PMID: 1673677 PMCID: PMC207927 DOI: 10.1128/jb.173.10.3261-3264.1991] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Individual mutations which affected each of the two Shine-Dalgarno sequences at the 5' untranslated region of the gltB gene of Escherichia coli were characterized. They were isolated in plasmids carrying a gltB'-'lacZ protein fusion preceded by the regulatory region of the gltBDF operon. Subcloning and nucleotide sequencing of approximately 1,206 bp of DNA encompassing the gltBDF regulatory region showed that the mutations affected the first base at each of the two identical Shine-Dalgarno sequences, SD1 and SD2, located 40 and 8 bases, respectively, upstream from the putative gltB open reading frame. Only mutation gltB2r227, an adenine in place of a guanine, affecting the first base of SD2, lowered beta-galactosidase expression significantly, i.e., about fivefold. The results suggest that SD2 is the preferred functional site at which ribosomes initiate gltB mRNA translation.
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Affiliation(s)
- L Velázquez
- Departamento de Biología Molecular, Universidad Nacional Autónoma de México, D.F
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30
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de Smit MH, van Duin J. Secondary structure of the ribosome binding site determines translational efficiency: a quantitative analysis. Proc Natl Acad Sci U S A 1990; 87:7668-72. [PMID: 2217199 PMCID: PMC54809 DOI: 10.1073/pnas.87.19.7668] [Citation(s) in RCA: 370] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have quantitatively analyzed the relationship between translational efficiency and the mRNA secondary structure in the initiation region. The stability of a defined hairpin structure containing a ribosome binding site was varied over 12 kcal/mol (1 cal = 4.184 J) by site-directed mutagenesis and the effects on protein yields were analyzed in vivo. The results reveal a strict correlation between translational efficiency and the stability of the helix. An increase in its delta G0 of -1.4 kcal/mol (i.e., less than the difference between an A.U and a G.C pair) corresponds to the reduction by a factor of 10 in initiation rate. Accordingly, a single nucleotide substitution led to the decrease by a factor of 500 in expression because it turned a mismatch in the helix into a match. We find no evidence that exposure of only the Shine-Dalgarno region or the start codon preferentially favors recognition. Translational efficiency is strictly correlated with the fraction of mRNA molecules in which the ribosome binding site is unfolded, indicating that initiation is completely dependent on spontaneous unfolding of the entire initiation region. Ribosomes appear not to recognize nucleotides outside the Shine-Dalgarno region and the initiation codon.
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Affiliation(s)
- M H de Smit
- Department of Biochemistry, Gorlaeus Laboratories, Leiden University, The Netherlands
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31
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Gross G, Mielke C, Hollatz I, Blöcker H, Frank R. RNA primary sequence or secondary structure in the translational initiation region controls expression of two variant interferon-beta genes in Escherichia coli. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)38210-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Abstract
Premature termination of translation in eubacteria, like Escherichia coli, often leads to reinitiation at nearby start codons. Restarts also occur in response to termination at the end of natural coding regions, where they serve to enforce translational coupling between adjacent cistrons. Here, we present a model in which the terminated but not released ribosome reaches neighboring initiation codons by lateral diffusion along the mRNA. The model is based on the finding that introduction of an additional start codon between the termination and the reinitiation site consistently obstructs ribosomes to reach the authentic restart site. Instead, the ribosome now begins protein synthesis at this newly introduced AUG codon. This ribosomal scanning-like movement is bidirectional, has a radius of action of more than 40 nucleotides in the model system used, and activates the first encountered restart site. The ribosomal reach in the upstream direction is less than in the downstream one, probably due to dislodging by elongating ribosomes. The proposed model has parallels with the scanning mechanism postulated for eukaryotic translational initiation and reinitiation.
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Affiliation(s)
- M R Adhin
- Department of Biochemistry, Leiden University, The Netherlands
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33
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Makoff AJ, Smallwood AE. The use of two-cistron constructions in improving the expression of a heterologous gene in E. coli. Nucleic Acids Res 1990; 18:1711-8. [PMID: 2110654 PMCID: PMC330587 DOI: 10.1093/nar/18.7.1711] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Many heterologous genes when cloned into bacterial expression vectors are poorly expressed because of an inefficient ribosome binding site (RBS). We have constructed a plasmid which expresses human gamma-interferon (gamma-IF), where the level of expression is limited by the RBS. Expression was increased by placing the gamma-IF sequence immediately downstream of a small translated sequence. The production of gamma-IF was dependent upon the efficiency of translation of this upstream cistron and could be increased to very high levels. The same upstream cistron would greatly improve the expression of gamma-IF in a plasmid where the RBS was very poor due to inhibitory secondary structure at the 5' end of its mRNA. However, it would not improve the efficiency of a poor RBS containing a weak Shine-Dalgarno sequence. The general utility of the two-cistron expression strategy to diagnose a weak RBS is discussed.
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Affiliation(s)
- A J Makoff
- Department of Molecular Biology, Wellcome Biotech, Beckenham, Kent, UK
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34
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Skripkin EA, Adhin MR, de Smit MH, van Duin J. Secondary structure of the central region of bacteriophage MS2 RNA. Conservation and biological significance. J Mol Biol 1990; 211:447-63. [PMID: 2407856 DOI: 10.1016/0022-2836(90)90364-r] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The RNA of the Escherichia coli RNA phages is highly structured with 75% of the nucleotides estimated to take part in base-pairing. We have used enzymatic and chemical sensitivity of nucleotides, phylogenetic sequence comparison and the phenotypes of constructed mutants to develop a secondary structure model for the central region (900 nucleotides) of the group I phage MS2. The RNA folds into a number of, mostly irregular, helices and is further condensed by several long-distance interactions. There is substantial conservation of helices between the related groups I and II, attesting to the relevance of discrete RNA folding. In general, the secondary structure is thought to be needed to prevent annealing of plus and minus strand and to confer protection against RNase. Superimposed, however, are features required to regulate translation and replication. The MS2 RNA section studied here contains three translational start sites, as well as the binding sites for the coat protein and the replicase enzyme. Considering the density of helices along the RNA, it is not unexpected to find that all these sites lie in helical regions. This fact, however, does not mean that these sites are recognized as secondary structure elements by their interaction partners. This holds true only for the coat protein binding site. The other four sites function in the unfolded state and the stability of the helix in which they are contained serves to negatively control their accessibility. Mutations that stabilize helices containing ribosomal binding sites reduce their efficiency and vice versa. Comparison of homologous helices in different phage RNAs indicates that base substitutions have occurred in such a way that the thermodynamic stability of the helix is maintained. The evolution of individual helices shows several distinct size-reduction patterns. We have observed codon deletions from loop areas and shortening of hairpins by base-pair deletions from either the bottom, the middle or the top of stem structures. Evidence for the coaxial stacking of some helical segments is discussed.
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Affiliation(s)
- E A Skripkin
- Department of Biochemistry, Gorlaeus Laboratories, Leiden University, The Netherlands
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35
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Schulz VP, Reznikoff WS. In vitro secondary structure analysis of mRNA from lacZ translation initiation mutants. J Mol Biol 1990; 211:427-45. [PMID: 2106583 DOI: 10.1016/0022-2836(90)90363-q] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
mRNA secondary structure can be an important determinant of the efficiency of translation initiation. To study the effect of secondary structure on translation initiation, in vitro secondary structure analysis was performed on 32 lacZ RNA transcripts that differ in their in vivo translation initiation efficiencies because of mutations. We have shown that well-translated RNA has a relatively unstructured translation initiation region in vitro. In contrast, the translation initiation region of many of the poorly translated RNA transcripts is involved in a stem-loop structure. Mutations that decrease the in vitro stability of the stem-loop increase the frequency of translation initiation. The sequences responsible for forming this stem-loop structure were localized to a small region of RNA. The results confirm some of the previous predictions of the RNA secondary structure of the mutant RNAs based on computer modeling, but they disagree with some of the predicted long-range interactions.
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Affiliation(s)
- V P Schulz
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706
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36
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de Smit MH, van Duin J. Control of prokaryotic translational initiation by mRNA secondary structure. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1990; 38:1-35. [PMID: 2183291 DOI: 10.1016/s0079-6603(08)60707-2] [Citation(s) in RCA: 170] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- M H de Smit
- Department of Biochemistry, Leiden University, The Netherlands
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37
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Spanjaard RA, van Dijk MC, Turion AJ, van Duin J. Expression of the rat interferon-alpha 1 gene in Escherichia coli controlled by the secondary structure of the translation-initiation region. Gene 1989; 80:345-51. [PMID: 2511076 DOI: 10.1016/0378-1119(89)90298-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A synthetic ribosome-binding site (RBS) containing a 7-nucleotide-long Shine-Dalgarno (SD) sequence was placed ahead of the rat interferon (IFN)-alpha 1 coding region. The translational efficiency of this construct was extremely low. Structural probing of transcripts with RNases T1 and U2 combined with computer predictions revealed the presence of a stable hairpin in which the SD region was base-paired to codons 3, 4 and 5 of the IFN mRNA. Each mutation in this stem changing an A-U to an A.C or a G-C a G.U pair increased translational efficiency about fourfold and this effect could be reversed by a compensating stabilizing substitution in the other strand of the stem. We conclude that the strength of an RBS is to a major degree determined by its involvement in secondary structure. We also show that the negative effect of secondary structure on the efficiency of an RBS can be overcome by allowing upstream translation to terminate within the base-paired region. In our clones, termination-dependent restarts occur at a frequency comparable to that taking place in constructs containing destabilized hairpins.
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Affiliation(s)
- R A Spanjaard
- Department of Biochemistry, University of Leiden, The Netherlands
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38
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Spanjaard RA, van Duin J. Translational reinitiation in the presence and absence of a Shine and Dalgarno sequence. Nucleic Acids Res 1989; 17:5501-7. [PMID: 2668889 PMCID: PMC318173 DOI: 10.1093/nar/17.14.5501] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The process of translational reinitiation in Escherichia coli was studied in a two cistron system where expression of the downstream reporter gene was dependent on translation of an upstream reading frame. The dependence was almost absolute. Upstream translation increased expression of the downstream gene by two to three orders of magnitude. This large difference allowed us to quantitate restarts in a meaningful manner. In the absence of a Shine and Dalgarno (SD) region reinitiation occurred but its efficiency was about 10% of that found in the SD carrying counterpart. We discuss three ways by which translational coupling between neighboring cistrons can be enforced.
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Affiliation(s)
- R A Spanjaard
- Department of Biochemistry, University of Leiden, The Netherlands
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39
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Ivey-Hoyle M, Steege DA. Translation of phage f1 gene VII occurs from an inherently defective initiation site made functional by coupling. J Mol Biol 1989; 208:233-44. [PMID: 2788746 DOI: 10.1016/0022-2836(89)90385-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Expression of the filamentous phage f1 gene VII is shown to be translationally coupled to that of the upstream gene V. Fusions of the gene VII initiation site to the lacZ coding region were used to determine that initiation at the VII site is completely dependent on the process of translation having proceeded up to a stop codon immediately upstream from the VII site. Coupled expression from the VII site was found to be inefficient, proportional to the level of upstream translation, and very sensitive to the distance from the functional upstream stop codon. Independent expression from the VII site was not observed, even in a deletion series designed to remove potentially masking RNA structure. On the basis of the VII site's dissimilarity to ribosome binding site sequences and its properties overall, we suggest that it inherently lacks the features required for independent recognition by ribosomes, and acquires the ability to initiate synthesis of gene VII protein by virtue of the coupling process.
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Affiliation(s)
- M Ivey-Hoyle
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
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40
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Adhin MR, van Duin J. Translational regulation of the lysis gene in RNA bacteriophage fr requires a UUG initiation codon. MOLECULAR & GENERAL GENETICS : MGG 1989; 218:137-42. [PMID: 2779514 DOI: 10.1007/bf00330576] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Single nucleotide substitutions identify a UUG triplet as the initiation codon of the lysis gene in RNA bacteriophage fr. This initiation codon is non-functional in de novo initiation but is activated by translational termination at the overlapping coat gene. The UUG initiation codon is crucial for gene regulation in the phage, as it excludes uncontrolled access of ribosomes to the start of the lysis gene. Replacement of UUG by either GUG or AUG results in the loss of genetic control of the lysis gene. A model is presented in which initiation factor IF3 proofreads de novo initiation at UUG codons.
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Affiliation(s)
- M R Adhin
- Department of Biochemistry, Leiden University, Gorlaeus Laboratoria, The Netherlands
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41
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Adhin MR, Hirashima A, van Duin J. Nucleotide sequence from the ssRNA bacteriophage JP34 resolves the discrepancy between serological and biophysical classification. Virology 1989; 170:238-42. [PMID: 2718383 DOI: 10.1016/0042-6822(89)90371-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The nucleotide sequence of the coat and lysis genes of the single-stranded RNA bacteriophage JP34 is presented. Serological inactivation studies classified this phage as an intermediate between groups I and II. We show that the nucleotide similarity with group I is less than 45% but more than 95% for group II, classifying JP34 as a member of group II. The altered serotype of JP34 is most likely due to the change of three critical amino acids of the coat protein to residues present in group I phage MS2 at the homologous positions. Serological characterization of RNA bacteriophages is thus not unambiguous. Phylogenetic sequence comparison between JP34, GA, and MS2 confirms the existence of a conserved helix in the coat gene of group I and group II phages. We also show that the JP34 coat and lysis genes can be expressed in cDNA clones and that the translation of the lysis gene is coupled to coat gene translation analogous to the regulation found in the group I phages.
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Affiliation(s)
- M R Adhin
- Department of Biochemistry, Leiden University, The Netherlands
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42
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Lindahl L, Archer RH, McCormick JR, Freedman LP, Zengel JM. Translational coupling of the two proximal genes in the S10 ribosomal protein operon of Escherichia coli. J Bacteriol 1989; 171:2639-45. [PMID: 2651412 PMCID: PMC209946 DOI: 10.1128/jb.171.5.2639-2645.1989] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We have examined the translational coupling between the first two genes in the S10 ribosomal protein operon. We isolated mutations blocking the translation of the first gene of the operon, coding for S10, and monitored their effects on translation of the downstream gene, coding for L3. All of the mutations inhibiting S10 synthesis also affected the synthesis of L3. However, these experiments were complicated by decreased mRNA synthesis resulting from transcription polarity, which we could only partially eliminate by using a rho-100 strain. To completely eliminate the problem of transcription polarity and obtain a more accurate measurement of the coupling, we replaced the natural S10 promoter with a promoter used by the bacteriophage T7 RNA polymerase. As expected, the T7 RNA polymerase was not subject to transcription polarity. Using this system, we were able to show that a complete abolishment of S10 translation resulted in an 80% inhibition of L3 synthesis. Other experiments show that the synthesis of L3 goes up as a function of increasing S10 synthesis, but the translational coupling does not assure strictly proportional output from the two genes.
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Affiliation(s)
- L Lindahl
- Department of Biology, University of Rochester, New York 14627
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43
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Climie SC, Friesen JD. In vivo and in vitro structural analysis of the rplJ mRNA leader of Escherichia coli. Protection by bound L10-L7/L12. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68160-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Berkhout B, Schmidt BF, van Strien A, van Boom J, van Westrenen J, van Duin J. Lysis gene of bacteriophage MS2 is activated by translation termination at the overlapping coat gene. J Mol Biol 1987; 195:517-24. [PMID: 3656424 DOI: 10.1016/0022-2836(87)90180-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The 3' boundary of the coat gene of the RNA bacteriophage MS2 lies 46 nucleotides downstream from the beginning of the lysis (L) cistron. The translation of both reading frames is coupled; the synthesis of the lysis protein does not occur unless translation of the overlapping coat gene takes place. In the preceding paper we showed that de novo initiation at the L gene is prevented by a hairpin structure that sequesters the ribosomal binding site. Here we examine how translation of the coat gene activates the L gene start site. The experiments show that the movement of ribosomes through the hairpin is in itself not sufficient to expose the lysis gene. Rather, the endpoint of translation is important. Termination at the natural end of the coat gene triggers the lysis response, but further downstream terminations do not. Activation of the L gene is suppressed when the stability of the lysis initiator hairpin is increased by mutations that create additional base-pairs. We assume that the ribosome, terminating at the coat reading frame, covers part of the lysis hairpin, thereby destabilizing the secondary structure. This may be sufficient to promote the binding of a vacant ribosome to the L gene start. Alternatively, the terminated but not yet released ribosome may reach the L gene start by random lateral movements along the mRNA and reinitiate there. The present findings are also discussed in relation to an earlier proposal for L gene activation.
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Affiliation(s)
- B Berkhout
- Department of Biochemistry, University of Leiden, The Netherlands
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