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Zhao X, Zhu C, Gao W, Xie H, Lyu Z, Zhao Q, Li Y. Rational construction of a high-quality and high-efficiency biosynthetic system and fermentation optimization for A82846B based on combinatorial strategies in Amycolatopsis orientalis. Microb Cell Fact 2024; 23:186. [PMID: 38943174 PMCID: PMC11212272 DOI: 10.1186/s12934-024-02464-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 06/18/2024] [Indexed: 07/01/2024] Open
Abstract
BACKGROUND Oritavancin is a new generation of semi-synthetic glycopeptide antibiotics against Gram-positive bacteria, which served as the first and only antibiotic with a single-dose therapeutic regimen to treat ABSSSI. A naturally occurring glycopeptide A82846B is the direct precursor of oritavancin. However, its application has been hampered by low yields and homologous impurities. This study established a multi-step combinatorial strategy to rationally construct a high-quality and high-efficiency biosynthesis system for A82846B and systematically optimize its fermentation process to break through the bottleneck of microbial fermentation production. RESULTS Firstly, based on the genome sequencing and analysis, we deleted putative competitive pathways and constructed a better A82846B-producing strain with a cleaner metabolic background, increasing A82846B production from 92 to 174 mg/L. Subsequently, the PhiC31 integrase system was introduced based on the CRISPR-Cas12a system. Then, the fermentation level of A82846B was improved to 226 mg/L by over-expressing the pathway-specific regulator StrR via the constructed PhiC31 system. Furthermore, overexpressing glycosyl-synthesis gene evaE enhanced the production to 332 mg/L due to the great conversion of the intermediate to target product. Finally, the scale-up production of A82846B reached 725 mg/L in a 15 L fermenter under fermentation optimization, which is the highest reported yield of A82846B without the generation of homologous impurities. CONCLUSION Under approaches including blocking competitive pathways, inserting site-specific recombination system, overexpressing regulator, overexpressing glycosyl-synthesis gene and optimizing fermentation process, a multi-step combinatorial strategy for the high-level production of A82846B was developed, constructing a high-producing strain AO-6. The combinatorial strategies employed here can be widely applied to improve the fermentation level of other microbial secondary metabolites, providing a reference for constructing an efficient microbial cell factory for high-value natural products.
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Affiliation(s)
- Xinyi Zhao
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China
| | - Chenyang Zhu
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China
| | - Wenli Gao
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China
| | - Huang Xie
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China
| | - Zhongyuan Lyu
- Institute of Biopharmaceuticals, School of Pharmaceutical Sciences, Taizhou University, Taizhou, 318000, China
| | - Qingwei Zhao
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China
| | - Yongquan Li
- First Affiliated Hospital and Institute of Pharmaceutical Biotechnology, Zhejiang University School of Medicine, Hangzhou, 310058, China.
- Zhejiang Provincial Key Lab for Microbial Biochemistry and Metabolic Engineering, Hangzhou, 310058, China.
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2
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Chen YW, Su BY, Van Duyne GD, Fogg P, Fan HF. The influence of coiled-coil motif of serine recombinase toward the directionality regulation. Biophys J 2023; 122:4656-4669. [PMID: 37974397 PMCID: PMC10754689 DOI: 10.1016/j.bpj.2023.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 08/25/2023] [Accepted: 11/14/2023] [Indexed: 11/19/2023] Open
Abstract
Serine integrases promote the recombination of two complementary DNA sequences, attP and attB, to create hybrid sequences, attL and attR. The reaction is unidirectional in the absence of an accessory protein called recombination directionality factor. We utilized tethered particle motion (TPM) experiments to investigate the reaction behaviors of two model serine integrases from Listeria innocua phage LI and Streptomyces coelicolor phage C31. Detailed kinetic analyses of wild-type and mutant proteins were carried out to verify the mechanisms of recombination directionality. In particular, we assessed the influence of a coiled-coil motif (CC) that is conserved in the C-terminal domain of serine integrases and is an important prerequisite for efficient recombination. Compared to wild type, we found that CC deletions in both serine integrases reduced the overall abundance of integrase (Int) att-site complexes and favored the formation of nonproductive complexes over recombination-competent complexes. Furthermore, the rate at which CC mutants formed productive synaptic complexes and disassembled aberrant nonproductive complexes was significantly reduced. It is notable that while the φC31 Int CC is essential for recombination, the LI Int CC plays an auxiliary role for recombination to stabilize protein-protein interactions and to control the directionality of the reaction.
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Affiliation(s)
- Yei-Wei Chen
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan; Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan; Aerosol Science Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Bo-Yu Su
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Gregory D Van Duyne
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Paul Fogg
- Biology Department and York Biomedical Research Institute (YBRI), University of York, York, United Kingdom.
| | - Hsiu-Fang Fan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan; Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan; Aerosol Science Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan.
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3
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Abioye J, Lawson-Williams M, Lecanda A, Calhoon B, McQue AL, Colloms SD, Stark WM, Olorunniji FJ. High fidelity one-pot DNA assembly using orthogonal serine integrases. Biotechnol J 2023; 18:e2200411. [PMID: 36504358 DOI: 10.1002/biot.202200411] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/14/2022]
Abstract
BACKGROUND Large serine integrases (LSIs, derived from temperate phages) have been adapted for use in a multipart DNA assembly process in vitro, called serine integrase recombinational assembly (SIRA). The versatility, efficiency, and fidelity of SIRA is limited by lack of a sufficient number of LSIs whose activities have been characterized in vitro. METHODS AND MAJOR RESULTS In this report, we compared the activities in vitro of 10 orthogonal LSIs to explore their suitability for multiplex SIRA reactions. We found that Bxb1, ϕR4, and TG1 integrases were the most active among the set we studied, but several others were also usable. As proof of principle, we demonstrated high-efficiency one-pot assembly of six DNA fragments (made by PCR) into a 7.5 kb plasmid that expresses the enzymes of the β-carotenoid pathway in Escherichia coli, using six different LSIs. We further showed that a combined approach using a few highly active LSIs, each acting on multiple pairs of att sites with distinct central dinucleotides, can be used to scale up "poly-part" gene assembly and editing. CONCLUSIONS AND IMPLICATIONS We conclude that use of multiple orthogonal integrases may be the most predictable, efficient, and programmable approach for SIRA and other in vitro applications.
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Affiliation(s)
- Jumai Abioye
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - Makeba Lawson-Williams
- School of Pharmacy and Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Liverpool, UK
| | - Alicia Lecanda
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - Brecken Calhoon
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - Arlene L McQue
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - Sean D Colloms
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - W Marshall Stark
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
| | - Femi J Olorunniji
- School of Molecular Biosciences, University of Glasgow, Glasgow, UK
- School of Pharmacy and Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Liverpool, UK
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4
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Abstract
Shuffling of genetic material via reconnection of proximal DNA segments is seen in meiosis and some cancers. In contrast with textbook pictures, reconnections are performed within an entangled environment and can result in knotting or linking, detrimental for cells. By performing Brownian dynamics simulations of reconnecting polymers under confinement, modeling the genome in vivo, we find a topological transition between a gas or liquid of unlinked rings and a gel-like structure with a large number of polydisperse linked rings. This transition can be triggered by increasing polymer stiffness or confinement. Our results suggest ways to design future topological materials, such as DNA-based gels involving recombinase proteins. DNA recombination is a ubiquitous process that ensures genetic diversity. Contrary to textbook pictures, DNA recombination, as well as generic DNA translocations, occurs in a confined and highly entangled environment. Inspired by this observation, here, we investigate a solution of semiflexible polymer rings undergoing generic cutting and reconnection operations under spherical confinement. Our setup may be realized using engineered DNA in the presence of recombinase proteins or by considering micelle-like components able to form living (or reversibly breakable) polymer rings. We find that in such systems, there is a topological gelation transition, which can be triggered by increasing either the stiffness or the concentration of the rings. Flexible or dilute polymers break into an ensemble of short, unlinked, and segregated rings, whereas sufficiently stiff or dense polymers self-assemble into a network of long, linked, and mixed loops, many of which are knotted. We predict that the two phases should behave qualitatively differently in elution experiments monitoring the escape dynamics from a permeabilized container. Besides shedding some light on the biophysics and topology of genomes undergoing DNA reconnection in vivo, our findings could be leveraged in vitro to design polymeric complex fluids—e.g., DNA-based complex fluids or living polymer networks—with desired topologies.
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5
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Round JW, Robeck LD, Eltis LD. An Integrative Toolbox for Synthetic Biology in Rhodococcus. ACS Synth Biol 2021; 10:2383-2395. [PMID: 34428025 DOI: 10.1021/acssynbio.1c00292] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The development of microbial cell factories requires robust synthetic biology tools to reduce design uncertainty and accelerate the design-build-test-learn process. Herein, we developed a suite of integrative genetic tools to facilitate the engineering of Rhodococcus, a genus of bacteria with considerable biocatalytic potential. We first created pRIME, a modular, copy-controlled integrative-vector, to provide a robust platform for strain engineering and characterizing genetic parts. This vector was then employed to benchmark a series of strong promoters. We found PM6 to be the strongest constitutive rhodococcal promoter, 2.5- to 3-fold stronger than the next in our study, while overall promoter activities ranged 23-fold between the weakest and strongest promoters during exponential growth. Next, we used an optimized variant of PM6 to develop hybrid-promoters and integrative vectors to allow for tetracycline-inducible gene expression in Rhodococcus. The best of the resulting hybrid-promoters maintained a maximal activity of ∼50% of PM6 and displayed an induction factor of ∼40-fold. Finally, we developed and implemented a uLoop-derived Golden Gate assembly strategy for high-throughput DNA assembly in Rhodococcus. To demonstrate the utility of our approaches, pRIME was used to engineer Rhodococcus jostii RHA1 to grow on vanillin at concentrations 10-fold higher than what the wild-type strain tolerated. Overall, this study provides a suite of tools that will accelerate the engineering of Rhodococcus for various biocatalytic applications, including the sustainable production of chemicals from lignin-derived aromatics.
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Affiliation(s)
- James W. Round
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Logan D. Robeck
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Lindsay D. Eltis
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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6
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Alam K, Hao J, Zhang Y, Li A. Synthetic biology-inspired strategies and tools for engineering of microbial natural product biosynthetic pathways. Biotechnol Adv 2021; 49:107759. [PMID: 33930523 DOI: 10.1016/j.biotechadv.2021.107759] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 03/28/2021] [Accepted: 04/23/2021] [Indexed: 02/08/2023]
Abstract
Microbial-derived natural products (NPs) and their derivative products are of great importance and used widely in many fields, especially in pharmaceutical industries. However, there is an immediate need to establish innovative approaches, strategies, and techniques to discover new NPs with novel or enhanced biological properties, due to the less productivity and higher cost on traditional drug discovery pipelines from natural bioresources. Revealing of untapped microbial cryptic biosynthetic gene clusters (BGCs) using DNA sequencing technology and bioinformatics tools makes genome mining possible for NP discovery from microorganisms. Meanwhile, new approaches and strategies in the area of synthetic biology offer great potentials for generation of new NPs by engineering or creating synthetic systems with improved and desired functions. Development of approaches, strategies and tools in synthetic biology can facilitate not only exploration and enhancement in supply, and also in the structural diversification of NPs. Here, we discussed recent advances in synthetic biology-inspired strategies, including bioinformatics and genetic engineering tools and approaches for identification, cloning, editing/refactoring of candidate biosynthetic pathways, construction of heterologous expression hosts, fitness optimization between target pathways and hosts and detection of NP production.
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Affiliation(s)
- Khorshed Alam
- Helmholtz International Lab for Anti-Infectives, Shandong University-Helmholtz Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, PR China.
| | - Jinfang Hao
- Helmholtz International Lab for Anti-Infectives, Shandong University-Helmholtz Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, PR China
| | - Youming Zhang
- Helmholtz International Lab for Anti-Infectives, Shandong University-Helmholtz Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, PR China.
| | - Aiying Li
- Helmholtz International Lab for Anti-Infectives, Shandong University-Helmholtz Institute of Biotechnology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, PR China.
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7
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Rowland SJ, Boocock MR, Burke ME, Rice PA, Stark WM. The protein-protein interactions required for assembly of the Tn3 resolution synapse. Mol Microbiol 2021; 114:952-965. [PMID: 33405333 DOI: 10.1111/mmi.14579] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/20/2020] [Accepted: 07/20/2020] [Indexed: 11/29/2022]
Abstract
The site-specific recombinase Tn3 resolvase initiates DNA strand exchange when two res recombination sites and six resolvase dimers interact to form a synapse. The detailed architecture of this intricate recombination machine remains unclear. We have clarified which of the potential dimer-dimer interactions are required for synapsis and recombination, using a novel complementation strategy that exploits a previously uncharacterized resolvase from Bartonella bacilliformis ("Bart"). Tn3 and Bart resolvases recognize different DNA motifs, via diverged C-terminal domains (CTDs). They also differ substantially at N-terminal domain (NTD) surfaces involved in dimerization and synapse assembly. We designed NTD-CTD hybrid proteins, and hybrid res sites containing both Tn3 and Bart dimer binding sites. Using these components in in vivo assays, we demonstrate that productive synapsis requires a specific "R" interface involving resolvase NTDs at all three dimer-binding sites in res. Synapses containing mixtures of wild-type Tn3 and Bart resolvase NTD dimers are recombination-defective, but activity can be restored by replacing patches of Tn3 resolvase R interface residues with Bart residues, or vice versa. We conclude that the Tn3/Bart family synapse is assembled exclusively by R interactions between resolvase dimers, except for the one special dimer-dimer interaction required for catalysis.
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Affiliation(s)
- Sally-J Rowland
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Martin R Boocock
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Mary E Burke
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Phoebe A Rice
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - W Marshall Stark
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK
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8
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Bowyer JE, Ding C, Weinberg BH, Wong WW, Bates DG. A mechanistic model of the BLADE platform predicts performance characteristics of 256 different synthetic DNA recombination circuits. PLoS Comput Biol 2020; 16:e1007849. [PMID: 33338034 PMCID: PMC7781486 DOI: 10.1371/journal.pcbi.1007849] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 01/04/2021] [Accepted: 11/03/2020] [Indexed: 11/26/2022] Open
Abstract
Boolean logic and arithmetic through DNA excision (BLADE) is a recently developed platform for implementing inducible and logical control over gene expression in mammalian cells, which has the potential to revolutionise cell engineering for therapeutic applications. This 2-input 2-output platform can implement 256 different logical circuits that exploit the specificity and stability of DNA recombination. Here, we develop the first mechanistic mathematical model of the 2-input BLADE platform based on Cre- and Flp-mediated DNA excision. After calibrating the model on experimental data from two circuits, we demonstrate close agreement between model outputs and data on the other 111 circuits that have so far been experimentally constructed using the 2-input BLADE platform. Model simulations of the remaining 143 circuits that have yet to be tested experimentally predict excellent performance of the 2-input BLADE platform across the range of possible circuits. Circuits from both the tested and untested subsets that perform less well consist of a disproportionally high number of STOP sequences. Model predictions suggested that circuit performance declines with a decrease in recombinase expression and new experimental data was generated that confirms this relationship.
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Affiliation(s)
- Jack E. Bowyer
- School of Engineering, University of Warwick, Coventry, United Kingdom
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, United Kingdom
| | - Chloe Ding
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Biological Design Center, Boston University, Boston, Massachusetts, United States of America
| | - Benjamin H. Weinberg
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Wilson W. Wong
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Biological Design Center, Boston University, Boston, Massachusetts, United States of America
| | - Declan G. Bates
- School of Engineering, University of Warwick, Coventry, United Kingdom
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, United Kingdom
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9
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Bowyer JE, Chakravarti D, Wong WW, Bates DG. Mechanistic modelling of tyrosine recombination reveals key parameters determining the performance of a CAR T cell switching circuit. ENGINEERING BIOLOGY 2020; 4:10-19. [PMID: 36970230 PMCID: PMC9996713 DOI: 10.1049/enb.2019.0020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/30/2020] [Accepted: 02/10/2020] [Indexed: 12/30/2022] Open
Abstract
Inducible genetic switches based on tyrosine recombinase-based DNA excision are a promising platform for the regulation and control of chimeric antigen receptor (CAR) T cell activity in cancer immunotherapy. These switches exploit the increased stability of DNA excision in tyrosine recombinases through an inversion-excision circuit design. Here, the authors develop the first mechanistic mathematical model of switching dynamics in tyrosine recombinases and validate it against experimental data through both global optimisation and statistical approximation approaches. Analysis of this model provides guidelines regarding which system parameters are best suited to experimental tuning in order to establish optimal switch performance in vivo. In particular, they find that the switching response can be made significantly faster by increasing the concentration of the inducer drug 4-OHT and/or by using promoters generating higher expression levels of the FlpO recombinase.
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Affiliation(s)
- Jack E. Bowyer
- School of Engineering University of Warwick Coventry CV4 7AL UK
- Warwick Integrative Synthetic Biology Centre Coventry CV4 7AL UK
| | - Deboki Chakravarti
- Department of Biomedical Engineering Boston University Boston MA 02215 USA
- Biological Design Center Boston University Boston MA 02215 USA
| | - Wilson W. Wong
- Department of Biomedical Engineering Boston University Boston MA 02215 USA
- Biological Design Center Boston University Boston MA 02215 USA
| | - Declan G. Bates
- School of Engineering University of Warwick Coventry CV4 7AL UK
- Warwick Integrative Synthetic Biology Centre Coventry CV4 7AL UK
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10
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O'Donnol D, Stasiak A, Buck D. Two convergent pathways of DNA knotting in replicating DNA molecules as revealed by θ-curve analysis. Nucleic Acids Res 2019; 46:9181-9188. [PMID: 29982678 PMCID: PMC6158496 DOI: 10.1093/nar/gky559] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 06/13/2018] [Indexed: 11/12/2022] Open
Abstract
During DNA replication in living cells some DNA knots are inadvertently produced by DNA topoisomerases facilitating progression of replication forks. The types of DNA knots formed are conditioned by the 3D organization of replicating DNA molecules. Therefore, by characterizing formed DNA knots it is possible to infer the 3D arrangement of replicating DNA molecules. This topological inference method is highly developed for knotted DNA circles. However, partially replicated DNA molecules have the form of θ-curves. In this article, we use mathematical formalism of θ-curves to characterize the full possibilities of how knotting can occur during replication of DNA molecules in vivo. To do this, we reanalyze earlier experimental studies of knotted, partially replicated DNA molecules and the previously proposed pathway of their formation. We propose a general model of knotting in replication intermediates, and demonstrate that there is an additional, equally important, parallel knotting pathway that also explains how DNA topoisomerases can produce experimentally observed knotted θ-curves. Interestingly, both pathways require intertwining of freshly replicated sister duplexes (precatenanes).
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Affiliation(s)
- Danielle O'Donnol
- Department of Mathematics, Indiana University Bloomington, 831 E. Third Street, Bloomington, IN 47405, USA
| | - Andrzej Stasiak
- Center for Integrative Genomics, University of Lausanne,1015 Lausanne, Switzerland.,Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Dorothy Buck
- Centre for Mathematical Biology, and Department of Mathematical Sciences, University of Bath, North Rd, Bath BA2 7AY, England
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11
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Fogg PCM, Younger E, Fernando BD, Khaleel T, Stark WM, Smith MCM. Recombination directionality factor gp3 binds ϕC31 integrase via the zinc domain, potentially affecting the trajectory of the coiled-coil motif. Nucleic Acids Res 2019; 46:1308-1320. [PMID: 29228292 PMCID: PMC5814800 DOI: 10.1093/nar/gkx1233] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 11/29/2017] [Indexed: 11/24/2022] Open
Abstract
To establish a prophage state, the genomic DNA of temperate bacteriophages normally becomes integrated into the genome of their host bacterium by integrase-mediated, site-specific DNA recombination. Serine integrases catalyse a single crossover between an attachment site in the host (attB) and a phage attachment site (attP) on the circularized phage genome to generate the integrated prophage DNA flanked by recombinant attachment sites, attL and attR. Exiting the prophage state and entry into the lytic growth cycle requires an additional phage-encoded protein, the recombination directionality factor or RDF, to mediate recombination between attL and attR and excision of the phage genome. The RDF is known to bind integrase and switch its activity from integration (attP x attB) to excision (attL x attR) but its precise mechanism is unclear. Here, we identify amino acid residues in the RDF, gp3, encoded by the Streptomyces phage ϕC31 and within the ϕC31 integrase itself that affect the gp3:Int interaction. We show that residue substitutions in integrase that reduce gp3 binding adversely affect both excision and integration reactions. The mutant integrase phenotypes are consistent with a model in which the RDF binds to a hinge region at the base of the coiled-coil motif in ϕC31 integrase.
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Affiliation(s)
- Paul C M Fogg
- Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK
| | - Ellen Younger
- Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Booshini D Fernando
- Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Thanafez Khaleel
- Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - W Marshall Stark
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow G12 8QQ, UK
| | - Margaret C M Smith
- Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK.,Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK
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12
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Huang H, Chai C, Yang S, Jiang W, Gu Y. Phage serine integrase-mediated genome engineering for efficient expression of chemical biosynthetic pathway in gas-fermenting Clostridium ljungdahlii. Metab Eng 2019; 52:293-302. [DOI: 10.1016/j.ymben.2019.01.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 12/19/2018] [Accepted: 01/07/2019] [Indexed: 10/27/2022]
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13
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Fan HF, Ma CH, Jayaram M. Single-Molecule Tethered Particle Motion: Stepwise Analyses of Site-Specific DNA Recombination. MICROMACHINES 2018; 9:E216. [PMID: 30424148 PMCID: PMC6187709 DOI: 10.3390/mi9050216] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/25/2018] [Accepted: 04/28/2018] [Indexed: 12/17/2022]
Abstract
Tethered particle motion/microscopy (TPM) is a biophysical tool used to analyze changes in the effective length of a polymer, tethered at one end, under changing conditions. The tether length is measured indirectly by recording the Brownian motion amplitude of a bead attached to the other end. In the biological realm, DNA, whose interactions with proteins are often accompanied by apparent or real changes in length, has almost exclusively been the subject of TPM studies. TPM has been employed to study DNA bending, looping and wrapping, DNA compaction, high-order DNA⁻protein assembly, and protein translocation along DNA. Our TPM analyses have focused on tyrosine and serine site-specific recombinases. Their pre-chemical interactions with DNA cause reversible changes in DNA length, detectable by TPM. The chemical steps of recombination, depending on the substrate and the type of recombinase, may result in a permanent length change. Single molecule TPM time traces provide thermodynamic and kinetic information on each step of the recombination pathway. They reveal how mechanistically related recombinases may differ in their early commitment to recombination, reversibility of individual steps, and in the rate-limiting step of the reaction. They shed light on the pre-chemical roles of catalytic residues, and on the mechanisms by which accessory proteins regulate recombination directionality.
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Affiliation(s)
- Hsiu-Fang Fan
- Biophotonics and Molecular Imaging Center, Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan.
| | - Chien-Hui Ma
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
| | - Makkuni Jayaram
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
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14
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Abstract
Serine integrases catalyze precise rearrangement of DNA through site-specific recombination of small sequences of DNA called attachment (att) sites. Unlike other site-specific recombinases, the recombination reaction driven by serine integrases is highly directional and can only be reversed in the presence of an accessory protein called a recombination directionality factor (RDF). The ability to control reaction directionality has led to the development of serine integrases as tools for controlled rearrangement and modification of DNA in synthetic biology, gene therapy, and biotechnology. This review discusses recent advances in serine integrase technologies focusing on their applications in genome engineering, DNA assembly, and logic and data storage devices.
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Affiliation(s)
- Christine A. Merrick
- School
of Biological Sciences, University of Edinburgh, Roger Land Building, Alexander Crum
Brown Road, Edinburgh EH9
3FF, U.K
| | - Jia Zhao
- Novo
Nordisk (China) Pharmaceuticals Co., Ltd., Lei Shing Hong Center, Guangshunnan Avenue, Beijing 100102, China
| | - Susan J. Rosser
- School
of Biological Sciences, University of Edinburgh, Roger Land Building, Alexander Crum
Brown Road, Edinburgh EH9
3FF, U.K
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15
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Olorunniji FJ, McPherson AL, Rosser SJ, Smith MCM, Colloms SD, Stark WM. Control of serine integrase recombination directionality by fusion with the directionality factor. Nucleic Acids Res 2017; 45:8635-8645. [PMID: 28666339 PMCID: PMC5737554 DOI: 10.1093/nar/gkx567] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/29/2017] [Indexed: 11/13/2022] Open
Abstract
Bacteriophage serine integrases are extensively used in biotechnology and synthetic biology for assembly and rearrangement of DNA sequences. Serine integrases promote recombination between two different DNA sites, attP and attB, to form recombinant attL and attR sites. The 'reverse' reaction requires another phage-encoded protein called the recombination directionality factor (RDF) in addition to integrase; RDF activates attL × attR recombination and inhibits attP × attB recombination. We show here that serine integrases can be fused to their cognate RDFs to create single proteins that catalyse efficient attL × attR recombination in vivo and in vitro, whereas attP × attB recombination efficiency is reduced. We provide evidence that activation of attL × attR recombination involves intra-subunit contacts between the integrase and RDF moieties of the fusion protein. Minor changes in the length and sequence of the integrase-RDF linker peptide did not affect fusion protein recombination activity. The efficiency and single-protein convenience of integrase-RDF fusion proteins make them potentially very advantageous for biotechnology/synthetic biology applications. Here, we demonstrate efficient gene cassette replacement in a synthetic metabolic pathway gene array as a proof of principle.
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Affiliation(s)
- Femi J Olorunniji
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
| | - Arlene L McPherson
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
| | - Susan J Rosser
- SynthSys - Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Roger Land Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JD, UK
| | - Margaret C M Smith
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
| | - Sean D Colloms
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
| | - W Marshall Stark
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
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16
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Goundaroulis D, Dorier J, Benedetti F, Stasiak A. Studies of global and local entanglements of individual protein chains using the concept of knotoids. Sci Rep 2017; 7:6309. [PMID: 28740166 PMCID: PMC5524787 DOI: 10.1038/s41598-017-06649-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/20/2017] [Indexed: 11/23/2022] Open
Abstract
We study here global and local entanglements of open protein chains by implementing the concept of knotoids. Knotoids have been introduced in 2012 by Vladimir Turaev as a generalization of knots in 3-dimensional space. More precisely, knotoids are diagrams representing projections of open curves in 3D space, in contrast to knot diagrams which represent projections of closed curves in 3D space. The intrinsic difference with classical knot theory is that the generalization provided by knotoids admits non-trivial topological entanglement of the open curves provided that their geometry is frozen as it is the case for crystallized proteins. Consequently, our approach doesn’t require the closure of chains into loops which implies that the geometry of analysed chains does not need to be changed by closure in order to characterize their topology. Our study revealed that the knotoid approach detects protein regions that were classified earlier as knotted and also new, topologically interesting regions that we classify as pre-knotted.
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Affiliation(s)
- Dimos Goundaroulis
- Center for Integrative Genomics, University of Lausanne, 1015, Lausanne, Switzerland.,Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland
| | - Julien Dorier
- Center for Integrative Genomics, University of Lausanne, 1015, Lausanne, Switzerland.,Vital-IT, SIB Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland
| | - Fabrizio Benedetti
- Center for Integrative Genomics, University of Lausanne, 1015, Lausanne, Switzerland.,Vital-IT, SIB Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland
| | - Andrzej Stasiak
- Center for Integrative Genomics, University of Lausanne, 1015, Lausanne, Switzerland. .,Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland.
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17
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Bowyer JE, Hsiao V, Wong WW, Bates DG. Mechanistic modelling of a recombinase‐based two‐input temporal logic gate. ENGINEERING BIOLOGY 2017. [DOI: 10.1049/enb.2017.0006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Jack E. Bowyer
- Warwick Integrative Synthetic Biology Centre, School of Engineering University of Warwick Coventry CV4 7AL UK
| | - Victoria Hsiao
- Biology and Biological Engineering California Institute of Technology Pasadena CA 91125 USA
| | - Wilson W. Wong
- Department of Biomedical Engineering Boston University Boston MA 02215 USA
| | - Declan G. Bates
- Warwick Integrative Synthetic Biology Centre, School of Engineering University of Warwick Coventry CV4 7AL UK
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18
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Stark WM. Making serine integrases work for us. Curr Opin Microbiol 2017; 38:130-136. [PMID: 28599144 DOI: 10.1016/j.mib.2017.04.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/12/2017] [Accepted: 04/13/2017] [Indexed: 01/19/2023]
Abstract
DNA site-specific recombinases are enzymes (often associated with mobile DNA elements) that catalyse breaking and rejoining of DNA strands at specific points, thereby bringing about precise genetic rearrangements. Serine integrases are a group of recombinases derived from bacteriophages. Their unusual properties, including directionality of recombination and simple site requirements, are leading to their development as efficient, versatile tools for applications in experimental biology, biotechnology, synthetic biology and gene therapy. This article summarizes our current knowledge of serine integrase structure and mechanism, then outlines key factors that affect the performance of these phage recombination systems. Recently published studies, that have expanded the repertoire of available systems and reveal system-specific characteristics, will help us to choose the best integrases for envisaged applications.
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Affiliation(s)
- W Marshall Stark
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, Scotland, United Kingdom.
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19
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Control of Recombination Directionality by the Listeria Phage A118 Protein Gp44 and the Coiled-Coil Motif of Its Serine Integrase. J Bacteriol 2017; 199:JB.00019-17. [PMID: 28289084 DOI: 10.1128/jb.00019-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/06/2017] [Indexed: 02/04/2023] Open
Abstract
The serine integrase of phage A118 catalyzes integrative recombination between attP on the phage and a specific attB locus on the chromosome of Listeria monocytogenes, but it is unable to promote excisive recombination between the hybrid attL and attR sites found on the integrated prophage without assistance by a recombination directionality factor (RDF). We have identified and characterized the phage-encoded RDF Gp44, which activates the A118 integrase for excision and inhibits integration. Gp44 binds to the C-terminal DNA binding domain of integrase, and we have localized the primary binding site to be within the mobile coiled-coil (CC) motif but distinct from the distal tip of the CC that is required for recombination. This interaction is sufficient to inhibit integration, but a second interaction involving the N-terminal end of Gp44 is also required to activate excision. We provide evidence that these two contacts modulate the trajectory of the CC motifs as they extend out from the integrase core in a manner dependent upon the identities of the four att sites. Our results support a model whereby Gp44 shapes the Int-bound complexes to control which att sites can synapse and recombine.IMPORTANCE Serine integrases mediate directional recombination between bacteriophage and bacterial chromosomes. These highly regulated site-specific recombination reactions are integral to the life cycle of temperate phage and, in the case of Listeria monocytogenes lysogenized by A118 family phage, are an essential virulence determinant. Serine integrases are also utilized as tools for genetic engineering and synthetic biology because of their exquisite unidirectional control of the DNA exchange reaction. Here, we identify and characterize the recombination directionality factor (RDF) that activates excision and inhibits integration reactions by the phage A118 integrase. We provide evidence that the A118 RDF binds to and modulates the trajectory of the long coiled-coil motif that extends from the large carboxyl-terminal DNA binding domain and is postulated to control the early steps of recombination site synapsis.
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20
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Genome Integration and Excision by a New Streptomyces Bacteriophage, ϕJoe. Appl Environ Microbiol 2017; 83:AEM.02767-16. [PMID: 28003200 PMCID: PMC5311408 DOI: 10.1128/aem.02767-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 12/18/2016] [Indexed: 01/27/2023] Open
Abstract
Bacteriophages are the source of many valuable tools for molecular biology and genetic manipulation. In Streptomyces, most DNA cloning vectors are based on serine integrase site-specific DNA recombination systems derived from phage. Because of their efficiency and simplicity, serine integrases are also used for diverse synthetic biology applications. Here, we present the genome of a new Streptomyces phage, ϕJoe, and investigate the conditions for integration and excision of the ϕJoe genome. ϕJoe belongs to the largest Streptomyces phage cluster (R4-like) and encodes a serine integrase. The attB site from Streptomyces venezuelae was used efficiently by an integrating plasmid, pCMF92, constructed using the ϕJoe int-attP locus. The attB site for ϕJoe integrase was occupied in several Streptomyces genomes, including that of S. coelicolor, by a mobile element that varies in gene content and size between host species. Serine integrases require a phage-encoded recombination directionality factor (RDF) to activate the excision reaction. The ϕJoe RDF was identified, and its function was confirmed in vivo. Both the integrase and RDF were active in in vitro recombination assays. The ϕJoe site-specific recombination system is likely to be an important addition to the synthetic biology and genome engineering toolbox. IMPORTANCEStreptomyces spp. are prolific producers of secondary metabolites, including many clinically useful antibiotics. Bacteriophage-derived integrases are important tools for genetic engineering, as they enable integration of heterologous DNA into the Streptomyces chromosome with ease and high efficiency. Recently, researchers have been applying phage integrases for a variety of applications in synthetic biology, including rapid assembly of novel combinations of genes, biosensors, and biocomputing. An important requirement for optimal experimental design and predictability when using integrases, however, is the need for multiple enzymes with different specificities for their integration sites. In order to provide a broad platform of integrases, we identified and validated the integrase from a newly isolated Streptomyces phage, ϕJoe. ϕJoe integrase is active in vitro and in vivo. The specific recognition site for integration is present in a wide range of different actinobacteria, including Streptomyces venezuelae, an emerging model bacterium in Streptomyces research.
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21
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Fan HF, Hsieh TS, Ma CH, Jayaram M. Single-molecule analysis of ϕC31 integrase-mediated site-specific recombination by tethered particle motion. Nucleic Acids Res 2016; 44:10804-10823. [PMID: 27986956 PMCID: PMC5159548 DOI: 10.1093/nar/gkw861] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/11/2016] [Accepted: 09/22/2016] [Indexed: 11/14/2022] Open
Abstract
Serine and tyrosine site-specific recombinases (SRs and YRs, respectively) provide templates for understanding the chemical mechanisms and conformational dynamics of strand cleavage/exchange between DNA partners. Current evidence suggests a rather intriguing mechanism for serine recombination, in which one half of the cleaved synaptic complex undergoes a 180° rotation relative to the other. The 'small' and 'large' SRs contain a compact amino-terminal catalytic domain, but differ conspicuously in their carboxyl-terminal domains. So far, only one serine recombinase has been analyzed using single substrate molecules. We now utilized single-molecule tethered particle motion (TPM) to follow step-by-step recombination catalyzed by a large SR, phage ϕC31 integrase. The integrase promotes unidirectional DNA exchange between attB and attP sites to integrate the phage genome into the host chromosome. The recombination directionality factor (RDF; ϕC31 gp3) activates the excision reaction (attL × attR). From integrase-induced changes in TPM in the presence or absence of gp3, we delineated the individual steps of recombination and their kinetic features. The gp3 protein appears to regulate recombination directionality by selectively promoting or excluding active conformations of the synapse formed by specific att site partners. Our results support a 'gated rotation' of the synaptic complex between DNA cleavage and joining.
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Affiliation(s)
- Hsiu-Fang Fan
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, 112, Taiwan
- Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, 112, Taiwan
| | - Tao-Shih Hsieh
- Institute of Cellular and Organismic Biology Academia Sinica, 115, Taiwan
| | - Chien-Hui Ma
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Makkuni Jayaram
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
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22
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Bowyer J, Zhao J, Subsoontorn P, Wong W, Rosser S, Bates D. Mechanistic Modeling of a Rewritable Recombinase Addressable Data Module. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:1161-1170. [PMID: 27244749 DOI: 10.1109/tbcas.2016.2526668] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Many of the most important applications predicted to arise from Synthetic Biology will require engineered cellular memory with the capability to store data in a rewritable and reversible manner upon induction by transient stimuli. DNA recombination provides an ideal platform for cellular data storage and has allowed the development of a rewritable recombinase addressable data (RAD) module, capable of efficient data storage within a chromosome. Here, we develop the first detailed mechanistic model of DNA recombination, and validate it against a new set of in vitro data on recombination efficiencies across a range of different concentrations of integrase and gp3. Investigation of in vivo recombination dynamics using our model reveals the importance of fully accounting for all mechanistic features of DNA recombination in order to accurately predict the effect of different switching strategies on RAD module performance, and highlights its usefulness as a design tool for building future synthetic circuitry.
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23
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Keenholtz RA, Grindley NDF, Hatfull GF, Marko JF. Crossover-site sequence and DNA torsional stress control strand interchanges by the Bxb1 site-specific serine recombinase. Nucleic Acids Res 2016; 44:8921-8932. [PMID: 27550179 PMCID: PMC5062993 DOI: 10.1093/nar/gkw724] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 08/08/2016] [Indexed: 01/01/2023] Open
Abstract
DNA segment exchange by site-specific serine recombinases (SRs) is thought to proceed by rigid-body rotation of the two halves of the synaptic complex, following the cleavages that create the two pairs of exchangeable ends. It remains unresolved how the amount of rotation occurring between cleavage and religation is controlled. We report single-DNA experiments for Bxb1 integrase, a model SR, where dynamics of individual synapses were observed, using relaxation of supercoiling to report on cleavage and rotation events. Relaxation events often consist of multiple rotations, with the number of rotations per relaxation event and rotation velocity sensitive to DNA sequence at the center of the recombination crossover site, torsional stress and salt concentration. Bulk and single-DNA experiments indicate that the thermodynamic stability of the annealed, but cleaved, crossover sites controls ligation efficiency of recombinant and parental synaptic complexes, regulating the number of rotations during a breakage-religation cycle. The outcome is consistent with a ‘controlled rotation’ model analogous to that observed for type IB topoisomerases, with religation probability varying in accord with DNA base-pairing free energies at the crossover site. Significantly, we find no evidence for a special regulatory mechanism favoring ligation and product release after a single 180° rotation.
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Affiliation(s)
- Ross A Keenholtz
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Nigel D F Grindley
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Graham F Hatfull
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - John F Marko
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
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24
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Pokhilko A, Zhao J, Ebenhöh O, Smith MCM, Stark WM, Colloms SD. The mechanism of ϕC31 integrase directionality: experimental analysis and computational modelling. Nucleic Acids Res 2016; 44:7360-72. [PMID: 27387286 PMCID: PMC5009753 DOI: 10.1093/nar/gkw616] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/28/2016] [Indexed: 02/04/2023] Open
Abstract
Serine integrases, DNA site-specific recombinases used by bacteriophages for integration and excision of their DNA to and from their host genomes, are increasingly being used as tools for programmed rearrangements of DNA molecules for biotechnology and synthetic biology. A useful feature of serine integrases is the simple regulation and unidirectionality of their reactions. Recombination between the phage attP and host attB sites is promoted by the serine integrase alone, giving recombinant attL and attR sites, whereas the ‘reverse’ reaction (between attL and attR) requires an additional protein, the recombination directionality factor (RDF). Here, we present new experimental data on the kinetics and regulation of recombination reactions mediated by ϕC31 integrase and its RDF, and use these data as the basis for a mathematical model of the reactions. The model accounts for the unidirectionality of the attP × attB and attL × attR reactions by hypothesizing the formation of structurally distinct, kinetically stable integrase–DNA product complexes, dependent on the presence or absence of RDF. The model accounts for all the available experimental data, and predicts how mutations of the proteins or alterations of reaction conditions might increase the conversion efficiency of recombination.
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Affiliation(s)
- Alexandra Pokhilko
- Institute of Molecular, Cell and Systems Biology, Bower Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Jia Zhao
- Institute of Molecular, Cell and Systems Biology, Bower Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Oliver Ebenhöh
- Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine-University, Universitätsstraße 1, D-40225 Düsseldorf, Germany Institute for Complex Systems and Mathematical Biology, University of Aberdeen, AB24 3UE, UK
| | - Margaret C M Smith
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
| | - W Marshall Stark
- Institute of Molecular, Cell and Systems Biology, Bower Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Sean D Colloms
- Institute of Molecular, Cell and Systems Biology, Bower Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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25
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Abstract
The large serine recombinases (LSRs) are a family of enzymes, encoded in temperate phage genomes or on mobile elements, that precisely cut and recombine DNA in a highly controllable and predictable way. In phage integration, the LSRs act at specific sites, the attP site in the phage and the attB site in the host chromosome, where cleavage and strand exchange leads to the integrated prophage flanked by the recombinant sites attL and attR. The prophage can excise by recombination between attL and attR but this requires a phage-encoded accessory protein, the recombination directionality factor (RDF). Although the LSRs can bind specifically to all the recombination sites, only specific integrase-bound sites can pair in a synaptic complex prior to strand exchange. Recent structural information has led to a breakthrough in our understanding of the mechanism of the LSRs, notably how the LSRs bind to their substrates and how LSRs display this site-selectivity. We also understand that the RDFs exercise control over the LSRs by protein-protein interactions. Other recent work with the LSRs have contributed to our understanding of how all serine recombinases undergo strand exchange subunit rotation, facilitated by surfaces that resemble a molecular bearing.
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26
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Xiao B, McLean MM, Lei X, Marko JF, Johnson RC. Controlled rotation mechanism of DNA strand exchange by the Hin serine recombinase. Sci Rep 2016; 6:23697. [PMID: 27032966 PMCID: PMC4817059 DOI: 10.1038/srep23697] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 03/14/2016] [Indexed: 11/30/2022] Open
Abstract
DNA strand exchange by serine recombinases has been proposed to occur by a large-scale rotation of halves of the recombinase tetramer. Here we provide the first direct physical evidence for the subunit rotation mechanism for the Hin serine invertase. Single-DNA looping assays using an activated mutant (Hin-H107Y) reveal specific synapses between two hix sites. Two-DNA “braiding” experiments, where separate DNA molecules carrying a single hix are interwound, show that Hin-H107Y cleaves both hix sites and mediates multi-step rotational relaxation of the interwinding. The variable numbers of rotations in the DNA braid experiments are in accord with data from bulk experiments that follow DNA topological changes accompanying recombination by the hyperactive enzyme. The relatively slow Hin rotation rates, combined with pauses, indicate considerable rotary friction between synapsed subunit pairs. A rotational pausing mechanism intrinsic to serine recombinases is likely to be crucial for DNA ligation and for preventing deleterious DNA rearrangements.
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Affiliation(s)
- Botao Xiao
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.,Department of Physics and Astronomy, Northwestern University, Evanston IL 60208.,Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Meghan M McLean
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles CA 90095-1737
| | - Xianbin Lei
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - John F Marko
- Department of Physics and Astronomy, Northwestern University, Evanston IL 60208.,Department of Molecular Biosciences, Northwestern University, Evanston IL 60208
| | - Reid C Johnson
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles CA 90095-1737
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27
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Bowyer J, Rosser S, Colloms S, Bates D. Development and experimental validation of a mechanistic model of in vitro DNA recombination. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:945-8. [PMID: 26736419 DOI: 10.1109/embc.2015.7318519] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Engineering cellular memory is a key area of research in which Synthetic Biology has already begun to make significant impacts. Recent work elucidating transcriptional memory devices has paved the way for the creation of bistable genetic switches based on DNA recombination. Attempts to experimentally design and build synthetic systems using recombinases have thus far been hindered by a lack of validated computational models that capture the mechanistic basis of DNA recombination. The predictive capabilities of such models could be exploited by Synthetic Biologists to reduce the number of iterative cycles required to align experimental results with design performance requirements. Here, we develop and validate the first detailed mechanistic model of DNA recombination, with a focus on how efficiently recombination can occur, and the model features required to replicate and predict experimental data.
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28
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Merrick C, Wardrope C, Paget J, Colloms S, Rosser S. Rapid Optimization of Engineered Metabolic Pathways with Serine Integrase Recombinational Assembly (SIRA). Methods Enzymol 2016; 575:285-317. [DOI: 10.1016/bs.mie.2016.02.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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29
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Chang Y, Johnson RC. Controlling tetramer formation, subunit rotation and DNA ligation during Hin-catalyzed DNA inversion. Nucleic Acids Res 2015; 43:6459-72. [PMID: 26056171 PMCID: PMC4513852 DOI: 10.1093/nar/gkv565] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/30/2015] [Accepted: 05/16/2015] [Indexed: 11/17/2022] Open
Abstract
Two critical steps controlling serine recombinase activity are the remodeling of dimers into the chemically active synaptic tetramer and the regulation of subunit rotation during DNA exchange. We identify a set of hydrophobic residues within the oligomerization helix that controls these steps by the Hin DNA invertase. Phe105 and Met109 insert into hydrophobic pockets within the catalytic domain of the same subunit to stabilize the inactive dimer conformation. These rotate out of the catalytic domain in the dimer and into the subunit rotation interface of the tetramer. About half of residue 105 and 109 substitutions gain the ability to generate stable synaptic tetramers and/or promote DNA chemistry without activation by the Fis/enhancer element. Phe106 replaces Phe105 in the catalytic domain pocket to stabilize the tetramer conformation. Significantly, many of the residue 105 and 109 substitutions support subunit rotation but impair ligation, implying a defect in rotational pausing at the tetrameric conformer poised for ligation. We propose that a ratchet-like surface involving Phe105, Met109 and Leu112 within the rotation interface functions to gate the subunit rotation reaction. Hydrophobic residues are present in analogous positions in other serine recombinases and likely perform similar functions.
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Affiliation(s)
- Yong Chang
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1737, USA
| | - Reid C Johnson
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1737, USA Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
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30
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Abstract
ABSTRACT
In site-specific recombination, two short DNA sequences (‘sites’) are each cut at specific points in both strands, and the cut ends are rejoined to new partners. The enzymes that mediate recognition of the sites and the subsequent cutting and rejoining steps are called recombinases. Most recombinases fall into one of two families according to similarities of their protein sequences and mechanisms; these families are known as the tyrosine recombinases and the serine recombinases, the names referring to the conserved amino acid residue that attacks the DNA phosphodiester and becomes covalently linked to a DNA strand end during catalysis. This chapter gives an overview of our current understanding of the serine recombinases, their types, biological roles, structures, catalytic mechanisms, mechanisms of regulation, and applications.
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31
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Fogg PCM, Colloms S, Rosser S, Stark M, Smith MCM. New applications for phage integrases. J Mol Biol 2014; 426:2703-16. [PMID: 24857859 PMCID: PMC4111918 DOI: 10.1016/j.jmb.2014.05.014] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 05/09/2014] [Accepted: 05/16/2014] [Indexed: 11/28/2022]
Abstract
Within the last 25 years, bacteriophage integrases have rapidly risen to prominence as genetic tools for a wide range of applications from basic cloning to genome engineering. Serine integrases such as that from ϕC31 and its relatives have found an especially wide range of applications within diverse micro-organisms right through to multi-cellular eukaryotes. Here, we review the mechanisms of the two major families of integrases, the tyrosine and serine integrases, and the advantages and disadvantages of each type as they are applied in genome engineering and synthetic biology. In particular, we focus on the new areas of metabolic pathway construction and optimization, biocomputing, heterologous expression and multiplexed assembly techniques. Integrases are versatile and efficient tools that can be used in conjunction with the various extant molecular biology tools to streamline the synthetic biology production line. Phage integrases are site-specific recombinases that mediate controlled and precise DNA integration and excision. The serine integrases, such as ϕC31 integrase, can be used for efficient recombination in heterologous hosts as they use short recombination substrates, they are directional and they do not require host factors. Both serine and tyrosine integrases, such as λ integrase, are versatile tools for DNA cloning and assembly in vivo and in vitro. Controlled expression of orthologous serine integrases and their cognate recombination directionality factors can be used to generate living biocomputers. Serine integrases are increasingly being exploited for synthetic biology applications.
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Affiliation(s)
- Paul C M Fogg
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
| | - Sean Colloms
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
| | - Susan Rosser
- School of Biological Sciences, University of Edinburgh, King's Building, Edinburgh EH9 3JR, UK
| | - Marshall Stark
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
| | - Margaret C M Smith
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK.
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Rutherford K, Van Duyne GD. The ins and outs of serine integrase site-specific recombination. Curr Opin Struct Biol 2014; 24:125-31. [PMID: 24509164 DOI: 10.1016/j.sbi.2014.01.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/27/2013] [Accepted: 01/08/2014] [Indexed: 11/19/2022]
Abstract
Serine integrases catalyze the integration and excision of phage genomes into and out of bacterial chromosomes in a highly specific and directional manner, making these proteins powerful tools for genome engineering. In 2013, the first structure of a serine integrase-DNA complex was reported. This work revealed how the phage attP sequence is recognized by the integrase and provided important clues about how serine integrases bind to other attachment site sequences. The resulting structural models indicate that distinct spatial arrangements of integrase domains are present for each attachment site complex. Here we describe how serine integrases may exploit this site-dependent domain arrangement to regulate the direction of recombination. We also discuss how phage-encoded recombination directionality factors could change this directionality by altering the nature of inter-subunit interactions.
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Affiliation(s)
- Karen Rutherford
- Department of Biochemistry & Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Gregory D Van Duyne
- Department of Biochemistry & Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
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Zhang L, Zhu B, Dai R, Zhao G, Ding X. Control of directionality in Streptomyces phage φBT1 integrase-mediated site-specific recombination. PLoS One 2013; 8:e80434. [PMID: 24278283 PMCID: PMC3836970 DOI: 10.1371/journal.pone.0080434] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Accepted: 10/02/2013] [Indexed: 11/19/2022] Open
Abstract
Streptomyces phage φBT1 integrates its genome into the attB site of the host chromosome with the attP site to generate attL and attR. The φBT1 integrase belongs to the large serine recombinase subfamily which directly binds to target sites to initiate double strand breakage and exchange. A recombination directionality factor (RDF) is commonly required for switching integration to excision. Here we report the characterization of the RDF protein for φBT1 recombination. The RDF, is a phage-encoded gp3 gene product (28 KDa), which allows efficient active excision between attL and attR, and inhibits integration between attB and attP; Gp3 can also catalyze topological relaxation with the integrase of supercoiled plasmids containing a single excision site. Further study showed that Gp3 could form a dimer and interact with the integrase whether it bound to the substrate or not. The synapse formation of attL or attR alone with integrase and Gp3 showed that synapsis did not discriminate between the two sites, indicating that complementarity of central dinucleotides is the sole determinant of outcome in correct excision synapses. Furthermore, both in vitro and in vivo evidence support that the RDFs of φBT1 and φC31 were fully exchangeable, despite the low amino acid sequence identity of the two integrases.
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Affiliation(s)
- Lin Zhang
- Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- Key Laboratory of Synthetic biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Binyan Zhu
- Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Ruixue Dai
- Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Guoping Zhao
- Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- Key Laboratory of Synthetic biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
- Shanghai-MOST Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, China
- Department of Microbiology and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China
- * E-mail: (GZ); (XD)
| | - Xiaoming Ding
- Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- * E-mail: (GZ); (XD)
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Colloms SD, Merrick CA, Olorunniji FJ, Stark WM, Smith MCM, Osbourn A, Keasling JD, Rosser SJ. Rapid metabolic pathway assembly and modification using serine integrase site-specific recombination. Nucleic Acids Res 2013; 42:e23. [PMID: 24225316 PMCID: PMC3936721 DOI: 10.1093/nar/gkt1101] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Synthetic biology requires effective methods to assemble DNA parts into devices and to modify these devices once made. Here we demonstrate a convenient rapid procedure for DNA fragment assembly using site-specific recombination by C31 integrase. Using six orthogonal attP/attB recombination site pairs with different overlap sequences, we can assemble up to five DNA fragments in a defined order and insert them into a plasmid vector in a single recombination reaction. C31 integrase-mediated assembly is highly efficient, allowing production of large libraries suitable for combinatorial gene assembly strategies. The resultant assemblies contain arrays of DNA cassettes separated by recombination sites, which can be used to manipulate the assembly by further recombination. We illustrate the utility of these procedures to (i) assemble functional metabolic pathways containing three, four or five genes; (ii) optimize productivity of two model metabolic pathways by combinatorial assembly with randomization of gene order or ribosome binding site strength; and (iii) modify an assembled metabolic pathway by gene replacement or addition.
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Affiliation(s)
- Sean D Colloms
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Bower Building, University Avenue, Glasgow G12 8QQ, Scotland, UK, Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK, Department of Metabolic Biology, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK, Joint BioEnergy Institute, Emeryville, CA 94608, USA, Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Singh S, Rockenbach K, Dedrick RM, VanDemark AP, Hatfull GF. Cross-talk between diverse serine integrases. J Mol Biol 2013; 426:318-31. [PMID: 24161951 DOI: 10.1016/j.jmb.2013.10.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 01/06/2023]
Abstract
Phage-encoded serine integrases are large serine recombinases that mediate integrative and excisive site-specific recombination of temperate phage genomes. They are well suited for use in heterologous systems and for synthetic genetic circuits as the attP and attB attachment sites are small (<50 bp), there are no host factor or DNA supercoiling requirements, and they are strongly directional, doing only excisive recombination in the presence of a recombination directionality factor. Combining different recombinases that function independently and without cross-talk to construct complex synthetic circuits is desirable, and several different serine integrases are available. However, we show here that these functions are not reliably predictable, and we describe a pair of serine integrases encoded by mycobacteriophages Bxz2 and Peaches with unusual and unpredictable specificities. The integrases share only 59% amino acid sequence identity and the attP sites have fewer than 50% shared bases, but they use the same attB site and there is non-reciprocal cross-talk between the two systems. The DNA binding specificities do not result from differences in specific DNA contacts but from the constraints imposed by the configuration of the component half-sites within each of the attachment site DNAs.
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Affiliation(s)
- Shweta Singh
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15241, USA
| | - Kate Rockenbach
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15241, USA
| | - Rebekah M Dedrick
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15241, USA
| | - Andrew P VanDemark
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15241, USA
| | - Graham F Hatfull
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15241, USA.
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36
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Van Duyne GD, Rutherford K. Large serine recombinase domain structure and attachment site binding. Crit Rev Biochem Mol Biol 2013; 48:476-91. [PMID: 23980849 DOI: 10.3109/10409238.2013.831807] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Large serine recombinases (LSRs) catalyze the movement of DNA elements into and out of bacterial chromosomes using site-specific recombination between short DNA "attachment sites". The LSRs that function as bacteriophage integrases carry out integration between attachment sites in the phage (attP) and in the host (attB). This process is highly directional; the reverse excision reaction between the product attL and attR sites does not occur in the absence of a phage-encoded recombination directionality factor, nor does recombination typically occur between other pairings of attachment sites. Although the mechanics of strand exchange are reasonably well understood through studies of the closely related resolvase and invertase serine recombinases, many of the fundamental aspects of the LSR reactions have until recently remained poorly understood on a structural level. In this review, we discuss the results of several years worth of biochemical and molecular genetic studies of LSRs in light of recently described structural models of LSR-DNA complexes. The focus is understanding LSR domain structure, how LSRs bind to the attP and attB attachment sites, and the differences between attP-binding and attB-binding modes. The simplicity, site-selectivity and strong directionality of the LSRs has led to their use as important tools in a number of genetic engineering applications in a wide variety of organisms. Given the important potential role of LSR enzymes in genetic engineering and gene therapy, understanding the structure and DNA-binding properties of LSRs is of fundamental importance for those seeking to enhance or alter specificity and functionality in these systems.
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Affiliation(s)
- Gregory D Van Duyne
- Department of Biochemistry & Biophysics, Perelman School of Medicine, University of Pennsylvania , Philadelphia , USA
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