1
|
Mich JK, Sunil S, Johansen N, Martinez RA, Leytze M, Gore BB, Mahoney JT, Ben-Simon Y, Bishaw Y, Brouner K, Campos J, Canfield R, Casper T, Dee N, Egdorf T, Gary A, Gibson S, Goldy J, Groce EL, Hirschstein D, Loftus L, Lusk N, Malone J, Martin NX, Monet D, Omstead V, Opitz-Araya X, Oster A, Pom CA, Potekhina L, Reding M, Rimorin C, Ruiz A, Sedeño-Cortés AE, Shapovalova NV, Taormina M, Taskin N, Tieu M, Valera Cuevas NJ, Weed N, Way S, Yao Z, McMillen DA, Kunst M, McGraw M, Thyagarajan B, Waters J, Bakken TE, Yao S, Smith KA, Svoboda K, Podgorski K, Kojima Y, Horwitz GD, Zeng H, Daigle TL, Lein ES, Tasic B, Ting JT, Levi BP. Enhancer-AAVs allow genetic access to oligodendrocytes and diverse populations of astrocytes across species. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558718. [PMID: 37790503 PMCID: PMC10542530 DOI: 10.1101/2023.09.20.558718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Proper brain function requires the assembly and function of diverse populations of neurons and glia. Single cell gene expression studies have mostly focused on characterization of neuronal cell diversity; however, recent studies have revealed substantial diversity of glial cells, particularly astrocytes. To better understand glial cell types and their roles in neurobiology, we built a new suite of adeno-associated viral (AAV)-based genetic tools to enable genetic access to astrocytes and oligodendrocytes. These oligodendrocyte and astrocyte enhancer-AAVs are highly specific (usually > 95% cell type specificity) with variable expression levels, and our astrocyte enhancer-AAVs show multiple distinct expression patterns reflecting the spatial distribution of astrocyte cell types. To provide the best glial-specific functional tools, several enhancer-AAVs were: optimized for higher expression levels, shown to be functional and specific in rat and macaque, shown to maintain specific activity in epilepsy where traditional promoters changed activity, and used to drive functional transgenes in astrocytes including Cre recombinase and acetylcholine-responsive sensor iAChSnFR. The astrocyte-specific iAChSnFR revealed a clear reward-dependent acetylcholine response in astrocytes of the nucleus accumbens during reinforcement learning. Together, this collection of glial enhancer-AAVs will enable characterization of astrocyte and oligodendrocyte populations and their roles across species, disease states, and behavioral epochs.
Collapse
|
2
|
Yamauchi Y, Matsukura H, Motone K, Ueda M, Aoki W. Evaluation of a library of loxP variants with a wide range of recombination efficiencies by Cre. PLoS One 2022; 17:e0276657. [PMID: 36269789 PMCID: PMC9586403 DOI: 10.1371/journal.pone.0276657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 10/11/2022] [Indexed: 11/18/2022] Open
Abstract
Sparse labeling of individual cells is an important approach in neuroscience and many other fields of research. Various methods have been developed to sparsely label only a small population of cells; however, there is no simple and reproducible strategy for managing the probability of sparse labeling at desired levels. Here, we aimed to develop a novel methodology based on the Cre-lox system to regulate sparseness at desired levels, and we purely analyzed cleavage efficiencies of loxP mutants by Cre. We hypothesized that mutations in the loxP sequence reduce the recognition efficiency by Cre, which enables the regulation of the sparseness level of gene expression. In this research, we mutagenized the loxP sequence and analyzed a library of loxP variants. We evaluated more than 1000 mutant loxP sequences, including mutants with reduced excision efficiencies by Cre ranging from 0.51% to 59%. This result suggests that these mutant loxP sequences can be useful in regulating the sparseness of genetic labeling at desired levels.
Collapse
Affiliation(s)
- Yuji Yamauchi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
- Japan Society for the Promotion of Science, Sakyo-ku, Kyoto, Japan
| | - Hidenori Matsukura
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Keisuke Motone
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, Washington, United States of America
| | - Mitsuyoshi Ueda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Wataru Aoki
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
- * E-mail:
| |
Collapse
|
3
|
Fort PE, Losiewicz MK, Elghazi L, Kong D, Cras-Méneur C, Fingar DC, Kimball SR, Rajala RVS, Smith AJ, Ali RR, Abcouwer SF, Gardner TW. mTORC1 regulates high levels of protein synthesis in retinal ganglion cells of adult mice. J Biol Chem 2022; 298:101944. [PMID: 35447116 PMCID: PMC9117545 DOI: 10.1016/j.jbc.2022.101944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 02/02/2023] Open
Abstract
Mechanistic target of rapamycin (mTOR) and mTOR complex 1 (mTORC1), linchpins of the nutrient sensing and protein synthesis pathways, are present at relatively high levels in the ganglion cell layer (GCL) and retinal ganglion cells (RGCs) of rodent and human retinas. However, the role of mTORCs in the control of protein synthesis in RGC is unknown. Here, we applied the SUrface SEnsing of Translation (SUnSET) method of nascent protein labeling to localize and quantify protein synthesis in the retinas of adult mice. We also used intravitreal injection of an adeno-associated virus 2 vector encoding Cre recombinase in the eyes of mtor- or rptor-floxed mice to conditionally knockout either both mTORCs or only mTORC1, respectively, in cells within the GCL. A novel vector encoding an inactive Cre mutant (CreΔC) served as control. We found that retinal protein synthesis was highest in the GCL, particularly in RGC. Negation of both complexes or only mTORC1 significantly reduced protein synthesis in RGC. In addition, loss of mTORC1 function caused a significant reduction in the pan-RGC marker, RNA-binding protein with multiple splicing, with little decrease of the total number of cells in the RGC layer, even at 25 weeks after adeno-associated virus-Cre injection. These findings reveal that mTORC1 signaling is necessary for maintaining the high rate of protein synthesis in RGCs of adult rodents, but it may not be essential to maintain RGC viability. These findings may also be relevant to understanding the pathophysiology of RGC disorders, including glaucoma, diabetic retinopathy, and optic neuropathies.
Collapse
Affiliation(s)
- Patrice E Fort
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA; Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Mandy K Losiewicz
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lynda Elghazi
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Dejuan Kong
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Corentin Cras-Méneur
- Internal Medicine (MEND Division), University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Diane C Fingar
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Scot R Kimball
- Cellular & Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, USA
| | - Raju V S Rajala
- Departments of Ophthalmology and Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Alexander J Smith
- Centre for Gene Therapy and Regenerative Medicine, King's College London, England, United Kingdom
| | - Robin R Ali
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA; Centre for Gene Therapy and Regenerative Medicine, King's College London, England, United Kingdom
| | - Steven F Abcouwer
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA.
| | - Thomas W Gardner
- Ophthalmology & Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA; Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; Internal Medicine (MEND Division), University of Michigan Medical School, Ann Arbor, Michigan, USA
| |
Collapse
|
4
|
Stachowski K, Norris AS, Potter D, Wysocki VH, Foster MP. Mechanisms of Cre recombinase synaptic complex assembly and activation illuminated by Cryo-EM. Nucleic Acids Res 2022; 50:1753-1769. [PMID: 35104890 PMCID: PMC8860596 DOI: 10.1093/nar/gkac032] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 01/04/2022] [Accepted: 01/12/2022] [Indexed: 12/15/2022] Open
Abstract
Cre recombinase selectively recognizes DNA and prevents non-specific DNA cleavage through an orchestrated series of assembly intermediates. Cre recombines two loxP DNA sequences featuring a pair of palindromic recombinase binding elements and an asymmetric spacer region, by assembly of a tetrameric synaptic complex, cleavage of an opposing pair of strands, and formation of a Holliday junction intermediate. We used Cre and loxP variants to isolate the monomeric Cre-loxP (54 kDa), dimeric Cre2-loxP (110 kDa), and tetrameric Cre4-loxP2 assembly intermediates, and determined their structures using cryo-EM to resolutions of 3.9, 4.5 and 3.2 Å, respectively. Progressive and asymmetric bending of the spacer region along the assembly pathway enables formation of increasingly intimate interfaces between Cre protomers and illuminates the structural bases of biased loxP strand cleavage order and half-the-sites activity. Application of 3D variability analysis to the tetramer data reveals constrained conformational sampling along the pathway between protomer activation and Holliday junction isomerization. These findings underscore the importance of protein and DNA flexibility in Cre-mediated site selection, controlled activation of alternating protomers, the basis for biased strand cleavage order, and recombination efficiency. Such considerations may advance development of site-specific recombinases for use in gene editing applications.
Collapse
Affiliation(s)
- Kye Stachowski
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Andrew S Norris
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.,Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Devante Potter
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Vicki H Wysocki
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.,Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Mark P Foster
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| |
Collapse
|
5
|
Fukushima T, Tanaka Y, Adachi K, Masuyama N, Tsuchiya A, Asada S, Ishiguro S, Mori H, Seki M, Yachie N, Goyama S, Kitamura T. CRISPR/Cas9-mediated base-editing enables a chain reaction through sequential repair of sgRNA scaffold mutations. Sci Rep 2021; 11:23889. [PMID: 34903756 PMCID: PMC8668876 DOI: 10.1038/s41598-021-02986-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 11/19/2021] [Indexed: 11/15/2022] Open
Abstract
Cell behavior is controlled by complex gene regulatory networks. Although studies have uncovered diverse roles of individual genes, it has been challenging to record or control sequential genetic events in living cells. In this study, we designed two cellular chain reaction systems that enable sequential sgRNA activation in mammalian cells using a nickase Cas9 tethering of a cytosine nucleotide deaminase (nCas9-CDA). In these systems, thymidine (T)-to-cytosine (C) substitutions in the scaffold region of the sgRNA or the TATA box-containing loxP sequence (TATAloxP) are corrected by the nCas9-CDA, leading to activation of the next sgRNA. These reactions can occur multiple times, resulting in cellular chain reactions. As a proof of concept, we established a chain reaction by repairing sgRNA scaffold mutations in 293 T cells. Importantly, the results obtained in yeast or in vitro did not match those obtained in mammalian cells, suggesting that in vivo chain reactions need to be optimized in appropriate cellular contexts. Our system may lay the foundation for building cellular chain reaction systems that have a broad utility in the future biomedical research.
Collapse
Affiliation(s)
- Tsuyoshi Fukushima
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Yosuke Tanaka
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
| | - Keito Adachi
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Nanami Masuyama
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
- School of Biomedical Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Akiho Tsuchiya
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Shuhei Asada
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
- The Institute of Laboratory Animals, Tokyo Women's Medical University, Tokyo, Japan
| | - Soh Ishiguro
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
- School of Biomedical Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Hideto Mori
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
| | - Motoaki Seki
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
| | - Nozomu Yachie
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, 153-8904, Japan
- School of Biomedical Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Susumu Goyama
- Division of Molecular Oncology, Graduate School of Frontier Sciences, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
| | - Toshio Kitamura
- Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
| |
Collapse
|
6
|
Liu R, Long Q, Zou X, Wang Y, Pei Y. DNA methylation occurring in Cre-expressing cells inhibits loxP recombination and silences loxP-sandwiched genes. THE NEW PHYTOLOGIST 2021; 231:210-224. [PMID: 33742463 DOI: 10.1111/nph.17353] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
The low DNA recombination efficiency of site-specific recombinase systems in plants limits their application; however, the underlying mechanism is unknown. We evaluate the gene deletion performance of four recombinase systems (Cre/loxP, Flp/FRT, KD/KDRT and B3/B3RT) in tobacco where the recombinases are under the control of germline-specific promoters. We find that the expression of these recombinases results mostly in gene silencing rather than gene deletion. Using the Cre/loxP system as a model, we reveal that the region flanked by loxP sites (floxed) is hypermethylated, which prevents floxed genes from deletion while silencing the expression of the genes. We further show CG methylation alone in the recombinase binding element of the loxP site is unable to impede gene deletion; instead, CHH methylation in the crossover region is required to inhibit loxP recombination. Our study illustrates the important role of recombinase-induced DNA methylation in the inhibition of site-specific DNA recombination and uncovers the mechanism underlying recombinase-associated gene silence in plants.
Collapse
Affiliation(s)
- Ruochen Liu
- Chongqing Key Laboratory of Application and Safety Control of Genetically Modified Crops; Biotechnology Research Center, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing, 400715, China
| | - Qin Long
- Chongqing Key Laboratory of Application and Safety Control of Genetically Modified Crops; Biotechnology Research Center, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing, 400715, China
| | - Xiuping Zou
- Chongqing Key Laboratory of Application and Safety Control of Genetically Modified Crops; Biotechnology Research Center, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing, 400715, China
| | - You Wang
- Chongqing Key Laboratory of Application and Safety Control of Genetically Modified Crops; Biotechnology Research Center, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing, 400715, China
| | - Yan Pei
- Chongqing Key Laboratory of Application and Safety Control of Genetically Modified Crops; Biotechnology Research Center, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing, 400715, China
| |
Collapse
|
7
|
Soni A, Augsburg M, Buchholz F, Pisabarro MT. Nearest-neighbor amino acids of specificity-determining residues influence the activity of engineered Cre-type recombinases. Sci Rep 2020; 10:13985. [PMID: 32814809 PMCID: PMC7438526 DOI: 10.1038/s41598-020-70867-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 08/03/2020] [Indexed: 11/29/2022] Open
Abstract
The tyrosine-type site-specific DNA recombinase Cre recombines its target site, loxP, with high activity and specificity without cross-recombining the target sites of highly related recombinases. Understanding how Cre achieves this precision is key to be able to rationally engineer site-specific recombinases (SSRs) for genome editing applications. Previous work has revealed key residues for target site selectivity in the Cre/loxP and the related Dre/rox recombinase systems. However, enzymes in which these residues were changed to the respective counterpart only showed weak activity on the foreign target site. Here, we use molecular modeling and dynamics simulation techniques to comprehensively explore the mechanisms by which these residues determine target recognition in the context of their flanking regions in the protein-DNA interface, and we establish a structure-based rationale for the design of improved recombination activities. Our theoretical models reveal that nearest-neighbors to the specificity-determining residues are important players for enhancing SSR activity on the foreign target site. Based on the established rationale, we design new Cre variants with improved rox recombination activities, which we validate experimentally. Our work provides new insights into the target recognition mechanisms of Cre-like recombinases and represents an important step towards the rational design of SSRs for applied genome engineering.
Collapse
Affiliation(s)
- Anjali Soni
- Structural Bioinformatics, BIOTEC, TU Dresden, Tatzberg 47-51, 01307, Dresden, Germany
| | - Martina Augsburg
- University Carl Gustav Carus and Medical Faculty, UCC, Medical Systems Biology, TU Dresden, Fetscherstrasse 74, Dresden, Germany
| | - Frank Buchholz
- University Carl Gustav Carus and Medical Faculty, UCC, Medical Systems Biology, TU Dresden, Fetscherstrasse 74, Dresden, Germany
| | - M Teresa Pisabarro
- Structural Bioinformatics, BIOTEC, TU Dresden, Tatzberg 47-51, 01307, Dresden, Germany.
| |
Collapse
|
8
|
Bessen JL, Afeyan LK, Dančík V, Koblan LW, Thompson DB, Leichner C, Clemons PA, Liu DR. High-resolution specificity profiling and off-target prediction for site-specific DNA recombinases. Nat Commun 2019; 10:1937. [PMID: 31028261 PMCID: PMC6486577 DOI: 10.1038/s41467-019-09987-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/05/2019] [Indexed: 12/26/2022] Open
Abstract
The development of site-specific recombinases (SSRs) as genome editing agents is limited by the difficulty of altering their native DNA specificities. Here we describe Rec-seq, a method for revealing the DNA specificity determinants and potential off-target substrates of SSRs in a comprehensive and unbiased manner. We applied Rec-seq to characterize the DNA specificity determinants of several natural and evolved SSRs including Cre, evolved variants of Cre, and other SSR family members. Rec-seq profiling of these enzymes and mutants thereof revealed previously uncharacterized SSR interactions, including specificity determinants not evident from SSR:DNA structures. Finally, we used Rec-seq specificity profiles to predict off-target substrates of Tre and Brec1 recombinases, including endogenous human genomic sequences, and confirmed their ability to recombine these off-target sequences in human cells. These findings establish Rec-seq as a high-resolution method for rapidly characterizing the DNA specificity of recombinases with single-nucleotide resolution, and for informing their further development. The development of site-specific recombinases as genome editing tools is limited by the difficulty of altering their DNA sequence specificity. Here the authors present Rec-seq, a method for identifying specificity determinants and off-target substrates of recombinases in an unbiased manner.
Collapse
Affiliation(s)
- Jeffrey L Bessen
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138, USA
| | - Lena K Afeyan
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138, USA
| | - Vlado Dančík
- Chemical Biology and Therapeutics Science Program, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Luke W Koblan
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138, USA
| | - David B Thompson
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA.,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138, USA
| | | | - Paul A Clemons
- Chemical Biology and Therapeutics Science Program, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA. .,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA. .,Howard Hughes Medical Institute, Harvard University, Cambridge, MA, 02138, USA.
| |
Collapse
|
9
|
A Cre Transcription Fidelity Reporter Identifies GreA as a Major RNA Proofreading Factor in Escherichia coli. Genetics 2017; 206:179-187. [PMID: 28341651 PMCID: PMC5419468 DOI: 10.1534/genetics.116.198960] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/04/2017] [Indexed: 12/21/2022] Open
Abstract
We made a coupled genetic reporter that detects rare transcription misincorporation errors to measure RNA polymerase transcription fidelity in Escherichia coli. Using this reporter, we demonstrated in vivo that the transcript cleavage factor GreA, but not GreB, is essential for proofreading of a transcription error where a riboA has been misincorporated instead of a riboG. A greA mutant strain had more than a 100-fold increase in transcription errors relative to wild-type or a greB mutant. However, overexpression of GreB in ΔgreA cells reduced the misincorporation errors to wild-type levels, demonstrating that GreB at high concentration could substitute for GreA in RNA proofreading activity in vivo.
Collapse
|
10
|
Metabolic Engineering of Raoultella ornithinolytica BF60 for Production of 2,5-Furandicarboxylic Acid from 5-Hydroxymethylfurfural. Appl Environ Microbiol 2016; 83:AEM.02312-16. [PMID: 27795308 DOI: 10.1128/aem.02312-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 09/17/2016] [Indexed: 01/15/2023] Open
Abstract
2,5-Furandicarboxylic acid (FDCA) is an important renewable biotechnological building block because it serves as an environmentally friendly substitute for terephthalic acid in the production of polyesters. Currently, FDCA is produced mainly via chemical oxidation, which can cause severe environmental pollution. In this study, we developed an environmentally friendly process for the production of FDCA from 5-hydroxymethyl furfural (5-HMF) using a newly isolated strain, Raoultella ornithinolytica BF60. First, R. ornithinolytica BF60 was identified by screening and was isolated. Its maximal FDCA titer was 7.9 g/liter, and the maximal molar conversion ratio of 5-HMF to FDCA was 51.0% (mol/mol) under optimal conditions (100 mM 5-HMF, 45 g/liter whole-cell biocatalyst, 30°C, and 50 mM phosphate buffer [pH 8.0]). Next, dcaD, encoding dicarboxylic acid decarboxylase, was mutated to block FDCA degradation to furoic acid, thus increasing FDCA production to 9.2 g/liter. Subsequently, aldR, encoding aldehyde reductase, was mutated to prevent the catabolism of 5-HMF to HMF alcohol, further increasing the FDCA titer, to 11.3 g/liter. Finally, the gene encoding aldehyde dehydrogenase 1 was overexpressed. The FDCA titer increased to 13.9 g/liter, 1.7 times that of the wild-type strain, and the molar conversion ratio increased to 89.0%. IMPORTANCE In this work, we developed an ecofriendly bioprocess for green production of FDCA in engineered R. ornithinolytica This report provides a starting point for further metabolic engineering aimed at a process for industrial production of FDCA using R. ornithinolytica.
Collapse
|
11
|
Abstract
The site-specific recombinase encoded by bacteriophage λ (Int) is responsible for integrating and excising the viral chromosome into and out of the chromosome of its Escherichia coli host. Int carries out a reaction that is highly directional, tightly regulated, and depends upon an ensemble of accessory DNA bending proteins acting on 240 bp of DNA encoding 16 protein binding sites. This additional complexity enables two pathways, integrative and excisive recombination, whose opposite, and effectively irreversible, directions are dictated by different physiological and environmental signals. Int recombinase is a heterobivalent DNA binding protein and each of the four Int protomers, within a multiprotein 400 kDa recombinogenic complex, is thought to bind and, with the aid of DNA bending proteins, bridge one arm- and one core-type DNA site. In the 12 years since the publication of the last review focused solely on the λ site-specific recombination pathway in Mobile DNA II, there has been a great deal of progress in elucidating the molecular details of this pathway. The most dramatic advances in our understanding of the reaction have been in the area of X-ray crystallography where protein-DNA structures have now been determined for of all of the DNA-protein interfaces driving the Int pathway. Building on this foundation of structures, it has been possible to derive models for the assembly of components that determine the regulatory apparatus in the P-arm, and for the overall architectures that define excisive and integrative recombinogenic complexes. The most fundamental additional mechanistic insights derive from the application of hexapeptide inhibitors and single molecule kinetics.
Collapse
|
12
|
Abstract
The use of Cre recombinase to carry out conditional mutagenesis of transgenes and insert DNA cassettes into eukaryotic chromosomes is widespread. In addition to the numerous in vivo and in vitro applications that have been reported since Cre was first shown to function in yeast and mammalian cells nearly 30 years ago, the Cre-loxP system has also played an important role in understanding the mechanism of recombination by the tyrosine recombinase family of site-specific recombinases. The simplicity of this system, requiring only a single recombinase enzyme and short recombination sequences for robust activity in a variety of contexts, has been an important factor in both cases. This review discusses advances in the Cre recombinase field that have occurred over the past 12 years since the publication of Mobile DNA II. The focus is on those recent contributions that have provided new mechanistic insights into the reaction. Also discussed are modifications of Cre and/or the loxP sequence that have led to improvements in genome engineering applications.
Collapse
|
13
|
A genetic assay for transcription errors reveals multilayer control of RNA polymerase II fidelity. PLoS Genet 2014; 10:e1004532. [PMID: 25232834 PMCID: PMC4168980 DOI: 10.1371/journal.pgen.1004532] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 06/11/2014] [Indexed: 11/19/2022] Open
Abstract
We developed a highly sensitive assay to detect transcription errors in vivo. The assay is based on suppression of a missense mutation in the active site tyrosine in the Cre recombinase. Because Cre acts as tetramer, background from translation errors are negligible. Functional Cre resulting from rare transcription errors that restore the tyrosine codon can be detected by Cre-dependent rearrangement of reporter genes. Hence, transient transcription errors are captured as stable genetic changes. We used this Cre-based reporter to screen for mutations of Saccharomyces cerevisiae RPB1 (RPO21) that increase the level of misincorporation during transcription. The mutations are in three domains of Rpb1, the trigger loop, the bridge helix, and in sites involved in binding to TFIIS. Biochemical characterization demonstrates that these variants have elevated misincorporation, and/or ability to extend mispaired bases, or defects in TFIIS mediated editing.
Collapse
|
14
|
Sharma S, Zhu J. Immunologic applications of conditional gene modification technology in the mouse. ACTA ACUST UNITED AC 2014; 105:10.34.1-10.34.13. [PMID: 24700321 DOI: 10.1002/0471142735.im1034s105] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Since the success of homologous recombination in altering mouse genome and the discovery of Cre-loxP system, the combination of these two breakthroughs has created important applications for studying the immune system in the mouse. Here, we briefly summarize the general principles of this technology and its applications in studying immune cell development and responses; such implications include conditional gene knockout and inducible and/or tissue-specific gene over-expression, as well as lineage fate mapping. We then discuss the pros and cons of a few commonly used Cre-expressing mouse lines for studying lymphocyte development and functions. We also raise several general issues, such as efficiency of gene deletion, leaky activity of Cre, and Cre toxicity, all of which may have profound impacts on data interpretation. Finally, we selectively list some useful links to the Web sites as valuable mouse resources.
Collapse
Affiliation(s)
- Suveena Sharma
- Molecular and Cellular Immunoregulation Unit, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Jinfang Zhu
- Molecular and Cellular Immunoregulation Unit, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| |
Collapse
|
15
|
Gaj T, Sirk SJ, Barbas CF. Expanding the scope of site-specific recombinases for genetic and metabolic engineering. Biotechnol Bioeng 2013; 111:1-15. [PMID: 23982993 DOI: 10.1002/bit.25096] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 12/20/2022]
Abstract
Site-specific recombinases are tremendously valuable tools for basic research and genetic engineering. By promoting high-fidelity DNA modifications, site-specific recombination systems have empowered researchers with unprecedented control over diverse biological functions, enabling countless insights into cellular structure and function. The rigid target specificities of many sites-specific recombinases, however, have limited their adoption in fields that require highly flexible recognition abilities. As a result, intense effort has been directed toward altering the properties of site-specific recombination systems by protein engineering. Here, we review key developments in the rational design and directed molecular evolution of site-specific recombinases, highlighting the numerous applications of these enzymes across diverse fields of study.
Collapse
Affiliation(s)
- Thomas Gaj
- The Skaggs Institute for Chemical Biology and the Departments of Chemistry and Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, 92037
| | | | | |
Collapse
|
16
|
Warth L, Altenbuchner J. The tyrosine recombinase MrpA and its target sequence: a mutational analysis of the recombination site mrpS resulting in a new left element/right element (LE/RE) deletion system. Arch Microbiol 2013; 195:617-36. [PMID: 23861149 DOI: 10.1007/s00203-013-0910-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 06/06/2013] [Accepted: 06/22/2013] [Indexed: 11/28/2022]
Abstract
MrpA is the multimer resolution protein of the Streptomyces coelicolor A3(2) plasmid SCP2*. Previously, MrpA was found to be a site-specific tyrosine recombinase that acts with the 36-bp recombination site mrpS. The present report gives a comprehensive characterization of the composition as well as the position of the spacer and MrpA binding sites within mrpS. Experiments revealed a spacer consisting of 6 remarkably variable nucleotides in the middle of the mrpS-site. A reduction in the spacer to 5 nucleotides abolished recombination. Investigation of the MrpA binding sites showed the importance of its 15 nucleotides on an effective recombination. Among almost randomly exchangeable nucleotides, two nucleotides were identified as essential for MrpA binding. Alteration of either of these nucleotides led to a reduction in MrpA binding down to 2 % or even to no binding. Based on these results, a new left element/right element (LE/RE) deletion system was developed. The constructed heteromeric mrpS-sites are efficiently resolved by MrpA. The resulting double mutated (LE/RE) site can no longer be used as a recombination site by MrpA. The system has been successfully applied for the generation of multiple-targeted deletions in the genome of E. coli.
Collapse
Affiliation(s)
- Lydia Warth
- Institut für Industrielle Genetik, Universität Stuttgart, Germany
| | | |
Collapse
|
17
|
Eroshenko N, Church GM. Mutants of Cre recombinase with improved accuracy. Nat Commun 2013; 4:2509. [PMID: 24056590 PMCID: PMC3972015 DOI: 10.1038/ncomms3509] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 08/27/2013] [Indexed: 01/17/2023] Open
Abstract
Despite rapid advances in genome engineering technologies, inserting genes into precise locations in the human genome remains an outstanding problem. It has been suggested that site-specific recombinases can be adapted towards use as transgene delivery vectors. The specificity of recombinases can be altered either with directed evolution or via fusions to modular DNA-binding domains. Unfortunately, both wild-type and altered variants often have detectable activities at off-target sites. Here we use bacterial selections to identify mutations in the dimerization surface of Cre recombinase (R32V, R32M and 303GVSdup) that improve the accuracy of recombination. The mutants are functional in bacteria, in human cells and in vitro (except for 303GVSdup, which we did not purify), and have improved selectivity against both model off-target sites and the entire E. coli genome. We propose that destabilizing binding cooperativity may be a general strategy for improving the accuracy of dimeric DNA-binding proteins.
Collapse
Affiliation(s)
- Nikolai Eroshenko
- Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA
| | | |
Collapse
|
18
|
[Progress in Cre/lox site-specific recombination system in higher eukaryotes]. YI CHUAN = HEREDITAS 2012; 34:177-89. [PMID: 22382059 DOI: 10.3724/sp.j.1005.2012.00177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cre/lox system derived from P1 bacteriaphage can quickly and effectively achieve gene insertion, deletion, replacement, and inversion by means of site-specific recombination. As one of the most important tools for gene targeting at present, Cre/lox system has been widely used in Arabidopsis thaliana, Oryza sativa L., Mus musculus, Drosophila melanogaster, Danio rerio, and other higher eukaryotic organisms. This review roundly described the basic profile of Cre/lox system, and its application in higher eukaryotes. In addition, we also discussed the main problems and developmental trend of the Cre/lox system in this review, which can be a good reference for using Cre/lox system to realize the gene manipulations of the different high eukaryotic organisms.
Collapse
|
19
|
Suzuki E, Nakayama M. VCre/VloxP and SCre/SloxP: new site-specific recombination systems for genome engineering. Nucleic Acids Res 2011; 39:e49. [PMID: 21288882 PMCID: PMC3082901 DOI: 10.1093/nar/gkq1280] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We developed two new site-specific recombination systems named VCre/VloxP and SCre/SloxP for genome engineering. Their recognition sites are different from Cre recognition sites because VCre and SCre recombinases share less protein similarity with Cre, even though the basic 13-8-13 structures of their recognition sites are identical. Mutant VloxP and SloxP, which have the same uses as mutant loxP, were also developed. VCre/VloxP and SCre/SloxP in combination with Cre/loxP and Flp/FRT systems can serve as powerful tools for genome engineering, especially when used to genetically modify both alleles of a single gene in mouse and human cells.
Collapse
Affiliation(s)
- Emiko Suzuki
- Department of Human Genome Research, Kazusa DNA Research Institute, Graduate School of Pharmaceutical Sciences, Chiba University, 2-6-7 Kazusa-Kamatari, Kisarazu, Chiba 292-0818, Japan
| | | |
Collapse
|
20
|
Chatterjee PK, Shakes LA, Stennett N, Richardson VL, Malcolm TL, Harewood KR. Replacing the wild type loxP site in BACs from the public domain with lox66 using a lox66 transposon. BMC Res Notes 2010; 3:38. [PMID: 20170521 PMCID: PMC2841073 DOI: 10.1186/1756-0500-3-38] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 02/19/2010] [Indexed: 11/27/2022] Open
Abstract
Background Chromatin adjoining the site of integration of a transgene affects expression and renders comparisons of closely related transgenes, such as those derived from a BAC deletion series retrofitted with enhancer-traps, unreliable. Gene targeting to a pre-determined site on the chromosome is likely to alleviate the problem. Findings A general procedure to replace the loxP site located at one end of genomic DNA inserts in BACs with lox66 is described. Truncating insert DNA from the loxP end with a Tn10 transposon carrying a lox66 site simultaneously substitutes the loxP with a lox66 sequence. The replacement occurs with high stringency, and the procedure should be applicable to all BACs in the public domain. Cre recombination of loxP with lox66 or lox71 was found to be as efficient as another loxP site during phage P1 transduction of small plasmids containing those sites. However the end-deletion of insert DNA in BACs using a lox66 transposon occurred at no more than 20% the efficiency observed with a loxP transposon. Differences in the ability of Cre protein available at different stages of the P1 life cycle to recombine identical versus non-identical lox-sites is likely responsible for this discrepancy. A possible mechanism to explain these findings is discussed. Conclusions The loxP/lox66 replacement procedure should allow targeting BACs to a pre-positioned lox71 site in zebrafish chromosomes; a system where homologous recombination-mediated "knock-in" technology is unavailable.
Collapse
Affiliation(s)
- Pradeep K Chatterjee
- Department of Chemistry, North Carolina Central University, 1801 Fayetteville Street, Durham, NC 27707, USA.
| | | | | | | | | | | |
Collapse
|
21
|
Abstract
From bacterial viruses to humans, site-specific recombination and transposition are the major pathways for rearranging genomes on both long- and short-time scales. The site-specific pathways can be divided into 2 groups based on whether they are stochastic or regulated. Recombinases Cre and lambda Int are well-studied examples of each group, respectively. Both have been widely exploited as powerful and flexible tools for genetic engineering: Cre primarily in vivo and lambda Int primarily in vitro. Although Cre and Int use the same mechanism of DNA strand exchange, their respective reaction pathways are very different. Cre-mediated recombination is bidirectional, unregulated, does not require accessory proteins, and has a minimal symmetric DNA target. We show that when Cre is fused to the small N-terminal domain of Int, the resulting chimeric Cre recombines complex higher-order DNA targets comprising >200 bp encoding 16 protein-binding sites. This recombination requires the IHF protein, is unidirectional, and is regulated by the relative levels of the 3 accessory proteins, IHF, Xis, and Fis. In one direction, recombination depends on the Xis protein, and in the other direction it is inhibited by Xis. It is striking that regulated directionality and complexity can be conferred in a simple chimeric construction. We suggest that the relative ease of constructing a chimeric Cre with these properties may simulate the evolutionary interconversions responsible for the large variety of site-specific recombinases observed in Archaea, Eubacteria, and Eukarya.
Collapse
|
22
|
Type II secretory pathway for surface secretion of DraD invasin from the uropathogenic Escherichia coli Dr+ strain. J Bacteriol 2008; 190:5044-56. [PMID: 18502864 DOI: 10.1128/jb.00224-08] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The virulence of the uropathogenic Escherichia coli Dr(+) IH11128 strain is associated with the presence of Dr fimbrial structures and a DraD invasin which can act as a fimbrial capping domain at the bacterial cell surface. However, a recent study suggests that the DraD protein is surface exposed in two forms: fimbria associated and fimbria nonassociated (prone to interaction with the N-terminal extension of the DraE protein located on the fimbrial tip). The actual mechanism of DraD surface secretion is presently unknown. We identified a previously unrecognized type II secretory pathway (secreton) in the uropathogenic E. coli Dr(+) strain which is well conserved among gram-negative bacteria and used mainly for secretion of virulence determinants. An active secreton is composed of 12 to 15 different proteins, among which GspD functions as an outer-membrane channel to permit extrusion of proteins in a folded state. Therefore, we inactivated the pathway by inserting the group II intron into a gspD gene of the type II secretion machinery by site-specific recombination. DraD secretion by the E. coli Dr(+) and gspD mutant strains was determined by immunofluorescence microscopy (with antibodies raised against DraD) and an assay of cell binding between bacteria and HeLa cells. The specificity of DraD-mediated bacterial binding for the integrin receptor was confirmed by examination of the adhesion of DraD-coated beads to HeLa cells in the presence and absence of alpha(5)beta(1) monoclonal antibodies. The investigations that we performed showed that type II secretion in E. coli Dr(+) strains leads to DraD translocation at the bacterial cell surfaces.
Collapse
|
23
|
Gelato KA, Martin SS, Liu PH, Saunders AA, Baldwin EP. Spatially directed assembly of a heterotetrameric Cre-Lox synapse restricts recombination specificity. J Mol Biol 2008; 378:653-65. [PMID: 18374357 DOI: 10.1016/j.jmb.2008.02.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 02/13/2008] [Accepted: 02/25/2008] [Indexed: 12/21/2022]
Abstract
The pseudo-fourfold homotetrameric synapse formed by Cre protein and target DNA restricts site-specific recombination to sequences containing dyad-symmetric Cre-binding repeats. Mixtures of engineered altered-specificity Cre monomers can form heterotetramers that recombine nonidentical asymmetric sequences, allowing greater flexibility for target site selection in the genome of interest. However, the variety of tetramers allowed by random subunit association increases the chances of unintended reactivity at nontarget sites. This problem can be circumvented by specifying a unique spatial arrangement of heterotetramer subunits. By reconfiguring intersubunit protein-protein contacts, we directed the assembly of two different Cre monomers, each having a distinct DNA sequence specificity, in an alternating (ABAB) configuration. This designed heterotetramer preferentially recombined a particular pair of asymmetric Lox sites over other pairs, whereas a mixture of freely associating subunits showed little bias. Alone, the engineered monomers had reduced reactivity towards both dyad-symmetric and asymmetric sites. Specificity arose because the organization of Cre-binding repeats of the preferred substrate matched the programmed arrangement of the subunits in the heterotetrameric synapse. When this "spatial matching" principle is applied, Cre-mediated recombination can be directed to asymmetric DNA sequences with greater fidelity.
Collapse
Affiliation(s)
- Kathy A Gelato
- Biochemistry and Molecular Biology Graduate Group, University of California, Davis, CA 95616, USA
| | | | | | | | | |
Collapse
|
24
|
Sheren J, Langer SJ, Leinwand LA. A randomized library approach to identifying functional lox site domains for the Cre recombinase. Nucleic Acids Res 2007; 35:5464-73. [PMID: 17702764 PMCID: PMC2018622 DOI: 10.1093/nar/gkm604] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The bacteriophage P1 Cre/loxP site-specific recombination system is a useful tool in a number of genetic engineering processes. The Cre recombinase has been shown to act on DNA sequences that vary considerably from that of its bacteriophage recognition sequence, loxP. However, little is known about the sequence requirements for functional lox-like sequences. In this study, we have implemented a randomized library approach to identify the sequence characteristics of functional lox site domains. We created a randomized spacer library and a randomized arm library, and then tested them for recombination in vivo and in vitro. Results from the spacer library show that, while there is great plasticity, identity between spacer pairs is the most important factor influencing function, especially in in vitro reactions. The presence of one completely randomized arm in a functional loxP recombination reaction revealed that only three wild-type loxP arms are necessary for successful recombination in Cre-expressing bacteria, and that there are nucleotide preferences at the first three and last three positions of the randomized arm for the most efficiently recombined sequences. Finally, we found that in vitro Cre recombination reactions are much more stringent for evaluating which sequences can support efficient recombination compared to the 294-CRE system.
Collapse
Affiliation(s)
- Jamie Sheren
- University of Colorado, Department of Molecular, Cellular and Developmental Biology, 347 UCB, Boulder, CO 80309-0347, USA.
| | | | | |
Collapse
|
25
|
Gelato KA, Martin SS, Wong S, Baldwin EP. Multiple levels of affinity-dependent DNA discrimination in Cre-LoxP recombination. Biochemistry 2006; 45:12216-26. [PMID: 17014075 PMCID: PMC2891539 DOI: 10.1021/bi0605235] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cre recombinase residue Arg259 mediates a canonical bidentate hydrogen-bonded contact with Gua27 of its LoxP DNA substrate. Substituting Cyt8-Gua27 with the three other basepairs, to give LoxAT, LoxTA, and LoxGC, reduced Cre-mediated recombination in vitro, with the preference order of Gua27 > Ade27 approximately Thy27 >> Cyt27. While LoxAT and LoxTA exhibited 2.5-fold reduced affinity and 2.5-5-fold slower reaction rates, LoxGC was a barely functional substrate. Its maximum level of turnover was 6-fold reduced over other substrates, and it exhibited 8.5-fold reduced Cre binding and 6.3-fold slower turnover rate. With LoxP, the rate-limiting step for recombination occurs after protein-DNA complex assembly but before completion of the first strand exchange to form the Holliday junction (HJ) intermediate. With the mutant substrates, it occurs after HJ formation. Using an increased DNA-binding E262Q/E266Q "CreQQ" variant, all four substrates react more readily, but with much less difference between them, and maintained the earlier rate-limiting step. The data indicate that Cre discriminates substrates through differences in (i) concentration dependence of active complex assembly, (ii) turnover rate, and (iii) maximum yield of product at saturation, all of which are functions of the Cre-DNA binding interaction. CreQQ suppression of Lox mutant defects implies that coupling between binding and turnover involves a change in Cre subunit DNA affinities during the "conformational switch" that occurs prior to the second strand exchange. These results provide an example of how a DNA-binding enzyme can exert specificity via affinity modulation of conformational transitions that occur along its reaction pathway.
Collapse
Affiliation(s)
| | | | | | - Enoch P. Baldwin
- Corresponding author: Phone: (530) 752-1108. FAX (530) 752-3085.
| |
Collapse
|
26
|
Cuellar W, Gaudin A, Solórzano D, Casas A, Nopo L, Chudalayandi P, Medrano G, Kreuze J, Ghislain M. Self-excision of the antibiotic resistance gene nptII using a heat inducible Cre-loxP system from transgenic potato. PLANT MOLECULAR BIOLOGY 2006; 62:71-82. [PMID: 16912912 DOI: 10.1007/s11103-006-9004-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 04/12/2006] [Indexed: 05/11/2023]
Abstract
Resistance to antibiotics mediated by selectable marker genes remains a powerful selection tool for transgenic event production. However, regulatory agencies and consumer concerns favor these to be eliminated from food crops. Several excision systems exist but none have been optimized or shown to be functional for clonally propagated crops. The excision of the nptII gene conferring resistance to kanamycin has been achieved here using a gene construct based on a heat-inducible cre gene producing a recombinase that eliminates cre and nptII genes flanked by two loxP sites. First-generation regenerants with the Cre-loxP system were obtained by selection on kanamycin media. Following a heat treatment, second generation regenerants were screened for excision by PCR using nptII, cre, and T-DNA borders primers. Excision efficiency appeared to be at 4.7% depending on the heat treatment. The footprint of the excision was shown by sequencing between T-DNA borders to correspond to a perfect recombination event. Selectable marker-free sprouts were also obtained from tubers of transgenic events when submitted to similar heat treatment at 4% frequency. Spontaneous excision was not observed out of 196 regenerants from untreated transgenic explants. Biosafety concerns are minimized because the expression of cre gene driven by the hsp70 promoter of Drosophila melanogaster was remarkably low even under heat activation and no functional loxP site were found in published Solanum sequence database. A new plant transformation vector pCIP54/55 was developed including a multiple cloning site and the self-excision system which should be a useful tool not only for marker genes in potato but for any gene or sequence removal in any plant.
Collapse
Affiliation(s)
- Wilmer Cuellar
- Applied Biotechnology Laboratory, Germplasm enhancement and Crop Improvement Division, International Potato Center CIP, P.O. Box 1558, Lima 12, Peru
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Maragathavally KJ, Kaminski JM, Coates CJ. Chimeric Mos1 and piggyBac transposases result in site-directed integration. FASEB J 2006; 20:1880-2. [PMID: 16877528 DOI: 10.1096/fj.05-5485fje] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Genetic transformation systems based on Mos1 and piggyBac transposable elements are used to achieve stable chromosomal integration. However, integration sites are randomly distributed in the genome and transgene expression can be influenced by position effects. We developed a novel technology that utilizes chimeric transposases to direct integration into specific sites on a target DNA molecule. The Gal4 DNA binding domain was fused to the NH(2) terminus of the Mos1 and piggyBac transposases and a target plasmid was created that contained upstream activating sequences (UAS), to which the Gal4 DBD binds with high affinity. The transpositional activity of the Gal4-Mos1 transposase was 12.7-fold higher compared to controls where the Gal4-UAS interaction was absent and 96% of the recovered transposition products were identical, with integration occurring at the same TA site. In a parallel experiment, a Gal4-piggyBac transposase resulted in an 11.6-fold increase in transpositional activity compared to controls, with 67% of the integrations occurring at a single TTAA site. This technology has the potential to minimize nonspecific integration events that may result in insertional mutagenesis and reduced fitness. Site-directed integration will be advantageous to the manipulation of genomes, study of gene function, and for the development of gene therapy techniques.
Collapse
Affiliation(s)
- K J Maragathavally
- Department of Entomology, Texas A&M University, College Station, Texas, USA
| | | | | |
Collapse
|
28
|
Saraf-Levy T, Santoro SW, Volpin H, Kushnirsky T, Eyal Y, Schultz PG, Gidoni D, Carmi N. Site-specific recombination of asymmetric lox sites mediated by a heterotetrameric Cre recombinase complex. Bioorg Med Chem 2006; 14:3081-9. [PMID: 16412655 DOI: 10.1016/j.bmc.2005.12.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2005] [Revised: 12/12/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
Previous reports have demonstrated that new Cre recombinase specificities can be developed for symmetrically designed lox mutants through directed evolution. The development of Cre variants that allow the recombination of true asymmetric lox mutant sites has not yet been addressed, however. In the present study, we demonstrate that a mixture of two different site-specific Cre recombinase molecules (wt Cre and a mutant Cre) catalyzes efficient recombination between two asymmetric lox sites in vitro, presumably via formation of a functionally active heterotetrameric complex. The results may broaden the application of site-specific recombination in basic and applied research, including the custom-design of recombinases for natural, asymmetric, and lox-related target sequences present in the genome. Future applications may potentially include genomic manipulations, for example, site-specific integrations, deletions or substitutions within precise regions of the genomes of mammalians and other organisms.
Collapse
Affiliation(s)
- Talia Saraf-Levy
- Institute of Plant Sciences, A.R.O, The Volcani Center, PO Box 6, Bet-Dagan 50250, Israel
| | | | | | | | | | | | | | | |
Collapse
|
29
|
Coates CJ, Kaminski JM, Summers JB, Segal DJ, Miller AD, Kolb AF. Site-directed genome modification: derivatives of DNA-modifying enzymes as targeting tools. Trends Biotechnol 2005; 23:407-19. [PMID: 15993503 DOI: 10.1016/j.tibtech.2005.06.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 04/14/2005] [Accepted: 06/14/2005] [Indexed: 01/11/2023]
Abstract
The modification of mammalian genomes is an important goal in gene therapy and animal transgenesis. To generate stable genetic and biochemical changes, the therapeutic genes or transgenes need to be incorporated into the host genome. Ideally, the integration of the foreign gene should occur at sites that ensure their continual expression in the absence of any unwanted side effects on cellular metabolism. In this article, we discuss the opportunities provided by natural DNA-modifying enzymes, such as transposases, recombinases and integrases, to mediate the stable integration of foreign genes into host genomes. In addition, we discuss the approaches that have been taken to improve the efficiency and to modify the site-specificity of these enzymes.
Collapse
Affiliation(s)
- Craig J Coates
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA
| | | | | | | | | | | |
Collapse
|
30
|
Akopian A, Marshall Stark W. Site‐Specific DNA Recombinases as Instruments for Genomic Surgery. ADVANCES IN GENETICS 2005; 55:1-23. [PMID: 16291210 DOI: 10.1016/s0065-2660(05)55001-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Site-specific DNA recombinases can "cut and paste" DNA. For example, they can promote excision of specific DNA segments or insertion of new DNA segments in specific places. However, natural recombinases act only at their cognate recombination sites, so current applications are limited to genetically modified organisms in which these sites have been introduced into the genome. Transposases also catalyze DNA rearrangements; they promote insertion of specific DNA sequences but at nonspecific locations. Applicability of site-specific recombinases and transposases in experimental genetics, biotechnology, and gene therapy would be much wider if they could be re-engineered so as to act specifically at chosen sequences within an organism's natural genome. This review will discuss progress towards the creation of such "designer" recombinases.
Collapse
Affiliation(s)
- Aram Akopian
- Institute of Biomedical & Life Sciences University of Glasgow, Glasgow G11 6NU, Scotland, UK
| | | |
Collapse
|
31
|
Sauer B, McDermott J. DNA recombination with a heterospecific Cre homolog identified from comparison of the pac-c1 regions of P1-related phages. Nucleic Acids Res 2004; 32:6086-95. [PMID: 15550568 PMCID: PMC534624 DOI: 10.1093/nar/gkh941] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sequencing of the 7 kb immC region from four P1-related phages identified a novel DNA recombinase that exhibits many Cre-like characteristics, including recombination in mammalian cells, but which has a distinctly different DNA specificity. DNA sequence comparison to the P1 immC region showed that all phages had related DNA terminase, C1 repressor and DNA recombinase genes. Although these genes from phages P7, phi(w39) and p15B were highly similar to those from P1, those of phage D6 showed significant divergence. Moreover, the D6 sequence showed evidence of DNA deletion and substitution in this region relative to the other phages. Characterization of the D6 site-specific DNA recombinase (Dre) showed that it was a tyrosine recombinase closely related to the P1 Cre recombinase, but that it had a distinct DNA specificity for a 32 bp DNA site (rox). Cre and Dre are heterospecific: Cre did not catalyze recombination at rox sites and Dre did not catalyze recombination at lox sites. Like Cre, Dre catalyzed both integrative and excisive recombination and required no other phage-encoded proteins for recombination. Dre-mediated recombination in mammalian cells showed that, like Cre, no host bacterial proteins are required for efficient Dre-mediated site-specific DNA recombination.
Collapse
Affiliation(s)
- Brian Sauer
- Stowers Institute, 1000 E 50th Street, Kansas City, MO 64110, USA.
| | | |
Collapse
|
32
|
Chatterjee PK, Shakes LA, Srivastava DK, Garland DM, Harewood KR, Moore KJ, Coren JS. Mutually exclusive recombination of wild-type and mutant loxP sites in vivo facilitates transposon-mediated deletions from both ends of genomic DNA in PACs. Nucleic Acids Res 2004; 32:5668-76. [PMID: 15494454 PMCID: PMC524307 DOI: 10.1093/nar/gkh900] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Recombination of wild-type and mutant loxP sites mediated by wild-type Cre protein was analyzed in vivo using a sensitive phage P1 transduction assay. Contrary to some earlier reports, recombination between loxP sites was found to be highly specific: a loxP site recombined in vivo only with another of identical sequence, with no crossover recombination either between a wild-type and mutant site; or between two different mutant sites tested. Mutant loxP sites of identical sequence recombined as efficiently as wild-type. The highly specific and efficient recombination of mutant loxP sites in vivo helped in developing a procedure to progressively truncate DNA from either end of large genomic inserts in P1-derived artificial chromosomes (PACs) using transposons that carry either a wild-type or mutant loxP sequence. PAC libraries of human DNA were constructed with inserts flanked by a wild-type and one of the two mutant loxP sites, and deletions from both ends generated in clones using newly constructed wild-type and mutant loxP transposons. Analysis of the results provides new insight into the very large co-integrates formed during P1 transduction of plasmids with loxP sites: a model with tri- and possibly multimeric co-integrates comprising the PAC plasmid, phage DNA, and transposon plasmid(s) as intermediates in the cell appears best to fit the data. The ability to truncate a large piece of DNA from both ends is likely to facilitate functionally mapping gene boundaries more efficiently, and make available precisely trimmed genes in their chromosomal contexts for therapeutic applications.
Collapse
Affiliation(s)
- Pradeep K Chatterjee
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 1801 Fayetteville Street, Durham, NC 27707, USA.
| | | | | | | | | | | | | |
Collapse
|
33
|
Affiliation(s)
- Larry Gilbertson
- Monsanto Company, 700 Chesterfield Parkway North, Chesterfield, MO 63017-1732, USA.
| |
Collapse
|
34
|
Chen Y, Rice PA. New insight into site-specific recombination from Flp recombinase-DNA structures. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2003; 32:135-59. [PMID: 12598365 DOI: 10.1146/annurev.biophys.32.110601.141732] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The lamba integrase, or tyrosine-based family of site-specific recombinases, plays an important role in a variety of biological processes by inserting, excising, and inverting DNA segments. Flp, encoded by the yeast 2-mum plasmid, is the best-characterized eukaryotic member of this family and is responsible for maintaining the copy number of this plasmid. Over the past several years, structural and biochemical studies have shed light on the details of a common catalytic scheme utilized by these enzymes with interesting variations under different biological contexts. The emergence of new Flp structures and solution data provides insights not only into its unique mechanism of active site assembly and activity regulation but also into the specific contributions of certain protein residues to catalysis.
Collapse
Affiliation(s)
- Yu Chen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA.
| | | |
Collapse
|
35
|
Baldwin EP, Martin SS, Abel J, Gelato KA, Kim H, Schultz PG, Santoro SW. A Specificity Switch in Selected Cre Recombinase Variants Is Mediated by Macromolecular Plasticity and Water. ACTA ACUST UNITED AC 2003; 10:1085-94. [PMID: 14652076 PMCID: PMC2891429 DOI: 10.1016/j.chembiol.2003.10.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The basis for the altered DNA specificities of two Cre recombinase variants, obtained by mutation and selection, was revealed by their cocrystal structures. The proteins share similar substitutions but differ in their preferences for the natural LoxP substrate and an engineered substrate that is inactive with wild-type Cre, LoxM7. One variant preferentially recombines LoxM7 and contacts the substituted bases through a hydrated network of novel interlocking protein-DNA contacts. The other variant recognizes both LoxP and LoxM7 utilizing the same DNA backbone contact but different base contacts, facilitated by an unexpected DNA shift. Assisted by water, novel interaction networks can arise from few protein substitutions, suggesting how new DNA binding specificities might evolve. The contributions of macromolecular plasticity and water networks in specific DNA recognition observed here present a challenge for predictive schemes.
Collapse
Affiliation(s)
- Enoch P Baldwin
- Section of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA.
| | | | | | | | | | | | | |
Collapse
|
36
|
Thomson JG, Rucker EB, Piedrahita JA. Mutational analysis of loxP sites for efficient Cre-mediated insertion into genomic DNA. Genesis 2003; 36:162-7. [PMID: 12872248 DOI: 10.1002/gene.10211] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Cre/loxP system has been used in transgenic models primarily to excise DNA flanked by loxP sites for gene deletion. However, the insertion reaction is more difficult to control since the excision event is kinetically favored. Mutant loxP sites favoring integration were identified using a novel, bacterial screening system. Utilizing lambda integrase, mutant loxP sites were placed at the E. coli attB site and the excision-insertion ratios of incoming DNA plasmids carrying a second, complementary mutant loxP site were determined. Comparison of 50 mutant loxP sites combinations to the native loxP site revealed that mutations to the inner 6 bp of the Cre binding domain severely inhibited recombination, while those in the outer 8 bps were more tolerated. The most efficient loxP combinations resulted in 1421-fold and 1529-fold increases in relative integration rates over wild-type loxP sites. These loxP mutants could be exploited for site-directed "tag and insert" recombination experiments.
Collapse
Affiliation(s)
- James G Thomson
- Department of Veterinary Anatomy and Public Health, Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, Texas, USA
| | | | | |
Collapse
|
37
|
Martin SS, Chu VC, Baldwin E. Modulation of the active complex assembly and turnover rate by protein-DNA interactions in Cre-LoxP recombination. Biochemistry 2003; 42:6814-26. [PMID: 12779336 PMCID: PMC2885442 DOI: 10.1021/bi0272306] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cre promotes recombination at the 34 bp LoxP sequence. Substitution of a critical C-G base pair in LoxP with an A-T base pair, to give LoxAT, reduced Cre binding in vitro and abolished recombination in vivo [Hartung, M., and Kisters-Woike, B. (1998) J. Biol. Chem. 273, 22884-22891].We demonstrated that LoxAT can be recombined in vitro. However, Cre discriminates against this substrate both before and after DNA binding. The preference for LoxP over LoxAT is the result of reduced binding and a slower turnover rate, amplified by changes in cooperativity of complex assembly. With LoxAT, similar levels of substrate turnover required 2-2.5-fold higher protein-DNA concentrations compared to LoxP, but the sigmoidal behavior of the concentration dependence was more pronounced. Further, the Cre-LoxAT complexes reacted 4-5-fold more slowly. In the 2.3 A resolution Cre-LoxAT complex structure, the major groove Arg259-guanine interaction was disrupted, explaining the reduced binding. Overall structural shifts and mobility changes indicate more favorable interactions between subunits, providing a hypothesis for the reduced turnover rate. Concomitant with the displacement of Arg259 from the DNA, adjacent charged residues Glu262 and Glu266 shifted to form salt bridges with the Arg259 guanidinium moiety. Substitution of Glu262 and Glu266 with glutamine increased Cre complex assembly efficiency and reaction rates with both LoxAT and LoxP, but diminished Cre's ability to distinguish them. The increased rate of this variant suggests that DNA substrate binding and turnover are coupled. The improved efficiency, made at some expense of sequence discrimination, may be useful for enhancing recombination in vivo.
Collapse
Affiliation(s)
- Shelley S. Martin
- Section of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, California 95616
| | - Victor C. Chu
- Section of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, California 95616
| | - Enoch Baldwin
- Section of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, California 95616
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616
- To whom correspondence should be addressed. . Phone: (530) 752-1108. Fax: (530) 752-3085
| |
Collapse
|
38
|
Abstract
Cre recombinase is now widely used to carry out complex manipulations of DNA molecules both in vitro and in vivo. For in vitro experiments, there is a clear need for highly pure preparations of Cre and of Cre mutants that serve as controls or supply an altered activity or specificity. In vivo experiments utilizing Cre variants also often require in vitro characterization and some applications involve transfection of purified enzyme to achieve transient activity in the cell. This review outlines a detailed protocol for purification of native Cre and describes straightforward assays that can be used to test for recombination activity in vitro. The design of experiments to trap the intermediates of Cre-loxP site-specific recombination for biophysical studies is also presented. The methods described should be useful to any investigator with a need for purified Cre recombinase and should be broadly applicable to related site-specific recombination systems.
Collapse
Affiliation(s)
- Kaushik Ghosh
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | | |
Collapse
|
39
|
Tronche F, Casanova E, Turiault M, Sahly I, Kellendonk C. When reverse genetics meets physiology: the use of site-specific recombinases in mice. FEBS Lett 2002; 529:116-21. [PMID: 12354622 DOI: 10.1016/s0014-5793(02)03266-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The use of site-specific recombinases enables the precise introduction of defined genetic mutations into the mouse genome. In theory, any deletion, point mutation, inversion or translocation can be modeled in mice. Because gene targeting is controlled both spatially and temporally, the function of a given gene can be studied in the desired cell types and at a specific time point. This 'genetic dissection' allows to define gene function in development, physiology or behavior. In this review, we focus on the technical possibilities of Cre and other site-specific recombinases but also discuss their limitations.
Collapse
Affiliation(s)
- François Tronche
- CNRS FRE2401, Molecular Genetics, Neurophysiology and Behavior, Institute of Biology, Collège de France, 11 place Marcelin Berthelot, 75231 Cedex 5, Paris, France.
| | | | | | | | | |
Collapse
|
40
|
Abstract
The targeted modification of the mammalian genome has a variety of applications in research, medicine, and biotechnology. Site-specific recombinases have become significant tools in all of these areas. Conditional gene targeting using site-specific recombinases has enabled the functional analysis of genes, which cannot be inactivated in the germline. The site-specific integration of adeno-associated virus, a major gene therapy vehicle, relies on the recombinase activity of the viral rep proteins. Site-specific recombinases also allow the precise integration of open reading frames encoding pharmaceutically relevant proteins into highly active gene loci in cell lines and transgenic animals. These goals have been accomplished by using a variety of genetic strategies but only a few recombinase proteins. However, the vast repertoire of recombinases, which has recently become available as a result of large-scale sequencing projects, may provide a rich source for the development of novel strategies to precisely alter mammalian genomes.
Collapse
Affiliation(s)
- Andreas F Kolb
- Cell Physiology Group, Hannah Research Institute, Ayr, United Kingdom.
| |
Collapse
|
41
|
Rüfer AW, Sauer B. Non-contact positions impose site selectivity on Cre recombinase. Nucleic Acids Res 2002; 30:2764-71. [PMID: 12087159 PMCID: PMC117054 DOI: 10.1093/nar/gkf399] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A first step in Cre-mediated site-specific DNA recombination is binding to the two 13 bp repeats of the 34 bp site loxP. Several nucleotides within loxP do not directly contact the bound enzyme, yet mutation at two of these base pairs, at positions 11 and 12 in each repeat, results in a 100 000-fold reduction in recombination. To understand better how Cre selects DNA sequences for recombination, we combined DNA shuffling mutagenesis and a forward selection strategy to obtain Cre mutants that recombine at 100% efficiency a mutant loxK2 site carrying these dinucleotide changes. The role of the several mutations found in these Cre isolates was analyzed both in vivo and biochemically with purified enzymes. A single mutation at E262 accounts for most but not all of the enhanced activity at loxK2. Secondary mutations act in one or more of three ways: enhancement of loxK2 binding, accelerated synthesis of Cre in vivo or faster DNA recombination at the alternative spacer region present in loxK2. Systematic analysis of all 20 natural amino acids at position E262 shows that the naturally occurring glutamate residue at this position provides the optimal balance of efficiency of recombination at loxP and maximal discrimination against loxK2.
Collapse
Affiliation(s)
- Andreas W Rüfer
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | | |
Collapse
|
42
|
Santoro SW, Schultz PG. Directed evolution of the site specificity of Cre recombinase. Proc Natl Acad Sci U S A 2002; 99:4185-90. [PMID: 11904359 PMCID: PMC123623 DOI: 10.1073/pnas.022039799] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2002] [Indexed: 11/18/2022] Open
Abstract
Cre recombinase from bacteriophage P1 recognizes a 34-bp recombination site, loxP, with exquisite sequence specificity and catalyzes the site-specific insertion, excision, or rearrangement of DNA. To better understand the molecular basis of protein-DNA recognition and generate recombinases with altered specificities, we have developed a directed evolution strategy that can be used to identify recombinases that recognize variant loxP sites. To be selected, members of a library of Cre variants produced by targeted random mutagenesis must rapidly catalyze recombination, in vivo, between two variant loxP sites that are located on a reporter plasmid. Recombination results in an altered pattern of fluorescent protein expression that can be identified by flow cytometry. Fluorescence-activated cell sorting can be used either to screen positively for recombinase variants that recognize a novel loxP site, or negatively for variants that cannot recognize the wild-type loxP site. The use of positive screening alone resulted in a relaxation of recombination site specificity, whereas a combination of positive and negative screening resulted in a switching of specificity. One of the identified recombinases selectively recombines a novel recombination site and operates at a rate identical to that of wild-type Cre. Analysis of the sequences of the resulting Cre variants provides insight into the evolution of these altered specificities. This and other systems should contribute to our understanding of protein-DNA recognition and may eventually be used to evolve custom-tailored recombinases that can be used for gene study and inactivation.
Collapse
Affiliation(s)
- Stephen W Santoro
- Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, SR202, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | | |
Collapse
|
43
|
Rassoulzadegan M, Magliano M, Cuzin F. Transvection effects involving DNA methylation during meiosis in the mouse. EMBO J 2002; 21:440-50. [PMID: 11823436 PMCID: PMC125843 DOI: 10.1093/emboj/21.3.440] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
High efficiencies of recombination between LoxP elements were initially recorded when the Cre recombinase was expressed in meiotic spermatocytes. However, it was unexpectedly found that LoxP recombination fell to very low values at the second generation of mice expressing Cre during meiosis. The inability of the LoxP elements to serve as recombination substrates was correlated with cytosine methylation, initially in LoxP and transgene sequences, but later extending for distances of at least several kilobases into chromosomal sequences. It also affected the allelic locus, implying a transfer of structural information between alleles similar to the transvection phenomenon described in Drosophila. Once initiated following Cre-LoxP interaction, neither cis-extension nor transvection of the methylated state required the continuous expression of Cre, as they occurred both in germinal and somatic cells and in the fraction of the offspring that had not inherited the Sycp1-Cre transgene. Therefore, these processes depend on a physiological mechanism of establishment and extension of an epigenetic state, for which they provide an experimental model.
Collapse
Affiliation(s)
| | | | - François Cuzin
- Unité 470 de l’Institut National de la Santé et de la Recherche Médicale Université de Nice-Sophia Antipolis, Nice, France
Corresponding author e-mail:
| |
Collapse
|
44
|
Sclimenti CR, Thyagarajan B, Calos MP. Directed evolution of a recombinase for improved genomic integration at a native human sequence. Nucleic Acids Res 2001; 29:5044-51. [PMID: 11812835 PMCID: PMC97615 DOI: 10.1093/nar/29.24.5044] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We previously established that a unidirectional site-specific recombinase, the phage phiC31 integrase, can mediate integration into mammalian chromosomes. The enzyme directs integration of plasmids bearing the phage attB recognition site into pseudo attP sites, a set of native sequences related to the phage attP recognition site. Here we use two cycles of DNA shuffling and screening in Escherichia coli to obtain evolved integrases that possess significant improvements in integration frequency and sequence specificity at a pseudo attP sequence located on human chromosome 8, when measured in the native genomic environment of living human cells. Such integrases represent custom integration tools that will be useful for modifying the genomes of higher eukaryotic cells.
Collapse
Affiliation(s)
- C R Sclimenti
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
| | | | | |
Collapse
|
45
|
Woods KC, Martin SS, Chu VC, Baldwin EP. Quasi-equivalence in site-specific recombinase structure and function: crystal structure and activity of trimeric Cre recombinase bound to a three-way Lox DNA junction. J Mol Biol 2001; 313:49-69. [PMID: 11601846 DOI: 10.1006/jmbi.2001.5012] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The crystal structure of a novel Cre-Lox synapse was solved using phases from multiple isomorphous replacement and anomalous scattering, and refined to 2.05 A resolution. In this complex, a symmetric protein trimer is bound to a Y-shaped three-way DNA junction, a marked departure from the pseudo-4-fold symmetrical tetramer associated with Cre-mediated LoxP recombination. The three-way DNA junction was accommodated by a simple kink without significant distortion of the adjoining DNA duplexes. Although the mean angle between DNA arms in the Y and X structures was similar, adjacent Cre trimer subunits rotated 29 degrees relative to those in the tetramers. This rotation was accommodated at the protein-protein and DNA-DNA interfaces by interactions that are "quasi-equivalent" to those in the tetramer, analogous to packing differences of chemically identical viral subunits at non-equivalent positions in icosahedral capsids. This structural quasi-equivalence extends to function as Cre can bind to, cleave and perform strand transfer with a three-way Lox substrate. The structure explains the dual recognition of three and four-way junctions by site-specific recombinases as being due to shared structural features between the differently branched substrates and plasticity of the protein-protein interfaces. To our knowledge, this is the first direct demonstration of quasi-equivalence in both the assembly and function of an oligomeric enzyme.
Collapse
Affiliation(s)
- K C Woods
- Section of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | | | | | | |
Collapse
|
46
|
Abstract
One of the most powerful tools that the molecular biology revolution has given us is the ability to turn genes on and off at our discretion. In the mouse, this has been accomplished by using binary systems in which gene expression is dependent on the interaction of two components, resulting in either transcriptional transactivation or DNA recombination. During recent years, these systems have been used to analyse complex and multi-staged biological processes, such as embryogenesis and cancer, with unprecedented precision. Here, I review these systems and discuss certain studies that exemplify the advantages and limitations of each system.
Collapse
Affiliation(s)
- M Lewandoski
- Section of Genetics of Vertebrate Development, Laboratory of Cancer and Developmental Biology, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201, USA.
| |
Collapse
|
47
|
Wang Z, Engler P, Longacre A, Storb U. An efficient method for high-fidelity BAC/PAC retrofitting with a selectable marker for mammalian cell transfection. Genome Res 2001; 11:137-42. [PMID: 11156622 PMCID: PMC311050 DOI: 10.1101/gr.159001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Large-scale genomic sequencing projects have provided DNA sequence information for many genes, but the biological functions for most of them will only be known through functional studies. Bacterial artificial chromosomes (BACs) and P1-derived artificial chromosomes (PACs) are large genomic clones stably maintained in bacteria and are very important in functional studies through transfection because of their large size and stability. Because most BAC or PAC vectors do not have a mammalian selection marker, transfecting mammalian cells with genes cloned in BACs or PACs requires the insertion into the BAC/PAC of a mammalian selectable marker. However, currently available procedures are not satisfactory in efficiency and fidelity. We describe a very simple and efficient procedure that allows one to retrofit dozens of BACs in a day with no detectable deletions or unwanted recombination. We use a BAC/PAC retrofitting vector that, on transformation into competent BAC or PAC strains, will catalyze the specific insertion of itself into BAC/PAC vectors through in vivo cre/loxP site-specific recombination.
Collapse
Affiliation(s)
- Z Wang
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA
| | | | | | | |
Collapse
|
48
|
Lee YS, Kim ST, Kim GW, Lee M, Park JS. An engineeredloxsequence containing part of a long terminal repeat of HIV-1 permits Cre recombinase-mediated DNA excision. Biochem Cell Biol 2000. [DOI: 10.1139/o00-067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In our previous report, one 34-bp sequence from a long terminal repeat (LTR) of human immunodeficiency virus type 1 (HIV-1) clone, loxLTR-1, was proposed as a target site for site-specific excision by modified Cre recombinase. To support this suggestion, an engineered lox sequence, designated loxIL1, was made. This variant lox has the corresponding sequence of loxLTR-1 at the spacer region and the last two bases of inverted repeat sequence. Through in vitro recombination assay, loxIL1 also allowed the wild-type Cre to specifically recombine the sequence. An in vitro DNA binding experiment with mutants CreK244R and CreK244L revealed that lysine 244 of Cre plays an important role in interaction with the engineered lox. This result suggests that loxLTR-1 would be a candidate for antiviral strategy using site-specific recombinase.Key words: Cre/lox recombination system, sequence similarity, protein-DNA interaction, long terminal repeat, HIV-1 therapy.
Collapse
|
49
|
Kim ST, Kim GW, Lee YS, Park JS. Characterization of Cre-loxP interaction in the major groove: Hint for structural distortion of mutant Cre and possible strategy for HIV-1 therapy. J Cell Biochem 2000. [DOI: 10.1002/1097-4644(20010301)80:3<321::aid-jcb40>3.0.co;2-c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|