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Johnson LA, Mart RJ, Allemann RK. A Photoresponsive Homing Endonuclease for Programmed DNA Cleavage. ACS Synth Biol 2024; 13:195-205. [PMID: 38061193 PMCID: PMC10804406 DOI: 10.1021/acssynbio.3c00425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/08/2023] [Accepted: 11/13/2023] [Indexed: 01/23/2024]
Abstract
Homing endonucleases are used in a wide range of biotechnological applications including gene editing, in gene drive systems, and for the modification of DNA structures, arrays, and prodrugs. However, controlling nuclease activity and sequence specificity remain key challenges when developing new tools. Here a photoresponsive homing endonuclease was engineered for optical control of DNA cleavage by partitioning DNA binding and nuclease domains of the monomeric homing endonuclease I-TevI into independent polypeptide chains. Use of the Aureochrome1a light-oxygen-voltage domain delivered control of dimerization with light. Illumination reduced the concentration needed to achieve 50% cleavage of the homing target site by 6-fold when compared to the dark state, resulting in an up to 9-fold difference in final yields between cleavage products. I-TevI nucleases with and without a native I-TevI zinc finger motif displayed different nuclease activity and sequence preference impacting the promiscuity of the nuclease domain. By harnessing an alternative DNA binding domain, target preference was reprogrammed only when the nuclease lacked the I-TevI zinc finger motif. This work establishes a first-generation photoresponsive platform for spatiotemporal activation of DNA cleavage.
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Affiliation(s)
- Luke A. Johnson
- School of Chemistry, Cardiff
University, Main Building, Park Place, CF10 3AT, Cardiff, U.K.
| | | | - Rudolf K. Allemann
- School of Chemistry, Cardiff
University, Main Building, Park Place, CF10 3AT, Cardiff, U.K.
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2
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Wolfs JM, Hamilton TA, Lant JT, Laforet M, Zhang J, Salemi LM, Gloor GB, Schild-Poulter C, Edgell DR. Biasing genome-editing events toward precise length deletions with an RNA-guided TevCas9 dual nuclease. Proc Natl Acad Sci U S A 2016; 113:14988-14993. [PMID: 27956611 PMCID: PMC5206545 DOI: 10.1073/pnas.1616343114] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The CRISPR/Cas9 nuclease is commonly used to make gene knockouts. The blunt DNA ends generated by cleavage can be efficiently ligated by the classical nonhomologous end-joining repair pathway (c-NHEJ), regenerating the target site. This repair creates a cycle of cleavage, ligation, and target site regeneration that persists until sufficient modification of the DNA break by alternative NHEJ prevents further Cas9 cutting, generating a heterogeneous population of insertions and deletions typical of gene knockouts. Here, we develop a strategy to escape this cycle and bias events toward defined length deletions by creating an RNA-guided dual active site nuclease that generates two noncompatible DNA breaks at a target site, effectively deleting the majority of the target site such that it cannot be regenerated. The TevCas9 nuclease, a fusion of the I-TevI nuclease domain to Cas9, functions robustly in HEK293 cells and generates 33- to 36-bp deletions at frequencies up to 40%. Deep sequencing revealed minimal processing of TevCas9 products, consistent with protection of the DNA ends from exonucleolytic degradation and repair by the c-NHEJ pathway. Directed evolution experiments identified I-TevI variants with broadened targeting range, making TevCas9 an easy-to-use reagent. Our results highlight how the sequence-tolerant cleavage properties of the I-TevI homing endonuclease can be harnessed to enhance Cas9 applications, circumventing the cleavage and ligation cycle and biasing genome-editing events toward defined length deletions.
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Affiliation(s)
- Jason M Wolfs
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Thomas A Hamilton
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Jeremy T Lant
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Marcon Laforet
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Jenny Zhang
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Louisa M Salemi
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5B7, Canada
| | - Gregory B Gloor
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | - Caroline Schild-Poulter
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5B7, Canada
| | - David R Edgell
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada;
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3
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Roy AC, Wilson GG, Edgell DR. Perpetuating the homing endonuclease life cycle: identification of mutations that modulate and change I-TevI cleavage preference. Nucleic Acids Res 2016; 44:7350-9. [PMID: 27387281 PMCID: PMC5009752 DOI: 10.1093/nar/gkw614] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 06/27/2016] [Indexed: 11/14/2022] Open
Abstract
Homing endonucleases are sequence-tolerant DNA endonucleases that act as mobile genetic elements. The ability of homing endonucleases to cleave substrates with multiple nucleotide substitutions suggests a high degree of adaptability in that changing or modulating cleavage preference would require relatively few amino acid substitutions. Here, using directed evolution experiments with the GIY-YIG homing endonuclease I-TevI that targets the thymidylate synthase gene of phage T4, we readily isolated variants that dramatically broadened I-TevI cleavage preference, as well as variants that fine-tuned cleavage preference. By combining substitutions, we observed an ∼10 000-fold improvement in cleavage on some substrates not cleaved by the wild-type enzyme, correlating with a decrease in readout of information content at the cleavage site. Strikingly, we were able to change the cleavage preference of I-TevI to that of the isoschizomer I-BmoI which targets a different cleavage site in the thymidylate synthase gene, recapitulating the evolution of cleavage preference in this family of homing endonucleases. Our results define a strategy to isolate GIY-YIG nuclease domains with distinct cleavage preferences, and provide insight into how homing endonucleases may escape a dead-end life cycle in a population of saturated target sites by promoting transposition to different target sites.
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Affiliation(s)
- Alexander C Roy
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | | | - David R Edgell
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
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4
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Abstract
Homing endonucleases are strong drivers of genetic exchange and horizontal transfer of both their own genes and their local genetic environment. The mechanisms that govern the function and evolution of these genetic oddities have been well documented over the past few decades at the genetic, biochemical, and structural levels. This wealth of information has led to the manipulation and reprogramming of the endonucleases and to their exploitation in genome editing for use as therapeutic agents, for insect vector control and in agriculture. In this chapter we summarize the molecular properties of homing endonucleases and discuss their strengths and weaknesses in genome editing as compared to other site-specific nucleases such as zinc finger endonucleases, TALEN, and CRISPR-derived endonucleases.
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Kleinstiver BP, Wolfs JM, Edgell DR. The monomeric GIY-YIG homing endonuclease I-BmoI uses a molecular anchor and a flexible tether to sequentially nick DNA. Nucleic Acids Res 2013; 41:5413-27. [PMID: 23558745 PMCID: PMC3664794 DOI: 10.1093/nar/gkt186] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The GIY-YIG nuclease domain is found within protein scaffolds that participate in diverse cellular pathways and contains a single active site that hydrolyzes DNA by a one-metal ion mechanism. GIY-YIG homing endonucleases (GIY-HEs) are two-domain proteins with N-terminal GIY-YIG nuclease domains connected to C-terminal DNA-binding and they are thought to function as monomers. Using I-BmoI as a model GIY-HE, we test mechanisms by which the single active site is used to generate a double-strand break. We show that I-BmoI is partially disordered in the absence of substrate, and that the GIY-YIG domain alone has weak affinity for DNA. Significantly, we show that I-BmoI functions as a monomer at all steps of the reaction pathway and does not transiently dimerize or use sequential transesterification reactions to cleave substrate. Our results are consistent with the I-BmoI DNA-binding domain acting as a molecular anchor to tether the GIY-YIG domain to substrate, permitting rotation of the GIY-YIG domain to sequentially nick each DNA strand. These data highlight the mechanistic differences between monomeric GIY-HEs and dimeric or tetrameric GIY-YIG restriction enzymes, and they have implications for the use of the GIY-YIG domain in genome-editing applications.
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Affiliation(s)
- Benjamin P Kleinstiver
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada
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6
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Abstract
Targeted manipulation of complex genomes often requires the introduction of a double-strand break at defined locations by site-specific DNA endonucleases. Here, we describe a monomeric nuclease domain derived from GIY-YIG homing endonucleases for genome-editing applications. Fusion of the GIY-YIG nuclease domain to three-member zinc-finger DNA binding domains generated chimeric GIY-zinc finger endonucleases (GIY-ZFEs). Significantly, the I-TevI-derived fusions (Tev-ZFEs) function in vitro as monomers to introduce a double-strand break, and discriminate in vitro and in bacterial and yeast assays against substrates lacking a preferred 5'-CNNNG-3' cleavage motif. The Tev-ZFEs function to induce recombination in a yeast-based assay with activity on par with a homodimeric Zif268 zinc-finger nuclease. We also fused the I-TevI nuclease domain to a catalytically inactive LADGLIDADG homing endonuclease (LHE) scaffold. The monomeric Tev-LHEs are active in vivo and similarly discriminate against substrates lacking the 5'-CNNNG-3' motif. The monomeric Tev-ZFEs and Tev-LHEs are distinct from the FokI-derived zinc-finger nuclease and TAL effector nuclease platforms as the GIY-YIG domain alleviates the requirement to design two nuclease fusions to target a given sequence, highlighting the diversity of nuclease domains with distinctive biochemical properties suitable for genome-editing applications.
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Kleinstiver BP, Bérubé-Janzen W, Fernandes AD, Edgell DR. Divalent metal ion differentially regulates the sequential nicking reactions of the GIY-YIG homing endonuclease I-BmoI. PLoS One 2011; 6:e23804. [PMID: 21887323 PMCID: PMC3161791 DOI: 10.1371/journal.pone.0023804] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 07/26/2011] [Indexed: 01/30/2023] Open
Abstract
Homing endonucleases are site-specific DNA endonucleases that function as mobile genetic elements by introducing double-strand breaks or nicks at defined locations. Of the major families of homing endonucleases, the modular GIY-YIG endonucleases are least understood in terms of mechanism. The GIY-YIG homing endonuclease I-BmoI generates a double-strand break by sequential nicking reactions during which the single active site of the GIY-YIG nuclease domain must undergo a substantial reorganization. Here, we show that divalent metal ion plays a significant role in regulating the two independent nicking reactions by I-BmoI. Rate constant determination for each nicking reaction revealed that limiting divalent metal ion has a greater impact on the second strand than the first strand nicking reaction. We also show that substrate mutations within the I-BmoI cleavage site can modulate the first strand nicking reaction over a 314-fold range. Additionally, in-gel DNA footprinting with mutant substrates and modeling of an I-BmoI-substrate complex suggest that amino acid contacts to a critical GC-2 base pair are required to induce a bottom-strand distortion that likely directs conformational changes for reaction progress. Collectively, our data implies mechanistic roles for divalent metal ion and substrate bases, suggesting that divalent metal ion facilitates the re-positioning of the GIY-YIG nuclease domain between sequential nicking reactions.
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Affiliation(s)
- Benjamin P. Kleinstiver
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Wesley Bérubé-Janzen
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Andrew D. Fernandes
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
- Department of Applied Mathematics, The University of Western Ontario, London, Ontario, Canada
| | - David R. Edgell
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
- * E-mail:
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Robbins JB, Smith D, Belfort M. Redox-responsive zinc finger fidelity switch in homing endonuclease and intron promiscuity in oxidative stress. Curr Biol 2011; 21:243-8. [PMID: 21256016 DOI: 10.1016/j.cub.2011.01.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 12/10/2010] [Accepted: 01/04/2011] [Indexed: 12/24/2022]
Abstract
It is well understood how mobile introns home to allelic sites, but how they are stimulated to transpose to ectopic locations on an evolutionary timescale is unclear. Here we show that a group I intron can move to degenerate sites under oxidizing conditions. The phage T4 td intron endonuclease, I-TevI, is responsible for this infidelity. We demonstrate that I-TevI, which promotes mobility and is subject to autorepression and translational control, is also regulated posttranslationally by a redox mechanism. Redox regulation is exercised by a zinc finger (ZF) in a linker that connects the catalytic domain of I-TevI to the DNA binding domain. Four cysteines coordinate Zn(2+) in the ZF, which ensures that I-TevI cleaves its DNA substrate at a fixed distance, 23-25 nucleotides upstream of the intron insertion site. We show that the fidelity of I-TevI cleavage is controlled by redox-responsive Zn(2+) cycling. When the ZF is mutated, or after exposure of the wild-type I-TevI to H(2)O(2), intron homing to degenerate sites is increased, likely because of indiscriminate DNA cleavage. These results suggest a mechanism for rapid intron dispersal, joining recent descriptions of the activation of biomolecular processes by oxidative stress through cysteine chemistry.
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Affiliation(s)
- Justin B Robbins
- Wadsworth Center, New York State Department of Health, Center for Medical Science, 150 New Scotland Avenue, Albany, NY 12208, USA
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Edgell DR, Gibb EA, Belfort M. Mobile DNA elements in T4 and related phages. Virol J 2010; 7:290. [PMID: 21029434 PMCID: PMC2988022 DOI: 10.1186/1743-422x-7-290] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 10/28/2010] [Indexed: 12/30/2022] Open
Abstract
Mobile genetic elements are common inhabitants of virtually every genome where they can exert profound influences on genome structure and function in addition to promoting their own spread within and between genomes. Phage T4 and related phage have long served as a model system for understanding the molecular mechanisms by which a certain class of mobile DNA, homing endonucleases, promote their spread. Homing endonucleases are site-specific DNA endonucleases that initiate mobility by introducing double-strand breaks at defined positions in genomes lacking the endonuclease gene, stimulating repair and recombination pathways that mobilize the endonuclease coding region. In phage T4, homing endonucleases were first discovered as encoded within the self-splicing td, nrdB and nrdD introns of T4. Genomic data has revealed that homing endonucleases are extremely widespread in T-even-like phage, as evidenced by the astounding fact that ~11% of the T4 genome encodes homing endonuclease genes, with most of them located outside of self-splicing introns. Detailed studies of the mobile td intron and its encoded endonuclease, I-TevI, have laid the foundation for genetic, biochemical and structural aspects that regulate the mobility process, and more recently have provided insights into regulation of homing endonuclease function. Here, we summarize the current state of knowledge regarding T4-encoded homing endonucleases, with particular emphasis on the td/I-TevI model system. We also discuss recent progress in the biology of free-standing endonucleases, and present areas of future research for this fascinating class of mobile genetic elements.
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Affiliation(s)
- David R Edgell
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON N6A5C1, Canada.
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10
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Kleinstiver BP, Fernandes AD, Gloor GB, Edgell DR. A unified genetic, computational and experimental framework identifies functionally relevant residues of the homing endonuclease I-BmoI. Nucleic Acids Res 2010; 38:2411-27. [PMID: 20061372 PMCID: PMC2853131 DOI: 10.1093/nar/gkp1223] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 12/18/2009] [Accepted: 12/20/2009] [Indexed: 11/14/2022] Open
Abstract
Insight into protein structure and function is best obtained through a synthesis of experimental, structural and bioinformatic data. Here, we outline a framework that we call MUSE (mutual information, unigenic evolution and structure-guided elucidation), which facilitated the identification of previously unknown residues that are relevant for function of the GIY-YIG homing endonuclease I-BmoI. Our approach synthesizes three types of data: mutual information analyses that identify co-evolving residues within the GIY-YIG catalytic domain; a unigenic evolution strategy that identifies hyper- and hypo-mutable residues of I-BmoI; and interpretation of the unigenic and co-evolution data using a homology model. In particular, we identify novel positions within the GIY-YIG domain as functionally important. Proof-of-principle experiments implicate the non-conserved I71 as functionally relevant, with an I71N mutant accumulating a nicked cleavage intermediate. Moreover, many additional positions within the catalytic, linker and C-terminal domains of I-BmoI were implicated as important for function. Our results represent a platform on which to pursue future studies of I-BmoI and other GIY-YIG-containing proteins, and demonstrate that MUSE can successfully identify novel functionally critical residues that would be ignored in a traditional structure-function analysis within an extensively studied small domain of approximately 90 amino acids.
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Affiliation(s)
- Benjamin P. Kleinstiver
- Department of Biochemistry, Schulich School of Medicine & Dentistry and Department of Applied Mathematics, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Andrew D. Fernandes
- Department of Biochemistry, Schulich School of Medicine & Dentistry and Department of Applied Mathematics, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Gregory B. Gloor
- Department of Biochemistry, Schulich School of Medicine & Dentistry and Department of Applied Mathematics, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - David R. Edgell
- Department of Biochemistry, Schulich School of Medicine & Dentistry and Department of Applied Mathematics, The University of Western Ontario, London, ON N6A 5C1, Canada
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Marcaida MJ, Muñoz IG, Blanco FJ, Prieto J, Montoya G. Homing endonucleases: from basics to therapeutic applications. Cell Mol Life Sci 2010; 67:727-48. [PMID: 19915993 PMCID: PMC11115532 DOI: 10.1007/s00018-009-0188-y] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 10/16/2009] [Accepted: 10/19/2009] [Indexed: 10/20/2022]
Abstract
Homing endonucleases (HE) are double-stranded DNAses that target large recognition sites (12-40 bp). HE-encoding sequences are usually embedded in either introns or inteins. Their recognition sites are extremely rare, with none or only a few of these sites present in a mammalian-sized genome. However, these enzymes, unlike standard restriction endonucleases, tolerate some sequence degeneracy within their recognition sequence. Several members of this enzyme family have been used as templates to engineer tools to cleave DNA sequences that differ from their original wild-type targets. These custom HEs can be used to stimulate double-strand break homologous recombination in cells, to induce the repair of defective genes with very low toxicity levels. The use of tailored HEs opens up new possibilities for gene therapy in patients with monogenic diseases that can be treated ex vivo. This review provides an overview of recent advances in this field.
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Affiliation(s)
- Maria J. Marcaida
- Macromolecular Crystallography Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fdez. Almagro 3, 28029 Madrid, Spain
| | - Inés G. Muñoz
- Macromolecular Crystallography Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fdez. Almagro 3, 28029 Madrid, Spain
| | - Francisco J. Blanco
- Ikerbasque Professor Structural Biology Unit, CIC bioGUNE, Parque Tecnológico de Vizcaya, 48160 Derio, Spain
| | - Jesús Prieto
- Macromolecular Crystallography Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fdez. Almagro 3, 28029 Madrid, Spain
| | - Guillermo Montoya
- Macromolecular Crystallography Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fdez. Almagro 3, 28029 Madrid, Spain
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Affiliation(s)
- Marlene Belfort
- Wadsworth Center, New York State Department of Health, and University at Albany, The State University of New York, Center for Medical Science, Albany, New York 12208, USA.
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