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Sheykholeslami N, Mirzaei H, Nami Y, Khandaghi J, Javadi A. Ecological and evolutionary dynamics of CRISPR-Cas systems in Clostridium botulinum: Insights from genome mining and comparative analysis. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2024; 123:105638. [PMID: 39002873 DOI: 10.1016/j.meegid.2024.105638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Revised: 06/11/2024] [Accepted: 07/07/2024] [Indexed: 07/15/2024]
Abstract
Understanding the prevalence and distribution of CRISPR-Cas systems across different strains can illuminate the ecological and evolutionary dynamics of Clostridium botulinum populations. In this study, we conducted genome mining to characterize the CRISPR-Cas systems of C. botulinum strains. Our analysis involved retrieving complete genome sequences of these strains and assessing the diversity, prevalence, and evolution of their CRISPR-Cas systems. Subsequently, we performed an analysis of homology in spacer sequences from identified CRISPR arrays to investigate and characterize the range of targeted phages and plasmids. Additionally, we investigated the evolutionary trajectory of C. botulinum strains under selective pressures from foreign invasive DNA. Our findings revealed that 306 strains possessed complete CRISPR-Cas structures, comprising 58% of the studied C. botulinum strains. Secondary structure prediction of consensus repeats indicated that subtype II-C, with longer stems compared to subtypes ID and IB, tended to form more stable RNA secondary structures. Moreover, protospacer motif analysis demonstrated that strains with subtype IB CRISPR-Cas systems exhibited 5'-CGG-3', 5'-CC-3', and 5'-CAT-3' motifs in the 3' flanking regions of protospacers. The diversity observed in CRISPR-Cas systems indicated their classification into subtypes IB, ID, II-C, III-B, and III-D. Furthermore, our results showed that systems with subtype ID and III-D frequently harbored similar spacer patterns. Moreover, analysis of spacer sequences homology with phage and prophage genomes highlighted the specific activities exhibited by subtype IB and III-B against phages and plasmids, providing valuable insights into the functional specialization within these systems.
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Affiliation(s)
- Naiymeh Sheykholeslami
- Department of Food Hygiene, Faculty of Veterinary Medicine, Tabriz Medical Sciences, Islamic Azad University, Tabriz, Iran
| | - Hamid Mirzaei
- Department of Food Hygiene, Faculty of Veterinary Medicine, Tabriz Medical Sciences, Islamic Azad University, Tabriz, Iran; Department of food Biotechnology, Biotechnology Research Center, Tabriz Branch, Islamic Azad University, Tabriz, Iran.
| | - Yousef Nami
- Department of Food Biotechnology, Branch for Northwest & West Region, Agricultural Biotechnology Research, Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Tabriz, Iran.
| | - Jalil Khandaghi
- Department of food Biotechnology, Biotechnology Research Center, Tabriz Branch, Islamic Azad University, Tabriz, Iran; Department of Food Science and Technology, Sarab Branch, Islamic Azad University, Sarab, Iran
| | - Afshin Javadi
- Department of Food Hygiene, Faculty of Veterinary Medicine, Tabriz Medical Sciences, Islamic Azad University, Tabriz, Iran; Department of food Biotechnology, Biotechnology Research Center, Tabriz Branch, Islamic Azad University, Tabriz, Iran
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2
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Kovalev MA, Davletshin AI, Karpov DS. Engineering Cas9: next generation of genomic editors. Appl Microbiol Biotechnol 2024; 108:209. [PMID: 38353732 PMCID: PMC10866799 DOI: 10.1007/s00253-024-13056-y] [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: 06/13/2023] [Revised: 02/05/2024] [Accepted: 02/06/2024] [Indexed: 02/16/2024]
Abstract
The Cas9 endonuclease of the CRISPR/Cas type IIA system from Streptococcus pyogenes is the heart of genome editing technology that can be used to treat human genetic and viral diseases. Despite its large size and other drawbacks, S. pyogenes Cas9 remains the most widely used genome editor. A vast amount of research is aimed at improving Cas9 as a promising genetic therapy. Strategies include directed evolution of the Cas9 protein, rational design, and domain swapping. The first generation of Cas9 editors comes directly from the wild-type protein. The next generation is obtained by combining mutations from the first-generation variants, adding new mutations to them, or refining mutations. This review summarizes and discusses recent advances and ways in the creation of next-generation genomic editors derived from S. pyogenes Cas9. KEY POINTS: • The next-generation Cas9-based editors are more active than in the first one. • PAM-relaxed variants of Cas9 are improved by increased specificity and activity. • Less mutagenic and immunogenic variants of Cas9 are created.
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Affiliation(s)
- Maxim A Kovalev
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Str., 32, 119991, Moscow, Russia
- Department of Biology, Lomonosov Moscow State University, 119234, Moscow, Russia
| | - Artem I Davletshin
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Str., 32, 119991, Moscow, Russia
| | - Dmitry S Karpov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Str., 32, 119991, Moscow, Russia.
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov Str., 32, 119991, Moscow, Russia.
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3
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Teng Y, Wang J, Jiang T, Zou Y, Yan Y. Engineering a Streptococcus Cas9 Ortholog with an RxQ PAM-Binding Motif for PAM-Free Gene Control in Bacteria. ACS Synth Biol 2023; 12:2764-2772. [PMID: 37643152 PMCID: PMC10510713 DOI: 10.1021/acssynbio.3c00366] [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: 06/14/2023] [Indexed: 08/31/2023]
Abstract
The RNA-guided Cas9 endonucleases have revolutionized gene editing and regulation, but their targeting scope is limited by the protospacer adjacent motif (PAM) requirement. The most extensively used SpCas9 from Streptococcus pyogenes recognizes the NGG PAM via an RxR PAM-binding motif within its PAM-interaction (PI) domain. To overcome the strict PAM requirement, we identified and characterized a Cas9 ortholog from Streptococcus equinus HC5 (SeHCas9) that shows high sequence identity with SpCas9 but harbors a different RxQ PAM-binding motif. Complete PAM profiling revealed that SeHCas9 recognized an NAG PAM and accommodated NKG and NAW PAMs. We investigated the PAM interaction mechanism by identifying the crucial role of R1336 within the RxQ motif in determining PAM specificity, as well as the essentiality of two conserved residues (R1152 and Q1229) across Cas9 orthologs bearing the RxQ motif for PAM recognition. Further protein engineering created two variants, SeHdCas9-Q1229R and SeHdCas9-RR, that showed robust repression across an NNG and NNN PAM range, respectively. Our work proposes a novel Cas9 PAM interaction mechanism and establishes PAM-free Cas9 variants for bacterial gene control with almost no targeting restriction.
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Affiliation(s)
- Yuxi Teng
- School of Chemical, Materials
and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| | - Jian Wang
- School of Chemical, Materials
and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| | - Tian Jiang
- School of Chemical, Materials
and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| | - Yusong Zou
- School of Chemical, Materials
and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| | - Yajun Yan
- School of Chemical, Materials
and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, Georgia 30602, United States
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4
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Kenney CT, Marraffini LA. Rarely acquired type II-A CRISPR-Cas spacers mediate anti-viral immunity through the targeting of a non-canonical PAM sequence. Nucleic Acids Res 2023; 51:7438-7450. [PMID: 37293964 PMCID: PMC10415147 DOI: 10.1093/nar/gkad501] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 05/23/2023] [Accepted: 06/07/2023] [Indexed: 06/10/2023] Open
Abstract
The Streptococcus pyogenes type II-A CRISPR-Cas systems provides adaptive immunity through the acquisition of short DNA sequences from invading viral genomes, called spacers. Spacers are transcribed into short RNA guides that match regions of the viral genome followed by a conserved NGG DNA motif, known as the PAM. These RNA guides, in turn, are used by the Cas9 nuclease to find and destroy complementary DNA targets within the viral genome. While most of the spacers present in bacterial populations that survive phage infection target protospacers flanked by NGG sequences, there is a small fraction that target non-canonical PAMs. Whether these spacers originate through accidental acquisition of phage sequences and/or provide efficient defense is unknown. Here we found that many of them match phage target regions flanked by an NAGG PAM. Despite being scarcely present in bacterial populations, NAGG spacers provide substantial immunity in vivo and generate RNA guides that support robust DNA cleavage by Cas9 in vitro; with both activities comparable to spacers that target sequences followed by the canonical AGG PAM. In contrast, acquisition experiments showed that NAGG spacers are acquired at very low frequencies. We therefore conclude that discrimination against these sequences occurs during immunization of the host. Our results reveal unexpected differences in PAM recognition during the spacer acquisition and targeting stages of the type II-A CRISPR-Cas immune response.
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Affiliation(s)
- Claire T Kenney
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - Luciano A Marraffini
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
- Howard Hughes Medical Institute, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
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5
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Ittiprasert W, Moescheid MF, Chaparro C, Mann VH, Quack T, Rodpai R, Miller A, Wisitpongpun P, Buakaew W, Mentink-Kane M, Schmid S, Popratiloff A, Grevelding CG, Grunau C, Brindley PJ. Targeted insertion and reporter transgene activity at a gene safe harbor of the human blood fluke, Schistosoma mansoni. CELL REPORTS METHODS 2023; 3:100535. [PMID: 37533651 PMCID: PMC10391569 DOI: 10.1016/j.crmeth.2023.100535] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 05/22/2023] [Accepted: 06/25/2023] [Indexed: 08/04/2023]
Abstract
The identification and characterization of genomic safe harbor sites (GSHs) can facilitate consistent transgene activity with minimal disruption to the host cell genome. We combined computational genome annotation and chromatin structure analysis to predict the location of four GSHs in the human blood fluke, Schistosoma mansoni, a major infectious pathogen of the tropics. A transgene was introduced via CRISPR-Cas-assisted homology-directed repair into one of the GSHs in the egg of the parasite. Gene editing efficiencies of 24% and transgene-encoded fluorescence of 75% of gene-edited schistosome eggs were observed. The approach advances functional genomics for schistosomes by providing a tractable path for generating transgenics using homology-directed, repair-catalyzed transgene insertion. We also suggest that this work will serve as a roadmap for the development of similar approaches in helminths more broadly.
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Affiliation(s)
- Wannaporn Ittiprasert
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
| | - Max F. Moescheid
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
- Institute of Parasitology, Biomedical Research Center Seltersberg, Justus Liebig University Giessen, Giessen, Germany
| | - Cristian Chaparro
- IHPE, University of Perpignan Via Domitia, CNRS, IFREMER, University Montpellier, Perpignan, France
| | - Victoria H. Mann
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
| | - Thomas Quack
- Institute of Parasitology, Biomedical Research Center Seltersberg, Justus Liebig University Giessen, Giessen, Germany
| | - Rutchanee Rodpai
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
- Department of Parasitology and Excellence in Medical Innovation, and Technology Research Group, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - André Miller
- Schistosomiasis Resource Center, Biomedical Research Institute, Rockville, MD 20850, USA
| | - Prapakorn Wisitpongpun
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
- Faculty of Medical Technology, Rangsit University, Pathum Thani 12000, Thailand
| | - Watunyoo Buakaew
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
- Department of Microbiology, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand
| | - Margaret Mentink-Kane
- Schistosomiasis Resource Center, Biomedical Research Institute, Rockville, MD 20850, USA
| | - Sarah Schmid
- Schistosomiasis Resource Center, Biomedical Research Institute, Rockville, MD 20850, USA
| | - Anastas Popratiloff
- Nanofabrication and Imaging Center, Science & Engineering Hall, George Washington University, Washington, DC 20052, USA
| | - Christoph G. Grevelding
- Institute of Parasitology, Biomedical Research Center Seltersberg, Justus Liebig University Giessen, Giessen, Germany
| | - Christoph Grunau
- IHPE, University of Perpignan Via Domitia, CNRS, IFREMER, University Montpellier, Perpignan, France
| | - Paul J. Brindley
- Department of Microbiology, Immunology & Tropical Medicine, School of Medicine & Health Sciences, George Washington University, Washington, DC 20037, USA
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6
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Collias D, Vialetto E, Yu J, Co K, Almási ÉDH, Rüttiger AS, Achmedov T, Strowig T, Beisel CL. Systematically attenuating DNA targeting enables CRISPR-driven editing in bacteria. Nat Commun 2023; 14:680. [PMID: 36754958 PMCID: PMC9908933 DOI: 10.1038/s41467-023-36283-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 01/25/2023] [Indexed: 02/10/2023] Open
Abstract
Bacterial genome editing commonly relies on chromosomal cleavage with Cas nucleases to counter-select against unedited cells. However, editing normally requires efficient recombination and high transformation efficiencies, which are unavailable in most strains. Here, we show that systematically attenuating DNA targeting activity enables RecA-mediated repair in different bacteria, allowing chromosomal cleavage to drive genome editing. Attenuation can be achieved by altering the format or expression strength of guide (g)RNAs; using nucleases with reduced cleavage activity; or engineering attenuated gRNAs (atgRNAs) with disruptive hairpins, perturbed nuclease-binding scaffolds, non-canonical PAMs, or guide mismatches. These modifications greatly increase cell counts and even improve the efficiency of different types of edits for Cas9 and Cas12a in Escherichia coli and Klebsiella oxytoca. We further apply atgRNAs to restore ampicillin sensitivity in Klebsiella pneumoniae, establishing a resistance marker for genetic studies. Attenuating DNA targeting thus offers a counterintuitive means to achieve CRISPR-driven editing across bacteria.
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Affiliation(s)
- Daphne Collias
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 27695, Raleigh, NC, USA
| | - Elena Vialetto
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
| | - Jiaqi Yu
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
| | - Khoa Co
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
| | - Éva D H Almási
- Helmholtz Centre for Infection Research (HZI), 38124, Braunschweig, Germany
| | - Ann-Sophie Rüttiger
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
| | - Tatjana Achmedov
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany
| | - Till Strowig
- Helmholtz Centre for Infection Research (HZI), 38124, Braunschweig, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, Braunschweig, Germany
| | - Chase L Beisel
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany.
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 27695, Raleigh, NC, USA.
- Medical Faculty, University of Würzburg, 97080, Würzburg, Germany.
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7
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Hänggeli KPA, Hemphill A, Müller N, Schimanski B, Olias P, Müller J, Boubaker G. Single- and duplex TaqMan-quantitative PCR for determining the copy numbers of integrated selection markers during site-specific mutagenesis in Toxoplasma gondii by CRISPR-Cas9. PLoS One 2022; 17:e0271011. [PMID: 36112587 PMCID: PMC9481009 DOI: 10.1371/journal.pone.0271011] [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: 06/21/2022] [Accepted: 09/04/2022] [Indexed: 11/30/2022] Open
Abstract
Herein, we developed a single and a duplex TaqMan quantitative PCR (qPCR) for absolute quantification of copy numbers of integrated dihydrofolate reductase-thymidylate synthase (mdhfr-ts) drug selectable marker for pyrimethamine resistance in Toxoplasma gondii knockouts (KOs). The single TaqMan qPCR amplifies a 174 bp DNA fragment of the inserted mdhfr-ts and of the wild-type (WT) dhfr-ts (wtdhfr-ts) which is present as single copy gene in Toxoplasma and encodes a sensitive enzyme to pyrimethamine. Thus, the copy number of the dhfr-ts fragment in a given DNA quantity from KO parasites with a single site-specific integration should be twice the number of dhfr-ts copies recorded in the same DNA quantity from WT parasites. The duplex TaqMan qPCR allows simultaneous amplification of the 174 bp dhfr-ts fragment and the T. gondii 529-bp repeat element. Accordingly, for a WT DNA sample, the determined number of tachyzoites given by dhfr-ts amplification is equal to the number of tachyzoites determined by amplification of the Toxoplasma 529-bp, resulting thus in a ratio of 1. However, for a KO clone having a single site-specific integration of mdhfr-ts, the calculated ratio is 2. We then applied both approaches to test T. gondii RH mutants in which the major surface antigen (SAG1) was disrupted through insertion of mdhfr-ts using CRISPR-Cas9. Results from both assays were in correlation showing a high accuracy in detecting KOs with multiple integrated mdhfr-ts. Southern blot analyses using BsaBI and DraIII confirmed qPCRs results. Both TaqMan qPCRs are needed for reliable diagnostic of T. gondii KOs following CRISPR-Cas9-mediated mutagenesis, particularly with respect to off-target effects resulting from multiple insertions of mdhfr-ts. The principle of the duplex TaqMan qPCR is applicable for other selectable markers in Toxoplasma. TaqMan qPCR tools may contribute to more frequent use of WT Toxoplasma strains during functional genomics.
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Affiliation(s)
- Kai Pascal Alexander Hänggeli
- Department of Infectious Diseases and Pathobiology, Institute of Parasitology, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Andrew Hemphill
- Department of Infectious Diseases and Pathobiology, Institute of Parasitology, University of Bern, Bern, Switzerland
- * E-mail: (GB); (AH)
| | - Norbert Müller
- Department of Infectious Diseases and Pathobiology, Institute of Parasitology, University of Bern, Bern, Switzerland
| | - Bernd Schimanski
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Philipp Olias
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Joachim Müller
- Department of Infectious Diseases and Pathobiology, Institute of Parasitology, University of Bern, Bern, Switzerland
| | - Ghalia Boubaker
- Department of Infectious Diseases and Pathobiology, Institute of Parasitology, University of Bern, Bern, Switzerland
- * E-mail: (GB); (AH)
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8
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Kang M, Zuo Z, Yin Z, Gu J. Molecular Mechanism of D1135E-Induced Discriminated CRISPR-Cas9 PAM Recognition. J Chem Inf Model 2022; 62:3057-3066. [PMID: 35666156 DOI: 10.1021/acs.jcim.1c01562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The off-target effects of Streptococcus pyogenes Cas9 (SpCas9) pose a significant challenge to harness it as a therapeutical approach. Two major factors can result in SpCas9 off-targeting: tolerance to target DNA-guide RNA (gRNA) mismatch and less stringent recognition of protospacer adjacent motif (PAM) flanking the target DNA. Despite the abundance of engineered SpCas9-gRNA variants with improved sensitivity to target DNA-gRNA mismatch, studies focusing on enhancing SpCas9 PAM recognition stringency are quite few. A recent pioneering study identified a D1135E variant of SpCas9 that exhibits much-reduced editing activity at the noncanonical NAG/NGA PAM sites while preserving robust on-target activity at the canonical NGG-flanking sites (N is any nucleobase). Herein, we aim to clarify the molecular mechanism by which this single D1135E mutation confers on SpCas9 enhanced specificity for PAM recognition by molecular dynamics simulations. The results suggest that the variant maintains the base-specific recognition for the canonical NGG PAM via four hydrogen bonds, akin to that in the wild type (WT) SpCas9. While the noncanonical NAG PAM is engaged to the two PAM-interacting arginine residues (i.e., R1333 and R1335) in WT SpCas9 via two to three hydrogen bonds, the D1135E variant prefers to establish two hydrogen bonds with the PAM bases, accounting for its minimal editing activity on the off-target sites with an NAG PAM. The impaired NAG recognition by D1135E SpCas9 results from the PAM duplex displacement such that the hydrogen bond of R1333 to the second PAM base is disfavored. We further propose a mechanistic model to delineate how the mutation perturbs the noncanonical PAM recognition. We anticipate that the mechanistic knowledge could be leveraged for continuous optimization of SpCas9 PAM recognition specificity toward high-precision demanding applications.
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Affiliation(s)
- Minjie Kang
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
| | - Zhicheng Zuo
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
- Shanghai Frontiers Science Research Center for Druggability of Cardiovascular noncoding RNA, Institute for Frontier Medical Technology, Shanghai University of Engineering Science, Shanghai 201620, China
| | - Zhixiang Yin
- School of Mathematics, Physics and Statistics, Shanghai University of Engineering Science, Shanghai 201620, China
| | - Jianrong Gu
- Informatization Office, Shanghai University of Engineering Science, Shanghai 201620, China
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9
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Spacer prioritization in CRISPR-Cas9 immunity is enabled by the leader RNA. Nat Microbiol 2022; 7:530-541. [PMID: 35314780 PMCID: PMC7612570 DOI: 10.1038/s41564-022-01074-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 02/01/2022] [Indexed: 11/08/2022]
Abstract
CRISPR-Cas systems store fragments of foreign DNA called spacers as immunological recordings used to combat future infections. Of the many spacers stored in a CRISPR array, the newest spacers are known to be prioritized for immune defense. However, the underlying mechanism remains unclear. Here we show that the leader region upstream of CRISPR arrays in CRISPR-Cas9 systems enhances CRISPR RNA (crRNA) processing from the newest spacer, prioritizing defense against the matching invader. Using the CRISPR-Cas9 system from Streptococcus pyogenes as a model, we found that the transcribed leader interacts with the conserved repeats bordering the newest spacer. The resulting interaction promotes tracrRNA hybridization with the second repeat, accelerating crRNA processing. Accordingly, disrupting this structure reduces the abundance of the associated crRNA and immune defense against targeted plasmids and bacteriophages. Beyond the S. pyogenes system, bioinformatics analyses revealed that leader-repeat structures appear across CRISPR-Cas9 systems. CRISPR-Cas systems thus possess an RNA-based mechanism to prioritize defense against the most recently encountered invaders.
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10
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Yu SY, Birkenshaw A, Thomson T, Carlaw T, Zhang LH, Ross CJD. Increasing the Targeting Scope of CRISPR Base Editing System Beyond NGG. CRISPR J 2022; 5:187-202. [PMID: 35238621 DOI: 10.1089/crispr.2021.0109] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Genome editing provides a new therapeutic strategy to cure genetic diseases. The recently developed CRISPR-Cas9 base editing technology has shown great potential to repair the majority of pathogenic point mutations in the patient's DNA precisely. Base editor is the fusion of a Cas9 nickase with a base-modifying enzyme that can change a nucleotide on a single strand of DNA without generating double-stranded DNA breaks. However, a major limitation in applying such a system is the prerequisite of a protospacer adjacent motif sequence at the desired position relative to the target site. Progress has been made to increase the targeting scope of base editors by engineering SpCas9 protein variants, establishing systems with broadened editing windows, characterizing new SpCas9 orthologs, and developing prime editing technology. In this review, we discuss recent progress in the development of CRISPR base editing, focusing on its targeting scope, and we provide a workflow for selecting a suitable base editor based on the target nucleotide sequences.
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Affiliation(s)
- Si-Yue Yu
- Faculty of Pharmaceutical Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Alexandra Birkenshaw
- Faculty of Pharmaceutical Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Tyler Thomson
- Faculty of Pharmaceutical Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Tiffany Carlaw
- Department of Medical Genetics, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Lin-Hua Zhang
- Faculty of Pharmaceutical Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Colin J D Ross
- Faculty of Pharmaceutical Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
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11
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Wimmer F, Englert F, Beisel CL. A TXTL-Based Assay to Rapidly Identify PAMs for CRISPR-Cas Systems with Multi-Protein Effector Complexes. Methods Mol Biol 2022; 2433:391-411. [PMID: 34985758 DOI: 10.1007/978-1-0716-1998-8_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Type I CRISPR-Cas systems represent the most common and diverse type of these prokaryotic defense systems and are being harnessed for a growing set of applications. As these systems rely on multi-protein effector complexes, their characterization remains challenging. Here, we report a rapid and straightforward method to characterize these systems in a cell-free transcription-translation (TXTL) system. A ribonucleoprotein complex is produced and binds to its target next to a recognized PAM, thereby preventing the targeted sequence from being cleaved by a restriction enzyme. Selection for uncleaved targeted plasmids leads to an enrichment of recognized sequences within a PAM library. This assay will aid the exploration of CRISPR-Cas diversity and evolution and help contribute new systems for CRISPR technologies and applications.
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Affiliation(s)
- Franziska Wimmer
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz-Centre for Infection Research (HZI), Würzburg, Germany
| | - Frank Englert
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz-Centre for Infection Research (HZI), Würzburg, Germany
| | - Chase L Beisel
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz-Centre for Infection Research (HZI), Würzburg, Germany.
- Medical Faculty, University of Würzburg, Würzburg, Germany.
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12
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Zhang F, Huang Z. Mechanistic insights into the versatile class II CRISPR toolbox. Trends Biochem Sci 2021; 47:433-450. [PMID: 34920928 DOI: 10.1016/j.tibs.2021.11.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 11/12/2021] [Accepted: 11/23/2021] [Indexed: 12/15/2022]
Abstract
The constantly expanding group of class II CRISPR-Cas (clustered regularly interspaced short palindromic repeats-associated) effectors and their engineered variants exhibit distinct editing modes and efficiency, fidelity, target range, and molecular size. Their enormous diversity of capabilities provides a formidable toolkit for a large array of technologies. We review the structural and biochemical mechanisms of versatile effector proteins from class II CRISPR-Cas systems to provide mechanistic insights into their target specificity, protospacer adjacent motif (PAM) restriction, and activity regulation, and discuss possible strategies to enhance genome-engineering tools in terms of accuracy, efficiency, applicability, and controllability.
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Affiliation(s)
- Fan Zhang
- HIT Center for Life Sciences, School of Life Science and Technology, Harbin Institute of Technology, Harbin 150080, China
| | - Zhiwei Huang
- HIT Center for Life Sciences, School of Life Science and Technology, Harbin Institute of Technology, Harbin 150080, China.
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13
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Base editing-coupled survival screening enabled high-sensitive analysis of PAM compatibility and finding of the new possible off-target. iScience 2021; 24:102769. [PMID: 34337358 PMCID: PMC8324807 DOI: 10.1016/j.isci.2021.102769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/20/2021] [Accepted: 06/21/2021] [Indexed: 11/21/2022] Open
Abstract
Base editing (BE) is a promising genome engineering tool for modifying DNA or RNA and has been widely used in various microorganisms as well as eukaryotic cells. Despite the proximal protospacer adjacent motif (PAM) is critical to the targeting range and off-target effect of BE, there is still lack of a specific approach to analyze the PAM pattern in BE systems. Here, we developed a base editing-coupled survival screening method. Using dCas9 from Streptococcus pyogenes (SpdCas9) and its variants xdCas9 3.7 and dCas9 NG as example, their PAM patterns in BE systems were extensively characterized using the NNNN PAM library with high sensitivity. In addition to the typical PAM recognition features, we observed more unique PAMs exhibiting BE activity. These PAM patterns will boost the finding of potential off-target editing event arising from non-canonical PAMs and provide the guidelines for PAM usage in the BE system.
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14
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Rabinowitz R, Offen D. Single-Base Resolution: Increasing the Specificity of the CRISPR-Cas System in Gene Editing. Mol Ther 2021; 29:937-948. [PMID: 33248248 PMCID: PMC7938333 DOI: 10.1016/j.ymthe.2020.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 11/02/2020] [Accepted: 11/05/2020] [Indexed: 12/26/2022] Open
Abstract
The CRISPR-Cas system holds great promise in the treatment of diseases caused by genetic variations. The Cas protein, an RNA-guided programmable nuclease, generates a double-strand break at precise genomic loci. However, the use of the clustered regularly interspersed short palindromic repeats (CRISPR)-Cas system to distinguish between single-nucleotide variations is challenging. The promiscuity of the guide RNA (gRNA) and its mismatch tolerance make allele-specific targeting an elusive goal. This review presents a meta-analysis of previous studies reporting position-dependent mismatch tolerance within the gRNA. We also examine the conservativity of the seed sequence, a region within the gRNA with stringent sequence dependency, and propose the existence of a subregion within the seed sequence with a higher degree of specificity. In addition, we summarize the reports on high-fidelity Cas nucleases with improved specificity and compare the standard gRNA design methodology to the single-nucleotide polymorphism (SNP)-derived protospacer adjacent motif (PAM) approach, an alternative method for allele-specific targeting. The combination of the two methods may be advantageous in designing CRISPR-based therapeutics and diagnostics for heterozygous patients.
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Affiliation(s)
- Roy Rabinowitz
- Department of Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Felsenstein Medical Research Center, Tel Aviv University, Tel Aviv, Israel.
| | - Daniel Offen
- Department of Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Felsenstein Medical Research Center, Tel Aviv University, Tel Aviv, Israel.
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15
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Walton RT, Hsu JY, Joung JK, Kleinstiver BP. Scalable characterization of the PAM requirements of CRISPR-Cas enzymes using HT-PAMDA. Nat Protoc 2021; 16:1511-1547. [PMID: 33547443 PMCID: PMC8063866 DOI: 10.1038/s41596-020-00465-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/18/2020] [Indexed: 12/23/2022]
Abstract
The continued expansion of the genome-editing toolbox necessitates methods to characterize important properties of CRISPR-Cas enzymes. One such property is the requirement for Cas proteins to recognize a protospacer-adjacent motif (PAM) in DNA target sites. The high-throughput PAM determination assay (HT-PAMDA) is a method that enables scalable characterization of the PAM preferences of different Cas proteins. Here, we provide a step-by-step protocol for the method, discuss experimental design considerations, and highlight how the method can be used to profile naturally occurring CRISPR-Cas9 enzymes, engineered derivatives with improved properties, orthologs of different classes (e.g., Cas12a), and even different platforms (e.g., base editors). A distinguishing feature of HT-PAMDA is that the enzymes are expressed in a cell type or organism of interest (e.g., mammalian cells), permitting scalable characterization and comparison of hundreds of enzymes in a relevant setting. HT-PAMDA does not require specialized equipment or expertise and is cost effective for multiplexed characterization of many enzymes. The protocol enables comprehensive PAM characterization of dozens or hundreds of Cas enzymes in parallel in <2 weeks.
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Affiliation(s)
- Russell T Walton
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Jonathan Y Hsu
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Molecular Pathology Unit, Center for Cancer Research and Center for Computational and Integrative Biology, Massachusetts General Hospital, Charlestown, MA, USA
- Department of Pathology, Harvard Medical School, Boston, MA, USA
| | - J Keith Joung
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA
- Molecular Pathology Unit, Center for Cancer Research and Center for Computational and Integrative Biology, Massachusetts General Hospital, Charlestown, MA, USA
- Department of Pathology, Harvard Medical School, Boston, MA, USA
| | - Benjamin P Kleinstiver
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA.
- Department of Pathology, Massachusetts General Hospital, Boston, MA, USA.
- Department of Pathology, Harvard Medical School, Boston, MA, USA.
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16
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Collias D, Beisel CL. CRISPR technologies and the search for the PAM-free nuclease. Nat Commun 2021; 12:555. [PMID: 33483498 PMCID: PMC7822910 DOI: 10.1038/s41467-020-20633-y] [Citation(s) in RCA: 132] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/03/2020] [Indexed: 12/20/2022] Open
Abstract
The ever-expanding set of CRISPR technologies and their programmable RNA-guided nucleases exhibit remarkable flexibility in DNA targeting. However, this flexibility comes with an ever-present constraint: the requirement for a protospacer adjacent motif (PAM) flanking each target. While PAMs play an essential role in self/nonself discrimination by CRISPR-Cas immune systems, this constraint has launched a far-reaching expedition for nucleases with relaxed PAM requirements. Here, we review ongoing efforts toward realizing PAM-free nucleases through natural ortholog mining and protein engineering. We also address potential consequences of fully eliminating PAM recognition and instead propose an alternative nuclease repertoire covering all possible PAM sequences.
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Affiliation(s)
- Daphne Collias
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA
| | - Chase L Beisel
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA.
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz Centre for Infection Research (HZI), 97080, Würzburg, Germany.
- Medical Faculty, University of Würzburg, 97080, Würzburg, Germany.
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17
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Goldberg GW, Spencer JM, Giganti DO, Camellato BR, Agmon N, Ichikawa DM, Boeke JD, Noyes MB. Engineered dual selection for directed evolution of SpCas9 PAM specificity. Nat Commun 2021; 12:349. [PMID: 33441553 PMCID: PMC7807044 DOI: 10.1038/s41467-020-20650-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 11/18/2020] [Indexed: 12/26/2022] Open
Abstract
The widely used Streptococcus pyogenes Cas9 (SpCas9) nuclease derives its DNA targeting specificity from protein-DNA contacts with protospacer adjacent motif (PAM) sequences, in addition to base-pairing interactions between its guide RNA and target DNA. Previous reports have established that the PAM specificity of SpCas9 can be altered via positive selection procedures for directed evolution or other protein engineering strategies. Here we exploit in vivo directed evolution systems that incorporate simultaneous positive and negative selection to evolve SpCas9 variants with commensurate or improved activity on NAG PAMs relative to wild type and reduced activity on NGG PAMs, particularly YGG PAMs. We also show that the PAM preferences of available evolutionary intermediates effectively determine whether similar counterselection PAMs elicit different selection stringencies, and demonstrate that negative selection can be specifically increased in a yeast selection system through the fusion of compensatory zinc fingers to SpCas9.
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Affiliation(s)
- Gregory W Goldberg
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA.
| | - Jeffrey M Spencer
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - David O Giganti
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Brendan R Camellato
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Neta Agmon
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
- Neochromosome, Inc., Alexandria Center for Life Science, New York, NY, 10016, USA
| | - David M Ichikawa
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Jef D Boeke
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
- Department of Biomedical Engineering, NYU Tandon School of Engineering, Brooklyn, NY, 11201, USA
| | - Marcus B Noyes
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA.
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18
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Malcı K, Walls LE, Rios-Solis L. Multiplex Genome Engineering Methods for Yeast Cell Factory Development. Front Bioeng Biotechnol 2020; 8:589468. [PMID: 33195154 PMCID: PMC7658401 DOI: 10.3389/fbioe.2020.589468] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/07/2020] [Indexed: 12/12/2022] Open
Abstract
As biotechnological applications of synthetic biology tools including multiplex genome engineering are expanding rapidly, the construction of strategically designed yeast cell factories becomes increasingly possible. This is largely due to recent advancements in genome editing methods like CRISPR/Cas tech and high-throughput omics tools. The model organism, baker's yeast (Saccharomyces cerevisiae) is an important synthetic biology chassis for high-value metabolite production. Multiplex genome engineering approaches can expedite the construction and fine tuning of effective heterologous pathways in yeast cell factories. Numerous multiplex genome editing techniques have emerged to capitalize on this recently. This review focuses on recent advancements in such tools, such as delta integration and rDNA cluster integration coupled with CRISPR-Cas tools to greatly enhance multi-integration efficiency. Examples of pre-placed gate systems which are an innovative alternative approach for multi-copy gene integration were also reviewed. In addition to multiple integration studies, multiplexing of alternative genome editing methods are also discussed. Finally, multiplex genome editing studies involving non-conventional yeasts and the importance of automation for efficient cell factory design and construction are considered. Coupling the CRISPR/Cas system with traditional yeast multiplex genome integration or donor DNA delivery methods expedites strain development through increased efficiency and accuracy. Novel approaches such as pre-placing synthetic sequences in the genome along with improved bioinformatics tools and automation technologies have the potential to further streamline the strain development process. In addition, the techniques discussed to engineer S. cerevisiae, can be adapted for use in other industrially important yeast species for cell factory development.
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Affiliation(s)
- Koray Malcı
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
| | - Laura E Walls
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
| | - Leonardo Rios-Solis
- Institute for Bioengineering, School of Engineering, The University of Edinburgh, Edinburgh, United Kingdom.,Centre for Synthetic and Systems Biology (SynthSys), The University of Edinburgh, Edinburgh, United Kingdom
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