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Villegas Kcam MC, Tsong AJ, Chappell J. Rational engineering of a modular bacterial CRISPR-Cas activation platform with expanded target range. Nucleic Acids Res 2021; 49:4793-4802. [PMID: 33823546 PMCID: PMC8096225 DOI: 10.1093/nar/gkab211] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 03/10/2021] [Accepted: 03/19/2021] [Indexed: 11/14/2022] Open
Abstract
CRISPR-Cas activator (CRISPRa) systems that selectively turn on transcription of a target gene are a potentially transformative technology for programming cellular function. While in eukaryotes versatile CRISPRa systems exist, in bacteria these systems suffer from a limited ability to activate different genes due to strict distance-dependent requirements of functional target binding sites, and require greater customization to optimize performance in different genetic and cellular contexts. To address this, we apply a rational protein engineering approach to create a new CRISPRa platform that is highly modular to allow for easy customization and has increased targeting flexibility through harnessing engineered Cas proteins. We first demonstrate that transcription activation domains can be recruited by CRISPR-Cas through noncovalent protein-protein interactions, which allows each component to be encoded on separate and easily interchangeable plasmid elements. We then exploit this modularity to rapidly screen a library of different activation domains, creating new systems with distinct regulatory properties. Furthermore, we demonstrate that by harnessing a library of circularly permuted Cas proteins, we can create CRISPRa systems that have different target binding site requirements, which together, allow for expanded target range.
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Affiliation(s)
| | - Annette J Tsong
- Department of BioSciences, Rice University, 6100 Main Street, MS 140, Houston, TX 77005, USA
| | - James Chappell
- Department of BioSciences, Rice University, 6100 Main Street, MS 140, Houston, TX 77005, USA
- Department of Bioengineering, Rice University, 6100 Main Street, MS 142, Houston, TX 77005, USA
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Graf M, Haas T, Müller F, Buchmann A, Harm-Bekbenbetova J, Freund A, Nieß A, Persicke M, Kalinowski J, Blombach B, Takors R. Continuous Adaptive Evolution of a Fast-Growing Corynebacterium glutamicum Strain Independent of Protocatechuate. Front Microbiol 2019; 10:1648. [PMID: 31447790 PMCID: PMC6691914 DOI: 10.3389/fmicb.2019.01648] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 07/03/2019] [Indexed: 12/30/2022] Open
Abstract
Corynebacterium glutamicum is a commonly applied host for the industrial production of amino acids. While valued for its robustness, it is somewhat inferior to competing strains such as Escherichia coli because of the relatively low growth rate of 0.40 h−1 in synthetic, industrial media. Accordingly, adaptive laboratory evolution (ALE) experiments were performed in continuous cultivation mode to select for a growth-improved host. To ensure industrial attractiveness, this ALE study aimed at a reduction of dependency on costly growth-boosting additives such as protocatechuate (PCA) or complex media supplements. Consequently, double selection pressures were installed consisting of a steady increase in growth rate demands and a parallel reduction of complex medium fractions. Selection yielded C. glutamicum EVO5 achieving 0.54 h−1 and 1.03 gGlc gCDW−1 h−1 in minimal medium without abovementioned supplements. Sequencing revealed 10 prominent mutations, three of them in key regulator genes.
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Affiliation(s)
- Michaela Graf
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Thorsten Haas
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Felix Müller
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Anina Buchmann
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | | | - Andreas Freund
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Alexander Nieß
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Marcus Persicke
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany
| | - Jörn Kalinowski
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany
| | - Bastian Blombach
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany.,Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Straubing, Germany
| | - Ralf Takors
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
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