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Becker NA, Peters JP, Lewis E, Daby CL, Clark K, Maher LJ. Engineered transcription activator-like effector dimer proteins confer DNA loop-dependent gene repression comparable to Lac repressor. Nucleic Acids Res 2024:gkae656. [PMID: 39077947 DOI: 10.1093/nar/gkae656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 07/06/2024] [Accepted: 07/16/2024] [Indexed: 07/31/2024] Open
Abstract
Natural prokaryotic gene repression systems often exploit DNA looping to increase the local concentration of gene repressor proteins at a regulated promoter via contributions from repressor proteins bound at distant sites. Using principles from the Escherichia coli lac operon we design analogous repression systems based on target sequence-programmable Transcription Activator-Like Effector dimer (TALED) proteins. Such engineered switches may be valuable for synthetic biology and therapeutic applications. Previous TALEDs with inducible non-covalent dimerization showed detectable, but limited, DNA loop-based repression due to the repressor protein dimerization equilibrium. Here, we show robust DNA loop-dependent bacterial promoter repression by covalent TALEDs and verify that DNA looping dramatically enhances promoter repression in E. coli. We characterize repression using a thermodynamic model that quantitates this favorable contribution of DNA looping. This analysis unequivocally and quantitatively demonstrates that optimized TALED proteins can drive loop-dependent promoter repression in E. coli comparable to the natural LacI repressor system. This work elucidates key design principles that set the stage for wide application of TALED-dependent DNA loop-based repression of target genes.
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Affiliation(s)
- Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Justin P Peters
- Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, IA 50614, USA
| | - Elizabeth Lewis
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Camden L Daby
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Karl Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
- Department of Animal Science, Texas A&M University, College Station, TX 77843, USA
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
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Tse DH, Becker NA, Young RT, Olson WK, Peters JP, Schwab TL, Clark KJ, Maher LJ. Designed architectural proteins that tune DNA looping in bacteria. Nucleic Acids Res 2021; 49:10382-10396. [PMID: 34478548 PMCID: PMC8501960 DOI: 10.1093/nar/gkab759] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/17/2021] [Accepted: 08/23/2021] [Indexed: 11/28/2022] Open
Abstract
Architectural proteins alter the shape of DNA. Some distort the double helix by introducing sharp kinks. This can serve to relieve strain in tightly-bent DNA structures. Here, we design and test artificial architectural proteins based on a sequence-specific Transcription Activator-like Effector (TALE) protein, either alone or fused to a eukaryotic high mobility group B (HMGB) DNA-bending domain. We hypothesized that TALE protein binding would stiffen DNA to bending and twisting, acting as an architectural protein that antagonizes the formation of small DNA loops. In contrast, fusion to an HMGB domain was hypothesized to generate a targeted DNA-bending architectural protein that facilitates DNA looping. We provide evidence from Escherichia coli Lac repressor gene regulatory loops supporting these hypotheses in living bacteria. Both data fitting to a thermodynamic DNA looping model and sophisticated molecular modeling support the interpretation of these results. We find that TALE protein binding inhibits looping by stiffening DNA to bending and twisting, while the Nhp6A domain enhances looping by bending DNA without introducing twisting flexibility. Our work illustrates artificial approaches to sculpt DNA geometry with functional consequences. Similar approaches may be applicable to tune the stability of small DNA loops in eukaryotes.
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Affiliation(s)
- David H Tse
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - Nicole A Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - Robert T Young
- Department of Chemistry and Chemical Biology, Rutgers, the State University of New Jersey, Center for Quantitative Biology, Piscataway, NJ 08854, USA
| | - Wilma K Olson
- Department of Chemistry and Chemical Biology, Rutgers, the State University of New Jersey, Center for Quantitative Biology, Piscataway, NJ 08854, USA
| | - Justin P Peters
- Department of Chemistry and Biochemistry, University of Northern Iowa, 1227 West 27th Street, Cedar Falls, IA 50614, USA
| | - Tanya L Schwab
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - Karl J Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, 200 First St. SW, Rochester, MN 55905, USA
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