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George JT, Acree C, Park JU, Kong M, Wiegand T, Pignot YL, Kellogg EH, Greene EC, Sternberg SH. Mechanism of target site selection by type V-K CRISPR-associated transposases. Science 2023; 382:eadj8543. [PMID: 37972161 PMCID: PMC10771339 DOI: 10.1126/science.adj8543] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/23/2023] [Indexed: 11/19/2023]
Abstract
CRISPR-associated transposases (CASTs) repurpose nuclease-deficient CRISPR effectors to catalyze RNA-guided transposition of large genetic payloads. Type V-K CASTs offer potential technology advantages but lack accuracy, and the molecular basis for this drawback has remained elusive. Here, we reveal that type V-K CASTs maintain an RNA-independent, "untargeted" transposition pathway alongside RNA-dependent integration, driven by the local availability of TnsC filaments. Using cryo-electron microscopy, single-molecule experiments, and high-throughput sequencing, we found that a minimal, CRISPR-less transpososome preferentially directs untargeted integration at AT-rich sites, with additional local specificity imparted by TnsB. By exploiting this knowledge, we suppressed untargeted transposition and increased type V-K CAST specificity up to 98.1% in cells without compromising on-target integration efficiency. These findings will inform further engineering of CAST systems for accurate, kilobase-scale genome engineering applications.
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Affiliation(s)
- Jerrin Thomas George
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Christopher Acree
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Jung-Un Park
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Muwen Kong
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Tanner Wiegand
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Yanis Luca Pignot
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Elizabeth H. Kellogg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Eric C. Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Samuel H. Sternberg
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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George JT, Acree C, Park JU, Kong M, Wiegand T, Pignot YL, Kellogg EH, Greene EC, Sternberg SH. Mechanism of target site selection by type V-K CRISPR-associated transposases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.14.548620. [PMID: 37503092 PMCID: PMC10370016 DOI: 10.1101/2023.07.14.548620] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Unlike canonical CRISPR-Cas systems that rely on RNA-guided nucleases for target cleavage, CRISPR-associated transposases (CASTs) repurpose nuclease-deficient CRISPR effectors to facilitate RNA-guided transposition of large genetic payloads. Type V-K CASTs offer several potential upsides for genome engineering, due to their compact size, easy programmability, and unidirectional integration. However, these systems are substantially less accurate than type I-F CASTs, and the molecular basis for this difference has remained elusive. Here we reveal that type V-K CASTs undergo two distinct mobilization pathways with remarkably different specificities: RNA-dependent and RNA-independent transposition. Whereas RNA-dependent transposition relies on Cas12k for accurate target selection, RNA-independent integration events are untargeted and primarily driven by the local availability of TnsC filaments. The cryo-EM structure of the untargeted complex reveals a TnsB-TnsC-TniQ transpososome that encompasses two turns of a TnsC filament and otherwise resembles major architectural aspects of the Cas12k-containing transpososome. Using single-molecule experiments and genome-wide meta-analyses, we found that AT-rich sites are preferred substrates for untargeted transposition and that the TnsB transposase also imparts local specificity, which collectively determine the precise insertion site. Knowledge of these motifs allowed us to direct untargeted transposition events to specific hotspot regions of a plasmid. Finally, by exploiting TnsB's preference for on-target integration and modulating the availability of TnsC, we suppressed RNA-independent transposition events and increased type V-K CAST specificity up to 98.1%, without compromising the efficiency of on-target integration. Collectively, our results reveal the importance of dissecting target site selection mechanisms and highlight new opportunities to leverage CAST systems for accurate, kilobase-scale genome engineering applications.
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Affiliation(s)
- Jerrin Thomas George
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Christopher Acree
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Present address: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212, USA
| | - Jung-Un Park
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
- Future address: Department of Structural Biology. St Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Muwen Kong
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Tanner Wiegand
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Yanis Luca Pignot
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Present address: Department of Biochemistry, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Elizabeth H. Kellogg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
- Future address: Department of Structural Biology. St Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Eric C. Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Samuel H. Sternberg
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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Righini M, Costa J, Zhou W. DNA bridges: A novel platform for single-molecule sequencing and other DNA-protein interaction applications. PLoS One 2021; 16:e0260428. [PMID: 34807931 PMCID: PMC8608331 DOI: 10.1371/journal.pone.0260428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 11/10/2021] [Indexed: 01/22/2023] Open
Abstract
DNA molecular combing is a technique that stretches thousands of long individual DNA molecules (up to 10 Mbp) into a parallel configuration on surface. It has previously been proposed to sequence these molecules by synthesis. However, this approach poses two critical challenges: 1-Combed DNA molecules are overstretched and therefore a nonoptimal substrate for polymerase extension. 2-The combing surface sterically impedes full enzymatic access to the DNA backbone. Here, we introduce a novel approach that attaches thousands of molecules to a removable surface, with a tunable stretching factor. Next, we dissolve portions of the surface, leaving the DNA molecules suspended as 'bridges'. We demonstrate that the suspended molecules are enzymatically accessible, and we have used an enzyme to incorporate labeled nucleotides, as predicted by the specific molecular sequence. Our results suggest that this novel platform is a promising candidate to achieve high-throughput sequencing of Mbp-long molecules, which could have additional genomic applications, such as the study of other protein-DNA interactions.
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Affiliation(s)
- Maurizio Righini
- Department of Advanced Research and Development, Centrillion Technologies, Palo Alto, California, United States of America
| | - Justin Costa
- Department of Advanced Research and Development, Centrillion Technologies, Palo Alto, California, United States of America
| | - Wei Zhou
- Department of Advanced Research and Development, Centrillion Technologies, Palo Alto, California, United States of America
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Roy U, Kwon Y, Sung P, Greene EC. Single-molecule studies of yeast Rad51 paralogs. Methods Enzymol 2021; 661:343-362. [PMID: 34776219 DOI: 10.1016/bs.mie.2021.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Homologous recombination (HR) is a conserved mechanism essential for the accurate repair of DNA double stranded breaks and the exchange of genetic information during meiosis. The key steps in HR are carried out by the RecA/Rad51 class of recombinases, which form a helical filament on single-stranded DNA (ssDNA) and catalyze homology search and strand exchange with a complementary duplex DNA target. In eukaryotes, assembly of the Rad51-ssDNA filament requires regulatory factors called mediators, including Rad51 paralogs. A mechanistic understanding of the role of Rad51 paralogs in HR has been hampered by the transient and diverse nature of intermediates formed with the Rad51-ssDNA filament, which cannot be resolved by traditional ensemble methods. The biochemical characterization of Rad51 paralogs, including the S. cerevisiae complex Rad55-Rad57 has also been limited by their propensity to aggregate. Here we describe the preparation of monodisperse GFP-tagged Rad55-Rad57 complex and the methodology for its analysis in our single-molecule DNA curtain assay.
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Affiliation(s)
- Upasana Roy
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, United States
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, TX, United States
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, TX, United States
| | - Eric C Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, United States.
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Kinetics of DNA Repair in Vicia faba Meristem Regeneration Following Replication Stress. Cells 2021; 10:cells10010088. [PMID: 33430297 PMCID: PMC7825715 DOI: 10.3390/cells10010088] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/29/2020] [Accepted: 01/04/2021] [Indexed: 12/14/2022] Open
Abstract
The astonishing survival abilities of Vicia faba, one the earliest domesticated plants, are associated, among other things, to the highly effective replication stress response system which ensures smooth cell division and proper preservation of genomic information. The most crucial pathway here seems to be the ataxia telangiectasia-mutated kinase (ATM)/ataxia telangiectasia and Rad3-related kinase (ATR)-dependent replication stress response mechanism, also present in humans. In this article, we attempted to take an in-depth look at the dynamics of regeneration from the effects of replication inhibition and cell cycle checkpoint overriding causing premature chromosome condensation (PCC) in terms of DNA damage repair and changes in replication dynamics. We were able to distinguish a unique behavior of replication factors at the very start of the regeneration process in the PCC-induced cells. We extended the experiment and decided to profile the changes in replication on the level of a single replication cluster of heterochromatin (both alone and with regard to its position in the nucleus), including the mathematical profiling of the size, activity and shape. The results obtained during these experiments led us to the conclusion that even “chaotic” events are dealt with in a proper degree of order.
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