1
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Luna R, Gómez-González B, Aguilera A. RNA biogenesis and RNA metabolism factors as R-loop suppressors: a hidden role in genome integrity. Genes Dev 2024; 38:504-527. [PMID: 38986581 PMCID: PMC11293400 DOI: 10.1101/gad.351853.124] [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] [Indexed: 07/12/2024]
Abstract
Genome integrity relies on the accuracy of DNA metabolism, but as appreciated for more than four decades, transcription enhances mutation and recombination frequencies. More recent research provided evidence for a previously unforeseen link between RNA and DNA metabolism, which is often related to the accumulation of DNA-RNA hybrids and R-loops. In addition to physiological roles, R-loops interfere with DNA replication and repair, providing a molecular scenario for the origin of genome instability. Here, we review current knowledge on the multiple RNA factors that prevent or resolve R-loops and consequent transcription-replication conflicts and thus act as modulators of genome dynamics.
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Affiliation(s)
- Rosa Luna
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Belén Gómez-González
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Andrés Aguilera
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain;
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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2
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Reginato G, Dello Stritto MR, Wang Y, Hao J, Pavani R, Schmitz M, Halder S, Morin V, Cannavo E, Ceppi I, Braunshier S, Acharya A, Ropars V, Charbonnier JB, Jinek M, Nussenzweig A, Ha T, Cejka P. HLTF disrupts Cas9-DNA post-cleavage complexes to allow DNA break processing. Nat Commun 2024; 15:5789. [PMID: 38987539 PMCID: PMC11237066 DOI: 10.1038/s41467-024-50080-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: 01/31/2024] [Accepted: 06/28/2024] [Indexed: 07/12/2024] Open
Abstract
The outcome of CRISPR-Cas-mediated genome modifications is dependent on DNA double-strand break (DSB) processing and repair pathway choice. Homology-directed repair (HDR) of protein-blocked DSBs requires DNA end resection that is initiated by the endonuclease activity of the MRE11 complex. Using reconstituted reactions, we show that Cas9 breaks are unexpectedly not directly resectable by the MRE11 complex. In contrast, breaks catalyzed by Cas12a are readily processed. Cas9, unlike Cas12a, bridges the broken ends, preventing DSB detection and processing by MRE11. We demonstrate that Cas9 must be dislocated after DNA cleavage to allow DNA end resection and repair. Using single molecule and bulk biochemical assays, we next find that the HLTF translocase directly removes Cas9 from broken ends, which allows DSB processing by DNA end resection or non-homologous end-joining machineries. Mechanistically, the activity of HLTF requires its HIRAN domain and the release of the 3'-end generated by the cleavage of the non-target DNA strand by the Cas9 RuvC domain. Consequently, HLTF removes the H840A but not the D10A Cas9 nickase. The removal of Cas9 H840A by HLTF explains the different cellular impact of the two Cas9 nickase variants in human cells, with potential implications for gene editing.
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Affiliation(s)
- Giordano Reginato
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Maria Rosaria Dello Stritto
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Yanbo Wang
- Department of Biophysics & Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, 21205, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jingzhou Hao
- Department of Biophysics, Johns Hopkins University, Baltimore, MD21218, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Raphael Pavani
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Michael Schmitz
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Swagata Halder
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
- Biological Systems Engineering, Plaksha University, Mohali, Punjab, 140306, India
| | - Vincent Morin
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Elda Cannavo
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Ilaria Ceppi
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Stefan Braunshier
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Ananya Acharya
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland
| | - Virginie Ropars
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Jean-Baptiste Charbonnier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Martin Jinek
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
| | - Andrè Nussenzweig
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Taekjip Ha
- Department of Biophysics & Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, 21205, USA
- Department of Biophysics, Johns Hopkins University, Baltimore, MD21218, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, 02115, USA
- Department of Pediatrics, Harvard Medical School, Boston, MA, 02115, USA
- Howard Hughes Medical Institute, Boston, MA, 02115, USA
| | - Petr Cejka
- Faculty of Biomedical Sciences, Institute for Research in Biomedicine, Università della Svizzera italiana (USI), 6500, Bellinzona, Switzerland.
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3
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Hegedus L, Toth A, Harami GM, Palinkas J, Karatayeva N, Sajben-Nagy E, Bene S, Afzali Jaktajdinani S, Kovacs M, Juhasz S, Burkovics P. Werner helicase interacting protein 1 contributes to G-quadruplex processing in human cells. Sci Rep 2024; 14:15740. [PMID: 38977862 PMCID: PMC11231340 DOI: 10.1038/s41598-024-66425-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: 04/25/2024] [Accepted: 07/01/2024] [Indexed: 07/10/2024] Open
Abstract
Genome replication is frequently impeded by highly stable DNA secondary structures, including G-quadruplex (G4) DNA, that can hinder the progression of the replication fork. Human WRNIP1 (Werner helicase Interacting Protein 1) associates with various components of the replication machinery and plays a crucial role in genome maintenance processes. However, its detailed function is still not fully understood. Here we show that human WRNIP1 interacts with G4 structures and provide evidence for its contribution to G4 processing. The absence of WRNIP1 results in elevated levels of G4 structures, DNA damage and chromosome aberrations following treatment with PhenDC3, a G4-stabilizing ligand. Additionally, we establish a functional and physical relationship between WRNIP1 and the PIF1 helicase in G4 processing. In summary, our results suggest that WRNIP1 aids genome replication and maintenance by regulating G4 processing and this activity relies on Pif1 DNA helicase.
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Affiliation(s)
- Lili Hegedus
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
| | - Agnes Toth
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Gabor M Harami
- ELTE-MTA Momentum Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
- Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Janos Palinkas
- ELTE-MTA Momentum Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Nargis Karatayeva
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Eniko Sajben-Nagy
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
| | - Szabolcs Bene
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
| | - Sara Afzali Jaktajdinani
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary
- Doctoral School of Biology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Mihaly Kovacs
- ELTE-MTA Momentum Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
- HUN-REN-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Szilvia Juhasz
- HCEMM Cancer Microbiome Core Group, Szeged, Hungary.
- Institute of Biochemistry, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary.
| | - Peter Burkovics
- Institute of Genetics, Biological Research Centre, HUN-REN Szeged, Szeged, Hungary.
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4
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Liu Z, van Veen E, Sánchez H, Solano B, Palmero Moya FJ, McCluskey KA, Ramírez Montero D, van Laar T, Dekker NH. A Biophysics Toolbox for Reliable Data Acquisition and Processing in Integrated Force-Confocal Fluorescence Microscopy. ACS PHOTONICS 2024; 11:1592-1603. [PMID: 38645993 PMCID: PMC11027178 DOI: 10.1021/acsphotonics.3c01739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 03/01/2024] [Accepted: 03/01/2024] [Indexed: 04/23/2024]
Abstract
Integrated single-molecule force-fluorescence spectroscopy setups allow for simultaneous fluorescence imaging and mechanical force manipulation and measurements on individual molecules, providing comprehensive dynamic and spatiotemporal information. Dual-beam optical tweezers (OT) combined with a confocal scanning microscope form a force-fluorescence spectroscopy apparatus broadly used to investigate various biological processes, in particular, protein:DNA interactions. Such experiments typically involve imaging of fluorescently labeled proteins bound to DNA and force spectroscopy measurements of trapped individual DNA molecules. Here, we present a versatile state-of-the-art toolbox including the preparation of protein:DNA complex samples, design of a microfluidic flow cell incorporated with OT, automation of OT-confocal scanning measurements, and the development and implementation of a streamlined data analysis package for force and fluorescence spectroscopy data processing. Its components can be adapted to any commercialized or home-built dual-beam OT setup equipped with a confocal scanning microscope, which will facilitate single-molecule force-fluorescence spectroscopy studies on a large variety of biological systems.
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Affiliation(s)
- Zhaowei Liu
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Edo van Veen
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Humberto Sánchez
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Belén Solano
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Francisco J. Palmero Moya
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Kaley A. McCluskey
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Daniel Ramírez Montero
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Theo van Laar
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Nynke H. Dekker
- Department
of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Clarendon
Laboratory, Department of Physics, University
of Oxford, Oxford OX1 3PU, U.K.
- Kavli
Institute of Nanoscience Discovery, University
of Oxford, Dorothy Crowfoot
Hodgkin Building, Oxford OX1 3QU, U.K.
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5
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Wollman AJM, Syeda AH, Howard JAL, Payne-Dwyer A, Leech A, Warecka D, Guy C, McGlynn P, Hawkins M, Leake MC. Tetrameric UvrD Helicase Is Located at the E. Coli Replisome due to Frequent Replication Blocks. J Mol Biol 2024; 436:168369. [PMID: 37977299 DOI: 10.1016/j.jmb.2023.168369] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 11/10/2023] [Accepted: 11/11/2023] [Indexed: 11/19/2023]
Abstract
DNA replication in all organisms must overcome nucleoprotein blocks to complete genome duplication. Accessory replicative helicases in Escherichia coli, Rep and UvrD, help remove these blocks and aid the re-initiation of replication. Mechanistic details of Rep function have emerged from recent live cell studies; however, the division of UvrD functions between its activities in DNA repair and role as an accessory helicase remain unclear in live cells. By integrating super-resolved single-molecule fluorescence microscopy with biochemical analysis, we find that UvrD self-associates into tetrameric assemblies and, unlike Rep, is not recruited to a specific replisome protein despite being found at approximately 80% of replication forks. Instead, its colocation with forks is likely due to the very high frequency of replication blocks composed of DNA-bound proteins, including RNA polymerase and factors involved in repairing DNA damage. Deleting rep and DNA repair factor genes mutS and uvrA, and inhibiting transcription through RNA polymerase mutation and antibiotic inhibition, indicates that the level of UvrD at the fork is dependent on UvrD's function. Our findings show that UvrD is recruited to sites of nucleoprotein blocks via different mechanisms to Rep and plays a multi-faceted role in ensuring successful DNA replication.
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Affiliation(s)
- Adam J M Wollman
- School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom; Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Aisha H Syeda
- School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom; Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Jamieson A L Howard
- School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom; Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Alex Payne-Dwyer
- School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom; Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Andrew Leech
- Bioscience Technology Facility, Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Dominika Warecka
- Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Colin Guy
- Covance Laboratories Ltd., Otley Road, Harrogate HG3 1PY, United Kingdom
| | - Peter McGlynn
- Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Michelle Hawkins
- Department of Biology, University of York, York YO10 5DD, United Kingdom
| | - Mark C Leake
- School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom; Department of Biology, University of York, York YO10 5DD, United Kingdom.
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6
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Kim S, Shin WH, Kang Y, Kim H, Lee JY. Direct visualization of replication and R-loop collision using single-molecule imaging. Nucleic Acids Res 2024; 52:259-273. [PMID: 37994723 PMCID: PMC10783495 DOI: 10.1093/nar/gkad1101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 10/12/2023] [Accepted: 11/06/2023] [Indexed: 11/24/2023] Open
Abstract
R-loops are three-stranded nucleic acid structures that can cause replication stress by blocking replication fork progression. However, the detailed mechanism underlying the collision of DNA replication forks and R-loops remains elusive. To investigate how R-loops induce replication stress, we use single-molecule fluorescence imaging to directly visualize the collision of replicating Phi29 DNA polymerase (Phi29 DNAp), the simplest replication system, and R-loops. We demonstrate that a single R-loop can block replication, and the blockage is more pronounced when an RNA-DNA hybrid is on the non-template strand. We show that this asymmetry results from secondary structure formation on the non-template strand, which impedes the progression of Phi29 DNAp. We also show that G-quadruplex formation on the displaced single-stranded DNA in an R-loop enhances the replication stalling. Moreover, we observe the collision between Phi29 DNAp and RNA transcripts synthesized by T7 RNA polymerase (T7 RNAp). RNA transcripts cause more stalling because of the presence of T7 RNAp. Our work provides insights into how R-loops impede DNA replication at single-molecule resolution.
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Affiliation(s)
- Subin Kim
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Woo Hee Shin
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Yujin Kang
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Hongtae Kim
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Ja Yil Lee
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- Institute of Basic Science Center for Genomic Integrity, Ulsan 44919, Republic of Korea
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7
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Ramírez Montero D, Liu Z, Dekker NH. De novo fabrication of custom-sequence plasmids for the synthesis of long DNA constructs with extrahelical features. Biophys J 2024; 123:31-41. [PMID: 37968907 PMCID: PMC10808024 DOI: 10.1016/j.bpj.2023.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 10/06/2023] [Accepted: 11/13/2023] [Indexed: 11/17/2023] Open
Abstract
DNA constructs for single-molecule experiments often require specific sequences and/or extrahelical/noncanonical structures to study DNA-processing mechanisms. The precise introduction of such structures requires extensive control of the sequence of the initial DNA substrate. A commonly used substrate in the synthesis of DNA constructs is plasmid DNA. Nevertheless, the controlled introduction of specific sequences and extrahelical/noncanonical structures into plasmids often requires several rounds of cloning on pre-existing plasmids whose sequence one cannot fully control. Here, we describe a simple and efficient way to synthesize 10.1-kb plasmids de novo using synthetic gBlocks that provides full control of the sequence. Using these plasmids, we developed a 1.5-day protocol to assemble 10.1-kb linear DNA constructs with end and internal modifications. As a proof of principle, we synthesize two different DNA constructs with biotinylated ends and one or two internal 3' single-stranded DNA flaps, characterize them using single-molecule force and fluorescence spectroscopy, and functionally validate them by showing that the eukaryotic replicative helicase Cdc45/Mcm2-7/GINS (CMG) binds the 3' single-stranded DNA flap and translocates in the expected direction. We anticipate that our approach can be used to synthesize custom-sequence DNA constructs for a variety of force and fluorescence single-molecule spectroscopy experiments to interrogate DNA replication, DNA repair, and transcription.
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Affiliation(s)
- Daniel Ramírez Montero
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Zhaowei Liu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands
| | - Nynke H Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands.
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8
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Whinn KS, Sharma N, van Oijen AM, Ghodke H. Single-Molecule Fluorescence Imaging of DNA Replication Stalling at Sites of Nucleoprotein Complexes. Methods Mol Biol 2024; 2694:215-234. [PMID: 37824007 DOI: 10.1007/978-1-0716-3377-9_11] [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: 10/13/2023]
Abstract
DNA replication in cells occurs on crowded and often damaged template DNA, forming potentially deleterious roadblocks to the progressing replication fork. Numerous tools have been developed to investigate the mechanisms of DNA replication and the fate of stalled replication forks. Here, we describe single-molecule fluorescence imaging methods to visualize processive DNA replication and replication fork stalling at site-specific nucleoprotein complexes. Using dCas9 as a protein barrier and rolling-circle DNA templates, we visualize effective, stable, and site-specific blocking of the Escherichia coli replisome. Additionally, we present a protocol to produce an 18-kb rolling-circle DNA template that provides increased spatial resolution in imaging the interplay between replisomes and roadblocks. These methods can be used to investigate encounters of the replisome with nucleoprotein complexes at the single-molecule level, providing important mechanistic details of replisome stalling and downstream rescue or restart pathways.
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Affiliation(s)
- Kelsey S Whinn
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Nischal Sharma
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Antoine M van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.
| | - Harshad Ghodke
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia.
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9
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Lewis JS, van Oijen AM, Spenkelink LM. Embracing Heterogeneity: Challenging the Paradigm of Replisomes as Deterministic Machines. Chem Rev 2023; 123:13419-13440. [PMID: 37971892 PMCID: PMC10790245 DOI: 10.1021/acs.chemrev.3c00436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Revised: 10/15/2023] [Accepted: 10/20/2023] [Indexed: 11/19/2023]
Abstract
The paradigm of cellular systems as deterministic machines has long guided our understanding of biology. Advancements in technology and methodology, however, have revealed a world of stochasticity, challenging the notion of determinism. Here, we explore the stochastic behavior of multi-protein complexes, using the DNA replication system (replisome) as a prime example. The faithful and timely copying of DNA depends on the simultaneous action of a large set of enzymes and scaffolding factors. This fundamental cellular process is underpinned by dynamic protein-nucleic acid assemblies that must transition between distinct conformations and compositional states. Traditionally viewed as a well-orchestrated molecular machine, recent experimental evidence has unveiled significant variability and heterogeneity in the replication process. In this review, we discuss recent advances in single-molecule approaches and single-particle cryo-EM, which have provided insights into the dynamic processes of DNA replication. We comment on the new challenges faced by structural biologists and biophysicists as they attempt to describe the dynamic cascade of events leading to replisome assembly, activation, and progression. The fundamental principles uncovered and yet to be discovered through the study of DNA replication will inform on similar operating principles for other multi-protein complexes.
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Affiliation(s)
- Jacob S. Lewis
- Macromolecular
Machines Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Antoine M. van Oijen
- Molecular
Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Lisanne M. Spenkelink
- Molecular
Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
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10
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Chib S, Griffin WC, Gao J, Proffitt DR, Byrd AK, Raney KD. Pif1 Helicase Mediates Remodeling of Protein-Nucleic Acid Complexes by Promoting Dissociation of Sub1 from G-Quadruplex DNA and Cdc13 from G-Rich Single-Stranded DNA. Biochemistry 2023; 62:3360-3372. [PMID: 37948114 PMCID: PMC10841737 DOI: 10.1021/acs.biochem.3c00441] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Pif1 is a molecular motor enzyme that is conserved from yeast to mammals. It translocates on ssDNA with a directional bias (5' → 3') and unwinds duplexes using the energy obtained from ATP hydrolysis. Pif1 is involved in dsDNA break repair, resolution of G-quadruplex (G4) structures, negative regulation of telomeres, and Okazaki fragment maturation. An important property of this helicase is to exert force and disrupt protein-DNA complexes, which may otherwise serve as barriers to various cellular pathways. Previously, Pif1 was reported to displace streptavidin from biotinylated DNA, Rap1 from telomeric DNA, and telomerase from DNA ends. Here, we have investigated the ability of S. cerevisiae Pif1 helicase to disrupt protein barriers from G4 and telomeric sites. Yeast chromatin-associated transcription coactivator Sub1 was characterized as a G4 binding protein. We found evidence for a physical interaction between Pif1 helicase and Sub1 protein. Here, we demonstrate that Pif1 is capable of catalyzing the disruption of Sub1-bound G4 structures in an ATP-dependent manner. We also investigated Pif1-mediated removal of yeast telomere-capping protein Cdc13 from DNA ends. Cdc13 exhibits a high-affinity interaction with an 11-mer derived from the yeast telomere sequence. Our results show that Pif1 uses its translocase activity to enhance the dissociation of this telomere-specific protein from its binding site. The rate of dissociation increased with an increase in the helicase loading site length. Additionally, we examined the biochemical mechanism for Pif1-catalyzed protein displacement by mutating the sequence of the telomeric 11-mer on the 5'-end and the 3'-end. The results support a model whereby Pif1 disrupts Cdc13 from the ssDNA in steps.
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Affiliation(s)
- Shubeena Chib
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Wezley C. Griffin
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Jun Gao
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - David R. Proffitt
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Alicia K. Byrd
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Kevin D. Raney
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205
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11
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Abstract
Transcription and replication both require large macromolecular complexes to act on a DNA template, yet these machineries cannot simultaneously act on the same DNA sequence. Conflicts between the replication and transcription machineries (transcription-replication conflicts, or TRCs) are widespread in both prokaryotes and eukaryotes and have the capacity to both cause DNA damage and compromise complete, faithful replication of the genome. This review will highlight recent studies investigating the genomic locations of TRCs and the mechanisms by which they may be prevented, mitigated, or resolved. We address work from both model organisms and mammalian systems but predominantly focus on multicellular eukaryotes owing to the additional complexities inherent in the coordination of replication and transcription in the context of cell type-specific gene expression and higher-order chromatin organization.
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Affiliation(s)
- Liana Goehring
- Department of Biochemistry & Molecular Pharmacology, New York University School of Medicine, New York, NY, USA;
| | - Tony T Huang
- Department of Biochemistry & Molecular Pharmacology, New York University School of Medicine, New York, NY, USA;
| | - Duncan J Smith
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY, USA;
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12
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Mersch K, Sokoloski J, Nguyen B, Galletto R, Lohman T. "Helicase" Activity promoted through dynamic interactions between a ssDNA translocase and a diffusing SSB protein. Proc Natl Acad Sci U S A 2023; 120:e2216777120. [PMID: 37011199 PMCID: PMC10104510 DOI: 10.1073/pnas.2216777120] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 03/06/2023] [Indexed: 04/05/2023] Open
Abstract
Replication protein A (RPA) is a eukaryotic single-stranded (ss) DNA-binding (SSB) protein that is essential for all aspects of genome maintenance. RPA binds ssDNA with high affinity but can also diffuse along ssDNA. By itself, RPA is capable of transiently disrupting short regions of duplex DNA by diffusing from a ssDNA that flanks the duplex DNA. Using single-molecule total internal reflection fluorescence and optical trapping combined with fluorescence approaches, we show that S. cerevisiae Pif1 can use its ATP-dependent 5' to 3' translocase activity to chemomechanically push a single human RPA (hRPA) heterotrimer directionally along ssDNA at rates comparable to those of Pif1 translocation alone. We further show that using its translocation activity, Pif1 can push hRPA from a ssDNA loading site into a duplex DNA causing stable disruption of at least 9 bp of duplex DNA. These results highlight the dynamic nature of hRPA enabling it to be readily reorganized even when bound tightly to ssDNA and demonstrate a mechanism by which directional DNA unwinding can be achieved through the combined action of a ssDNA translocase that pushes an SSB protein. These results highlight the two basic requirements for any processive DNA helicase: transient DNA base pair melting (supplied by hRPA) and ATP-dependent directional ssDNA translocation (supplied by Pif1) and that these functions can be unlinked by using two separate proteins.
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Affiliation(s)
- Kacey N. Mersch
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Joshua E. Sokoloski
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
- Department of Chemistry, Salisbury University, Salisbury, MD21801
| | - Binh Nguyen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Roberto Galletto
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
| | - Timothy M. Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO63110-1093
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13
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Stoy H, Zwicky K, Kuster D, Lang KS, Krietsch J, Crossley MP, Schmid JA, Cimprich KA, Merrikh H, Lopes M. Direct visualization of transcription-replication conflicts reveals post-replicative DNA:RNA hybrids. Nat Struct Mol Biol 2023; 30:348-359. [PMID: 36864174 PMCID: PMC10023573 DOI: 10.1038/s41594-023-00928-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 01/23/2023] [Indexed: 03/04/2023]
Abstract
Transcription-replication collisions (TRCs) are crucial determinants of genome instability. R-loops were linked to head-on TRCs and proposed to obstruct replication fork progression. The underlying mechanisms, however, remained elusive due to the lack of direct visualization and of non-ambiguous research tools. Here, we ascertained the stability of estrogen-induced R-loops on the human genome, visualized them directly by electron microscopy (EM), and measured R-loop frequency and size at the single-molecule level. Combining EM and immuno-labeling on locus-specific head-on TRCs in bacteria, we observed the frequent accumulation of DNA:RNA hybrids behind replication forks. These post-replicative structures are linked to fork slowing and reversal across conflict regions and are distinct from physiological DNA:RNA hybrids at Okazaki fragments. Comet assays on nascent DNA revealed a marked delay in nascent DNA maturation in multiple conditions previously linked to R-loop accumulation. Altogether, our findings suggest that TRC-associated replication interference entails transactions that follow initial R-loop bypass by the replication fork.
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Affiliation(s)
- Henriette Stoy
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Katharina Zwicky
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Danina Kuster
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Kevin S Lang
- Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, MN, USA
| | - Jana Krietsch
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Magdalena P Crossley
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jonas A Schmid
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Karlene A Cimprich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Houra Merrikh
- Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
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14
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Hall PM, Inman JT, Fulbright RM, Le TT, Brewer JJ, Lambert G, Darst SA, Wang MD. Polarity of the CRISPR roadblock to transcription. Nat Struct Mol Biol 2022; 29:1217-1227. [PMID: 36471058 PMCID: PMC9758054 DOI: 10.1038/s41594-022-00864-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 10/12/2022] [Indexed: 12/12/2022]
Abstract
CRISPR (clustered regularly interspaced short palindromic repeats) utility relies on a stable Cas effector complex binding to its target site. However, a Cas complex bound to DNA may be removed by motor proteins carrying out host processes and the mechanism governing this removal remains unclear. Intriguingly, during CRISPR interference, RNA polymerase (RNAP) progression is only fully blocked by a bound endonuclease-deficient Cas (dCas) from the protospacer adjacent motif (PAM)-proximal side. By mapping dCas-DNA interactions at high resolution, we discovered that the collapse of the dCas R-loop allows Escherichia coli RNAP read-through from the PAM-distal side for both Sp-dCas9 and As-dCas12a. This finding is not unique to RNAP and holds for the Mfd translocase. This mechanistic understanding allowed us to modulate the dCas R-loop stability by modifying the guide RNAs. This work highlights the importance of the R-loop in dCas-binding stability and provides valuable mechanistic insights for broad applications of CRISPR technology.
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Affiliation(s)
- Porter M Hall
- Biophysics Program, Cornell University, Ithaca, NY, USA
| | - James T Inman
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
| | - Robert M Fulbright
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Tung T Le
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA
| | - Joshua J Brewer
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Guillaume Lambert
- Department of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Seth A Darst
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Michelle D Wang
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY, USA.
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15
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Wilkinson EM, Spenkelink LM, van Oijen AM. Observing protein dynamics during DNA-lesion bypass by the replisome. Front Mol Biosci 2022; 9:968424. [PMID: 36213113 PMCID: PMC9534484 DOI: 10.3389/fmolb.2022.968424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 09/02/2022] [Indexed: 11/13/2022] Open
Abstract
Faithful DNA replication is essential for all life. A multi-protein complex called the replisome contains all the enzymatic activities required to facilitate DNA replication, including unwinding parental DNA and synthesizing two identical daughter molecules. Faithful DNA replication can be challenged by both intrinsic and extrinsic factors, which can result in roadblocks to replication, causing incomplete replication, genomic instability, and an increased mutational load. This increased mutational load can ultimately lead to a number of diseases, a notable example being cancer. A key example of a roadblock to replication is chemical modifications in the DNA caused by exposure to ultraviolet light. Protein dynamics are thought to play a crucial role to the molecular pathways that occur in the presence of such DNA lesions, including potential damage bypass. Therefore, many assays have been developed to study these dynamics. In this review, we discuss three methods that can be used to study protein dynamics during replisome–lesion encounters in replication reactions reconstituted from purified proteins. Specifically, we focus on ensemble biochemical assays, single-molecule fluorescence, and cryo-electron microscopy. We discuss two key model DNA replication systems, derived from Escherichia coli and Saccharomyces cerevisiae. The main methods of choice to study replication over the last decades have involved biochemical assays that rely on ensemble averaging. While these assays do not provide a direct readout of protein dynamics, they can often be inferred. More recently, single-molecule techniques including single-molecule fluorescence microscopy have been used to visualize replisomes encountering lesions in real time. In these experiments, individual proteins can be fluorescently labeled in order to observe the dynamics of specific proteins during DNA replication. Finally, cryo-electron microscopy can provide detailed structures of individual replisome components, which allows functional data to be interpreted in a structural context. While classic cryo-electron microscopy approaches provide static information, recent developments such as time-resolved cryo-electron microscopy help to bridge the gap between static structures and dynamic single-molecule techniques by visualizing sequential steps in biochemical pathways. In combination, these techniques will be capable of visualizing DNA replication and lesion encounter dynamics in real time, whilst observing the structural changes that facilitate these dynamics.
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Affiliation(s)
- Elise M. Wilkinson
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Lisanne M. Spenkelink
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
- *Correspondence: Lisanne M. Spenkelink, ; Antoine M. van Oijen,
| | - Antoine M. van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
- *Correspondence: Lisanne M. Spenkelink, ; Antoine M. van Oijen,
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16
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Zhou X, Pan Y, Qu Y, Ke X. Tideglusib Inhibits Pif1 Helicase of Bacteroides sp. via an Irreversible and Cys-380-Dependent Mechanism. ACS OMEGA 2022; 7:31289-31298. [PMID: 36092604 PMCID: PMC9453980 DOI: 10.1021/acsomega.2c03546] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Pif1 helicase plays multiple roles in maintaining genome stability, which is an attractive therapeutic target for helicase-related diseases, while small molecules targeting Pif1 are not yet available. In this study, we performed a fluorescence polarization-based high-throughput screening and identified that an FDA-approved drug, Tideglusib (TD), could inhibit the DNA-binding activity (IC50 = 6.2 ± 0.4 μM) and ATPase and helicase activity (IC50 = 2-4 μM) of Bacteroides sp. Pif1 (BaPif1), which was also confirmed with human Pif1. In addition, the TD analogue TDZD-8 displayed similar inhibitory effects on Pif1 activities. Notably, TD irreversibly inhibited BaPif1 and severely induced BaPif1 aggregation. Furthermore, inhibition of BaPif1 by TD was significantly attenuated in the presence of dithiothreitol, indicating that TD could be a thiol-reactive compound. We also identified that Cys-380 of BaPif1 is critical for the inhibition by TD, suggesting that TD inhibits BaPif1 via an irreversible and Cys-380-dependent mechanism.
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17
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Shaw AE, Kairamkonda S, Ghodke H, Schauer GD. Biochemical and single-molecule techniques to study accessory helicase resolution of R-loop proteins at stalled replication forks. Methods Enzymol 2022; 673:191-225. [PMID: 35965008 DOI: 10.1016/bs.mie.2022.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
R-loop proteins present a stable and robust blockade to the progression of a DNA replication fork during S-phase. The consequences of this block can include mutagenesis and other irreversible chromosomal catastrophes, causing genomic instability and disease. As such, further investigation into the molecular mechanisms underlying R-loop protein resolution is warranted. The critical role of non-replicative accessory helicases in R-loop protein resolution has increasingly come into light in recent years. Such helicases include the Pif1-family, monomeric helicases that have been studied in many different contexts and that have been ascribed to a multitude of separable protective functions in the cell. In this chapter, we present protocols to study R-loop protein resolution by Pif1 helicase at stalled replication forks using purified proteins, both at the biochemical and single-molecule level. Our system uses recombinant proteins expressed in Saccharomyces cerevisiae but could apply to practically any organism of interest due to the high interspecies homology of the proteins involved in DNA replication. The methods we outline are extensible to many systems and should be applicable to studying R-loop clearance by any Superfamily (SF) 1B helicase. These techniques will further enable mechanistic research on these critical but understudied components of the genomic maintenance program.
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Affiliation(s)
- Alisa E Shaw
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States
| | - Sreeya Kairamkonda
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States
| | - Harshad Ghodke
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia; Illawarra Health & Medical Research Institute, Wollongong, NSW, Australia
| | - Grant D Schauer
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States.
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18
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Valle-Orero J, Rieu M, Tran P, Joubert A, Raj S, Allemand JF, Croquette V, Boulé JB. Strand switching mechanism of Pif1 helicase induced by its collision with a G-quadruplex embedded in dsDNA. Nucleic Acids Res 2022; 50:8767-8778. [PMID: 35947696 PMCID: PMC9410907 DOI: 10.1093/nar/gkac667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 07/01/2022] [Accepted: 07/24/2022] [Indexed: 12/24/2022] Open
Abstract
G-rich sequences found at multiple sites throughout all genomes may form secondary structures called G-quadruplexes (G4), which act as roadblocks for molecular motors. Among the enzymes thought to process these structures, the Pif1 DNA helicase is considered as an archetypical G4-resolvase and its absence has been linked to G4-related genomic instabilities in yeast. Here we developed a single-molecule assay to observe Pif1 opening a DNA duplex and resolving the G4 in real time. In support of former enzymological studies, we show that the helicase reduces the lifetime of G4 from hours to seconds. However, we observe that in the presence of a G4, Pif1 exhibits a strong strand switching behavior, which can lead to Pif1 escaping G4 resolution, depending on the structural context surrounding the substrate. This behavior is also detected in the presence of other roadblocks (LNA or RNA). We propose that the efficiency of Pif1 to remove a roadblock (G4 or other) is affected by its strand switching behavior and depends on the context surrounding the obstacle. We discuss how this switching behavior may explain several aspects of Pif1 substrate preference and affect its activity as a G4 resolvase in vivo.
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Affiliation(s)
| | - Martin Rieu
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France,Institut de Biologie de l’École Normale Supérieure de Paris (IBENS), École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Phong Lan Thao Tran
- Structure et Instabilité des Génomes, Museum National d’Histoire Naturelle, INSERM, CNRS, Alliance Sorbonne Université, 75005 Paris, France
| | - Alexandra Joubert
- Structure et Instabilité des Génomes, Museum National d’Histoire Naturelle, INSERM, CNRS, Alliance Sorbonne Université, 75005 Paris, France
| | - Saurabh Raj
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - Jean-François Allemand
- Laboratoire de physique de L’École Normale Supérieure de Paris, CNRS, ENS, Université PSL, Sorbonne Université, Université Paris Cité, 75005 Paris, France,Institut de Biologie de l’École Normale Supérieure de Paris (IBENS), École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | | | - Jean-Baptiste Boulé
- To whom correspondence should be addressed. Tel: +33 140795616; Fax: +33 1407937050;
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19
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Brickner JR, Garzon JL, Cimprich KA. Walking a tightrope: The complex balancing act of R-loops in genome stability. Mol Cell 2022; 82:2267-2297. [PMID: 35508167 DOI: 10.1016/j.molcel.2022.04.014] [Citation(s) in RCA: 81] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/28/2022] [Accepted: 04/10/2022] [Indexed: 12/14/2022]
Abstract
Although transcription is an essential cellular process, it is paradoxically also a well-recognized cause of genomic instability. R-loops, non-B DNA structures formed when nascent RNA hybridizes to DNA to displace the non-template strand as single-stranded DNA (ssDNA), are partially responsible for this instability. Yet, recent work has begun to elucidate regulatory roles for R-loops in maintaining the genome. In this review, we discuss the cellular contexts in which R-loops contribute to genomic instability, particularly during DNA replication and double-strand break (DSB) repair. We also summarize the evidence that R-loops participate as an intermediate during repair and may influence pathway choice to preserve genomic integrity. Finally, we discuss the immunogenic potential of R-loops and highlight their links to disease should they become pathogenic.
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Affiliation(s)
- Joshua R Brickner
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jada L Garzon
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Karlene A Cimprich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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20
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Pérez-Martínez L, Wagner T, Luke B. Telomere Interacting Proteins and TERRA Regulation. Front Genet 2022; 13:872636. [PMID: 35464834 PMCID: PMC9024143 DOI: 10.3389/fgene.2022.872636] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/17/2022] [Indexed: 01/10/2023] Open
Abstract
Telomere shortening rates inversely correlate with life expectancy and hence it is critical to understand how telomere shortening is regulated. Recently, the telomeric non-coding RNA, TERRA has been implicated in the regulation of replicative senescence. To better understand how TERRA is regulated we employed a proteomics approach to look for potential RNA regulators that associate with telomeric sequences. Based on the results, we have identified proteins that may regulate TERRA in both a positive and negative manner, depending on the state of the telomere. In this mini-review, we discuss and speculate about these data to expand our understanding of TERRA and telomere interactors with respect to telomere shortening dynamics.
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Affiliation(s)
- Lara Pérez-Martínez
- Institute of Molecular Biology (IMB), Mainz, Germany
- IMDEA Food Institute, Madrid, Spain
| | - Tina Wagner
- Institute of Molecular Biology (IMB), Mainz, Germany
- Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg Universität, Mainz, Germany
| | - Brian Luke
- Institute of Molecular Biology (IMB), Mainz, Germany
- Institute of Developmental Biology and Neurobiology (IDN), Johannes Gutenberg Universität, Mainz, Germany
- *Correspondence: Brian Luke,
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21
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Malone EG, Thompson MD, Byrd AK. Role and Regulation of Pif1 Family Helicases at the Replication Fork. Int J Mol Sci 2022; 23:ijms23073736. [PMID: 35409096 PMCID: PMC8998199 DOI: 10.3390/ijms23073736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 02/04/2023] Open
Abstract
Pif1 helicases are a multifunctional family of DNA helicases that are important for many aspects of genomic stability in the nucleus and mitochondria. Pif1 helicases are conserved from bacteria to humans. Pif1 helicases play multiple roles at the replication fork, including promoting replication through many barriers such as G-quadruplex DNA, the rDNA replication fork barrier, tRNA genes, and R-loops. Pif1 helicases also regulate telomerase and promote replication termination, Okazaki fragment maturation, and break-induced replication. This review highlights many of the roles and regulations of Pif1 at the replication fork that promote cellular health and viability.
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Affiliation(s)
- Emory G. Malone
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
| | - Matthew D. Thompson
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
| | - Alicia K. Byrd
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
- Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
- Correspondence: ; Tel.: +1-501-526-6488
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22
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Scherr MJ, Wahab SA, Remus D, Duderstadt KE. Mobile origin-licensing factors confer resistance to conflicts with RNA polymerase. Cell Rep 2022; 38:110531. [PMID: 35320708 PMCID: PMC8961423 DOI: 10.1016/j.celrep.2022.110531] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 12/10/2021] [Accepted: 02/23/2022] [Indexed: 12/30/2022] Open
Abstract
Fundamental to our understanding of chromosome duplication is the idea that replication origins function both as sites where MCM helicases are loaded during the G1 phase and where synthesis begins in S phase. However, the temporal delay between phases exposes the replisome assembly pathway to potential disruption prior to replication. Using multicolor, single-molecule imaging, we systematically study the consequences of encounters between actively transcribing RNA polymerases (RNAPs) and replication initiation intermediates in the context of chromatin. We demonstrate that RNAP can push multiple licensed MCM helicases over long distances with nucleosomes ejected or displaced. Unexpectedly, we observe that MCM helicase loading intermediates also can be repositioned by RNAP and continue origin licensing after encounters with RNAP, providing a web of alternative origin specification pathways. Taken together, our observations reveal a surprising mobility in origin-licensing factors that confers resistance to the complex challenges posed by diverse obstacles encountered on chromosomes. RNA polymerase robustly pushes MCMs without slowing down Nucleosomes are ejected or pushed by MCMs during repositioning RNA polymerase can bypass ORC or activate ORC sliding and OCCM sliding Origin licensing continues after RNA polymerase encounters and relocalization
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Affiliation(s)
- Matthias J Scherr
- Structure and Dynamics of Molecular Machines, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Syafiq Abd Wahab
- Memorial Sloan Kettering Cancer Center, Molecular Biology Program, 1275 York Avenue, New York, NY 10065, USA
| | - Dirk Remus
- Memorial Sloan Kettering Cancer Center, Molecular Biology Program, 1275 York Avenue, New York, NY 10065, USA
| | - Karl E Duderstadt
- Structure and Dynamics of Molecular Machines, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Physik Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
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23
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Tingler M, Philipp M, Burkhalter MD. DNA Replication proteins in primary microcephaly syndromes. Biol Cell 2022; 114:143-159. [PMID: 35182397 DOI: 10.1111/boc.202100061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 01/28/2022] [Accepted: 01/31/2022] [Indexed: 11/30/2022]
Abstract
SCOPE Improper expansion of neural stem and progenitor cells during brain development manifests in primary microcephaly. It is characterized by a reduced head circumference, which correlates with a reduction in brain size. This often corresponds to a general underdevelopment of the brain and entails cognitive, behavioral and motoric retardation. In the past decade significant research efforts have been undertaken to identify genes and the molecular mechanisms underlying microcephaly. One such gene set encompasses factors required for DNA replication. Intriguingly, a growing body of evidence indicates that a substantial number of these genes mediate faithful centrosome and cilium function in addition to their canonical function in genome duplication. Here, we summarize, which DNA replication factors are associated with microcephaly syndromes and to which extent they impact on centrosomes and cilia. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Melanie Tingler
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, 72074, Germany
| | - Melanie Philipp
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, 72074, Germany
| | - Martin D Burkhalter
- Department of Experimental and Clinical Pharmacology and Pharmacogenomics, Section of Pharmacogenomics, Eberhard-Karls-University Tübingen, Tübingen, 72074, Germany
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24
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Byrd AK, Malone EG, Hazeslip L, Zafar MK, Harrison DK, Thompson MD, Gao J, Perumal SK, Marecki JC, Raney KD. A structural feature of Dda helicase which enhances displacement of streptavidin and trp repressor from DNA. Protein Sci 2022; 31:407-421. [PMID: 34761452 PMCID: PMC8819844 DOI: 10.1002/pro.4232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/01/2021] [Accepted: 11/03/2021] [Indexed: 02/03/2023]
Abstract
Helicases are molecular motors with many activities. They use the energy from ATP hydrolysis to unwind double-stranded nucleic acids while translocating on the single-stranded DNA. In addition to unwinding, many helicases are able to remove proteins from nucleic acids. Bacteriophage T4 Dda is able to displace a variety of DNA binding proteins and streptavidin bound to biotinylated oligonucleotides. We have identified a subdomain of Dda that when deleted, results in a protein variant that has nearly wild type activity for unwinding double-stranded DNA but exhibits greatly reduced streptavidin displacement activity. Interestingly, this domain has little effect on displacement of either gp32 or BamHI bound to DNA but does affect displacement of trp repressor from DNA. With this variant, we have identified residues which enhance displacement of some proteins from DNA.
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Affiliation(s)
- Alicia K. Byrd
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA,Winthrop P. Rockefeller Cancer InstituteUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Emory G. Malone
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Lindsey Hazeslip
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Maroof Khan Zafar
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - David K. Harrison
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Matthew D. Thompson
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Jun Gao
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Senthil K. Perumal
- Department of ChemistryThe Pennsylvania State UniversityUniversity ParkPennsylvaniaUSA
| | - John C. Marecki
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
| | - Kevin D. Raney
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA,Winthrop P. Rockefeller Cancer InstituteUniversity of Arkansas for Medical SciencesLittle RockArkansasUSA
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25
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Abstract
The gene encoding the Pif1 helicase was first discovered in a Saccharomyces cerevisiae genetic screen as a mutant that reduces recombination between mitochondrial respiratory mutants and was subsequently rediscovered in a screen for genes affecting the telomere length in the nucleus. It is now known that Pif1 is involved in numerous aspects of DNA metabolism. All known functions of Pif1 rely on binding to DNA substrates followed by ATP hydrolysis, coupling the energy released to translocation along DNA to unwind duplex DNA or alternative DNA secondary structures. The interaction of Pif1 with higher-order DNA structures, like G-quadruplex DNA, as well as the length of single-stranded (ss)DNA necessary for Pif1 loading have been widely studied. Here, to test the effects of ssDNA length, sequence, and structure on Pif1's biochemical activities in vitro, we used a suite of oligonucleotide-based substrates to perform a basic characterization of Pif1 ssDNA binding, ATPase activity, and helicase activity. Using recombinant, untagged S. cerevisiae Pif1, we found that Pif1 preferentially binds to structured G-rich ssDNA, but the preferred binding substrates failed to maximally stimulate ATPase activity. In helicase assays, significant DNA unwinding activity was detected at Pif1 concentrations as low as 250 pM. Helicase assays also demonstrated that Pif1 most efficiently unwinds DNA fork substrates with unstructured ssDNA tails. As the chemical step size of Pif1 has been determined to be 1 ATP per translocation or unwinding event, this implies that the highly structured DNA inhibits conformational changes in Pif1 that couple ATP hydrolysis to DNA translocation and unwinding.
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Affiliation(s)
- David G Nickens
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405, United States
| | - Matthew L Bochman
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405, United States
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26
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Abstract
Ring-shaped hexameric helicases are essential motor proteins that separate duplex nucleic acid strands for DNA replication, recombination, and transcriptional regulation. Two evolutionarily distinct lineages of these enzymes, predicated on RecA and AAA+ ATPase folds, have been identified and characterized to date. Hexameric helicases couple NTP hydrolysis with conformational changes that move nucleic acid substrates through a central pore in the enzyme. How hexameric helicases productively engage client DNA or RNA segments and use successive rounds of NTPase activity to power translocation and unwinding have been longstanding questions in the field. Recent structural and biophysical findings are beginning to reveal commonalities in NTP hydrolysis and substrate translocation by diverse hexameric helicase families. Here, we review these molecular mechanisms and highlight aspects of their function that are yet to be understood.
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27
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Kemiha S, Poli J, Lin YL, Lengronne A, Pasero P. Toxic R-loops: Cause or consequence of replication stress? DNA Repair (Amst) 2021; 107:103199. [PMID: 34399314 DOI: 10.1016/j.dnarep.2021.103199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/28/2021] [Accepted: 07/30/2021] [Indexed: 01/08/2023]
Abstract
Transcription-replication conflicts (TRCs) represent a potential source of endogenous replication stress (RS) and genomic instability in eukaryotic cells but the mechanisms that underlie this instability remain poorly understood. Part of the problem could come from non-B DNA structures called R-loops, which are formed of a RNA:DNA hybrid and a displaced ssDNA loop. In this review, we discuss different scenarios in which R-loops directly or indirectly interfere with DNA replication. We also present other types of TRCs that may not depend on R-loops to impede fork progression. Finally, we discuss alternative models in which toxic RNA:DNA hybrids form at stalled forks as a consequence - but not a cause - of replication stress and interfere with replication resumption.
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Affiliation(s)
- Samira Kemiha
- Institut de Génétique Humaine, CNRS et Université de Montpellier, Equipe labélisée Ligue contre le Cancer, Montpellier, France
| | - Jérôme Poli
- Institut de Génétique Humaine, CNRS et Université de Montpellier, Equipe labélisée Ligue contre le Cancer, Montpellier, France
| | - Yea-Lih Lin
- Institut de Génétique Humaine, CNRS et Université de Montpellier, Equipe labélisée Ligue contre le Cancer, Montpellier, France
| | - Armelle Lengronne
- Institut de Génétique Humaine, CNRS et Université de Montpellier, Equipe labélisée Ligue contre le Cancer, Montpellier, France
| | - Philippe Pasero
- Institut de Génétique Humaine, CNRS et Université de Montpellier, Equipe labélisée Ligue contre le Cancer, Montpellier, France.
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28
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Single-molecule studies of helicases and translocases in prokaryotic genome-maintenance pathways. DNA Repair (Amst) 2021; 108:103229. [PMID: 34601381 DOI: 10.1016/j.dnarep.2021.103229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 11/22/2022]
Abstract
Helicases involved in genomic maintenance are a class of nucleic-acid dependent ATPases that convert the energy of ATP hydrolysis into physical work to execute irreversible steps in DNA replication, repair, and recombination. Prokaryotic helicases provide simple models to understand broadly conserved molecular mechanisms involved in manipulating nucleic acids during genome maintenance. Our understanding of the catalytic properties, mechanisms of regulation, and roles of prokaryotic helicases in DNA metabolism has been assembled through a combination of genetic, biochemical, and structural methods, further refined by single-molecule approaches. Together, these investigations have constructed a framework for understanding the mechanisms that maintain genomic integrity in cells. This review discusses recent single-molecule insights into molecular mechanisms of prokaryotic helicases and translocases.
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29
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Spinks RR, Spenkelink LM, Dixon NE, van Oijen AM. Single-Molecule Insights Into the Dynamics of Replicative Helicases. Front Mol Biosci 2021; 8:741718. [PMID: 34513934 PMCID: PMC8426354 DOI: 10.3389/fmolb.2021.741718] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/13/2021] [Indexed: 11/13/2022] Open
Abstract
Helicases are molecular motors that translocate along single-stranded DNA and unwind duplex DNA. They rely on the consumption of chemical energy from nucleotide hydrolysis to drive their translocation. Specialized helicases play a critically important role in DNA replication by unwinding DNA at the front of the replication fork. The replicative helicases of the model systems bacteriophages T4 and T7, Escherichia coli and Saccharomyces cerevisiae have been extensively studied and characterized using biochemical methods. While powerful, their averaging over ensembles of molecules and reactions makes it challenging to uncover information related to intermediate states in the unwinding process and the dynamic helicase interactions within the replisome. Here, we describe single-molecule methods that have been developed in the last few decades and discuss the new details that these methods have revealed about replicative helicases. Applying methods such as FRET and optical and magnetic tweezers to individual helicases have made it possible to access the mechanistic aspects of unwinding. It is from these methods that we understand that the replicative helicases studied so far actively translocate and then passively unwind DNA, and that these hexameric enzymes must efficiently coordinate the stepping action of their subunits to achieve unwinding, where the size of each step is prone to variation. Single-molecule fluorescence microscopy methods have made it possible to visualize replicative helicases acting at replication forks and quantify their dynamics using multi-color colocalization, FRAP and FLIP. These fluorescence methods have made it possible to visualize helicases in replication initiation and dissect this intricate protein-assembly process. In a similar manner, single-molecule visualization of fluorescent replicative helicases acting in replication identified that, in contrast to the replicative polymerases, the helicase does not exchange. Instead, the replicative helicase acts as the stable component that serves to anchor the other replication factors to the replisome.
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Affiliation(s)
- Richard R Spinks
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Lisanne M Spenkelink
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Nicholas E Dixon
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Antoine M van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
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30
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Meir A, Greene EC. Srs2 and Pif1 as Model Systems for Understanding Sf1a and Sf1b Helicase Structure and Function. Genes (Basel) 2021; 12:1319. [PMID: 34573298 PMCID: PMC8469786 DOI: 10.3390/genes12091319] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/23/2021] [Accepted: 08/24/2021] [Indexed: 01/19/2023] Open
Abstract
Helicases are enzymes that convert the chemical energy stored in ATP into mechanical work, allowing them to move along and manipulate nucleic acids. The helicase superfamily 1 (Sf1) is one of the largest subgroups of helicases and they are required for a range of cellular activities across all domains of life. Sf1 helicases can be further subdivided into two classes called the Sf1a and Sf1b helicases, which move in opposite directions on nucleic acids. The results of this movement can range from the separation of strands within duplex nucleic acids to the physical remodeling or removal of nucleoprotein complexes. Here, we describe the characteristics of the Sf1a helicase Srs2 and the Sf1b helicase Pif1, both from the model organism Saccharomyces cerevisiae, focusing on the roles that they play in homologous recombination, a DNA repair pathway that is necessary for maintaining genome integrity.
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Affiliation(s)
| | - Eric C. Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY 10032, USA;
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31
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Lalonde M, Trauner M, Werner M, Hamperl S. Consequences and Resolution of Transcription-Replication Conflicts. Life (Basel) 2021; 11:life11070637. [PMID: 34209204 PMCID: PMC8303131 DOI: 10.3390/life11070637] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 06/28/2021] [Accepted: 06/28/2021] [Indexed: 11/17/2022] Open
Abstract
Transcription–replication conflicts occur when the two critical cellular machineries responsible for gene expression and genome duplication collide with each other on the same genomic location. Although both prokaryotic and eukaryotic cells have evolved multiple mechanisms to coordinate these processes on individual chromosomes, it is now clear that conflicts can arise due to aberrant transcription regulation and premature proliferation, leading to DNA replication stress and genomic instability. As both are considered hallmarks of aging and human diseases such as cancer, understanding the cellular consequences of conflicts is of paramount importance. In this article, we summarize our current knowledge on where and when collisions occur and how these encounters affect the genome and chromatin landscape of cells. Finally, we conclude with the different cellular pathways and multiple mechanisms that cells have put in place at conflict sites to ensure the resolution of conflicts and accurate genome duplication.
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32
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Shyian M, Shore D. Approaching Protein Barriers: Emerging Mechanisms of Replication Pausing in Eukaryotes. Front Cell Dev Biol 2021; 9:672510. [PMID: 34124054 PMCID: PMC8194067 DOI: 10.3389/fcell.2021.672510] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 05/03/2021] [Indexed: 11/13/2022] Open
Abstract
During nuclear DNA replication multiprotein replisome machines have to jointly traverse and duplicate the total length of each chromosome during each cell cycle. At certain genomic locations replisomes encounter tight DNA-protein complexes and slow down. This fork pausing is an active process involving recognition of a protein barrier by the approaching replisome via an evolutionarily conserved Fork Pausing/Protection Complex (FPC). Action of the FPC protects forks from collapse at both programmed and accidental protein barriers, thus promoting genome integrity. In addition, FPC stimulates the DNA replication checkpoint and regulates topological transitions near the replication fork. Eukaryotic cells have been proposed to employ physiological programmed fork pausing for various purposes, such as maintaining copy number at repetitive loci, precluding replication-transcription encounters, regulating kinetochore assembly, or controlling gene conversion events during mating-type switching. Here we review the growing number of approaches used to study replication pausing in vivo and in vitro as well as the characterization of additional factors recently reported to modulate fork pausing in different systems. Specifically, we focus on the positive role of topoisomerases in fork pausing. We describe a model where replisome progression is inherently cautious, which ensures general preservation of fork stability and genome integrity but can also carry out specialized functions at certain loci. Furthermore, we highlight classical and novel outstanding questions in the field and propose venues for addressing them. Given how little is known about replisome pausing at protein barriers in human cells more studies are required to address how conserved these mechanisms are.
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Affiliation(s)
- Maksym Shyian
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland
| | - David Shore
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland
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33
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Vrtis KB, Dewar JM, Chistol G, Wu RA, Graham TGW, Walter JC. Single-strand DNA breaks cause replisome disassembly. Mol Cell 2021; 81:1309-1318.e6. [PMID: 33484638 DOI: 10.1016/j.molcel.2020.12.039] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 12/11/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022]
Abstract
DNA damage impedes replication fork progression and threatens genome stability. Upon encounter with most DNA adducts, the replicative CMG helicase (CDC45-MCM2-7-GINS) stalls or uncouples from the point of synthesis, yet eventually resumes replication. However, little is known about the effect on replication of single-strand breaks or "nicks," which are abundant in mammalian cells. Using Xenopus egg extracts, we reveal that CMG collision with a nick in the leading strand template generates a blunt-ended double-strand break (DSB). Moreover, CMG, which encircles the leading strand template, "runs off" the end of the DSB. In contrast, CMG collision with a lagging strand nick generates a broken end with a single-stranded overhang. In this setting, CMG translocates along double-stranded DNA beyond the break and is then ubiquitylated and removed from chromatin by the same pathway used during replication termination. Our results show that nicks are uniquely dangerous DNA lesions that invariably cause replisome disassembly, and they suggest that CMG cannot be stored on dsDNA while cells resolve replication stress.
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Affiliation(s)
- Kyle B Vrtis
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Gheorghe Chistol
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Thomas G W Graham
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
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