1
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Olson O, Pelliciari S, Heron ED, Deegan TD. A common mechanism for recruiting the Rrm3 and RTEL1 accessory helicases to the eukaryotic replisome. EMBO J 2024:10.1038/s44318-024-00168-4. [PMID: 39039288 DOI: 10.1038/s44318-024-00168-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 06/24/2024] [Accepted: 06/26/2024] [Indexed: 07/24/2024] Open
Abstract
The eukaryotic replisome is assembled around the CMG (CDC45-MCM-GINS) replicative helicase, which encircles the leading-strand DNA template at replication forks. When CMG stalls during DNA replication termination, or at barriers such as DNA-protein crosslinks on the leading strand template, a second helicase is deployed on the lagging strand template to support replisome progression. How these 'accessory' helicases are targeted to the replisome to mediate barrier bypass and replication termination remains unknown. Here, by combining AlphaFold structural modelling with experimental validation, we show that the budding yeast Rrm3 accessory helicase contains two Short Linear Interaction Motifs (SLIMs) in its disordered N-terminus, which interact with CMG and the leading-strand DNA polymerase Polε on one side of the replisome. This flexible tether positions Rrm3 adjacent to the lagging strand template on which it translocates, and is critical for replication termination in vitro and Rrm3 function in vivo. The primary accessory helicase in metazoa, RTEL1, is evolutionarily unrelated to Rrm3, but binds to CMG and Polε in an analogous manner, revealing a conserved docking mechanism for accessory helicases in the eukaryotic replisome.
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Affiliation(s)
- Ottavia Olson
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Simone Pelliciari
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Emma D Heron
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Tom D Deegan
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK.
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2
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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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3
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Carrasco B, Torres R, Moreno-del Álamo M, Ramos C, Ayora S, Alonso JC. Processing of stalled replication forks in Bacillus subtilis. FEMS Microbiol Rev 2024; 48:fuad065. [PMID: 38052445 PMCID: PMC10804225 DOI: 10.1093/femsre/fuad065] [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: 08/14/2023] [Revised: 11/30/2023] [Accepted: 12/04/2023] [Indexed: 12/07/2023] Open
Abstract
Accurate DNA replication and transcription elongation are crucial for preventing the accumulation of unreplicated DNA and genomic instability. Cells have evolved multiple mechanisms to deal with impaired replication fork progression, challenged by both intrinsic and extrinsic impediments. The bacterium Bacillus subtilis, which adopts multiple forms of differentiation and development, serves as an excellent model system for studying the pathways required to cope with replication stress to preserve genomic stability. This review focuses on the genetics, single molecule choreography, and biochemical properties of the proteins that act to circumvent the replicative arrest allowing the resumption of DNA synthesis. The RecA recombinase, its mediators (RecO, RecR, and RadA/Sms) and modulators (RecF, RecX, RarA, RecU, RecD2, and PcrA), repair licensing (DisA), fork remodelers (RuvAB, RecG, RecD2, RadA/Sms, and PriA), Holliday junction resolvase (RecU), nucleases (RnhC and DinG), and translesion synthesis DNA polymerases (PolY1 and PolY2) are key functions required to overcome a replication stress, provided that the fork does not collapse.
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Affiliation(s)
- Begoña Carrasco
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
| | - Rubén Torres
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
| | - María Moreno-del Álamo
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
| | - Cristina Ramos
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
| | - Silvia Ayora
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
| | - Juan C Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin Str, 28049 Madrid, Spain
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4
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Wang Y, Fu H, Shi XJ, Zhao GP, Lyu LD. Genome-wide screen reveals cellular functions that counteract rifampicin lethality in Escherichia coli. Microbiol Spectr 2024; 12:e0289523. [PMID: 38054714 PMCID: PMC10782999 DOI: 10.1128/spectrum.02895-23] [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: 07/19/2023] [Accepted: 10/31/2023] [Indexed: 12/07/2023] Open
Abstract
IMPORTANCE Rifamycins are a group of antibiotics with a wide antibacterial spectrum. Although the binding target of rifamycin has been well characterized, the mechanisms underlying the discrepant killing efficacy between gram-negative and gram-positive bacteria remain poorly understood. Using a high-throughput screen combined with targeted gene knockouts in the gram-negative model organism Escherichia coli, we established that rifampicin efficacy is strongly dependent on several cellular pathways, including iron acquisition, DNA repair, aerobic respiration, and carbon metabolism. In addition, we provide evidence that these pathways modulate rifampicin efficacy in a manner distinct from redox-related killing. Our findings provide insights into the mechanism of rifamycin efficacy and may aid in the development of new antimicrobial adjuvants.
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Affiliation(s)
- Yu Wang
- Key Laboratory of Medical Molecular Virology of the Ministry of Education/National Health Commission, School of Basic Medical Sciences and Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Han Fu
- Key Laboratory of Medical Molecular Virology of the Ministry of Education/National Health Commission, School of Basic Medical Sciences and Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- CAS Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiao-Jie Shi
- Key Laboratory of Medical Molecular Virology of the Ministry of Education/National Health Commission, School of Basic Medical Sciences and Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Guo-Ping Zhao
- Key Laboratory of Medical Molecular Virology of the Ministry of Education/National Health Commission, School of Basic Medical Sciences and Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- CAS Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Liang-Dong Lyu
- Key Laboratory of Medical Molecular Virology of the Ministry of Education/National Health Commission, School of Basic Medical Sciences and Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Tuberculosis, Shanghai Clinical Research Center for Infectious Disease (Tuberculosis), Shanghai Pulmonary Hospital, Shanghai, China
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5
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Kumar C, Remus D. Looping out of control: R-loops in transcription-replication conflict. Chromosoma 2024; 133:37-56. [PMID: 37419963 PMCID: PMC10771546 DOI: 10.1007/s00412-023-00804-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 07/09/2023]
Abstract
Transcription-replication conflict is a major cause of replication stress that arises when replication forks collide with the transcription machinery. Replication fork stalling at sites of transcription compromises chromosome replication fidelity and can induce DNA damage with potentially deleterious consequences for genome stability and organismal health. The block to DNA replication by the transcription machinery is complex and can involve stalled or elongating RNA polymerases, promoter-bound transcription factor complexes, or DNA topology constraints. In addition, studies over the past two decades have identified co-transcriptional R-loops as a major source for impairment of DNA replication forks at active genes. However, how R-loops impede DNA replication at the molecular level is incompletely understood. Current evidence suggests that RNA:DNA hybrids, DNA secondary structures, stalled RNA polymerases, and condensed chromatin states associated with R-loops contribute to the of fork progression. Moreover, since both R-loops and replication forks are intrinsically asymmetric structures, the outcome of R-loop-replisome collisions is influenced by collision orientation. Collectively, the data suggest that the impact of R-loops on DNA replication is highly dependent on their specific structural composition. Here, we will summarize our current understanding of the molecular basis for R-loop-induced replication fork progression defects.
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Affiliation(s)
- Charanya Kumar
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, 10065, USA
| | - Dirk Remus
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, 10065, USA.
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6
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Bonde NJ, Wood EA, Myers KS, Place M, Keck JL, Cox MM. Identification of recG genetic interactions in Escherichia coli by transposon sequencing. J Bacteriol 2023; 205:e0018423. [PMID: 38019006 PMCID: PMC10870727 DOI: 10.1128/jb.00184-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 08/07/2023] [Indexed: 11/30/2023] Open
Abstract
IMPORTANCE DNA damage and subsequent DNA repair processes are mutagenic in nature and an important driver of evolution in prokaryotes, including antibiotic resistance development. Genetic screening approaches, such as transposon sequencing (Tn-seq), have provided important new insights into gene function and genetic relationships. Here, we employed Tn-seq to gain insight into the function of the recG gene, which renders Escherichia coli cells moderately sensitive to a variety of DNA-damaging agents when they are absent. The reported recG genetic interactions can be used in combination with future screens to aid in a more complete reconstruction of DNA repair pathways in bacteria.
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Affiliation(s)
- Nina J. Bonde
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Elizabeth A. Wood
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kevin S. Myers
- Great Lakes Bioenergy Research Center and the Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Michael Place
- Great Lakes Bioenergy Research Center and the Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - James L. Keck
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Michael M. Cox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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7
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Rosenberg SM. Life, the genome and everything. J Bacteriol 2023; 205:e0027223. [PMID: 38018999 PMCID: PMC10742612 DOI: 10.1128/jb.00272-23] [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: 11/30/2023] Open
Abstract
In this issue of the Journal of Bacteriology, N. J. Bonde, E. A. Wood, K. S. Myers, M. Place, J. L. Keck, and M. M. Cox (J Bacteriol 205:e00184-23, 2023, https//doi.org/10.1128/jb.00184-23) used an unbiased transposon-sequencing (Tn-seq) screen to identify proteins required for life when cells lose the RecG branched-DNA helicase (synthetic lethality). The proteins' identities indicate pathways that prevent endogenous DNA damage, pathways that prevent its homology-directed repair (HDR) "strand-exchange" intermediates between sister chromosomes, and pathways that resolve those intermediates. All avoid intermediate pile-up, which blocks chromosome segregation, causing "death-by-recombination." DNA damage is managed to regulate crucial but potentially lethal HDR.
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Affiliation(s)
- Susan M. Rosenberg
- Departments of Molecular & Human Genetics, Biochemistry & Molecular Biology, Molecular Virology and Microbiology, and the Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, USA
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8
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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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9
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Morcinek-Orłowska J, Walter B, Forquet R, Cysewski D, Carlier M, Mozolewski M, Meyer S, Glinkowska M. Interaction networks of Escherichia coli replication proteins under different bacterial growth conditions. Sci Data 2023; 10:788. [PMID: 37949936 PMCID: PMC10638427 DOI: 10.1038/s41597-023-02710-1] [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: 01/13/2023] [Accepted: 10/30/2023] [Indexed: 11/12/2023] Open
Abstract
In this work we analyzed protein-protein interactions (PPIs) formed by E. coli replication proteins under three disparate bacterial growth conditions. The chosen conditions corresponded to fast exponential growth, slow exponential growth and growth cessation at the stationary phase. We performed affinity purification coupled with mass spectrometry (AP-MS) of chromosomally expressed proteins (DnaA, DnaB, Hda, SeqA, DiaA, DnaG, HolD, NrdB), tagged with sequential peptide affinity (SPA) tag. Composition of protein complexes was characterized using MaxQuant software. To filter out unspecific interactions, we employed double negative control system and we proposed qualitative and quantitative data analysis strategies that can facilitate hits identification in other AP-MS datasets. Our motivation to undertake this task was still insufficient understanding of molecular mechanisms coupling DNA replication to cellular growth. Previous works suggested that such control mechanisms could involve physical interactions of replication factors with metabolic or cell envelope proteins. However, the dynamic replication protein interaction network (PIN) obtained in this study can be used to characterize links between DNA replication and various cellular processes in other contexts.
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Affiliation(s)
- Joanna Morcinek-Orłowska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Gdansk, 80-308, Poland
| | - Beata Walter
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Gdansk, 80-308, Poland
| | - Raphaël Forquet
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Dominik Cysewski
- Mass Spectrometry Laboratory, Institute of Biochemistry and Biophysics, PAS, Warsaw 02-106, Warszawa, Poland
| | - Maxime Carlier
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Michał Mozolewski
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Gdansk, 80-308, Poland
| | - Sam Meyer
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Monika Glinkowska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Gdansk, 80-308, Poland.
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10
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Das S, Forrest J, Kuzminov A. Synthetic lethal mutants in Escherichia coli define pathways necessary for survival with RNase H deficiency. J Bacteriol 2023; 205:e0028023. [PMID: 37819120 PMCID: PMC10601623 DOI: 10.1128/jb.00280-23] [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: 08/25/2023] [Accepted: 09/09/2023] [Indexed: 10/13/2023] Open
Abstract
Ribonucleotides frequently contaminate DNA and, if not removed, cause genomic instability. Consequently, all organisms are equipped with RNase H enzymes to remove RNA-DNA hybrids (RDHs). Escherichia coli lacking RNase HI (rnhA) and RNase HII (rnhB) enzymes, the ∆rnhA ∆rnhB double mutant, accumulates RDHs in its DNA. These RDHs can convert into RNA-containing DNA lesions (R-lesions) of unclear nature that compromise genomic stability. The ∆rnhAB double mutant has severe phenotypes, like growth inhibition, replication stress, sensitivity to ultraviolet radiation, SOS induction, increased chromosomal fragmentation, and defects in nucleoid organization. In this study, we found that RNase HI deficiency also alters wild-type levels of DNA supercoiling. Despite these severe chromosomal complications, ∆rnhAB double mutant survives, suggesting that dedicated pathways operate to avoid or repair R-lesions. To identify these pathways, we systematically searched for mutants synthetic lethal (colethal) with the rnhAB defect using an unbiased color screen and a candidate gene approach. We identified both novel and previously reported rnhAB-colethal and -coinhibited mutants, characterized them, and sorted them into avoidance or repair pathways. These mutants operate in various parts of nucleic acid metabolism, including replication fork progression, R-loop prevention and removal, nucleoid organization, tRNA modification, recombinational repair, and chromosome-dimer resolution, demonstrating the pleiotropic nature of RNase H deficiency. IMPORTANCE Ribonucleotides (rNs) are structurally very similar to deoxyribonucleotides. Consequently, rN contamination of DNA is common and pervasive across all domains of life. Failure to remove rNs from DNA has severe consequences, and all organisms are equipped with RNase H enzymes to remove RNA-DNA hybrids. RNase H deficiency leads to complications in bacteria, yeast, and mouse, and diseases like progressive external ophthalmoplegia (mitochondrial defects in RNASEH1) and Aicardi-Goutières syndrome (defects in RNASEH2) in humans. Escherichia coli ∆rnhAB mutant, deficient in RNases H, has severe chromosomal complications. Despite substantial problems, nearly half of the mutant population survives. We have identified novel and previously confirmed pathways in various parts of nucleic acid metabolism that ensure survival with RNase H deficiency.
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Affiliation(s)
- Sneha Das
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Jonathan Forrest
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Andrei Kuzminov
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
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11
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Hogins J, Xuan Z, Zimmern PE, Reitzer L. The distinct transcriptome of virulence-associated phylogenetic group B2 Escherichia coli. Microbiol Spectr 2023; 11:e0208523. [PMID: 37724859 PMCID: PMC10580932 DOI: 10.1128/spectrum.02085-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 07/28/2023] [Indexed: 09/21/2023] Open
Abstract
Escherichia coli strains of phylogenetic group B2 are often associated with urinary tract infections (UTIs) and several other diseases. Recent genomic and transcriptomic analyses have not suggested or identified specific genes required for virulence, but have instead suggested multiple virulence strategies and complex host-pathogen interactions. Previous analyses have not compared core gene expression between phylogenetic groups or between pathogens and nonpathogens within phylogenetic groups. We compared the core gene expression of 35 strains from three phylogenetic groups that included both pathogens and nonpathogens after growth in a medium that allowed comparable growth of both types of strains. K-means clustering suggested a B2 cluster with 17 group B2 strains and two group A strains; an AD cluster with six group A strains, five group D strains and one B2 strain; and four outliers which included the highly studied model uropathogenic E. coli strains UTI89 and CFT073. Half of the core genes were differentially expressed between B2 and AD cluster strains, including transcripts of genes for all aspects of macromolecular synthesis-replication, transcription, translation, and peptidoglycan synthesis-energy metabolism, and environmental-sensing transcriptional regulators. Notably, core gene expression between nonpathogenic and uropathogenic transcriptomes within phylogenetic groups did not differ. If differences between pathogens and nonpathogens exist, then the differences do not require transcriptional reprogramming. In summary, B2 cluster strains have a distinct transcription pattern that involves hundreds of genes. We propose that this transcription pattern is one factor that contributes to virulence. IMPORTANCE Escherichia coli is a diverse species and an opportunistic pathogen that is associated with various diseases, such as urinary tract infections. When examined, phylogenetic group B2 strains are more often associated with these diseases, but the specific properties that contribute to their virulence are not known. From a comparative transcriptomic analysis, we found that group B2 strains grown in a nutrient-rich medium had a distinct transcription pattern, which is the first evidence that core gene expression differs between phylogenetic groups. Understanding the consequences of group B2 transcription pattern will provide important information on basic E. coli biology, the basis for E. coli virulence, and possibly for developing therapies for a majority of urinary tract infections and other group B2-associated diseases.
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Affiliation(s)
- Jacob Hogins
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Zhenyu Xuan
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Philippe E. Zimmern
- Department of Urology, The University of Texas Southwestern, Dallas, Texas, USA
| | - Larry Reitzer
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
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12
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Rao TVP, Kuzminov A. Robust linear DNA degradation supports replication-initiation-defective mutants in Escherichia coli. G3 (BETHESDA, MD.) 2022; 12:jkac228. [PMID: 36165702 PMCID: PMC9635670 DOI: 10.1093/g3journal/jkac228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 08/22/2022] [Indexed: 06/16/2023]
Abstract
RecBCD helicase/nuclease supports replication fork progress via recombinational repair or linear DNA degradation, explaining recBC mutant synthetic lethality with replication elongation defects. Since replication initiation defects leave chromosomes without replication forks, these should be insensitive to the recBCD status. Surprisingly, we found that both Escherichia coli dnaA46(Ts) and dnaC2(Ts) initiation mutants at semi-permissive temperatures are also recBC-colethal. Interestingly, dnaA46 recBC lethality suppressors suggest underinitiation as the problem, while dnaC2 recBC suppressors signal overintiation. Using genetic and physical approaches, we studied the dnaA46 recBC synthetic lethality, for the possibility that RecBCD participates in replication initiation. Overproduced DnaA46 mutant protein interferes with growth of dnaA+ cells, while the residual viability of the dnaA46 recBC mutant depends on the auxiliary replicative helicase Rep, suggesting replication fork inhibition by the DnaA46 mutant protein. The dnaA46 mutant depends on linear DNA degradation by RecBCD, rather than on recombinational repair. At the same time, the dnaA46 defect also interacts with Holliday junction-moving defects, suggesting reversal of inhibited forks. However, in contrast to all known recBC-colethals, which fragment their chromosomes, the dnaA46 recBC mutant develops no chromosome fragmentation, indicating that its inhibited replication forks are stable. Physical measurements confirm replication inhibition in the dnaA46 mutant shifted to semi-permissive temperatures, both at the level of elongation and initiation, while RecBCD gradually restores elongation and then initiation. We propose that RecBCD-catalyzed resetting of inhibited replication forks allows replication to displace the "sticky" DnaA46(Ts) protein from the chromosomal DNA, mustering enough DnaA for new initiations.
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Affiliation(s)
| | - Andrei Kuzminov
- Corresponding author: Department of Microbiology, University of Illinois at Urbana-Champaign, B103 C&LSL, 601 South Goodwin Avenue, Urbana, IL 61801-3709, USA.
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13
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McLean EK, Nye TM, Lowder FC, Simmons LA. The Impact of RNA-DNA Hybrids on Genome Integrity in Bacteria. Annu Rev Microbiol 2022; 76:461-480. [PMID: 35655343 PMCID: PMC9527769 DOI: 10.1146/annurev-micro-102521-014450] [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: 09/10/2023]
Abstract
During the essential processes of DNA replication and transcription, RNA-DNA hybrid intermediates are formed that pose significant risks to genome integrity when left unresolved. To manage RNA-DNA hybrids, all cells rely on RNase H family enzymes that specifically cleave the RNA portion of the many different types of hybrids that form in vivo. Recent experimental advances have provided new insight into how RNA-DNA hybrids form and the consequences to genome integrity that ensue when persistent hybrids remain unresolved. Here we review the types of RNA-DNA hybrids, including R-loops, RNA primers, and ribonucleotide misincorporations, that form during DNA replication and transcription and discuss how each type of hybrid can contribute to genome instability in bacteria. Further, we discuss how bacterial RNase HI, HII, and HIII and bacterial FEN enzymes contribute to genome maintenance through the resolution of hybrids.
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Affiliation(s)
- Emma K McLean
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA;
| | - Taylor M Nye
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA;
- Current affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Frances C Lowder
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA;
| | - Lyle A Simmons
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA;
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14
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Blaine HC, Burke JT, Ravi J, Stallings CL. DciA Helicase Operators Exhibit Diversity across Bacterial Phyla. J Bacteriol 2022; 204:e0016322. [PMID: 35880876 PMCID: PMC9380583 DOI: 10.1128/jb.00163-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 06/21/2022] [Indexed: 01/28/2023] Open
Abstract
A fundamental requirement for life is the replication of an organism's DNA. Studies in Escherichia coli and Bacillus subtilis have set the paradigm for DNA replication in bacteria. During replication initiation in E. coli and B. subtilis, the replicative helicase is loaded onto the DNA at the origin of replication by an ATPase helicase loader. However, most bacteria do not encode homologs to the helicase loaders in E. coli and B. subtilis. Recent work has identified the DciA protein as a predicted helicase operator that may perform a function analogous to the helicase loaders in E. coli and B. subtilis. DciA proteins, which are defined by the presence of a DUF721 domain (termed the DciA domain herein), are conserved in most bacteria but have only been studied in mycobacteria and gammaproteobacteria (Pseudomonas aeruginosa and Vibrio cholerae). Sequences outside the DciA domain in Mycobacterium tuberculosis DciA are essential for protein function but are not conserved in the P. aeruginosa and V. cholerae homologs, raising questions regarding the conservation and evolution of DciA proteins across bacterial phyla. To comprehensively define the DciA protein family, we took a computational evolutionary approach and analyzed the domain architectures and sequence properties of DciA domain-containing proteins across the tree of life. These analyses identified lineage-specific domain architectures among DciA homologs, as well as broadly conserved sequence-structural motifs. The diversity of DciA proteins represents the evolution of helicase operation in bacterial DNA replication and highlights the need for phylum-specific analyses of this fundamental biological process. IMPORTANCE Despite the fundamental importance of DNA replication for life, this process remains understudied in bacteria outside Escherichia coli and Bacillus subtilis. In particular, most bacteria do not encode the helicase-loading proteins that are essential in E. coli and B. subtilis for DNA replication. Instead, most bacteria encode a DciA homolog that likely constitutes the predominant mechanism of helicase operation in bacteria. However, it is still unknown how DciA structure and function compare across diverse phyla that encode DciA proteins. In this study, we performed computational evolutionary analyses to uncover tremendous diversity among DciA homologs. These studies provide a significant advance in our understanding of an essential component of the bacterial DNA replication machinery.
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Affiliation(s)
- Helen C. Blaine
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri, USA
- Center for Women’s Infectious Disease Research, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Joseph T. Burke
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
- Genomics and Molecular Genetics Undergraduate Program, Michigan State University, East Lansing, Michigan, USA
| | - Janani Ravi
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Christina L. Stallings
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri, USA
- Center for Women’s Infectious Disease Research, Washington University School of Medicine, Saint Louis, Missouri, USA
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15
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Abstract
DNA looping has emerged as a central paradigm of transcriptional regulation, as it is shared across many living systems. One core property of DNA looping-based regulation is its ability to greatly enhance repression or activation of genes with only a few copies of transcriptional regulators. However, this property based on a small number of proteins raises the question of the robustness of such a mechanism with respect to the large intracellular perturbations taking place during growth and division of the cell. Here we address the issue of sensitivity to variations of intracellular parameters of gene regulation by DNA looping. We use the lac system as a prototype to experimentally identify the key features of the robustness of DNA looping in growing Escherichia coli cells. Surprisingly, we observe time intervals of tight repression spanning across division events, which can sometimes exceed 10 generations. Remarkably, the distribution of such long time intervals exhibits memoryless statistics that is mostly insensitive to repressor concentration, cell division events, and the number of distinct loops accessible to the system. By contrast, gene regulation becomes highly sensitive to these perturbations when DNA looping is absent. Using stochastic simulations, we propose that the observed robustness to division emerges from the competition between fast, multiple rebinding events of repressors and slow initiation rate of the RNA polymerase. We argue that fast rebinding events are a direct consequence of DNA looping that ensures robust gene repression across a range of intracellular perturbations.
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16
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Miropolskaya N, Petushkov I, Esyunina D, Kulbachinskiy A. Suppressor mutations in Escherichia coli RNA polymerase alter transcription initiation but do not affect translesion RNA synthesis in vitro. J Biol Chem 2022; 298:102099. [PMID: 35667439 PMCID: PMC9254596 DOI: 10.1016/j.jbc.2022.102099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/19/2022] Open
Abstract
Bacterial RNA polymerase (RNAP) coordinates transcription with DNA repair and replication. Many RNAP mutations have pleiotropic phenotypes with profound effects on transcription-coupled processes. One class of RNAP mutations (rpo*) has been shown to suppress mutations in regulatory factors responsible for changes in gene expression during stationary phase or starvation, as well as in factors involved in the restoration of replication forks after DNA damage. These mutations were suggested to affect the ability of RNAP to transcribe damaged DNA and to decrease the stability of transcription complexes, thus facilitating their dislodging during DNA replication and repair, although this was not explicitly demonstrated. Here, we obtained nine mutations of this class located around the DNA/RNA binding cleft of E. coli RNAP and analyzed their transcription properties in vitro. We found that these mutations decreased promoter complex stability to varying degrees and all decreased the activity of rRNA promoters. However, they did not have strong effects on elongation complex stability. Some mutations were shown to stimulate transcriptional pauses or decrease intrinsic RNA cleavage by RNAP, but none altered the ability of RNAP to transcribe DNA templates containing damaged nucleotides. Thus, we conclude that the suppressor phenotypes of the mutations are unlikely to result from direct effects on DNA lesion recognition by RNAP but may be primarily explained by changes in transcription initiation. Further analysis of the effects of these mutations on the genomic distribution of RNAP and its interactions with regulatory factors will be essential for understanding their diverse phenotypes in vivo.
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Affiliation(s)
- Nataliya Miropolskaya
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Moscow, Russia
| | - Ivan Petushkov
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Moscow, Russia
| | - Daria Esyunina
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Moscow, Russia.
| | - Andrey Kulbachinskiy
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Moscow, Russia.
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17
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Essential Role for an Isoform of Escherichia coli Translation Initiation Factor IF2 in Repair of Two-Ended DNA Double-Strand Breaks. J Bacteriol 2022; 204:e0057121. [PMID: 35343794 DOI: 10.1128/jb.00571-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In Escherichia coli, three isoforms of the essential translation initiation factor IF2 (IF2-1, IF2-2, and IF2-3) are generated from separate in-frame initiation codons in infB. The isoforms have earlier been suggested to additionally participate in DNA damage repair and replication restart. It is also known that the proteins RecA and RecBCD are needed for repair of DNA double-strand breaks (DSBs) in E. coli. Here, we show that strains lacking IF2-1 are profoundly sensitive to two-ended DSBs in DNA generated by radiomimetic agents phleomycin or bleomycin, or by endonuclease I-SceI. However, these strains remained tolerant to other DSB-generating genotoxic agents or perturbations to which recA and recBC mutants remained sensitive, such as to mitomycin C, type-2 DNA topoisomerase inhibitors, or DSB caused by palindrome cleavage behind a replication fork. Data from genome-wide copy number analyses following I-SceI cleavage at a single chromosomal locus suggested that, in a strain lacking IF2-1, the magnitude of recombination-dependent replication through replication restart mechanisms is largely preserved but the extent of DNA resection around the DSB site is reduced. We propose that in the absence of IF2-1 it is the synapsis of a RecA nucleoprotein filament to its homologous target that is weakened, which in turn leads to a specific failure in assembly of Ter-to-oriC directed replisomes needed for consummation of two-ended DSB repair. IMPORTANCE Double-strand breaks (DSBs) in DNA are major threats to genome integrity. In Escherichia coli, DSBs are repaired by RecA- and RecBCD-mediated homologous recombination (HR). This study demonstrates a critical role for an isoform (IF2-1) of the translation initiation factor IF2 in the repair of two-ended DSBs in E. coli (that can be generated by ionizing radiation, certain DNA-damaging chemicals, or endonuclease action). It is proposed that IF2-1 acts to facilitate the function of RecA in the synapsis between a pair of DNA molecules during HR.
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18
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Carrasco B, Moreno-del Álamo M, Torres R, Alonso JC. PcrA Dissociates RecA Filaments and the SsbA and RecO Mediators Counterbalance Such Activity. Front Mol Biosci 2022; 9:836211. [PMID: 35223992 PMCID: PMC8865920 DOI: 10.3389/fmolb.2022.836211] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/05/2022] [Indexed: 11/24/2022] Open
Abstract
PcrA depletion is lethal in wild-type Bacillus subtilis cells. The PcrA DNA helicase contributes to unwinding RNA from the template strand, backtracking the RNA polymerase, rescuing replication-transcription conflicts, and disassembling RecA from single-stranded DNA (ssDNA) by poorly understood mechanisms. We show that, in the presence of RecA, circa one PcrA/plasmid-size circular ssDNA (cssDNA) molecule hydrolyzes ATP at a rate similar to that on the isolated cssDNA. PcrA K37A, which poorly hydrolyses ATP, fails to displace RecA from cssDNA. SsbA inhibits and blocks the ATPase activities of PcrA and RecA, respectively. RecO partially antagonizes and counteracts the negative effect of SsbA on PcrA- and RecA-mediated ATP hydrolysis, respectively. Conversely, multiple PcrA molecules are required to inhibit RecA·ATP-mediated DNA strand exchange (DSE). RecO and SsbA poorly antagonize the PcrA inhibitory effect on RecA·ATP-mediated DSE. We propose that two separable PcrA functions exist: an iterative translocating PcrA monomer strips RecA from cssDNA to prevent unnecessary recombination with the mediators SsbA and RecO balancing such activity; and a PcrA cluster that disrupts DNA transactions, as RecA-mediated DSE.
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19
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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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20
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Jameson KH, Rudolph CJ, Hawkins M. Termination of DNA replication at Tus-ter barriers results in under-replication of template DNA. J Biol Chem 2021; 297:101409. [PMID: 34780717 DOI: 10.1016/j.jbc.2021.101409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 11/02/2021] [Accepted: 11/10/2021] [Indexed: 02/05/2023] Open
Abstract
The complete and accurate duplication of genomic information is vital to maintain genome stability in all domains of life. In Escherichia coli, replication termination, the final stage of the duplication process, is confined to the 'replication fork trap' region by multiple unidirectional fork barriers formed by the binding of Tus protein to genomic ter sites. Termination typically occurs away from Tus-ter complexes, but they become part of the fork fusion process when a delay to one replisome allows the second replisome to travel more than halfway around the chromosome. In this instance, replisome progression is blocked at the non-permissive interface of the Tus-ter complex, termination then occurs when a converging replisome meets the permissive interface. To investigate the consequences of replication fork fusion at Tus-ter complexes, we established a plasmid-based replication system where we could mimic the termination process at Tus-ter complexes in vitro. We developed a termination mapping assay to measure leading strand replication fork progression and demonstrate that the DNA template is under-replicated by 15-24 bases when replication forks fuse at Tus-ter complexes. This gap could not be closed by the addition of lagging strand processing enzymes or by the inclusion of several helicases that promote DNA replication. Our results indicate that accurate fork fusion at Tus-ter barriers requires further enzymatic processing, highlighting large gaps that still exist in our understanding of the final stages of chromosome duplication and the evolutionary advantage of having a replication fork trap.
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Affiliation(s)
- Katie H Jameson
- Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK
| | - Christian J Rudolph
- Division of Biosciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Michelle Hawkins
- Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK.
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21
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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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22
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Brüning JG, Marians KJ. Bypass of complex co-directional replication-transcription collisions by replisome skipping. Nucleic Acids Res 2021; 49:9870-9885. [PMID: 34469567 PMCID: PMC8464059 DOI: 10.1093/nar/gkab760] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/17/2021] [Accepted: 08/24/2021] [Indexed: 12/27/2022] Open
Abstract
Collisions between the replisome and RNA polymerases [RNAP(s)] are the main obstacle to DNA replication. These collisions can occur either head-on or co-directionally with respect to the direction of translocation of both complexes. Whereas head-on collisions require additional factors to be resolved, co-directional collisions are thought to be overcome by the replisome itself using the mRNA transcript as a primer. We show that mRNA takeover is utilized primarily after collisions with single RNAP complexes with short transcripts. Bypass of more complex transcription complexes requires the synthesis of a new primer downstream of the RNAP for the replisome to resume leading-strand synthesis. In both cases, bypass proceeds with displacement of the RNAP. Rep, Mfd, UvrD and RNase H can process the RNAP block and facilitate replisome bypass by promoting the formation of continuous leading strands. Bypass of co-directional RNAP(s) and/or R-loops is determined largely by the length of the obstacle that the replisome needs to traverse: R-loops are about equally as potent obstacles as RNAP arrays if they occupy the same length of the DNA template.
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Affiliation(s)
- Jan-Gert Brüning
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Kenneth J Marians
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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23
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Topoisomerase I Essentiality, DnaA-Independent Chromosomal Replication, and Transcription-Replication Conflict in Escherichia coli. J Bacteriol 2021; 203:e0019521. [PMID: 34124945 DOI: 10.1128/jb.00195-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Topoisomerase I (Topo I) of Escherichia coli, encoded by topA, acts to relax negative supercoils in DNA. Topo I deficiency results in hypernegative supercoiling, formation of transcription-associated RNA-DNA hybrids (R-loops), and DnaA- and oriC-independent constitutive stable DNA replication (cSDR), but some uncertainty persists as to whether topA is essential for viability in E. coli and related enterobacteria. Here, we show that several topA alleles, including ΔtopA, confer lethality in derivatives of wild-type E. coli strain MG1655. Viability in the absence of Topo I was restored with two perturbations, neither of which reversed the hypernegative supercoiling phenotype: (i) in a reduced-genome strain (MDS42) or (ii) by an RNA polymerase (RNAP) mutation, rpoB*35, that has been reported to alleviate the deleterious consequences of RNAP backtracking and transcription-replication conflicts. Four phenotypes related to cSDR were identified for topA mutants: (i) one of the topA alleles rescued ΔdnaA lethality; (ii) in dnaA+ derivatives, Topo I deficiency generated a characteristic copy number peak in the terminus region of the chromosome; (iii) topA was synthetically lethal with rnhA (encoding RNase HI, whose deficiency also confers cSDR); and (iv) topA rnhA synthetic lethality was itself rescued by ΔdnaA. We propose that the terminal lethal consequence of hypernegative DNA supercoiling in E. coli topA mutants is RNAP backtracking during transcription elongation and associated R-loop formation, which in turn leads to transcription-replication conflicts and to cSDR. IMPORTANCE In all life forms, double-helical DNA exists in a topologically supercoiled state. The enzymes DNA gyrase and topoisomerase I act, respectively, to introduce and to relax negative DNA supercoils in Escherichia coli. That gyrase deficiency leads to bacterial death is well established, but the essentiality of topoisomerase I for viability has been less certain. This study confirms that topoisomerase I is essential for E. coli viability and suggests that in its absence, aberrant chromosomal DNA replication and excessive transcription-replication conflicts occur that are responsible for lethality.
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24
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Nguyen B, Shinn MK, Weiland E, Lohman TM. Regulation of E. coli Rep helicase activity by PriC. J Mol Biol 2021; 433:167072. [PMID: 34081984 PMCID: PMC8941637 DOI: 10.1016/j.jmb.2021.167072] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 05/11/2021] [Accepted: 05/20/2021] [Indexed: 11/28/2022]
Abstract
Stalled DNA replication forks can result in incompletely replicated genomes and cell death. DNA replication restart pathways have evolved to deal with repair of stalled forks and E. coli Rep helicase functions in this capacity. Rep and an accessory protein, PriC, assemble at a stalled replication fork to facilitate loading of other replication proteins. A Rep monomer is a rapid and processive single stranded (ss) DNA translocase but needs to be activated to function as a helicase. Activation of Rep in vitro requires self-assembly to form a dimer, removal of its auto-inhibitory 2B sub-domain, or interactions with an accessory protein. Rep helicase activity has been shown to be stimulated by PriC, although the mechanism of activation is not clear. Using stopped flow kinetics, analytical sedimentation and single molecule fluorescence methods, we show that a PriC dimer activates the Rep monomer helicase and can also stimulate the Rep dimer helicase. We show that PriC can self-assemble to form dimers and tetramers and that Rep and PriC interact in the absence of DNA. We further show that PriC serves as a Rep processivity factor, presumably co-translocating with Rep during DNA unwinding. Activation is specific for Rep since PriC does not activate the UvrD helicase. Interaction of PriC with the C-terminal acidic tip of the ssDNA binding protein, SSB, eliminates Rep activation by stabilizing the PriC monomer. This suggests a likely mechanism for Rep activation by PriC at a stalled replication fork.
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Affiliation(s)
- Binh Nguyen
- Department of Biochemistry and Molecular Biophysics, Box 8231, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, United States
| | - Min Kyung Shinn
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Elizabeth Weiland
- Department of Biochemistry and Molecular Biophysics, Box 8231, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, United States
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Box 8231, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, United States.
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25
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Urrutia-Irazabal I, Ault JR, Sobott F, Savery NJ, Dillingham MS. Analysis of the PcrA-RNA polymerase complex reveals a helicase interaction motif and a role for PcrA/UvrD helicase in the suppression of R-loops. eLife 2021; 10:68829. [PMID: 34279225 PMCID: PMC8318588 DOI: 10.7554/elife.68829] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 07/16/2021] [Indexed: 12/12/2022] Open
Abstract
The PcrA/UvrD helicase binds directly to RNA polymerase (RNAP) but the structural basis for this interaction and its functional significance have remained unclear. In this work, we used biochemical assays and hydrogen-deuterium exchange coupled to mass spectrometry to study the PcrA-RNAP complex. We find that PcrA binds tightly to a transcription elongation complex in a manner dependent on protein:protein interaction with the conserved PcrA C-terminal Tudor domain. The helicase binds predominantly to two positions on the surface of RNAP. The PcrA C-terminal domain engages a conserved region in a lineage-specific insert within the β subunit which we identify as a helicase interaction motif present in many other PcrA partner proteins, including the nucleotide excision repair factor UvrB. The catalytic core of the helicase binds near the RNA and DNA exit channels and blocking PcrA activity in vivo leads to the accumulation of R-loops. We propose a role for PcrA as an R-loop suppression factor that helps to minimize conflicts between transcription and other processes on DNA including replication.
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Affiliation(s)
- Inigo Urrutia-Irazabal
- DNA:Protein Interactions Unit, School of Biochemistry, University of Bristol. Biomedical Sciences Building, University Walk, Bristol, United Kingdom
| | - James R Ault
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Frank Sobott
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Nigel J Savery
- DNA:Protein Interactions Unit, School of Biochemistry, University of Bristol. Biomedical Sciences Building, University Walk, Bristol, United Kingdom
| | - Mark S Dillingham
- DNA:Protein Interactions Unit, School of Biochemistry, University of Bristol. Biomedical Sciences Building, University Walk, Bristol, United Kingdom
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26
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Shepherd JW, Payne-Dwyer AL, Lee JE, Syeda A, Leake MC. Combining single-molecule super-resolved localization microscopy with fluorescence polarization imaging to study cellular processes. JPHYS PHOTONICS 2021. [DOI: 10.1088/2515-7647/ac015d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Super-resolution microscopy has catalyzed valuable insights into the sub-cellular, mechanistic details of many different biological processes across a wide range of cell types. Fluorescence polarization spectroscopy tools have also enabled important insights into cellular processes through identifying orientational changes of biological molecules typically at an ensemble level. Here, we combine these two biophysical methodologies in a single home-made instrument to enable the simultaneous detection of orthogonal fluorescence polarization signals from single fluorescent protein molecules used as common reporters on the localization of proteins in cellular processes. These enable measurement of spatial location to a super-resolved precision better than the diffraction-limited optical resolution, as well as estimation of molecular stoichiometry based on the brightness of individual fluorophores. In this innovation we have adapted a millisecond timescale microscope used for single-molecule detection to enable splitting of fluorescence polarization emissions into two separate imaging channels for s- and p-polarization signals, which are imaged onto separate halves of the same high sensitivity back-illuminated CMOS camera detector. We applied this fluorescence polarization super-resolved imaging modality to a range of test fluorescent samples relevant to the study of biological processes, including purified monomeric green fluorescent protein, single combed DNA molecules, and protein assemblies and complexes from live Escherichia coli and Saccharomyces cerevisiae cells. Our findings are qualitative but demonstrate promise in showing how fluorescence polarization and super-resolved localization microscopy can be combined on the same sample to enable simultaneous measurements of polarization and stoichiometry of tracked molecular complexes, as well as the translational diffusion coefficient.
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27
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Yi X, Khey J, Kazlauskas RJ, Travisano M. Plasmid hypermutation using a targeted artificial DNA replisome. SCIENCE ADVANCES 2021; 7:7/29/eabg8712. [PMID: 34272238 PMCID: PMC8284885 DOI: 10.1126/sciadv.abg8712] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/02/2021] [Indexed: 06/13/2023]
Abstract
Extensive exploration of a protein's sequence space for improved or new molecular functions requires in vivo evolution with large populations. But disentangling the evolution of a target protein from the rest of the proteome is challenging. Here, we designed a protein complex of a targeted artificial DNA replisome (TADR) that operates in live cells to processively replicate one strand of a plasmid with errors. It enhanced mutation rates of the target plasmid up to 2.3 × 105-fold with only a 78-fold increase in off-target mutagenesis. It was used to evolve itself to increase error rate and increase the efficiency of an efflux pump while simultaneously expanding the substrate repertoire. TADR enables multiple simultaneous substitutions to discover functions inaccessible by accumulating single substitutions, affording potential for solving hard problems in molecular evolution and developing biologic drugs and industrial catalysts.
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Affiliation(s)
- Xiao Yi
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
| | - Joleen Khey
- Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, MN, USA
| | - Romas J Kazlauskas
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
- Department of Biochemistry Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Michael Travisano
- BioTechnology Institute, University of Minnesota, Minneapolis, MN, USA.
- Department of Ecology Evolution and Behavior, University of Minnesota, Minneapolis, MN, USA
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28
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Moreno-del Álamo M, Carrasco B, Torres R, Alonso JC. Bacillus subtilis PcrA Helicase Removes Trafficking Barriers. Cells 2021; 10:935. [PMID: 33920686 PMCID: PMC8074105 DOI: 10.3390/cells10040935] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/12/2021] [Accepted: 04/14/2021] [Indexed: 12/27/2022] Open
Abstract
Bacillus subtilis PcrA interacts with the RNA polymerase and might contribute to mitigate replication-transcription conflicts (RTCs). We show that PcrA depletion lethality is partially suppressed by rnhB inactivation, but cell viability is significantly reduced by rnhC or dinG inactivation. Following PcrA depletion, cells lacking RnhC or DinG are extremely sensitive to DNA damage. Chromosome segregation is not further impaired by rnhB or dinG inactivation but is blocked by rnhC or recA inactivation upon PcrA depletion. Despite our efforts, we could not construct a ΔrnhC ΔrecA strain. These observations support the idea that PcrA dismantles RTCs. Purified PcrA, which binds single-stranded (ss) DNA over RNA, is a ssDNA-dependent ATPase and preferentially unwinds DNA in a 3'→5'direction. PcrA unwinds a 3'-tailed RNA of an RNA-DNA hybrid significantly faster than that of a DNA substrate. Our results suggest that a replicative stress, caused by mis-incorporated rNMPs, indirectly increases cell viability upon PcrA depletion. We propose that PcrA, in concert with RnhC or DinG, contributes to removing spontaneous or enzyme-driven R-loops, to counteract deleterious trafficking conflicts and preserve to genomic integrity.
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Affiliation(s)
| | | | | | - Juan Carlos Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain; (M.M.-d.Á.); (B.C.); (R.T.)
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29
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Dienerowitz M, Howard JAL, Quinn SD, Dienerowitz F, Leake MC. Single-molecule FRET dynamics of molecular motors in an ABEL trap. Methods 2021; 193:96-106. [PMID: 33571667 DOI: 10.1016/j.ymeth.2021.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/22/2021] [Accepted: 01/29/2021] [Indexed: 02/07/2023] Open
Abstract
Single-molecule Förster resonance energy transfer (smFRET) of molecular motors provides transformative insights into their dynamics and conformational changes both at high temporal and spatial resolution simultaneously. However, a key challenge of such FRET investigations is to observe a molecule in action for long enough without restricting its natural function. The Anti-Brownian ELectrokinetic Trap (ABEL trap) sets out to combine smFRET with molecular confinement to enable observation times of up to several seconds while removing any requirement of tethered surface attachment of the molecule in question. In addition, the ABEL trap's inherent ability to selectively capture FRET active molecules accelerates the data acquisition process. In this work we exemplify the capabilities of the ABEL trap in performing extended timescale smFRET measurements on the molecular motor Rep, which is crucial for removing protein blocks ahead of the advancing DNA replication machinery and for restarting stalled DNA replication. We are able to monitor single Rep molecules up to 6 seconds with sub-millisecond time resolution capturing multiple conformational switching events during the observation time. Here we provide a step-by-step guide for the rational design, construction and implementation of the ABEL trap for smFRET detection of Rep in vitro. We include details of how to model the electric potential at the trap site and use Hidden Markov analysis of the smFRET trajectories.
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Affiliation(s)
- Maria Dienerowitz
- Single-Molecule Microscopy Group, Universitätsklinikum Jena, Nonnenplan 2 - 4, 07743 Jena, Germany.
| | - Jamieson A L Howard
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; Department of Biology, University of York, Heslington, York YO10 5DD, UK
| | - Steven D Quinn
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
| | - Frank Dienerowitz
- Ernst-Abbe-Hochschule Jena, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
| | - Mark C Leake
- Department of Physics, University of York, Heslington, York YO10 5DD, UK; Department of Biology, University of York, Heslington, York YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK
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30
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Brüning JG, Marians KJ. Replisome bypass of transcription complexes and R-loops. Nucleic Acids Res 2020; 48:10353-10367. [PMID: 32926139 PMCID: PMC7544221 DOI: 10.1093/nar/gkaa741] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/22/2020] [Accepted: 08/25/2020] [Indexed: 12/16/2022] Open
Abstract
The vast majority of the genome is transcribed by RNA polymerases. G+C-rich regions of the chromosomes and negative superhelicity can promote the invasion of the DNA by RNA to form R-loops, which have been shown to block DNA replication and promote genome instability. However, it is unclear whether the R-loops themselves are sufficient to cause this instability or if additional factors are required. We have investigated replisome collisions with transcription complexes and R-loops using a reconstituted bacterial DNA replication system. RNA polymerase transcription complexes co-directionally oriented with the replication fork were transient blockages, whereas those oriented head-on were severe, stable blockages. On the other hand, replisomes easily bypassed R-loops on either template strand. Replication encounters with R-loops on the leading-strand template (co-directional) resulted in gaps in the nascent leading strand, whereas lagging-strand template R-loops (head-on) had little impact on replication fork progression. We conclude that whereas R-loops alone can act as transient replication blocks, most genome-destabilizing replication fork stalling likely occurs because of proteins bound to the R-loops.
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Affiliation(s)
- Jan-Gert Brüning
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Kenneth J Marians
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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31
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Wolak C, Ma HJ, Soubry N, Sandler SJ, Reyes-Lamothe R, Keck JL. Interaction with single-stranded DNA-binding protein localizes ribonuclease HI to DNA replication forks and facilitates R-loop removal. Mol Microbiol 2020; 114:495-509. [PMID: 32426857 PMCID: PMC7934204 DOI: 10.1111/mmi.14529] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 04/30/2020] [Accepted: 05/09/2020] [Indexed: 01/06/2023]
Abstract
DNA replication complexes (replisomes) routinely encounter proteins and unusual nucleic acid structures that can impede their progress. Barriers can include transcription complexes and R-loops that form when RNA hybridizes with complementary DNA templates behind RNA polymerases. Cells encode several RNA polymerase and R-loop clearance mechanisms to limit replisome exposure to these potential obstructions. One such mechanism is hydrolysis of R-loops by ribonuclease HI (RNase HI). Here, we examine the cellular role of the interaction between Escherichia coli RNase HI and the single-stranded DNA-binding protein (SSB) in this process. Interaction with SSB localizes RNase HI foci to DNA replication sites. Mutation of rnhA to encode an RNase HI variant that cannot interact with SSB but that maintains enzymatic activity (rnhAK60E) eliminates RNase HI foci. The mutation also produces a media-dependent slow-growth phenotype and an activated DNA damage response in cells lacking Rep helicase, which is an enzyme that disrupts stalled transcription complexes. RNA polymerase variants that are thought to increase or decrease R-loop accumulation enhance or suppress, respectively, the growth phenotype of rnhAK60E rep::kan strains. These results identify a cellular role for the RNase HI/SSB interaction in helping to clear R-loops that block DNA replication.
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Affiliation(s)
- Christine Wolak
- Department of Biomolecular Chemistry, 420 Henry Mall, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706
| | - Hui Jun Ma
- Department of Biology, McGill University, 3649 Sir William Osler, Montreal, QC, H3G 0B1, Canada
| | - Nicolas Soubry
- Department of Biology, McGill University, 3649 Sir William Osler, Montreal, QC, H3G 0B1, Canada
| | - Steven J. Sandler
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Rodrigo Reyes-Lamothe
- Department of Biology, McGill University, 3649 Sir William Osler, Montreal, QC, H3G 0B1, Canada
| | - James L. Keck
- Department of Biomolecular Chemistry, 420 Henry Mall, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706
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32
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Moreno-Del Alamo M, Torres R, Manfredi C, Ruiz-Masó JA, Del Solar G, Alonso JC. Bacillus subtilis PcrA Couples DNA Replication, Transcription, Recombination and Segregation. Front Mol Biosci 2020; 7:140. [PMID: 32793628 PMCID: PMC7385302 DOI: 10.3389/fmolb.2020.00140] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/10/2020] [Indexed: 01/08/2023] Open
Abstract
Bacillus subtilis PcrA abrogates replication-transcription conflicts in vivo and disrupts RecA nucleoprotein filaments in vitro. Inactivation of pcrA is lethal. We show that PcrA depletion lethality is suppressed by recJ (involved in end resection), recA (the recombinase), or mfd (transcription-coupled repair) inactivation, but not by inactivating end resection (addAB or recQ), positive and negative RecA modulators (rarA or recX and recU), or genes involved in the reactivation of a stalled RNA polymerase (recD2, helD, hepA, and ywqA). We also report that B. subtilis mutations previously designated as recL16 actually map to the recO locus, and confirm that PcrA depletion lethality is suppressed by recO inactivation. The pcrA gene is epistatic to recA or mfd, but it is not epistatic to addAB, recJ, recQ, recO16, rarA, recX, recU, recD2, helD, hepA, or ywqA in response to DNA damage. PcrA depletion led to the accumulation of unsegregated chromosomes, and this defect is increased by recQ, rarA, or recU inactivation. We propose that PcrA, which is crucial to maintain cell viability, is involved in different DNA transactions.
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Affiliation(s)
- María Moreno-Del Alamo
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, Madrid, Spain
| | - Rubén Torres
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, Madrid, Spain
| | - Candela Manfredi
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, Madrid, Spain
| | - José A Ruiz-Masó
- Centro de Investigaciones Biológicas Margarita Salas, CIB-CSIC, Madrid, Spain
| | - Gloria Del Solar
- Centro de Investigaciones Biológicas Margarita Salas, CIB-CSIC, Madrid, Spain
| | - Juan Carlos Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, Madrid, Spain
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33
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Syeda AH, Dimude JU, Skovgaard O, Rudolph CJ. Too Much of a Good Thing: How Ectopic DNA Replication Affects Bacterial Replication Dynamics. Front Microbiol 2020; 11:534. [PMID: 32351461 PMCID: PMC7174701 DOI: 10.3389/fmicb.2020.00534] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 03/12/2020] [Indexed: 12/15/2022] Open
Abstract
Each cell division requires the complete and accurate duplication of the entire genome. In bacteria, the duplication process of the often-circular chromosomes is initiated at a single origin per chromosome, resulting in two replication forks that traverse the chromosome in opposite directions. DNA synthesis is completed once the two forks fuse in a region diametrically opposite the origin. In some bacteria, such as Escherichia coli, the region where forks fuse forms a specialized termination area. Polar replication fork pause sites flanking this area can pause the progression of replication forks, thereby allowing forks to enter but not to leave. Transcription of all required genes has to take place simultaneously with genome duplication. As both of these genome trafficking processes share the same template, conflicts are unavoidable. In this review, we focus on recent attempts to add additional origins into various ectopic chromosomal locations of the E. coli chromosome. As ectopic origins disturb the native replichore arrangements, the problems resulting from such perturbations can give important insights into how genome trafficking processes are coordinated and the problems that arise if this coordination is disturbed. The data from these studies highlight that head-on replication–transcription conflicts are indeed highly problematic and multiple repair pathways are required to restart replication forks arrested at obstacles. In addition, the existing data also demonstrate that the replication fork trap in E. coli imposes significant constraints to genome duplication if ectopic origins are active. We describe the current models of how replication fork fusion events can cause serious problems for genome duplication, as well as models of how such problems might be alleviated both by a number of repair pathways as well as the replication fork trap system. Considering the problems associated both with head-on replication-transcription conflicts as well as head-on replication fork fusion events might provide clues of how these genome trafficking issues have contributed to shape the distinct architecture of bacterial chromosomes.
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Affiliation(s)
- Aisha H Syeda
- Department of Biology, University of York, York, United Kingdom
| | - Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Ole Skovgaard
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, United Kingdom
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34
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Brosh RM, Matson SW. History of DNA Helicases. Genes (Basel) 2020; 11:genes11030255. [PMID: 32120966 PMCID: PMC7140857 DOI: 10.3390/genes11030255] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
Since the discovery of the DNA double helix, there has been a fascination in understanding the molecular mechanisms and cellular processes that account for: (i) the transmission of genetic information from one generation to the next and (ii) the remarkable stability of the genome. Nucleic acid biologists have endeavored to unravel the mysteries of DNA not only to understand the processes of DNA replication, repair, recombination, and transcription but to also characterize the underlying basis of genetic diseases characterized by chromosomal instability. Perhaps unexpectedly at first, DNA helicases have arisen as a key class of enzymes to study in this latter capacity. From the first discovery of ATP-dependent DNA unwinding enzymes in the mid 1970's to the burgeoning of helicase-dependent pathways found to be prevalent in all kingdoms of life, the story of scientific discovery in helicase research is rich and informative. Over four decades after their discovery, we take this opportunity to provide a history of DNA helicases. No doubt, many chapters are left to be written. Nonetheless, at this juncture we are privileged to share our perspective on the DNA helicase field - where it has been, its current state, and where it is headed.
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Affiliation(s)
- Robert M. Brosh
- Section on DNA Helicases, Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
| | - Steven W. Matson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
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35
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Syeda AH, Wollman AJM, Hargreaves AL, Howard JAL, Brüning JG, McGlynn P, Leake MC. Single-molecule live cell imaging of Rep reveals the dynamic interplay between an accessory replicative helicase and the replisome. Nucleic Acids Res 2020; 47:6287-6298. [PMID: 31028385 PMCID: PMC6614839 DOI: 10.1093/nar/gkz298] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 04/01/2019] [Accepted: 04/24/2019] [Indexed: 12/21/2022] Open
Abstract
DNA replication must cope with nucleoprotein barriers that impair efficient replisome translocation. Biochemical and genetic studies indicate accessory helicases play essential roles in replication in the presence of nucleoprotein barriers, but how they operate inside the cell is unclear. With high-speed single-molecule microscopy we observed genomically-encoded fluorescent constructs of the accessory helicase Rep and core replisome protein DnaQ in live Escherichia coli cells. We demonstrate that Rep colocalizes with 70% of replication forks, with a hexameric stoichiometry, indicating maximal occupancy of the single DnaB hexamer. Rep associates dynamically with the replisome with an average dwell time of 6.5 ms dependent on ATP hydrolysis, indicating rapid binding then translocation away from the fork. We also imaged PriC replication restart factor and observe Rep-replisome association is also dependent on PriC. Our findings suggest two Rep-replisome populations in vivo: one continually associating with DnaB then translocating away to aid nucleoprotein barrier removal ahead of the fork, another assisting PriC-dependent reloading of DnaB if replisome progression fails. These findings reveal how a single helicase at the replisome provides two independent ways of underpinning replication of protein-bound DNA, a problem all organisms face as they replicate their genomes.
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Affiliation(s)
- Aisha H Syeda
- Department of Physics, University of York, York YO10 5DD, UK.,Department of Biology, University of York, York YO10 5DD, UK
| | - Adam J M Wollman
- Department of Physics, University of York, York YO10 5DD, UK.,Department of Biology, University of York, York YO10 5DD, UK
| | - Alex L Hargreaves
- Department of Physics, University of York, York YO10 5DD, UK.,Department of Biology, University of York, York YO10 5DD, UK
| | - Jamieson A L Howard
- Department of Physics, University of York, York YO10 5DD, UK.,Department of Biology, University of York, York YO10 5DD, UK
| | | | - Peter McGlynn
- Department of Biology, University of York, York YO10 5DD, UK
| | - Mark C Leake
- Department of Physics, University of York, York YO10 5DD, UK.,Department of Biology, University of York, York YO10 5DD, UK
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36
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Hawkins M, Dimude JU, Howard JAL, Smith AJ, Dillingham MS, Savery NJ, Rudolph CJ, McGlynn P. Direct removal of RNA polymerase barriers to replication by accessory replicative helicases. Nucleic Acids Res 2019; 47:5100-5113. [PMID: 30869136 PMCID: PMC6547429 DOI: 10.1093/nar/gkz170] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/22/2019] [Accepted: 03/08/2019] [Indexed: 11/24/2022] Open
Abstract
Bacterial genome duplication and transcription require simultaneous access to the same DNA template. Conflicts between the replisome and transcription machinery can lead to interruption of DNA replication and loss of genome stability. Pausing, stalling and backtracking of transcribing RNA polymerases add to this problem and present barriers to replisomes. Accessory helicases promote fork movement through nucleoprotein barriers and exist in viruses, bacteria and eukaryotes. Here, we show that stalled Escherichia coli transcription elongation complexes block reconstituted replisomes. This physiologically relevant block can be alleviated by the accessory helicase Rep or UvrD, resulting in the formation of full-length replication products. Accessory helicase action during replication-transcription collisions therefore promotes continued replication without leaving gaps in the DNA. In contrast, DinG does not promote replisome movement through stalled transcription complexes in vitro. However, our data demonstrate that DinG operates indirectly in vivo to reduce conflicts between replication and transcription. These results suggest that Rep and UvrD helicases operate on DNA at the replication fork whereas DinG helicase acts via a different mechanism.
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Affiliation(s)
- Michelle Hawkins
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
| | - Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | | | - Abigail J Smith
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Mark S Dillingham
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Nigel J Savery
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge UB8 3PH, UK
| | - Peter McGlynn
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
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37
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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38
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Makurath MA, Whitley KD, Nguyen B, Lohman TM, Chemla YR. Regulation of Rep helicase unwinding by an auto-inhibitory subdomain. Nucleic Acids Res 2019; 47:2523-2532. [PMID: 30690484 PMCID: PMC6412110 DOI: 10.1093/nar/gkz023] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 12/26/2018] [Accepted: 01/16/2019] [Indexed: 11/29/2022] Open
Abstract
Helicases are biomolecular motors that unwind nucleic acids, and their regulation is essential for proper maintenance of genomic integrity. Escherichia coli Rep helicase, whose primary role is to help restart stalled replication, serves as a model for Superfamily I helicases. The activity of Rep-like helicases is regulated by two factors: their oligomeric state, and the conformation of the flexible subdomain 2B. However, the mechanism of control is not well understood. To understand the factors that regulate the active state of Rep, here we investigate the behavior of a 2B-deficient variant (RepΔ2B) in relation to wild-type Rep (wtRep). Using a single-molecule optical tweezers assay, we explore the effects of oligomeric state, DNA geometry, and duplex stability on wtRep and RepΔ2B unwinding activity. We find that monomeric RepΔ2B unwinds more processively and at a higher speed than the activated, dimeric form of wtRep. The unwinding processivity of RepΔ2B and wtRep is primarily limited by ‘strand-switching’—during which the helicases alternate between strands of the duplex—which does not require the 2B subdomain, contrary to a previous proposal. We provide a quantitative model of the factors that enhance unwinding processivity. Our work sheds light on the mechanisms of regulation of unwinding by Rep-like helicases.
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Affiliation(s)
- Monika A Makurath
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Kevin D Whitley
- Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Binh Nguyen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yann R Chemla
- Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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39
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Perera HM, Behrmann MS, Hoang JM, Griffin WC, Trakselis MA. Contacts and context that regulate DNA helicase unwinding and replisome progression. Enzymes 2019; 45:183-223. [PMID: 31627877 DOI: 10.1016/bs.enz.2019.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hexameric DNA helicases involved in the separation of duplex DNA at the replication fork have a universal architecture but have evolved from two separate protein families. The consequences are that the regulation, translocation polarity, strand specificity, and architectural orientation varies between phage/bacteria to that of archaea/eukaryotes. Once assembled and activated for single strand DNA translocation and unwinding, the DNA polymerase couples tightly to the helicase forming a robust replisome complex. However, this helicase-polymerase interaction can be challenged by various forms of endogenous or exogenous agents that can stall the entire replisome or decouple DNA unwinding from synthesis. The consequences of decoupling can be severe, leading to a build-up of ssDNA requiring various pathways for replication fork restart. All told, the hexameric helicase sits prominently at the front of the replisome constantly responding to a variety of obstacles that require transient unwinding/reannealing, traversal of more stable blocks, and alternations in DNA unwinding speed that regulate replisome progression.
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Affiliation(s)
- Himasha M Perera
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Megan S Behrmann
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Joy M Hoang
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Wezley C Griffin
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Michael A Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States.
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40
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Niccum BA, Lee H, MohammedIsmail W, Tang H, Foster PL. The Symmetrical Wave Pattern of Base-Pair Substitution Rates across the Escherichia coli Chromosome Has Multiple Causes. mBio 2019; 10:e01226-19. [PMID: 31266871 PMCID: PMC6606806 DOI: 10.1128/mbio.01226-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 05/28/2019] [Indexed: 01/28/2023] Open
Abstract
Mutation accumulation experiments followed by whole-genome sequencing have revealed that, for several bacterial species, the rate of base-pair substitutions (BPSs) is not constant across the chromosome but varies in a wave-like pattern that is symmetrical about the origin of replication. The experiments reported here demonstrated that, in Escherichia coli, several interacting factors determine the wave. The origin is a major driver of BPS rates. When it is relocated, the BPS rates in a 1,000-kb region surrounding the new origin reproduce the pattern that surrounds the normal origin. However, the pattern across distant regions of the chromosome is unaltered and thus must be determined by other factors. Increasing the deoxynucleoside triphosphate (dNTP) concentration shifts the wave pattern away from the origin, supporting the hypothesis that fluctuations in dNTP pools coincident with replication firing contribute to the variations in the mutation rate. The nucleoid binding proteins (HU and Fis) and the terminus organizing protein (MatP) are also major factors. These proteins alter the three-dimensional structure of the DNA, and results suggest that mutation rates increase when highly structured DNA is replicated. Biases in error correction by proofreading and mismatch repair, both of which may be responsive to dNTP concentrations and DNA structure, also are major determinants of the wave pattern. These factors should apply to most bacterial and, possibly, eukaryotic genomes and suggest that different areas of the genome evolve at different rates.IMPORTANCE It has been found in several species of bacteria that the rate at which single base pairs are mutated is not constant across the genome but varies in a wave-like pattern that is symmetrical about the origin of replication. Using Escherichia coli as our model system, we show that this pattern is the result of several interconnected factors. First, the timing and progression of replication are important in determining the wave pattern. Second, the three-dimensional structure of the DNA is also a factor, and the results suggest that mutation rates increase when highly structured DNA is replicated. Finally, biases in error correction, which may be responsive both to the progression of DNA synthesis and to DNA structure, are major determinants of the wave pattern. These factors should apply to most bacterial and, possibly, eukaryotic genomes and suggest that different areas of the genome evolve at different rates.
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Affiliation(s)
- Brittany A Niccum
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Heewook Lee
- School of Informatics, Computing, and Engineering, Indiana University, Bloomington, Indiana, USA
| | - Wazim MohammedIsmail
- School of Informatics, Computing, and Engineering, Indiana University, Bloomington, Indiana, USA
| | - Haixu Tang
- School of Informatics, Computing, and Engineering, Indiana University, Bloomington, Indiana, USA
| | - Patricia L Foster
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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41
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Hizume K, Araki H. Replication fork pausing at protein barriers on chromosomes. FEBS Lett 2019; 593:1449-1458. [PMID: 31199500 DOI: 10.1002/1873-3468.13481] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 06/07/2019] [Accepted: 06/10/2019] [Indexed: 12/16/2022]
Abstract
When a cell divides prior to completion of DNA replication, serious DNA damage may occur. Thus, in addition to accuracy, the processivity of the replication forks is important. DNA synthesis at replication forks should be completed in time, and forks overcome aberrant structures on the template DNA, including damaged sites, using trans-lesion synthesis, occasionally introducing mutations. By contrast, the protein barrier built on the DNA is known to block the progression of replication forks at specific chromosomal loci. Such protein barriers avert any collision of replication and transcription machineries, or control the recombination of specific loci. The components and the mechanisms of action of protein barriers have been revealed mainly using genetic and biochemical techniques. In addition to proteins involved in replication fork pausing, the interaction of the replicative helicase and DNA polymerase is also essential for replication fork pausing. Here, we provide an overview of replication fork pausing at protein barriers.
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Affiliation(s)
- Kohji Hizume
- Division of RI Laboratory, Biomedical Research Center, Saitama Medical University, Japan
| | - Hiroyuki Araki
- Microbial Genetics Laboratory, National Institute of Genetics, Mishima, Japan.,Department of Genetics, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Mishima, Japan
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42
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Brüning JG, Howard JAL, Myka KK, Dillingham MS, McGlynn P. The 2B subdomain of Rep helicase links translocation along DNA with protein displacement. Nucleic Acids Res 2019; 46:8917-8925. [PMID: 30060236 PMCID: PMC6158625 DOI: 10.1093/nar/gky673] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 07/17/2018] [Indexed: 12/22/2022] Open
Abstract
Helicases catalyse DNA and RNA strand separation. Proteins bound to the nucleic acid must also be displaced in order to unwind DNA. This is exemplified by accessory helicases that clear protein barriers from DNA ahead of advancing replication forks. How helicases catalyse DNA unwinding is increasingly well understood but how protein displacement is achieved is unclear. Escherichia coli Rep accessory replicative helicase lacking one of its four subdomains, 2B, has been shown to be hyperactivated for DNA unwinding in vitro but we show here that RepΔ2B is, in contrast, deficient in displacing proteins from DNA. This defect correlates with an inability to promote replication of protein-bound DNA in vitro and lack of accessory helicase function in vivo. Defective protein displacement is manifested on double-stranded and single-stranded DNA. Thus binding and distortion of duplex DNA by the 2B subdomain ahead of the helicase is not the missing function responsible for this deficiency. These data demonstrate that protein displacement from DNA is not simply achieved by helicase translocation alone. They also imply that helicases may have evolved different specific features to optimise DNA unwinding and protein displacement, both of which are now recognised as key functions in all aspects of nucleic acid metabolism.
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Affiliation(s)
| | | | - Kamila K Myka
- Department of Biology, University of York, York YO10 5DD, UK
| | - Mark S Dillingham
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Peter McGlynn
- Department of Biology, University of York, York YO10 5DD, UK
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43
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Liu X, Seet JX, Shi Y, Bianco PR. Rep and UvrD Antagonize One Another at Stalled Replication Forks and This Is Exacerbated by SSB. ACS OMEGA 2019; 4:5180-5196. [PMID: 30949615 PMCID: PMC6441946 DOI: 10.1021/acsomega.8b02375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/27/2019] [Indexed: 06/09/2023]
Abstract
The Rep and UvrD DNA helicases are proposed to act at stalled DNA replication forks to facilitate replication restart when RNA polymerase stalls forks. To clarify the role of these DNA helicases in fork rescue, we used a coupled spectrophotometric ATPase assay to determine how they act on model fork substrates. For both enzymes, activity is low on regressed fork structures, suggesting that they act prior to the regression step that generates a Holliday junction. In fact, the preferred cofactors for both enzymes are forks with a gap in the nascent leading strand, consistent with the 3'-5' direction of translocation. Surprisingly, for Rep, this specificity is altered in the presence of stoichiometric amounts of a single-strand DNA-binding protein (SSB) relative to a fork with a gap in the nascent lagging strand. Even though Rep and UvrD are similar in structure, elevated concentrations of SSB inhibit Rep, but they have little to no effect on UvrD. Furthermore, Rep and UvrD antagonize one another at a fork. This is surprising given that these helicases have been shown to form a heterodimer and are proposed to act together to rescue an RNA polymerase-stalled fork. Consequently, the results herein indicate that although Rep and UvrD can act on similar fork substrates, they cannot function on the same fork simultaneously.
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Affiliation(s)
- Xiaoyi Liu
- Center
for Single Molecule Biophysics, Department of Microbiology and
Immunology, Department of Biochemistry, University
at Buffalo, Buffalo, New York 14214, United
States
| | - Jiun Xiang Seet
- Center
for Single Molecule Biophysics, Department of Microbiology and
Immunology, Department of Biochemistry, University
at Buffalo, Buffalo, New York 14214, United
States
| | - Yi Shi
- Center
for Single Molecule Biophysics, Department of Microbiology and
Immunology, Department of Biochemistry, University
at Buffalo, Buffalo, New York 14214, United
States
| | - Piero R. Bianco
- Center
for Single Molecule Biophysics, Department of Microbiology and
Immunology, Department of Biochemistry, University
at Buffalo, Buffalo, New York 14214, United
States
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44
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Sparks JL, Chistol G, Gao AO, Räschle M, Larsen NB, Mann M, Duxin JP, Walter JC. The CMG Helicase Bypasses DNA-Protein Cross-Links to Facilitate Their Repair. Cell 2018; 176:167-181.e21. [PMID: 30595447 DOI: 10.1016/j.cell.2018.10.053] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 09/13/2018] [Accepted: 10/24/2018] [Indexed: 02/04/2023]
Abstract
Covalent DNA-protein cross-links (DPCs) impede replication fork progression and threaten genome integrity. Using Xenopus egg extracts, we previously showed that replication fork collision with DPCs causes their proteolysis, followed by translesion DNA synthesis. We show here that when DPC proteolysis is blocked, the replicative DNA helicase CMG (CDC45, MCM2-7, GINS), which travels on the leading strand template, bypasses an intact leading strand DPC. Single-molecule imaging reveals that GINS does not dissociate from CMG during bypass and that CMG slows dramatically after bypass, likely due to uncoupling from the stalled leading strand. The DNA helicase RTEL1 facilitates bypass, apparently by generating single-stranded DNA beyond the DPC. The absence of RTEL1 impairs DPC proteolysis, suggesting that CMG must bypass the DPC to enable proteolysis. Our results suggest a mechanism that prevents inadvertent CMG destruction by DPC proteases, and they reveal CMG's remarkable capacity to overcome obstacles on its translocation strand.
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Affiliation(s)
- Justin L Sparks
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Gheorghe Chistol
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Alan O Gao
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Markus Räschle
- Department of Molecular Biotechnology and Systems Biology, Technical University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Nicolai B Larsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Matthias Mann
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark; Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Julien P Duxin
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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45
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Weaver GM, Mettrick KA, Corocher TA, Graham A, Grainge I. Replication fork collapse at a protein-DNA roadblock leads to fork reversal, promoted by the RecQ helicase. Mol Microbiol 2018; 111:455-472. [PMID: 30466158 DOI: 10.1111/mmi.14166] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2018] [Indexed: 11/27/2022]
Abstract
Proteins that bind DNA are the cause of the majority of impediments to replication fork progression and can lead to subsequent collapse of the replication fork. Failure to deal with fork collapse efficiently leads to mutation or cell death. Several models have been proposed for how a cell processes a stalled or collapsed replication fork; eukaryotes and bacteria are not dissimilar in terms of the general pathways undertaken to deal with these events. This study shows that replication fork regression, the combination of replication fork reversal leading to formation of a Holliday Junction along with exonuclease digestion, is the preferred pathway for dealing with a collapsed fork in Escherichia coli. Direct endo-nuclease activity at the replication fork was not observed. The protein that had the greatest effect on these fork processing events was the RecQ helicase, while RecG and RuvABC, which have previously been implicated in this process, were found to play a lesser role. Eukaryotic RecQ homologues, BLM and WRN, have also been implicated in processing events following replication fork collapse and may reflect a conserved mechanism. Finally, the SOS response was not induced by the protein-DNA roadblock under these conditions, so did not affect fork processing.
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Affiliation(s)
- Georgia M Weaver
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Karla A Mettrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Tayla-Ann Corocher
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Adam Graham
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
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46
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Dimude JU, Midgley-Smith SL, Rudolph CJ. Replication-transcription conflicts trigger extensive DNA degradation in Escherichia coli cells lacking RecBCD. DNA Repair (Amst) 2018; 70:37-48. [PMID: 30145455 DOI: 10.1016/j.dnarep.2018.08.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/15/2018] [Accepted: 08/16/2018] [Indexed: 11/17/2022]
Abstract
Bacterial chromosome duplication is initiated at a single origin (oriC). Two forks are assembled and proceed in opposite directions with high speed and processivity until they fuse and terminate in a specialised area opposite to oriC. Proceeding forks are often blocked by tightly-bound protein-DNA complexes, topological strain or various DNA lesions. In Escherichia coli the RecBCD protein complex is a key player in the processing of double-stranded DNA (dsDNA) ends. It has important roles in the repair of dsDNA breaks and the restart of forks stalled at sites of replication-transcription conflicts. In addition, ΔrecB cells show substantial amounts of DNA degradation in the termination area. In this study we show that head-on encounters of replication and transcription at a highly-transcribed rrn operon expose fork structures to degradation by nucleases such as SbcCD. SbcCD is also mostly responsible for the degradation in the termination area of ΔrecB cells. However, additional processes exacerbate degradation specifically in this location. Replication profiles from ΔrecB cells in which the chromosome is linearized at two different locations highlight that the location of replication termination can have some impact on the degradation observed. Our data improve our understanding of the role of RecBCD at sites of replication-transcription conflicts as well as the final stages of chromosome duplication. However, they also highlight that current models are insufficient and cannot explain all the molecular details in cells lacking RecBCD.
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Affiliation(s)
- Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Sarah L Midgley-Smith
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK.
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47
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Origins Left, Right, and Centre: Increasing the Number of Initiation Sites in the Escherichia coli Chromosome. Genes (Basel) 2018; 9:genes9080376. [PMID: 30060465 PMCID: PMC6116050 DOI: 10.3390/genes9080376] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 07/20/2018] [Accepted: 07/23/2018] [Indexed: 11/17/2022] Open
Abstract
The bacterium Escherichia coli contains a single circular chromosome with a defined architecture. DNA replication initiates at a single origin called oriC. Two replication forks are assembled and proceed in opposite directions until they fuse in a specialised zone opposite the origin. This termination area is flanked by polar replication fork pause sites that allow forks to enter, but not to leave. Thus, the chromosome is divided into two replichores, each replicated by a single replication fork. Recently, we analysed the replication parameters in E. coli cells, in which an ectopic origin termed oriZ was integrated in the right-hand replichore. Two major obstacles to replication were identified: (1) head-on replication⁻transcription conflicts at highly transcribed rrn operons, and (2) the replication fork trap. Here, we describe replication parameters in cells with ectopic origins, termed oriX and oriY, integrated into the left-hand replichore, and a triple origin construct with oriX integrated in the left-hand and oriZ in the right-hand replichore. Our data again highlight both replication⁻transcription conflicts and the replication fork trap as important obstacles to DNA replication, and we describe a number of spontaneous large genomic rearrangements which successfully alleviate some of the problems arising from having an additional origin in an ectopic location. However, our data reveal additional factors that impact efficient chromosome duplication, highlighting the complexity of chromosomal architecture.
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48
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Abstract
In all organisms, replication impairments are an important source of genome rearrangements, mainly because of the formation of double-stranded DNA (dsDNA) ends at inactivated replication forks. Three reactions for the formation of dsDNA ends at replication forks were originally described for Escherichia coli and became seminal models for all organisms: the encounter of replication forks with preexisting single-stranded DNA (ssDNA) interruptions, replication fork reversal, and head-to-tail collisions of successive replication rounds. Here, we first review the experimental evidence that now allows us to know when, where, and how these three different reactions occur in E. coli. Next, we recall our recent studies showing that in wild-type E. coli, spontaneous replication fork breakage occurs in 18% of cells at each generation. We propose that it results from the replication of preexisting nicks or gaps, since it does not involve replication fork reversal or head-to-tail fork collisions. In the recB mutant, deficient for double-strand break (DSB) repair, fork breakage triggers DSBs in the chromosome terminus during cell division, a reaction that is heritable for several generations. Finally, we recapitulate several observations suggesting that restart from intact inactivated replication forks and restart from recombination intermediates require different sets of enzymatic activities. The finding that 18% of cells suffer replication fork breakage suggests that DNA remains intact at most inactivated forks. Similarly, only 18% of cells need the helicase loader for replication restart, which leads us to speculate that the replicative helicase remains on DNA at intact inactivated replication forks and is reactivated by the replication restart proteins.
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49
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Lang KS, Merrikh H. The Clash of Macromolecular Titans: Replication-Transcription Conflicts in Bacteria. Annu Rev Microbiol 2018; 72:71-88. [PMID: 29856930 DOI: 10.1146/annurev-micro-090817-062514] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Within the last decade, it has become clear that DNA replication and transcription are routinely in conflict with each other in growing cells. Much of the seminal work on this topic has been carried out in bacteria, specifically, Escherichia coli and Bacillus subtilis; therefore, studies of conflicts in these species deserve special attention. Collectively, the recent findings on conflicts have fundamentally changed the way we think about DNA replication in vivo. Furthermore, new insights on this topic have revealed that the conflicts between replication and transcription significantly influence many key parameters of cellular function, including genome organization, mutagenesis, and evolution of stress response and virulence genes. In this review, we discuss the consequences of replication-transcription conflicts on the life of bacteria and describe some key strategies cells use to resolve them. We put special emphasis on two critical aspects of these encounters: ( a) the consequences of conflicts on replisome stability and dynamics, and ( b) the resulting increase in spontaneous mutagenesis.
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Affiliation(s)
- Kevin S Lang
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA;
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA; .,Department of Genome Sciences, University of Washington, Seattle, Washington 98195-5061, USA
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50
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Windgassen TA, Wessel SR, Bhattacharyya B, Keck JL. Mechanisms of bacterial DNA replication restart. Nucleic Acids Res 2018; 46:504-519. [PMID: 29202195 PMCID: PMC5778457 DOI: 10.1093/nar/gkx1203] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 11/15/2017] [Accepted: 11/20/2017] [Indexed: 12/21/2022] Open
Abstract
Multi-protein DNA replication complexes called replisomes perform the essential process of copying cellular genetic information prior to cell division. Under ideal conditions, replisomes dissociate only after the entire genome has been duplicated. However, DNA replication rarely occurs without interruptions that can dislodge replisomes from DNA. Such events produce incompletely replicated chromosomes that, if left unrepaired, prevent the segregation of full genomes to daughter cells. To mitigate this threat, cells have evolved 'DNA replication restart' pathways that have been best defined in bacteria. Replication restart requires recognition and remodeling of abandoned replication forks by DNA replication restart proteins followed by reloading of the replicative DNA helicase, which subsequently directs assembly of the remaining replisome subunits. This review summarizes our current understanding of the mechanisms underlying replication restart and the proteins that drive the process in Escherichia coli (PriA, PriB, PriC and DnaT).
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Affiliation(s)
- Tricia A Windgassen
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
| | - Sarah R Wessel
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
- Department of Biochemistry, Vanderbilt School of Medicine, Nashville, TN 37205, USA
| | - Basudeb Bhattacharyya
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
- Department of Chemistry and Biochemistry, University of Wisconsin-La Crosse, La Crosse, WI 54601, USA
| | - James L Keck
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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