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Tominaga K, Ozaki S, Sato S, Katayama T, Nishimura Y, Omae K, Iwasaki W. Frequent nonhomologous replacement of replicative helicase loaders by viruses in Vibrionaceae. Proc Natl Acad Sci U S A 2024; 121:e2317954121. [PMID: 38683976 PMCID: PMC11087808 DOI: 10.1073/pnas.2317954121] [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: 10/18/2023] [Accepted: 03/14/2024] [Indexed: 05/02/2024] Open
Abstract
Several microbial genomes lack textbook-defined essential genes. If an essential gene is absent from a genome, then an evolutionarily independent gene of unknown function complements its function. Here, we identified frequent nonhomologous replacement of an essential component of DNA replication initiation, a replicative helicase loader gene, in Vibrionaceae. Our analysis of Vibrionaceae genomes revealed two genes with unknown function, named vdhL1 and vdhL2, that were substantially enriched in genomes without the known helicase-loader genes. These genes showed no sequence similarities to genes with known function but encoded proteins structurally similar with a viral helicase loader. Analyses of genomic syntenies and coevolution with helicase genes suggested that vdhL1/2 encodes a helicase loader. The in vitro assay showed that Vibrio harveyi VdhL1 and Vibrio ezurae VdhL2 promote the helicase activity of DnaB. Furthermore, molecular phylogenetics suggested that vdhL1/2 were derived from phages and replaced an intrinsic helicase loader gene of Vibrionaceae over 20 times. This high replacement frequency implies the host's advantage in acquiring a viral helicase loader gene.
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Affiliation(s)
- Kento Tominaga
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba277-0882, Japan
| | - Shogo Ozaki
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka812-8582, Japan
| | - Shohei Sato
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka812-8582, Japan
| | - Tsutomu Katayama
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka812-8582, Japan
| | - Yuki Nishimura
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba277-0882, Japan
| | - Kimiho Omae
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba277-0882, Japan
| | - Wataru Iwasaki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba277-0882, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba277-0882, Japan
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba277-8564, Japan
- Institute for Quantitative Biosciences, The University of Tokyo, Tokyo113-0032, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo113-8657, Japan
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2
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Acharya A, Bret H, Huang JW, Mütze M, Göse M, Kissling VM, Seidel R, Ciccia A, Guérois R, Cejka P. Mechanism of DNA unwinding by MCM8-9 in complex with HROB. Nat Commun 2024; 15:3584. [PMID: 38678026 PMCID: PMC11055865 DOI: 10.1038/s41467-024-47936-8] [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: 06/16/2023] [Accepted: 04/15/2024] [Indexed: 04/29/2024] Open
Abstract
HROB promotes the MCM8-9 helicase in DNA damage response. To understand how HROB activates MCM8-9, we defined their interaction interface. We showed that HROB makes important yet transient contacts with both MCM8 and MCM9, and binds the MCM8-9 heterodimer with the highest affinity. MCM8-9-HROB prefer branched DNA structures, and display low DNA unwinding processivity. MCM8-9 unwinds DNA as a hexamer that assembles from dimers on DNA in the presence of ATP. The hexamer involves two repeating protein-protein interfaces between the alternating MCM8 and MCM9 subunits. One of these interfaces is quite stable and forms an obligate heterodimer across which HROB binds. The other interface is labile and mediates hexamer assembly, independently of HROB. The ATPase site formed at the labile interface contributes disproportionally more to DNA unwinding than that at the stable interface. Here, we show that HROB promotes DNA unwinding downstream of MCM8-9 loading and ring formation on ssDNA.
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Affiliation(s)
- Ananya Acharya
- Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, Bellinzona, 6500, Switzerland
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland
| | - Hélène Bret
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Jen-Wei Huang
- Department of Genetics and Development, Institute for Cancer Genetics, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Martin Mütze
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Martin Göse
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Vera Maria Kissling
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland
- Particles-Biology Interactions Laboratory, Department of Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa), St. Gallen, 9014, Switzerland
| | - Ralf Seidel
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Alberto Ciccia
- Department of Genetics and Development, Institute for Cancer Genetics, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raphaël Guérois
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
| | - Petr Cejka
- Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, Bellinzona, 6500, Switzerland.
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland.
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3
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Li Y, Zhu J, Guo Y, Yan R. Structural insight into the assembly and working mechanism of helicase-primase D5 from Mpox virus. Nat Struct Mol Biol 2024; 31:68-81. [PMID: 38177671 DOI: 10.1038/s41594-023-01142-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 09/27/2023] [Indexed: 01/06/2024]
Abstract
The Mpox pandemic, caused by the Mpox virus (or monkeypox virus, MPXV), has gained global attention. The D5 protein, a putative helicase-primase found in MPXV, plays a vital role in viral replication and genome uncoating. Here we determined multiple cryo-EM structures of full-length hexameric D5 in diverse states. These states were captured during ATP hydrolysis while moving along the single-stranded DNA (ssDNA) track. Through comprehensive structural analysis combined with the helicase activity system, we revealed that when the primase domain is truncated or the interaction between the primase and helicase domains is disrupted, the double-stranded DNA (dsDNA) unwinds into ssDNA, suggesting a critical regulatory role of the primase domain. Two transition states bound with ssDNA substrate during unwinding reveals that two ATP molecules were consumed to drive DNA moving forward two nucleotides. Collectively, our findings shed light on the molecular mechanism that links ATP hydrolysis to the DNA unwinding in poxviruses.
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Affiliation(s)
- Yaning Li
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jing Zhu
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, China
| | - Yingying Guo
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, China.
| | - Renhong Yan
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, China.
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4
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Pelliciari S, Bodet-Lefèvre S, Fenyk S, Stevens D, Winterhalter C, Schramm FD, Pintar S, Burnham DR, Merces G, Richardson TT, Tashiro Y, Hubbard J, Yardimci H, Ilangovan A, Murray H. The bacterial replication origin BUS promotes nucleobase capture. Nat Commun 2023; 14:8339. [PMID: 38097584 PMCID: PMC10721633 DOI: 10.1038/s41467-023-43823-w] [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: 02/13/2023] [Accepted: 11/21/2023] [Indexed: 12/17/2023] Open
Abstract
Genome duplication is essential for the proliferation of cellular life and this process is generally initiated by dedicated replication proteins at chromosome origins. In bacteria, DNA replication is initiated by the ubiquitous DnaA protein, which assembles into an oligomeric complex at the chromosome origin (oriC) that engages both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) to promote DNA duplex opening. However, the mechanism of DnaA specifically opening a replication origin was unknown. Here we show that Bacillus subtilis DnaAATP assembles into a continuous oligomer at the site of DNA melting, extending from a dsDNA anchor to engage a single DNA strand. Within this complex, two nucleobases of each ssDNA binding motif (DnaA-trio) are captured within a dinucleotide binding pocket created by adjacent DnaA proteins. These results provide a molecular basis for DnaA specifically engaging the conserved sequence elements within the bacterial chromosome origin basal unwinding system (BUS).
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Affiliation(s)
- Simone Pelliciari
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Salomé Bodet-Lefèvre
- Centre for Molecular Cell Biology, School of Biological and Behavioural Sciences, Queen Mary University of London, Newark Street, London, E1 2AT, UK
| | - Stepan Fenyk
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Daniel Stevens
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Charles Winterhalter
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Frederic D Schramm
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Sara Pintar
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Daniel R Burnham
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - George Merces
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Tomas T Richardson
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Yumiko Tashiro
- Centre for Molecular Cell Biology, School of Biological and Behavioural Sciences, Queen Mary University of London, Newark Street, London, E1 2AT, UK
| | - Julia Hubbard
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
| | - Hasan Yardimci
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Aravindan Ilangovan
- Centre for Molecular Cell Biology, School of Biological and Behavioural Sciences, Queen Mary University of London, Newark Street, London, E1 2AT, UK.
| | - Heath Murray
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK.
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5
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Pellegrini L. The CMG DNA helicase and the core replisome. Curr Opin Struct Biol 2023; 81:102612. [PMID: 37244171 DOI: 10.1016/j.sbi.2023.102612] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 04/19/2023] [Accepted: 04/25/2023] [Indexed: 05/29/2023]
Abstract
Eukaryotic DNA replication is performed by the replisome, a large and dynamic multi-protein machine endowed with the required enzymatic components for the synthesis of new DNA. Recent cryo-electron microscopy (cryoEM) analyses have revealed the conserved architecture of the core eukaryotic replisome, comprising the CMG (Cdc45-MCM-GINS) DNA helicase, the leading-strand DNA polymerase epsilon, the Timeless-Tipin heterodimer, the hub protein AND-1 and the checkpoint protein Claspin. These results bid well for arriving soon at an integrated understanding of the structural basis of semi-discontinuous DNA replication. They further set the scene for the characterisation of the mechanisms that interface DNA synthesis with concurrent processes such as DNA repair, propagation of chromatin structure and establishment of sister chromatid cohesion.
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6
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Acharya A, Bret H, Huang JW, Mütze M, Göse M, Kissling V, Seidel R, Ciccia A, Guérois R, Cejka P. Mechanism of DNA unwinding by hexameric MCM8-9 in complex with HROB. RESEARCH SQUARE 2023:rs.3.rs-3054483. [PMID: 37461676 PMCID: PMC10350107 DOI: 10.21203/rs.3.rs-3054483/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/24/2023]
Abstract
The human MCM8-9 helicase functions in concert with HROB in the context of homologous recombination, but its precise function is unknown. To gain insights into how HROB regulates MCM8-9, we first used molecular modeling and biochemistry to define their interaction interface. We show that HROB makes important contacts with both MCM8 and MCM9 subunits, which directly promotes its DNA-dependent ATPase and helicase activities. MCM8-9-HROB preferentially binds and unwinds branched DNA structures, and single-molecule experiments reveal a low DNA unwinding processivity. MCM8-9 unwinds DNA as a hexameric complex that assembles from dimers on DNA in the presence of ATP, which is prerequisite for its helicase function. The hexamer formation thus involves two repeating protein-protein interfaces forming between the alternating MCM8 and MCM9 subunits. One of these interfaces is rather stable and forms an obligate heterodimer, while the other interface is labile and mediates the assembly of the hexamer on DNA, independently of HROB. The ATPase site composed of the subunits forming the labile interface disproportionally contributes to DNA unwinding. HROB does not affect the MCM8-9 ring formation, but promotes DNA unwinding downstream by possibly coordinating ATP hydrolysis with structural transitions accompanying translocation of MCM8-9 on DNA.
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Affiliation(s)
- Ananya Acharya
- Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, Bellinzona, 6500, Switzerland
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland
| | - Hélène Bret
- Institute for Integrative Biology of the Cell (I2BC), Commissariat à l’Energie Atomique, Centre National de la Recherche Scientifique, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, 91190, France
| | - Jen-Wei Huang
- Department of Genetics and Development, Institute for Cancer Genetics, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Martin Mütze
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Martin Göse
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Vera Kissling
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland
| | - Ralf Seidel
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Alberto Ciccia
- Department of Genetics and Development, Institute for Cancer Genetics, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raphaël Guérois
- Institute for Integrative Biology of the Cell (I2BC), Commissariat à l’Energie Atomique, Centre National de la Recherche Scientifique, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, 91190, France
| | - Petr Cejka
- Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, Bellinzona, 6500, Switzerland
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, 8093, Switzerland
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7
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Acharya A, Bret H, Huang JW, Mütze M, Göse M, Kissling V, Seidel R, Ciccia A, Guérois R, Cejka P. Mechanism of DNA unwinding by hexameric MCM8-9 in complex with HROB. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.12.544631. [PMID: 37398313 PMCID: PMC10312610 DOI: 10.1101/2023.06.12.544631] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The human MCM8-9 helicase functions in concert with HROB in the context of homologous recombination, but its precise function is unknown. To gain insights into how HROB regulates MCM8-9, we first used molecular modeling and biochemistry to define their interaction interface. We show that HROB makes important contacts with both MCM8 and MCM9 subunits, which directly promotes its DNA-dependent ATPase and helicase activities. MCM8-9-HROB preferentially binds and unwinds branched DNA structures, and single-molecule experiments reveal a low DNA unwinding processivity. MCM8-9 unwinds DNA as a hexameric complex that assembles from dimers on DNA in the presence of ATP, which is prerequisite for its helicase function. The hexamer formation thus involves two repeating protein-protein interfaces forming between the alternating MCM8 and MCM9 subunits. One of these interfaces is rather stable and forms an obligate heterodimer, while the other interface is labile and mediates the assembly of the hexamer on DNA, independently of HROB. The ATPase site composed of the subunits forming the labile interface disproportionally contributes to DNA unwinding. HROB does not affect the MCM8-9 ring formation, but promotes DNA unwinding downstream by possibly coordinating ATP hydrolysis with structural transitions accompanying translocation of MCM8-9 on DNA.
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8
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Hayashi T, Yano N, Kora K, Yokoyama A, Maizuru K, Kayaki T, Nishikawa K, Osawa M, Niwa A, Takenouchi T, Hijikata A, Shirai T, Suzuki H, Kosaki K, Saito MK, Takita J, Yoshida T. Involvement of mTOR pathway in neurodegeneration in NSF-related developmental and epileptic encephalopathy. Hum Mol Genet 2023; 32:1683-1697. [PMID: 36645181 PMCID: PMC10162430 DOI: 10.1093/hmg/ddad008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 01/08/2023] [Accepted: 01/11/2023] [Indexed: 01/17/2023] Open
Abstract
Membrane fusion is mediated by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. During neurotransmitter exocytosis, SNARE proteins on a synaptic vesicle and the target membrane form a complex, resulting in neurotransmitter release. N-ethylmaleimide-sensitive factor (NSF), a homohexameric ATPase, disassembles the complex, allowing individual SNARE proteins to be recycled. Recently, the association between pathogenic NSF variants and developmental and epileptic encephalopathy (DEE) was reported; however, the molecular pathomechanism of NSF-related DEE remains unclear. Here, three patients with de novo heterozygous NSF variants were presented, of which two were associated with DEE and one with a very mild phenotype. One of the DEE patients also had hypocalcemia from parathyroid hormone deficiency and neuromuscular junction impairment. Using PC12 cells, a neurosecretion model, we show that NSF with DEE-associated variants impaired the recycling of vesicular membrane proteins and vesicle enlargement in response to exocytotic stimulation. In addition, DEE-associated variants caused neurodegenerative change and defective autophagy through overactivation of the mammalian/mechanistic target of rapamycin (mTOR) pathway. Treatment with rapamycin, an mTOR inhibitor or overexpression of wild-type NSF ameliorated these phenotypes. Furthermore, neurons differentiated from patient-derived induced pluripotent stem cells showed neurite degeneration, which was also alleviated by rapamycin treatment or gene correction using genome editing. Protein structure analysis of NSF revealed that DEE-associated variants might disrupt the transmission of the conformational change of NSF monomers and consequently halt the rotation of ATP hydrolysis, indicating a dominant negative mechanism. In conclusion, this study elucidates the pathomechanism underlying NSF-related DEE and identifies a potential therapeutic approach.
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Affiliation(s)
- Takahiro Hayashi
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Naoko Yano
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Kengo Kora
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Atsushi Yokoyama
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Kanako Maizuru
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Taisei Kayaki
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Kinuko Nishikawa
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Mitsujiro Osawa
- Thyas Co. Ltd, Kyoto 606-8501, Japan
- Department of Clinical Application, Center for iPS Cell Research and Application (CiRA) Kyoto University, Kyoto 606-8507, Japan
| | - Akira Niwa
- Department of Clinical Application, Center for iPS Cell Research and Application (CiRA) Kyoto University, Kyoto 606-8507, Japan
| | - Toshiki Takenouchi
- Department of Pediatrics, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Atsushi Hijikata
- Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829, Japan
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Tsuyoshi Shirai
- Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829, Japan
| | - Hisato Suzuki
- Center for Medical Genetics, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Kenjiro Kosaki
- Center for Medical Genetics, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Megumu K Saito
- Department of Clinical Application, Center for iPS Cell Research and Application (CiRA) Kyoto University, Kyoto 606-8507, Japan
| | - Junko Takita
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Takeshi Yoshida
- Department of Pediatrics, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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9
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Blaine HC, Simmons LA, Stallings CL. Diverse Mechanisms of Helicase Loading during DNA Replication Initiation in Bacteria. J Bacteriol 2023; 205:e0048722. [PMID: 36877032 PMCID: PMC10128896 DOI: 10.1128/jb.00487-22] [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: 03/07/2023] Open
Abstract
Initiation of DNA replication is required for cell viability and passage of genetic information to the next generation. Studies in Escherichia coli and Bacillus subtilis have established ATPases associated with diverse cellular activities (AAA+) as essential proteins required for loading of the replicative helicase at replication origins. AAA+ ATPases DnaC in E. coli and DnaI in B. subtilis have long been considered the paradigm for helicase loading during replication in bacteria. Recently, it has become increasingly clear that most bacteria lack DnaC/DnaI homologs. Instead, most bacteria express a protein homologous to the newly described DciA (dnaC/dnaI antecedent) protein. DciA is not an ATPase, and yet it serves as a helicase operator, providing a function analogous to that of DnaC and DnaI across diverse bacterial species. The recent discovery of DciA and of other alternative mechanisms of helicase loading in bacteria has changed our understanding of DNA replication initiation. In this review, we highlight recent discoveries, detailing what is currently known about the replicative helicase loading process across bacterial species, and we discuss the critical questions that remain to be investigated.
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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
| | - Lyle A. Simmons
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, 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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10
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Yang J, Sun Y, Wang Y, Hao W, Cheng K. Structural and DNA end resection study of the bacterial NurA-HerA complex. BMC Biol 2023; 21:42. [PMID: 36829173 PMCID: PMC9960219 DOI: 10.1186/s12915-023-01542-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 02/10/2023] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND The nuclease NurA and the ATPase/translocase HerA play a vital role in repair of double-strand breaks (DSB) during the homologous recombination in archaea. A NurA-HerA complex is known to mediate DSB DNA end resection, leading to formation of a free 3' end used to search for the homologous sequence. Despite the structures of individual archaeal types of NurA and HerA having been reported, there is limited information regarding the molecular mechanisms underlying this process. Some bacteria also possess homologs of NurA and HerA; however, the bacterial type of this complex, as well as the detailed mechanisms underlying the joining of NurA-HerA in DSB DNA end resection, remains unclear. RESULTS We report for the first time the crystal structures of Deinococcus radiodurans HerA (drHerA) in the nucleotide-free and ADP-binding modes. A D. radiodurans NurA-HerA complex structure was constructed according to a low-resolution cryo-electron microscopy map. We performed site-directed mutagenesis to map the drNurA-HerA interaction sites, suggesting that their interaction is mainly mediated by ionic links, in contrast to previously characterized archaeal NurA-HerA interactions. The key residues responsible for the DNA translocation activity, DNA unwinding activity, and catalytic activities of the drNurA-HerA complex were identified. A HerA/FtsK-specific translocation-related motif (TR motif) that guarantees the processivity of double-stranded DNA (dsDNA) translocation was identified. Moreover, a mechanism for the translocation-regulated resection of the 5' tail of broken dsDNA and the corresponding generation of a recombinogenic 3' single-stranded DNA tail by the drNurA-HerA complex was elucidated. CONCLUSIONS Our work provides new insights into the mechanism underlying bacterial NurA-HerA-mediated DSB DNA end resection, and the way this complex digests the 5' tail of a DNA duplex and provides long 3' free end for strand invasion in the bacterial homologous recombination process.
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Affiliation(s)
- Jieyu Yang
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Yiyang Sun
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Ying Wang
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Wanshan Hao
- grid.410595.c0000 0001 2230 9154Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121 China
| | - Kaiying Cheng
- Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Department of Immunology and Pathogen Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121, China. .,State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China.
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11
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A Fijivirus Major Viroplasm Protein Shows RNA-Stimulated ATPase Activity by Adopting Pentameric and Hexameric Assemblies of Dimers. mBio 2023; 14:e0002323. [PMID: 36786587 PMCID: PMC10128069 DOI: 10.1128/mbio.00023-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Fijiviruses replicate and package their genomes within viroplasms in a process involving RNA-RNA and RNA-protein interactions. Here, we demonstrate that the 24 C-terminal residues (C-arm) of the P9-1 major viroplasm protein of the mal de Río Cuarto virus (MRCV) are required for its multimerization and the formation of viroplasm-like structures. Using an integrative structural approach, the C-arm was found to be dispensable for P9-1 dimer assembly but essential for the formation of pentamers and hexamers of dimers (decamers and dodecamers), which favored RNA binding. Although both P9-1 and P9-1ΔC-arm catalyzed ATP with similar activities, an RNA-stimulated ATPase activity was only detected in the full-length protein, indicating a C-arm-mediated interaction between the ATP catalytic site and the allosteric RNA binding sites in the (do)decameric assemblies. A stronger preference to bind phosphate moieties in the decamer was predicted, suggesting that the allosteric modulation of ATPase activity by RNA is favored in this structural conformation. Our work reveals the structural versatility of a fijivirus major viroplasm protein and provides clues to its mechanism of action. IMPORTANCE The mal de Río Cuarto virus (MRCV) causes an important maize disease in Argentina. MRCV replicates in several species of Gramineae plants and planthopper vectors. The viral factories, also called viroplasms, have been studied in detail in animal reovirids. This work reveals that a major viroplasm protein of MRCV forms previously unidentified structural arrangements and provides evidence that it may simultaneously adopt two distinct quaternary assemblies. Furthermore, our work uncovers an allosteric communication between the ATP and RNA binding sites that is favored in the multimeric arrangements. Our results contribute to the understanding of plant reovirids viroplasm structure and function and pave the way for the design of antiviral strategies for disease control.
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12
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Ozaki S, Wang D, Wakasugi Y, Itani N, Katayama T. The Caulobacter crescentus DciA promotes chromosome replication through topological loading of the DnaB replicative helicase at replication forks. Nucleic Acids Res 2022; 50:12896-12912. [PMID: 36484102 PMCID: PMC9825169 DOI: 10.1093/nar/gkac1146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 11/04/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022] Open
Abstract
The replicative DNA helicase translocates on single-stranded DNA to drive replication forks during chromosome replication. In most bacteria the ubiquitous replicative helicase, DnaB, co-evolved with the accessory subunit DciA, but how they function remains incompletely understood. Here, using the model bacterium Caulobacter crescentus, we demonstrate that DciA plays a prominent role in DNA replication fork maintenance. Cell cycle analyses using a synchronized Caulobacter cell population showed that cells devoid of DciA exhibit a severe delay in fork progression. Biochemical characterization revealed that the DnaB helicase in its default state forms a hexamer that inhibits self-loading onto single-stranded DNA. We found that upon binding to DciA, the DnaB hexamer undergoes conformational changes required for encircling single-stranded DNA, thereby establishing the replication fork. Further investigation of the functional structure of DciA revealed that the C-terminus of DciA includes conserved leucine residues responsible for DnaB binding and is essential for DciA in vivo functions. We propose that DciA stimulates loading of DnaB onto single strands through topological isomerization of the DnaB structure, thereby ensuring fork progression. Given that the DnaB-DciA modules are widespread among eubacterial species, our findings suggest that a common mechanism underlies chromosome replication.
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Affiliation(s)
| | | | | | - Naoto Itani
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan
| | - Tsutomu Katayama
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan
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13
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SV40 T-antigen uses a DNA shearing mechanism to initiate origin unwinding. Proc Natl Acad Sci U S A 2022; 119:e2216240119. [PMID: 36442086 PMCID: PMC9894130 DOI: 10.1073/pnas.2216240119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Duplication of DNA genomes requires unwinding of the double-strand (ds) DNA so that each single strand (ss) can be copied by a DNA polymerase. The genomes of eukaryotic cells are unwound by two ring-shaped hexameric helicases that initially encircle dsDNA but transition to ssDNA for function as replicative helicases. How the duplex is initially unwound, and the role of the two helicases in this process, is poorly understood. We recently described an initiation mechanism for eukaryotes in which the two helicases are directed inward toward one another and shear the duplex open by pulling on opposite strands of the duplex while encircling dsDNA [L. D. Langston, M. E. O'Donnell, eLife 8, e46515 (2019)]. Two head-to-head T-Antigen helicases are long known to be loaded at the SV40 origin. We show here that T-Antigen tracks head (N-tier) first on ssDNA, opposite the direction proposed for decades. We also find that SV40 T-Antigen tracks directionally while encircling dsDNA and mainly tracks on one strand of the duplex in the same orientation as during ssDNA translocation. Further, two inward directed T-Antigen helicases on dsDNA are able to melt a 150-bp duplex. These findings explain the "rabbit ear" DNA loops observed at the SV40 origin by electron microscopy and reconfigure how the DNA loops emerge from the double hexamer relative to earlier models. Thus, the mechanism of DNA shearing by two opposing helicases is conserved in a eukaryotic viral helicase and may be widely used to initiate origin unwinding of dsDNA genomes.
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14
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Ma C, Wu D, Chen Q, Gao N. Structural dynamics of AAA + ATPase Drg1 and mechanism of benzo-diazaborine inhibition. Nat Commun 2022; 13:6765. [PMID: 36351914 PMCID: PMC9646744 DOI: 10.1038/s41467-022-34511-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 10/27/2022] [Indexed: 11/11/2022] Open
Abstract
The type II AAA + ATPase Drg1 is a ribosome assembly factor, functioning to release Rlp24 from the pre-60S particle just exported from nucleus, and its activity in can be inhibited by a drug molecule diazaborine. However, molecular mechanisms of Drg1-mediated Rlp24 removal and diazaborine-mediated inhibition are not fully understood. Here, we report Drg1 structures in different nucleotide-binding and benzo-diazaborine treated states. Drg1 hexamers transits between two extreme conformations (planar or helical arrangement of protomers). By forming covalent adducts with ATP molecules in both ATPase domain, benzo-diazaborine locks Drg1 hexamers in a symmetric and non-productive conformation to inhibits both inter-protomer and inter-ring communication of Drg1 hexamers. We also obtained a substrate-engaged mutant Drg1 structure, in which conserved pore-loops form a spiral staircase to interact with the polypeptide through a sequence-independent manner. Structure-based mutagenesis data highlight the functional importance of the pore-loop, the D1-D2 linker and the inter-subunit signaling motif of Drg1, which share similar regulatory mechanisms with p97. Our results suggest that Drg1 may function as an unfoldase that threads a substrate protein within the pre-60S particle.
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Affiliation(s)
- Chengying Ma
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, 100871 Beijing, China ,Changping Laboratory, 102206 Beijing, China
| | - Damu Wu
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, 100871 Beijing, China
| | - Qian Chen
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, 100871 Beijing, China
| | - Ning Gao
- grid.11135.370000 0001 2256 9319State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, 100871 Beijing, China ,Changping Laboratory, 102206 Beijing, China ,grid.11135.370000 0001 2256 9319National Biomedical Imaging Center, Peking University, 100871 Beijing, China
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15
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Hutin S, Ling WL, Tarbouriech N, Schoehn G, Grimm C, Fischer U, Burmeister WP. The Vaccinia Virus DNA Helicase Structure from Combined Single-Particle Cryo-Electron Microscopy and AlphaFold2 Prediction. Viruses 2022; 14:2206. [PMID: 36298761 PMCID: PMC9611036 DOI: 10.3390/v14102206] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 10/02/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
Poxviruses are large DNA viruses with a linear double-stranded DNA genome circularized at the extremities. The helicase-primase D5, composed of six identical 90 kDa subunits, is required for DNA replication. D5 consists of a primase fragment flexibly attached to the hexameric C-terminal polypeptide (res. 323-785) with confirmed nucleotide hydrolase and DNA-binding activity but an elusive helicase activity. We determined its structure by single-particle cryo-electron microscopy. It displays an AAA+ helicase core flanked by N- and C-terminal domains. Model building was greatly helped by the predicted structure of D5 using AlphaFold2. The 3.9 Å structure of the N-terminal domain forms a well-defined tight ring while the resolution decreases towards the C-terminus, still allowing the fit of the predicted structure. The N-terminal domain is partially present in papillomavirus E1 and polyomavirus LTA helicases, as well as in a bacteriophage NrS-1 helicase domain, which is also closely related to the AAA+ helicase domain of D5. Using the Pfam domain database, a D5_N domain followed by DUF5906 and Pox_D5 domains could be assigned to the cryo-EM structure, providing the first 3D structures for D5_N and Pox_D5 domains. The same domain organization has been identified in a family of putative helicases from large DNA viruses, bacteriophages, and selfish DNA elements.
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Affiliation(s)
- Stephanie Hutin
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes (UGA), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 38000 Grenoble, France
| | - Wai Li Ling
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes (UGA), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 38000 Grenoble, France
| | - Nicolas Tarbouriech
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes (UGA), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 38000 Grenoble, France
| | - Guy Schoehn
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes (UGA), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 38000 Grenoble, France
| | - Clemens Grimm
- Biozentrum, University of Würzburg, 97070 Würzburg, Germany
| | - Utz Fischer
- Biozentrum, University of Würzburg, 97070 Würzburg, Germany
| | - Wim P. Burmeister
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes (UGA), Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 38000 Grenoble, France
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16
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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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17
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Convergent evolution in two bacterial replicative helicase loaders. Trends Biochem Sci 2022; 47:620-630. [DOI: 10.1016/j.tibs.2022.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 02/06/2022] [Accepted: 02/08/2022] [Indexed: 12/23/2022]
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18
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CMG helicase can use ATPγS to unwind DNA: Implications for the rate-limiting step in the reaction mechanism. Proc Natl Acad Sci U S A 2022; 119:2119580119. [PMID: 35042821 PMCID: PMC8794833 DOI: 10.1073/pnas.2119580119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2021] [Indexed: 11/18/2022] Open
Abstract
The adenosine triphosphate (ATP) analog ATPγS often greatly slows or prevents enzymatic ATP hydrolysis. The eukaryotic CMG (Cdc45, Mcm2 to 7, GINS) replicative helicase is presumed unable to hydrolyze ATPγS and thus unable to perform DNA unwinding, as documented for certain other helicases. Consequently, ATPγS is often used to "preload" CMG onto forked DNA substrates without unwinding before adding ATP to initiate helicase activity. We find here that CMG does hydrolyze ATPγS and couples it to DNA unwinding. Indeed, the rate of unwinding of a 20- and 30-mer duplex fork of different sequences by CMG is only reduced 1- to 1.5-fold using ATPγS compared with ATP. These findings imply that a conformational change is the rate-limiting step during CMG unwinding, not hydrolysis. Instead of using ATPγS for loading CMG onto DNA, we demonstrate here that nonhydrolyzable adenylyl-imidodiphosphate (AMP-PNP) can be used to preload CMG onto a forked DNA substrate without unwinding.
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19
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Abstract
Rho is a hexameric bacterial RNA helicase, which became a paradigm of factor-dependent transcription termination. The broadly accepted ("textbook") model posits a series of steps, wherein Rho first binds C-rich Rho utilization (rut) sites on nascent RNA, uses its ATP-dependent translocase activity to catch up with RNA polymerase (RNAP), and either pulls the transcript from the elongation complex or pushes RNAP forward, thus terminating transcription. However, this appealingly simple mechano-chemical model lacks a biological realism and is increasingly at odds with genetic and biochemical data. Here, we summarize recent structural and biochemical studies that have advanced our understanding of molecular details of RNA recognition, termination signaling, and RNAP inactivation in Rho-dependent transcription termination, rebalancing the view in favor of an alternative "allosteric" mechanism. In the revised model, Rho binds RNAP early in elongation assisted by the cofactors NusA and NusG, forming a pre-termination complex (PTC). The formation of PTC allows Rho to continuously sample nascent transcripts for a termination signal, which subsequently traps the elongation complex in an inactive state prior to its dissociation.
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Affiliation(s)
- Zhitai Hao
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Vladimir Svetlov
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA.,Howard Hughes Medical Institute, New York University School of Medicine, New York, Ny, USA
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