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Puri N, Fernandez AJ, O'Shea Murray VL, McMillan S, Keck JL, Berger JM. The molecular coupling between substrate recognition and ATP turnover in a AAA+ hexameric helicase loader. eLife 2021; 10:64232. [PMID: 34036936 PMCID: PMC8213410 DOI: 10.7554/elife.64232] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 05/25/2021] [Indexed: 11/16/2022] Open
Abstract
In many bacteria and eukaryotes, replication fork establishment requires the controlled loading of hexameric, ring-shaped helicases around DNA by AAA+(ATPases Associated with various cellular Activities) ATPases. How loading factors use ATP to control helicase deposition is poorly understood. Here, we dissect how specific ATPase elements of Escherichia coli DnaC, an archetypal loader for the bacterial DnaB helicase, play distinct roles in helicase loading and the activation of DNA unwinding. We have identified a new element, the arginine-coupler, which regulates the switch-like behavior of DnaC to prevent futile ATPase cycling and maintains loader responsiveness to replication restart systems. Our data help explain how the ATPase cycle of a AAA+-family helicase loader is channeled into productive action on its target; comparative studies indicate that elements analogous to the Arg-coupler are present in related, switch-like AAA+ proteins that control replicative helicase loading in eukaryotes, as well as in polymerase clamp loading and certain classes of DNA transposases.
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Affiliation(s)
- Neha Puri
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, United States
| | - Amy J Fernandez
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, United States
| | - Valerie L O'Shea Murray
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, United States.,Saul Ewing Arnstein & Lehr, LLP, Centre Square West, Philadelphia, United States
| | - Sarah McMillan
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, United States
| | - James L Keck
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, United States
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, United States
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Zink IA, Fouqueau T, Tarrason Risa G, Werner F, Baum B, Bläsi U, Schleper C. Comparative CRISPR type III-based knockdown of essential genes in hyperthermophilic Sulfolobales and the evasion of lethal gene silencing. RNA Biol 2021; 18:421-434. [PMID: 32957821 PMCID: PMC7951960 DOI: 10.1080/15476286.2020.1813411] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/22/2020] [Accepted: 08/16/2020] [Indexed: 02/07/2023] Open
Abstract
CRISPR type III systems, which are abundantly found in archaea, recognize and degrade RNA in their specific response to invading nucleic acids. Therefore, these systems can be harnessed for gene knockdown technologies even in hyperthermophilic archaea to study essential genes. We show here the broader usability of this posttranscriptional silencing technology by expanding the application to further essential genes and systematically analysing and comparing silencing thresholds and escape mutants. Synthetic guide RNAs expressed from miniCRISPR cassettes were used to silence genes involved in cell division (cdvA), transcription (rpo8), and RNA metabolism (smAP2) of the two crenarchaeal model organisms Saccharolobus solfataricus and Sulfolobus acidocaldarius. Results were systematically analysed together with those obtained from earlier experiments of cell wall biogenesis (slaB) and translation (aif5A). Comparison of over 100 individual transformants revealed gene-specific silencing maxima ranging between 40 and 75%, which induced specific knockdown phenotypes leading to growth retardation. Exceedance of this threshold by strong miniCRISPR constructs was not tolerated and led to specific mutation of the silencing miniCRISPR array and phenotypical reversion of cultures. In two thirds of sequenced reverted cultures, the targeting spacers were found to be precisely excised from the miniCRISPR array, indicating a still hypothetical, but highly active recombination system acting on the dynamics of CRISPR spacer arrays. Our results indicate that CRISPR type III - based silencing is a broadly applicable tool to study in vivo functions of essential genes in Sulfolobales which underlies a specific mechanism to avoid malignant silencing overdose.
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Affiliation(s)
- Isabelle Anna Zink
- Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Thomas Fouqueau
- RNAP Lab, Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Gabriel Tarrason Risa
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Finn Werner
- RNAP Lab, Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Buzz Baum
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Udo Bläsi
- Max Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Christa Schleper
- Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
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Kaguni JM. The Macromolecular Machines that Duplicate the Escherichia coli Chromosome as Targets for Drug Discovery. Antibiotics (Basel) 2018. [PMID: 29538288 PMCID: PMC5872134 DOI: 10.3390/antibiotics7010023] [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] [Indexed: 12/29/2022] Open
Abstract
DNA replication is an essential process. Although the fundamental strategies to duplicate chromosomes are similar in all free-living organisms, the enzymes of the three domains of life that perform similar functions in DNA replication differ in amino acid sequence and their three-dimensional structures. Moreover, the respective proteins generally utilize different enzymatic mechanisms. Hence, the replication proteins that are highly conserved among bacterial species are attractive targets to develop novel antibiotics as the compounds are unlikely to demonstrate off-target effects. For those proteins that differ among bacteria, compounds that are species-specific may be found. Escherichia coli has been developed as a model system to study DNA replication, serving as a benchmark for comparison. This review summarizes the functions of individual E. coli proteins, and the compounds that inhibit them.
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Affiliation(s)
- Jon M Kaguni
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA.
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Abstract
The initiation of chromosomal DNA replication starts at a replication origin, which in bacteria is a discrete locus that contains DNA sequence motifs recognized by an initiator protein whose role is to assemble the replication fork machinery at this site. In bacteria with a single chromosome, DnaA is the initiator and is highly conserved in all bacteria. As an adenine nucleotide binding protein, DnaA bound to ATP is active in the assembly of a DnaA oligomer onto these sites. Other proteins modulate DnaA oligomerization via their interaction with the N-terminal region of DnaA. Following the DnaA-dependent unwinding of an AT-rich region within the replication origin, DnaA then mediates the binding of DnaB, the replicative DNA helicase, in a complex with DnaC to form an intermediate named the prepriming complex. In the formation of this intermediate, the helicase is loaded onto the unwound region within the replication origin. As DnaC bound to DnaB inhibits its activity as a DNA helicase, DnaC must dissociate to activate DnaB. Apparently, the interaction of DnaB with primase (DnaG) and primer formation leads to the release of DnaC from DnaB, which is coordinated with or followed by translocation of DnaB to the junction of the replication fork. There, DnaB is able to coordinate its activity as a DNA helicase with the cellular replicase, DNA polymerase III holoenzyme, which uses the primers made by primase for leading strand DNA synthesis.
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Affiliation(s)
- S Chodavarapu
- Michigan State University, East Lansing, MI, United States
| | - J M Kaguni
- Michigan State University, East Lansing, MI, United States.
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Felczak MM, Sage JM, Hupert-Kocurek K, Aykul S, Kaguni JM. Substitutions of Conserved Residues in the C-terminal Region of DnaC Cause Thermolability in Helicase Loading. J Biol Chem 2016; 291:4803-12. [PMID: 26728455 DOI: 10.1074/jbc.m115.708586] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Indexed: 11/06/2022] Open
Abstract
The DnaB-DnaC complex binds to the unwound DNA within the Escherichia coli replication origin in the helicase loading process, but the biochemical events that lead to its stable binding are uncertain. This study characterizes the function of specific C-terminal residues of DnaC. Genetic and biochemical characterization of proteins bearing F231S and W233L substitutions of DnaC reveals that their activity is thermolabile. Because the mutants remain able to form a complex with DnaB at 30 and 37 °C, their thermolability is not explained by an impaired interaction with DnaB. Photo-cross-linking experiments and biosensor analysis show an altered affinity of these mutants compared with wild type DnaC for single-stranded DNA, suggesting that the substitutions affect DNA binding. Despite this difference, their activity in DNA binding is not thermolabile. The substitutions also drastically reduce the affinity of DnaC for ATP as measured by the binding of a fluorescent ATP analogue (MANT-ATP) and by UV cross-linking of radiolabeled ATP. Experiments show that an elevated temperature substantially inhibits both mutants in their ability to load the DnaB-DnaC complex at a DnaA box. Because a decreased ATP concentration exacerbates their thermolabile behavior, we suggest that the F231S and W233L substitutions are thermolabile in ATP binding, which correlates with defective helicase loading at an elevated temperature.
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Affiliation(s)
- Magdalena M Felczak
- From the Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319
| | - Jay M Sage
- From the Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319
| | - Katarzyna Hupert-Kocurek
- From the Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319
| | - Senem Aykul
- From the Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319
| | - Jon M Kaguni
- From the Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319
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Suk S, Kim Y, Bak G, Lee Y. Identification of a Temperature-Sensitive Mutation in the ribE Gene of an Escherichia coli Keio Collection Strain. B KOREAN CHEM SOC 2014. [DOI: 10.5012/bkcs.2014.35.7.2175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Replication initiation at the Escherichia coli chromosomal origin. Curr Opin Chem Biol 2011; 15:606-13. [PMID: 21856207 DOI: 10.1016/j.cbpa.2011.07.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 11/24/2022]
Abstract
To initiate DNA replication, DnaA recognizes and binds to specific sequences within the Escherichia coli chromosomal origin (oriC), and then unwinds a region within oriC. Next, DnaA interacts with DnaB helicase in loading the DnaB-DnaC complex on each separated strand. Primer formation by primase (DnaG) induces the dissociation of DnaC from DnaB, which involves the hydrolysis of ATP bound to DnaC. Recent evidence indicates that DnaC acts as a checkpoint in the transition from initiation to the elongation stage of DNA replication. Freed from DnaC, DnaB helicase unwinds the parental duplex DNA while interacting the cellular replicase, DNA polymerase III holoenzyme, and primase as it intermittently forms primers that are extended by the replicase in duplicating the chromosome.
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Morita Y, Narita SI, Tomida J, Tokuda H, Kawamura Y. Application of an inducible system to engineer unmarked conditional mutants of essential genes of Pseudomonas aeruginosa. J Microbiol Methods 2010; 82:205-13. [PMID: 20538017 DOI: 10.1016/j.mimet.2010.06.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/24/2010] [Accepted: 06/01/2010] [Indexed: 12/31/2022]
Abstract
The Phi CTX-based integration vector pYM101 harboring a tightly controlled modified phage T7 early gene promoter/LacI(q) repressor (T7/LacI) system was constructed for the generation of unmarked conditional mutants in Pseudomonas aeruginosa. Promoter activity of the T7/LacI system was demonstrated to be dependent on the presence of the inducer isopropyl -beta-D-1-thiogalactopyranoside (IPTG), as evaluated by measuring beta-galactosidase activity. In the absence of the inducer, the promoter was silent as its activity was lower than those of a promoter-less lacZ control. Unmarked conditional mutants of four predicted essential genes (lolCDE (PA2988-86), lpxC (PA4406), rho (PA5239), and def (PA0019)) were successfully constructed using this recombination system. In the absence of IPTG, the growth of all mutants was repressed; however, the addition of either 0.1 or 1mM IPTG restored growth rates to levels nearly identical to wild-type cells. It was therefore demonstrated that the inducible integration vector pYM101 is suitable for the creation of unmarked conditional mutants of P. aeruginosa, and is particularly useful for examining the function of essential genes.
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Affiliation(s)
- Yuji Morita
- Department of Microbiology, School of Pharmacy, Aichi Gakuin University, Nagoya, Aichi, Japan
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Makowska-Grzyska M, Kaguni JM. Primase directs the release of DnaC from DnaB. Mol Cell 2010; 37:90-101. [PMID: 20129058 DOI: 10.1016/j.molcel.2009.12.031] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/03/2009] [Accepted: 12/18/2009] [Indexed: 10/20/2022]
Abstract
An AAA+ ATPase, DnaC, delivers DnaB helicase at the E. coli chromosomal origin by a poorly understood process. This report shows that mutant proteins bearing alanine substitutions for two conserved arginines in a motif named box VII are defective in DNA replication, but this deficiency does not arise from impaired interactions with ATP, DnaB, or single-stranded DNA. Despite their ability to deliver DnaB to the chromosomal origin to form the prepriming complex, this intermediate is inactive. Quantitative analysis of the prepriming complex suggests that the DnaB-DnaC complex contains three DnaC monomers per DnaB hexamer and that the interaction of primase with DnaB and primer formation triggers the release of DnaC, but not the mutants, from DnaB. The interaction of primase with DnaB and the release of DnaC mark discrete events in the transition from initiation to the elongation stage of DNA replication.
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Affiliation(s)
- Magdalena Makowska-Grzyska
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA
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