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Hong Y, Ye F, Qian J, Gao X, Inman JT, Wang MD. Optical torque calculations and measurements for DNA torsional studies. Biophys J 2024:S0006-3495(24)00444-2. [PMID: 38961622 DOI: 10.1016/j.bpj.2024.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 05/20/2024] [Accepted: 07/01/2024] [Indexed: 07/05/2024] Open
Abstract
The angular optical trap (AOT) is a powerful instrument for measuring the torsional and rotational properties of a biological molecule. Thus far, AOT studies of DNA torsional mechanics have been carried out using a high numerical aperture oil-immersion objective, which permits strong trapping but inevitably introduces spherical aberrations due to the glass-aqueous interface. However, the impact of these aberrations on torque measurements is not fully understood experimentally, partly due to a lack of theoretical guidance. Here, we present a numerical platform based on the finite element method to calculate forces and torques on a trapped quartz cylinder. We have also developed a new experimental method to accurately determine the shift in the trapping position due to the spherical aberrations by using a DNA molecule as a distance ruler. We found that the calculated and measured focal shift ratios are in good agreement. We further determined how the angular trap stiffness depends on the trap height and the cylinder displacement from the trap center and found full agreement between predictions and measurements. As a further verification of the methodology, we showed that DNA torsional properties, which are intrinsic to DNA, could be determined robustly under different trap heights and cylinder displacements. Thus, this work has laid both a theoretical and experimental framework that can be readily extended to investigate the trapping forces and torques exerted on particles with arbitrary shapes and optical properties.
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Affiliation(s)
- Yifeng Hong
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York
| | - Fan Ye
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Jin Qian
- Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Xiang Gao
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - James T Inman
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York
| | - Michelle D Wang
- Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York.
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2
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Olivi L, Bagchus C, Pool V, Bekkering E, Speckner K, Offerhaus H, Wu W, Depken M, Martens KA, Staals RJ, Hohlbein J. Live-cell imaging reveals the trade-off between target search flexibility and efficiency for Cas9 and Cas12a. Nucleic Acids Res 2024; 52:5241-5256. [PMID: 38647045 PMCID: PMC11109954 DOI: 10.1093/nar/gkae283] [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: 11/16/2023] [Revised: 03/25/2024] [Accepted: 04/04/2024] [Indexed: 04/25/2024] Open
Abstract
CRISPR-Cas systems have widely been adopted as genome editing tools, with two frequently employed Cas nucleases being SpyCas9 and LbCas12a. Although both nucleases use RNA guides to find and cleave target DNA sites, the two enzymes differ in terms of protospacer-adjacent motif (PAM) requirements, guide architecture and cleavage mechanism. In the last years, rational engineering led to the creation of PAM-relaxed variants SpRYCas9 and impLbCas12a to broaden the targetable DNA space. By employing their catalytically inactive variants (dCas9/dCas12a), we quantified how the protein-specific characteristics impact the target search process. To allow quantification, we fused these nucleases to the photoactivatable fluorescent protein PAmCherry2.1 and performed single-particle tracking in cells of Escherichia coli. From our tracking analysis, we derived kinetic parameters for each nuclease with a non-targeting RNA guide, strongly suggesting that interrogation of DNA by LbdCas12a variants proceeds faster than that of SpydCas9. In the presence of a targeting RNA guide, both simulations and imaging of cells confirmed that LbdCas12a variants are faster and more efficient in finding a specific target site. Our work demonstrates the trade-off of relaxing PAM requirements in SpydCas9 and LbdCas12a using a powerful framework, which can be applied to other nucleases to quantify their DNA target search.
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Affiliation(s)
- Lorenzo Olivi
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Cleo Bagchus
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
| | - Victor Pool
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
| | - Ezra Bekkering
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
| | - Konstantin Speckner
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
| | - Hidde Offerhaus
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Wen Y Wu
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Martin Depken
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Koen J A Martens
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
| | - Raymond H J Staals
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Johannes Hohlbein
- Laboratory of Biophysics, Wageningen University & Research, Wageningen, The Netherlands
- Microspectroscopy Research Facility, Wageningen University & Research, Wageningen, The Netherlands
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3
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Hibshman GN, Bravo JPK, Hooper MM, Dangerfield TL, Zhang H, Finkelstein IJ, Johnson KA, Taylor DW. Unraveling the mechanisms of PAMless DNA interrogation by SpRY-Cas9. Nat Commun 2024; 15:3663. [PMID: 38688943 PMCID: PMC11061278 DOI: 10.1038/s41467-024-47830-3] [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: 02/21/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024] Open
Abstract
CRISPR-Cas9 is a powerful tool for genome editing, but the strict requirement for an NGG protospacer-adjacent motif (PAM) sequence immediately next to the DNA target limits the number of editable genes. Recently developed Cas9 variants have been engineered with relaxed PAM requirements, including SpG-Cas9 (SpG) and the nearly PAM-less SpRY-Cas9 (SpRY). However, the molecular mechanisms of how SpRY recognizes all potential PAM sequences remains unclear. Here, we combine structural and biochemical approaches to determine how SpRY interrogates DNA and recognizes target sites. Divergent PAM sequences can be accommodated through conformational flexibility within the PAM-interacting region, which facilitates tight binding to off-target DNA sequences. Nuclease activation occurs ~1000-fold slower than for Streptococcus pyogenes Cas9, enabling us to directly visualize multiple on-pathway intermediate states. Experiments with SpG position it as an intermediate enzyme between Cas9 and SpRY. Our findings shed light on the molecular mechanisms of PAMless genome editing.
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Affiliation(s)
- Grace N Hibshman
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
- Interdisciplinary Life Sciences Graduate Programs, Austin, TX, 78712, USA
| | - Jack P K Bravo
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA.
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria.
| | - Matthew M Hooper
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
- Interdisciplinary Life Sciences Graduate Programs, Austin, TX, 78712, USA
| | - Tyler L Dangerfield
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
| | - Hongshan Zhang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
- Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
- Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Kenneth A Johnson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
- Interdisciplinary Life Sciences Graduate Programs, Austin, TX, 78712, USA
| | - David W Taylor
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA.
- Interdisciplinary Life Sciences Graduate Programs, Austin, TX, 78712, USA.
- Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX, 78712, USA.
- LIVESTRONG Cancer Institutes, Dell Medical School, Austin, TX, 78712, USA.
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Hoque ME, Kabir ML, Shiekh S, Balci H, Basu S. Stalling of Transcription by Putative G-quadruplex Sequences and CRISPR-dCas9. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.17.585391. [PMID: 38559215 PMCID: PMC10979993 DOI: 10.1101/2024.03.17.585391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Putative G-quadruplex forming sequences (PQS) have been identified in promoter sequences of prominent genes that are implicated among others in cancer and neurological disorders. We explored mechanistic aspects of CRISPR-dCas9-mediated gene expression regulation, which is transient and sequence specific unlike alternative approaches that lack such specificity or create permanent mutations, using the PQS in tyrosine hydroxylase (TH) and c-Myc promoters as model systems. We performed in vitro ensemble and single molecule investigations to study whether G-quadruplex (GQ) structures or dCas9 impede T7 RNA polymerase (RNAP) elongation process and whether orientation of these factors is significant. Our results demonstrate that dCas9 is more likely to block RNAP progression when the non-template strand is targeted. While the GQ in TH promoter was effectively destabilized when the dCas9 target site partially overlapped with the PQS, the c-Myc GQ remained folded and stalled RNAP elongation. We also determined that a minimum separation between the transcription start site and the dCas9 target site is required for effective stalling of RNAP by dCas9. Our study provides significant insights about the factors that impact dCas9-mediated transcription regulation when dCas9 targets the vicinity of sequences that form secondary structures and provides practical guidelines for designing guide RNA sequences.
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Affiliation(s)
- Mohammed Enamul Hoque
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA
| | - Mohammad Lutful Kabir
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA
| | - Sajad Shiekh
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Hamza Balci
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Soumitra Basu
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA
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5
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Cosgrove BD, Bounds LR, Taylor CK, Su AL, Rizzo AJ, Barrera A, Crawford GE, Hoffman BD, Gersbach CA. Mechanosensitive genomic enhancers potentiate the cellular response to matrix stiffness. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.574997. [PMID: 38260455 PMCID: PMC10802421 DOI: 10.1101/2024.01.10.574997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Epigenetic control of cellular transcription and phenotype is influenced by changes in the cellular microenvironment, yet how mechanical cues from these microenvironments precisely influence epigenetic state to regulate transcription remains largely unmapped. Here, we combine genome-wide epigenome profiling, epigenome editing, and phenotypic and single-cell RNA-seq CRISPR screening to identify a new class of genomic enhancers that responds to the mechanical microenvironment. These 'mechanoenhancers' could be active on either soft or stiff extracellular matrix contexts, and regulated transcription to influence critical cell functions including apoptosis, mechanotransduction, proliferation, and migration. Epigenetic editing of mechanoenhancers on rigid materials tuned gene expression to levels observed on softer materials, thereby reprogramming the cellular response to the mechanical microenvironment. These editing approaches may enable the precise alteration of mechanically-driven disease states.
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Affiliation(s)
- Brian D. Cosgrove
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
| | - Lexi R. Bounds
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
| | - Carson Key Taylor
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
| | - Alan L. Su
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
| | - Anthony J. Rizzo
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
| | - Alejandro Barrera
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
- Department of Biostatistics and Bioinformatics, Duke University; Durham, NC 27708, USA
| | - Gregory E. Crawford
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
- Department of Pediatrics, Duke University Medical Center; Durham, NC 27708, USA
| | - Brenton D. Hoffman
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Department of Cell Biology, Duke University; Durham, NC 27708, USA
| | - Charles A. Gersbach
- Department of Biomedical Engineering, Duke University; Durham, NC 27708, USA
- Center for Advanced Genomic Technologies, Duke University; Durham, NC 27708, USA
- Department of Cell Biology, Duke University; Durham, NC 27708, USA
- Department of Surgery, Duke University Medical Center; Durham, NC 27708, USA
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6
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Piya D, Nolan N, Moore ML, Ramirez Hernandez LA, Cress BF, Young R, Arkin AP, Mutalik VK. Systematic and scalable genome-wide essentiality mapping to identify nonessential genes in phages. PLoS Biol 2023; 21:e3002416. [PMID: 38048319 PMCID: PMC10695390 DOI: 10.1371/journal.pbio.3002416] [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: 05/23/2023] [Accepted: 11/02/2023] [Indexed: 12/06/2023] Open
Abstract
Phages are one of the key ecological drivers of microbial community dynamics, function, and evolution. Despite their importance in bacterial ecology and evolutionary processes, phage genes are poorly characterized, hampering their usage in a variety of biotechnological applications. Methods to characterize such genes, even those critical to the phage life cycle, are labor intensive and are generally phage specific. Here, we develop a systematic gene essentiality mapping method scalable to new phage-host combinations that facilitate the identification of nonessential genes. As a proof of concept, we use an arrayed genome-wide CRISPR interference (CRISPRi) assay to map gene essentiality landscape in the canonical coliphages λ and P1. Results from a single panel of CRISPRi probes largely recapitulate the essential gene roster determined from decades of genetic analysis for lambda and provide new insights into essential and nonessential loci in P1. We present evidence of how CRISPRi polarity can lead to false positive gene essentiality assignments and recommend caution towards interpreting CRISPRi data on gene essentiality when applied to less studied phages. Finally, we show that we can engineer phages by inserting DNA barcodes into newly identified inessential regions, which will empower processes of identification, quantification, and tracking of phages in diverse applications.
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Affiliation(s)
- Denish Piya
- Innovative Genomics Institute, University of California-Berkeley, Berkeley, California, United States of America
| | - Nicholas Nolan
- Department of Bioengineering, University of California-Berkeley, Berkeley, California, United States of America
| | - Madeline L. Moore
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Luis A. Ramirez Hernandez
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Brady F. Cress
- Innovative Genomics Institute, University of California-Berkeley, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, California, United States of America
| | - Ry Young
- Department of Biochemistry and Biophysics, Center for Phage Technology, Texas A&M University, College Station, Texas, United States of America
| | - Adam P. Arkin
- Innovative Genomics Institute, University of California-Berkeley, Berkeley, California, United States of America
- Department of Bioengineering, University of California-Berkeley, Berkeley, California, United States of America
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Vivek K. Mutalik
- Innovative Genomics Institute, University of California-Berkeley, Berkeley, California, United States of America
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
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7
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Zukher I, Dujardin G, Sousa-Luís R, Proudfoot NJ. Elongation roadblocks mediated by dCas9 across human genes modulate transcription and nascent RNA processing. Nat Struct Mol Biol 2023; 30:1536-1548. [PMID: 37783853 PMCID: PMC10584677 DOI: 10.1038/s41594-023-01090-9] [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: 06/14/2022] [Accepted: 08/04/2023] [Indexed: 10/04/2023]
Abstract
Non-cleaving Cas9 (dCas9) is widely employed to manipulate specific gene loci, often with scant regard for unintended transcriptional effects. We demonstrate here that dCas9 mediates precise RNA polymerase II transcriptional pausing followed by transcription termination and potential alternative polyadenylation. By contrast, alternative splicing is unaffected, likely requiring more sustained alteration to elongation speed. The effect on transcription is orientation specific, with pausing only being induced when dCas9-associated guide RNA anneals to the non-template strand. Targeting the template strand induces minimal effects on transcription elongation and thus provides a neutral approach to recruit dCas9-linked effector domains to specific gene regions. In essence, we evaluate molecular effects of targeting dCas9 to mammalian transcription units. In so doing, we also provide new information on elongation by RNA polymerase II and coupled pre-mRNA processing.
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Affiliation(s)
- Inna Zukher
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
| | - Gwendal Dujardin
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Rui Sousa-Luís
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Nick J Proudfoot
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
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Hao N, Donnelly AJ, Dodd IB, Shearwin KE. When push comes to shove - RNA polymerase and DNA-bound protein roadblocks. Biophys Rev 2023; 15:355-366. [PMID: 37396453 PMCID: PMC10310618 DOI: 10.1007/s12551-023-01064-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 05/21/2023] [Indexed: 07/04/2023] Open
Abstract
In recent years, transcriptional roadblocking has emerged as a crucial regulatory mechanism in gene expression, whereby other DNA-bound obstacles can block the progression of transcribing RNA polymerase (RNAP), leading to RNAP pausing and ultimately dissociation from the DNA template. In this review, we discuss the mechanisms by which transcriptional roadblocks can impede RNAP progression, as well as how RNAP can overcome these obstacles to continue transcription. We examine different DNA-binding proteins involved in transcriptional roadblocking and their biophysical properties that determine their effectiveness in blocking RNAP progression. The catalytically dead CRISPR-Cas (dCas) protein is used as an example of an engineered programmable roadblock, and the current literature in understanding the polarity of dCas roadblocking is also discussed. Finally, we delve into a stochastic model of transcriptional roadblocking and highlight the importance of transcription factor binding kinetics and its resistance to dislodgement by an elongating RNAP in determining the strength of a roadblock.
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Affiliation(s)
- Nan Hao
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Alana J. Donnelly
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Ian B. Dodd
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Keith E. Shearwin
- Department of Molecular and Biomedical Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
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