1
|
Casella C, Ballaz SJ. Genotoxic and neurotoxic potential of intracellular nanoplastics: A review. J Appl Toxicol 2024. [PMID: 38494651 DOI: 10.1002/jat.4598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 02/18/2024] [Accepted: 02/24/2024] [Indexed: 03/19/2024]
Abstract
Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.
Collapse
Affiliation(s)
- Claudio Casella
- Department Chemical and Environmental Engineering, University of Oviedo, Oviedo, Spain
| | | |
Collapse
|
2
|
Redcenko O, Tumova M, Draber P. Simplified PCR-Based Quantification of Proteins with DNA Aptamers and Methylcellulose as a Blocking Agent. Int J Mol Sci 2023; 25:347. [PMID: 38203527 PMCID: PMC10779054 DOI: 10.3390/ijms25010347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024] Open
Abstract
Due to their unique three-dimensional structure, DNA or RNA oligonucleotide aptamers bind to various molecules with high affinity and specificity. Aptamers, alone or in combination with antibodies, can be used to sensitively quantify target molecules by quantitative real-time polymerase chain reaction (qPCR). However, the assays are often complicated and unreliable. In this study, we explored the feasibility of performing the entire assay on wells of routinely used polypropylene PCR plates. We found that polypropylene wells efficiently bind proteins. This allows the entire assay to be run in a single well. To minimize nonspecific binding of the assay components to the polypropylene wells, we tested various blocking agents and identified methylcellulose as an effective alternative to the commonly used BSA. Methylcellulose not only demonstrates comparable or superior blocking capabilities but also offers the advantage of a well-defined composition and non-animal origin. Our findings support the utilization of aptamers, either alone or in combination with antibodies, for sensitive quantification of selected molecules immobilized in polypropylene PCR wells in a streamlined one-well qPCR assay under well-defined conditions.
Collapse
Affiliation(s)
| | | | - Petr Draber
- Laboratory of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic; (O.R.); (M.T.)
| |
Collapse
|
3
|
Sobol MS, Kaster AK. Back to Basics: A Simplified Improvement to Multiple Displacement Amplification for Microbial Single-Cell Genomics. Int J Mol Sci 2023; 24. [PMID: 36901710 DOI: 10.3390/ijms24054270] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/23/2023] [Accepted: 02/15/2023] [Indexed: 02/25/2023] Open
Abstract
Microbial single-cell genomics (SCG) provides access to the genomes of rare and uncultured microorganisms and is a complementary method to metagenomics. Due to the femtogram-levels of DNA in a single microbial cell, sequencing the genome requires whole genome amplification (WGA) as a preliminary step. However, the most common WGA method, multiple displacement amplification (MDA), is known to be costly and biased against specific genomic regions, preventing high-throughput applications and resulting in uneven genome coverage. Thus, obtaining high-quality genomes from many taxa, especially minority members of microbial communities, becomes difficult. Here, we present a volume reduction approach that significantly reduces costs while improving genome coverage and uniformity of DNA amplification products in standard 384-well plates. Our results demonstrate that further volume reduction in specialized and complex setups (e.g., microfluidic chips) is likely unnecessary to obtain higher-quality microbial genomes. This volume reduction method makes SCG more feasible for future studies, thus helping to broaden our knowledge on the diversity and function of understudied and uncharacterized microorganisms in the environment.
Collapse
|
4
|
Chakraborty S, Luchena C, Elton JJ, Schilling MP, Reischl M, Roux M, Levkin PA, Popova AA. "Cells-to-cDNA on Chip": Phenotypic Assessment and Gene Expression Analysis from Live Cells in Nanoliter Volumes Using Droplet Microarrays. Adv Healthc Mater 2022; 11:e2102493. [PMID: 35285171 DOI: 10.1002/adhm.202102493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 02/08/2022] [Indexed: 11/11/2022]
Abstract
In vitro cell-based experiments are particularly important in fundamental biological research. Microscopy-based readouts to identify cellular changes in response to various stimuli are a popular choice, but gene expression analysis is essential to delineate the underlying molecular dynamics in cells. However, cell-based experiments often suffer from interexperimental variation, especially while using different readout methods. Therefore, establishment of platforms that allow for cell screening, along with parallel investigations of morphological features, as well as gene expression levels, is crucial. The droplet microarray (DMA) platform enables cell screening in hundreds of nanoliter droplets. In this study, a "Cells-to-cDNA on Chip" method is developed enabling on-chip mRNA isolation from live cells and conversion to cDNA in individual droplets of 200 nL. This novel method works efficiently to obtain cDNA from different cell numbers, down to single cell per droplet. This is the first established miniaturized on-chip strategy that enables the entire course of cell screening, phenotypic microscopy-based assessments along with mRNA isolation and its conversion to cDNA for gene expression analysis by real-time PCR on an open DMA platform. The principle demonstrated in this study sets a beginning for myriad of possible applications to obtain detailed information about the molecular dynamics in cultured cells.
Collapse
Affiliation(s)
- Shraddha Chakraborty
- Institute of Biological and Chemical Systems‐Functional Molecular Systems Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| | - Charlotte Luchena
- Institute of Biological and Chemical Systems‐Functional Molecular Systems Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| | - Jonathan J. Elton
- Institute of Biological and Chemical Systems‐Functional Molecular Systems Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| | - Marcel P. Schilling
- Institute for Automation and Applied Informatics Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| | - Markus Reischl
- Institute for Automation and Applied Informatics Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| | - Margaux Roux
- Cellenion SASU Bioserra 2, 60 avenue Rockefeller Lyon 69008 France
| | - Pavel A. Levkin
- Institute of Biological and Chemical Systems‐Functional Molecular Systems Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
- Institute of Organic Chemistry Karlsruhe Institute of Technology Fritz‐Haber Weg 6 Karlsruhe 76131 Germany
| | - Anna A. Popova
- Institute of Biological and Chemical Systems‐Functional Molecular Systems Karlsruhe Institute of Technology Hermann‐von‐Helmholtz‐Platz 1 Eggenstein‐Leopoldshafen 76344 Germany
| |
Collapse
|
5
|
Wise NM, Wagner SJ, Worst TJ, Sprague JE, Oechsle CM. Comparison of swab types for collection and analysis of microorganisms. Microbiologyopen 2021; 10:e1244. [PMID: 34964289 PMCID: PMC8591448 DOI: 10.1002/mbo3.1244] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/27/2021] [Indexed: 12/02/2022] Open
Abstract
The human microbiome has begun to emerge as a potential forensic tool, with varied applications ranging from unique identification to investigative leads that link individuals and/or locations. The relative abundance of the combined DNA of the microbiome, compared to human nuclear DNA, may expand potential sources of biological evidence, especially in cases with transfer or low-copy number DNA samples. This work sought to determine the optimal swab type for the collection and analysis of microorganisms. A bacterium (Proteus mirabilis) was deposited by pipette onto four swab types (cotton, flocked, dental applicators, and dissolvable), and extraction and real-time PCR quantitation of the bacterial DNA were performed, which allowed for absolute microbial DNA recovery and comparison of yields across the four sampling substrates. Flocked swabs had the highest yield (~1240 ng) compared to the cotton swabs (~184 ng), dental applicators (~533 ng), and dissolvable swabs (~430 ng). The collection efficiency was further evaluated for cotton and flocked swabs using dried microbial samples spotted onto non-porous surfaces (treated wood, glass, plastic, and tile). Flocked swabs performed consistently better across wood, glass, and tile, but showed decreased recovery from plastic. The cotton swabs failed in the recovery of P. mirabilis DNA across all surfaces. Knowing the appropriate sampling substrate will be useful as others continue to investigate the use of the microbiome as a forensics tool.
Collapse
Affiliation(s)
- Natalie M. Wise
- Ohio Attorney General’s Center for The Future of Forensic ScienceBowling Green State UniversityBowling GreenOhioUSA
| | - Sarah J. Wagner
- Ohio Attorney General’s Center for The Future of Forensic ScienceBowling Green State UniversityBowling GreenOhioUSA
| | - Travis J. Worst
- Ohio Attorney General’s Center for The Future of Forensic ScienceBowling Green State UniversityBowling GreenOhioUSA
| | - Jon E. Sprague
- Ohio Attorney General’s Center for The Future of Forensic ScienceBowling Green State UniversityBowling GreenOhioUSA
| | - Crystal M. Oechsle
- Ohio Attorney General’s Center for The Future of Forensic ScienceBowling Green State UniversityBowling GreenOhioUSA
| |
Collapse
|
6
|
Narvaez Villarrubia CW, Tumas KC, Chauhan R, MacDonald T, Dattelbaum AM, Omberg K, Gupta G. Long-term stabilization of DNA at room temperature using a one-step microwave assisted process. Emergent Mater 2021; 5:307-314. [PMID: 33778372 PMCID: PMC7986179 DOI: 10.1007/s42247-021-00208-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
UNLABELLED Long-term stabilization of DNA is needed for forensic, clinical, in-field operations and numerous other applications. Although freezing (<-20 °C) and dry storage are currently the preferential methods for long-term storage, a noticeable pre-analytical degradation of DNA over time, upfront capital investment and recurring costs have demonstrated a need for an alternative long-term room-temperature preservation method. Herein, we report a novel, fast (~5 min) silica sol-gel preparation method using a standard microwave-initiated polymerization reaction amenable to stabilization of DNA. The method involves use of one chemical, tetramethoxy silane (TMOS) and eliminates the use of alcohol as co-solvent and catalysts such as acids. In addition, the process involves minimal technical expertise, thus making it an ideal choice for resource-challenged countries and in-field applications. The sol-gel is capable to store and stabilize Escherichia coli DNA in ambient conditions for 210 days. DNA recovered from the sol-gel showed no significant nucleolytic and/or oxidative degradation, outperforming conventional storage conditions at -20 °C, and reported state-of-the-art technology. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s42247-021-00208-3.
Collapse
Affiliation(s)
| | - Keyla C. Tumas
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM USA
| | - Rajat Chauhan
- Department of Bioengineering, University of Louisville, Louisville, KY 40292 USA
| | - Thomas MacDonald
- Materials Physics and Applications Divison, Los Alamos National Laboratory, Los Alamos, NM USA
| | - Andrew M. Dattelbaum
- Materials Physics and Applications Divison, Los Alamos National Laboratory, Los Alamos, NM USA
| | - Kristin Omberg
- Materials Physics and Applications Divison, Los Alamos National Laboratory, Los Alamos, NM USA
| | - Gautam Gupta
- Department of Chemical Engineering, University of Louisville, Louisville, KY 40292 USA
| |
Collapse
|
7
|
Onsbring H, Tice AK, Barton BT, Brown MW, Ettema TJG. An efficient single-cell transcriptomics workflow for microbial eukaryotes benchmarked on Giardia intestinalis cells. BMC Genomics 2020; 21:448. [PMID: 32600266 PMCID: PMC7325058 DOI: 10.1186/s12864-020-06858-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 06/22/2020] [Indexed: 01/08/2023] Open
Abstract
Background Most diversity in the eukaryotic tree of life is represented by microbial eukaryotes, which is a polyphyletic group also referred to as protists. Among the protists, currently sequenced genomes and transcriptomes give a biased view of the actual diversity. This biased view is partly caused by the scientific community, which has prioritized certain microbes of biomedical and agricultural importance. Additionally, some protists remain difficult to maintain in cultures, which further influences what has been studied. It is now possible to bypass the time-consuming process of cultivation and directly analyze the gene content of single protist cells. Single-cell genomics was used in the first experiments where individual protists cells were genomically explored. Unfortunately, single-cell genomics for protists is often associated with low genome recovery and the assembly process can be complicated because of repetitive intergenic regions. Sequencing repetitive sequences can be avoided if single-cell transcriptomics is used, which only targets the part of the genome that is transcribed. Results In this study we test different modifications of Smart-seq2, a single-cell RNA sequencing protocol originally developed for mammalian cells, to establish a robust and more cost-efficient workflow for protists. The diplomonad Giardia intestinalis was used in all experiments and the available genome for this species allowed us to benchmark our results. We could observe increased transcript recovery when freeze-thaw cycles were added as an extra step to the Smart-seq2 protocol. Further we reduced the reaction volume and purified the amplified cDNA with alternative beads to test different cost-reducing changes of Smart-seq2. Neither improved the procedure, and reducing the volumes by half led to significantly fewer genes detected. We also added a 5′ biotin modification to our primers and reduced the concentration of oligo-dT, to potentially reduce generation of artifacts. Except adding freeze-thaw cycles and reducing the volume, no other modifications lead to a significant change in gene detection. Therefore, we suggest adding freeze-thaw cycles to Smart-seq2 when working with protists and further consider our other modification described to improve cost and time-efficiency. Conclusions The presented single-cell RNA sequencing workflow represents an efficient method to explore the diversity and cell biology of individual protist cells.
Collapse
Affiliation(s)
- Henning Onsbring
- Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, 75123, Uppsala, Sweden
| | - Alexander K Tice
- Department of Biological Sciences, Mississippi State University, Starkville, Mississippi State, USA
| | - Brandon T Barton
- Department of Biological Sciences, Mississippi State University, Starkville, Mississippi State, USA
| | - Matthew W Brown
- Department of Biological Sciences, Mississippi State University, Starkville, Mississippi State, USA
| | - Thijs J G Ettema
- Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, 75123, Uppsala, Sweden. .,Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, the Netherlands.
| |
Collapse
|
8
|
Baymiev AK, Baymiev AK, Kuluev BR, Shvets KY, Yamidanov RS, Matniyazov RT, Chemeris DA, Zubov VV, Alekseev YI, Mavzyutov AR, Ivanenkov YA, Chemeris AV. Modern Approaches to Differentiation of Live and Dead Bacteria Using Selective Amplification of Nucleic Acids. Microbiology (Reading) 2020. [DOI: 10.1134/s0026261720010038] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
|
9
|
Trinh KTL, Zhang Y, Lee NY. One-step DNA purification and amplification on an integrated plastic microdevice for on-site identification of foodborne pathogens. Anal Chim Acta 2018; 1040:63-73. [DOI: 10.1016/j.aca.2018.06.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/06/2018] [Accepted: 06/18/2018] [Indexed: 11/16/2022]
|
10
|
Zhong J, Ye Z, Lenz SW, Clark CR, Bharucha A, Farrugia G, Robertson KD, Zhang Z, Ordog T, Lee JH. Purification of nanogram-range immunoprecipitated DNA in ChIP-seq application. BMC Genomics 2017; 18:985. [PMID: 29268714 PMCID: PMC5740926 DOI: 10.1186/s12864-017-4371-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 12/08/2017] [Indexed: 11/10/2022] Open
Abstract
Background Chromatin immunoprecipitation-sequencing (ChIP-seq) is a widely used epigenetic approach for investigating genome-wide protein-DNA interactions in cells and tissues. The approach has been relatively well established but several key steps still require further improvement. As a part of the procedure, immnoprecipitated DNA must undergo purification and library preparation for subsequent high-throughput sequencing. Current ChIP protocols typically yield nanogram quantities of immunoprecipitated DNA mainly depending on the target of interest and starting chromatin input amount. However, little information exists on the performance of reagents used for the purification of such minute amounts of immunoprecipitated DNA in ChIP elution buffer and their effects on ChIP-seq data. Here, we compared DNA recovery, library preparation efficiency, and ChIP-seq results obtained with several commercial DNA purification reagents applied to 1 ng ChIP DNA and also investigated the impact of conditions under which ChIP DNA is stored. Results We compared DNA recovery of ten commercial DNA purification reagents and phenol/chloroform extraction from 1 to 50 ng of immunopreciptated DNA in ChIP elution buffer. The recovery yield was significantly different with 1 ng of DNA while similar in higher DNA amounts. We also observed that the low nanogram range of purified DNA is prone to loss during storage depending on the type of polypropylene tube used. The immunoprecipitated DNA equivalent to 1 ng of purified DNA was subject to DNA purification and library preparation to evaluate the performance of four better performing purification reagents in ChIP-seq applications. Quantification of library DNAs indicated the selected purification kits have a negligible impact on the efficiency of library preparation. The resulting ChIP-seq data were comparable with the dataset generated by ENCODE consortium and were highly correlated between the data from different purification reagents. Conclusions This study provides comparative data on commercial DNA purification reagents applied to nanogram-range immunopreciptated ChIP DNA and evidence for the importance of storage conditions of low nanogram-range purified DNA. We verified consistent high performance of a subset of the tested reagents. These results will facilitate the improvement of ChIP-seq methodology for low-input applications. Electronic supplementary material The online version of this article (10.1186/s12864-017-4371-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Jian Zhong
- Epigenomics Development Laboratory, Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Zhenqing Ye
- Division of Biomedical Statistics and Informatics, Department of Health Science Research, Mayo Clinic, Rochester, MN, 55905, USA
| | - Samuel W Lenz
- Epigenomics Development Laboratory, Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Chad R Clark
- Epigenomics Development Laboratory, Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Adil Bharucha
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Gianrico Farrugia
- Enteric Neuroscience Program, Mayo Clinic, Rochester, MN, 55905, USA
| | - Keith D Robertson
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, 55905, USA.,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, 55905, USA.,Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA
| | - Zhiguo Zhang
- Department of Pediatrics and Department of Genetics and Development, Institute for Cancer Genetics, Columbia University, New York, NY, 10032, USA
| | - Tamas Ordog
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, 55905, USA.,Enteric Neuroscience Program, Mayo Clinic, Rochester, MN, 55905, USA.,Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
| | - Jeong-Heon Lee
- Epigenomics Development Laboratory, Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA. .,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, 55905, USA. .,Epigenomics Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, 55905, USA.
| |
Collapse
|
11
|
Bronkhorst AJ, Aucamp J, Pretorius PJ. Cell-free DNA: Preanalytical variables. Clin Chim Acta 2015; 450:243-53. [DOI: 10.1016/j.cca.2015.08.028] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/17/2015] [Accepted: 08/30/2015] [Indexed: 12/11/2022]
|
12
|
Swaran YC, Welch L. A comparison between direct PCR and extraction to generate DNA profiles from samples retrieved from various substrates. Forensic Sci Int Genet 2012; 6:407-12. [DOI: 10.1016/j.fsigen.2011.08.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 07/27/2011] [Accepted: 08/22/2011] [Indexed: 11/20/2022]
|
13
|
Affiliation(s)
- Emil Paleček
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, 612
65 Brno, Czech Republic
| | - Martin Bartošík
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, 612
65 Brno, Czech Republic
| |
Collapse
|
14
|
Exner M. Laboratory Controls and Standards. In: Persing DH, Tenover FC, Tang Y, Nolle FS, Hayden RT, van Belkum A, editors. Molecular Microbiology. Wiley; 2011. pp. 899-909. [DOI: 10.1128/9781555816834.ch58] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
15
|
Abstract
The field of molecular paleontology has recently made significant contributions to anthropology and biology. Hundreds of ancient DNA studies have been published, but none has targeted fossil coralline algae. Using regions of the SSU gene, we analyzed rDNA from fossil coralline algae of varying ages and states of preservation from Spain, Papua New Guinea (PNG), and the Great Barrier Reef (GBR). Specimens from PNG, GBR, and some localities from Spain did not contain endogenous ancient DNA. Reproducible sequence data were obtained from specimens ∼550 years old from near Cadiz, Spain, and from rocky-shore deposits in Carboneras, Almeria Province of Spain (∼78,000 years before present [YBP]). Based on BLAST searches and a phylogenetic analysis of sequences, an undescribed coralline alga belonging to the Melobesioideae was discovered in the Carboneras material as well as the following coralline genera: Jania, Lithophyllum, Lithothamnion, Mesophyllum, and Phymatolithon. DNA from fleshy brown and red macroalgae was also discovered in the specimens from Carboneras. The coralline algae identified using molecular techniques were in agreement with those based on morphological methods. The identified taxa are common in the present-day southeastern Spain littoral zone. Amino acid racemization, concentration ratios, and specific concentrations failed to show a correlation between biomolecular preservation and PCR amplification success. Results suggest that molecular investigations on fossil algae, although limited by technical difficulties, are feasible. Validity of our results was established using authentication criteria and a self-critical approach to compliance.
Collapse
Affiliation(s)
- Jeffery R Hughey
- Division of Math, Science, and Health Professions, Hartnell College, 156 Homestead Ave., Salinas, California 93950, USADepartamento de Estratigrafía y Paleontología, Universidad de Granada, 18002, Granada, SpainSchool of Botany, La Trobe University, Bundoora, Victoria 3083, AustraliaSchool of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
| | - Juan C Braga
- Division of Math, Science, and Health Professions, Hartnell College, 156 Homestead Ave., Salinas, California 93950, USADepartamento de Estratigrafía y Paleontología, Universidad de Granada, 18002, Granada, SpainSchool of Botany, La Trobe University, Bundoora, Victoria 3083, AustraliaSchool of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
| | - Julio Aguirre
- Division of Math, Science, and Health Professions, Hartnell College, 156 Homestead Ave., Salinas, California 93950, USADepartamento de Estratigrafía y Paleontología, Universidad de Granada, 18002, Granada, SpainSchool of Botany, La Trobe University, Bundoora, Victoria 3083, AustraliaSchool of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
| | - William J Woelkerling
- Division of Math, Science, and Health Professions, Hartnell College, 156 Homestead Ave., Salinas, California 93950, USADepartamento de Estratigrafía y Paleontología, Universidad de Granada, 18002, Granada, SpainSchool of Botany, La Trobe University, Bundoora, Victoria 3083, AustraliaSchool of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
| | - Jody M Webster
- Division of Math, Science, and Health Professions, Hartnell College, 156 Homestead Ave., Salinas, California 93950, USADepartamento de Estratigrafía y Paleontología, Universidad de Granada, 18002, Granada, SpainSchool of Botany, La Trobe University, Bundoora, Victoria 3083, AustraliaSchool of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
| |
Collapse
|
16
|
Neschastnova AA, Gasanova VK, Popenko VI, Lambrinakos A, Belitsky GA, Cotton RGH, Yakubovskaya MG. Spontaneous DNA-DNA interaction of homologous duplexes and factors affecting the result of heteroduplex formation. Biol Chem 2006; 387:257-61. [PMID: 16542146 DOI: 10.1515/bc.2006.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Mutation detection and mismatch repair investigations based on heteroduplex formation require a linear DNA structure. DNA branching, described previously under physiological conditions, has been analysed in the heteroduplex formation process. Symmetrical chi-structures were detected after heteroduplex formation by gel electrophoresis and electron microscopy. Buffer composition, DNA concentration and duplex end-sequences influence DNA branching. Duplexes with homologous central regions but non-complementary ends do not form hybrid heteroduplexes or hybrid Holliday junctions. Our results explain the requirements for efficient heteroduplex formation, which were previously determined empirically: special solution composition, optimal DNA concentration and GC clamps. This provides the theoretical background for further optimisation of the procedure.
Collapse
Affiliation(s)
- Anna A Neschastnova
- Institute of Carcinogenesis, Blokhin Cancer Research Centre, Russian Academy of Medical Sciences, Kashirskoye Shosse 24, Moscow 115478, Russia.
| | | | | | | | | | | | | |
Collapse
|
17
|
Nayak DP, Lehmann S, Reichl U. Downstream processing of MDCK cell-derived equine influenza virus. J Chromatogr B Analyt Technol Biomed Life Sci 2005; 823:75-81. [PMID: 16009601 DOI: 10.1016/j.jchromb.2005.05.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Revised: 04/28/2005] [Accepted: 05/21/2005] [Indexed: 11/29/2022]
Abstract
A microcarrier-based process was used to produce equine influenza virus (A/Equi 2 (H3N8), Newmarket 1/93) in Madin Darby Canine kidney (MDCK) cells. The virus was purified in a sequence of downstream processing steps comprising of depth filtration, inactivation, ultrafiltration (UF) and gel filtration. In the ultrafiltration step, the hemagglutinin (HA) was recovered to 100%. A high increase of neuraminidase (NA) activity indicated the removal of some inhibitory compounds during this step. At the same time, the level of contaminating proteins and DNA was reduced by more than 88%. In the subsequent size exclusion chromatography (Sepharose CL 2B), the recovery of HA and NA in the "virus peak" was 37.8 and 59.8%, respectively compared to the concentrated feed material. Inconsistencies in the overall mass balance for HA and NA (70.0 and 69.2%) during gel filtration indicated non-specific interactions of the inactivated virus to the gel matrix which is supported by a HA recovery of about 50% in shake flask experiments performed as a control. Overall 35.8% of HA and 291.6% of NA were recovered. More than 95.7% of the host cell proteins and 98.7% of the host cell DNA were removed during downstream processing.
Collapse
Affiliation(s)
- Deba Prasad Nayak
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, D-39106 Magdeburg, Germany
| | | | | |
Collapse
|
18
|
|
19
|
Hoorfar J, Malorny B, Abdulmawjood A, Cook N, Wagner M, Fach P. Practical considerations in design of internal amplification controls for diagnostic PCR assays. J Clin Microbiol 2004; 42:1863-8. [PMID: 15131141 PMCID: PMC404670 DOI: 10.1128/jcm.42.5.1863-1868.2004] [Citation(s) in RCA: 310] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- J Hoorfar
- Danish Food and Veterinary Research Institute, DK-1790 Copenhagen, Denmark.
| | | | | | | | | | | |
Collapse
|
20
|
Gaillard C, Shlyakhtenko LS, Lyubchenko YL, Strauss F. Structural analysis of hemicatenated DNA loops. BMC Struct Biol 2002; 2:7. [PMID: 12450412 PMCID: PMC139983 DOI: 10.1186/1472-6807-2-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2002] [Accepted: 11/26/2002] [Indexed: 11/10/2022]
Abstract
BACKGROUND We have previously isolated a stable alternative DNA structure, which was formed in vitro by reassociation of the strands of DNA fragments containing a 62 bp tract of the CA-microsatellite poly(CA).poly(TG). In the model which was proposed for this structure the double helix is folded into a loop, the base of the loop consists of a DNA junction in which one of the strands of one duplex passes between the two strands of the other duplex, forming a DNA hemicatenane in a hemiknot structure. The hemiknot DNA structures obtained with long CA/TG inserts have been imaged by AFM allowing us to directly visualize the loops. RESULTS Here we have analyzed this structure with several different techniques: high-resolution gel electrophoresis, probing by digestion with single stranded DNA-specific nucleases or with DNase I, modification with chemicals specific for unpaired bases, and atomic force microscopy. The data show a change in DNA structure localized to the CA/TG sequence and allow us to better understand the structure of this alternative conformation and the mechanism of its formation. CONCLUSIONS The present work is in good agreement with the model of hemicatenated DNA loop proposed previously. In the presence of protein HMGB1, shifted reassociation of the strands of DNA fragments containing a tract of the poly(CA).poly(TG) microsatellite leads to the formation of DNA loops maintained at their base by a hemicatenated junction located within the repetitive sequence. No mobility of the junction along the DNA molecule could be detected under the conditions used. The novel possibility to prepare DNA hemicatenanes should be useful to further study this alternative DNA structure and its involvement in replication or recombination.
Collapse
Affiliation(s)
- Claire Gaillard
- Institut Jacques Monod, 2 place Jussieu, 75251 Paris 05, France
| | - Luda S Shlyakhtenko
- Department of Biology, Arizona State University, Tempe, AZ 85287-2701, U.S.A
| | - Yuri L Lyubchenko
- Department of Biology, Arizona State University, Tempe, AZ 85287-2701, U.S.A
- Department of Microbiology, Arizona State University, Tempe, AZ 85287-2701, U.S.A
| | | |
Collapse
|
21
|
Yakubovskaya MG, Neschastnova AA, Humphrey KE, Babon JJ, Popenko VI, Smith MJ, Lambrinakos A, Lipatova ZV, Dobrovolskaia MA, Cappai R, Masters CL, Belitsky GA, Cotton RG. Interaction of linear homologous DNA duplexes via Holliday junction formation. Eur J Biochem 2001; 268:7-14. [PMID: 11121096 DOI: 10.1046/j.1432-1327.2001.01861.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Interaction of linear homologous DNA duplexes by formation of Holliday junctions was revealed by electrophoresis and confirmed by electron microscopy. The phenomenon was demonstrated using a model of five purified PCR products of different size and sequence. The double-stranded structure of interacting DNA fragments was confirmed using several consecutive purifications, S1-nuclease analysis, and electron microscopy. Formation of Holliday junctions depends on DNA concentration. A thermodynamic equilibrium between duplexes and Holliday junctions was shown. We propose that homologous duplex interaction is initiated by nucleation of several dissociated terminal base pairs of two fragments. This process is followed by branch migration creating a population of Holliday junctions with the branch point at different sites. Finally, Holliday junctions are resolved via branch migration to new or previously existing duplexes. The phenomenon is a new property of DNA. This type of DNA-DNA interaction may contribute to the process of Holliday junction formation in vivo controlled by DNA conformation and DNA-protein interactions. It is of practical significance for optimization of different PCR-based methods of gene analysis, especially those involving heteroduplex formation.
Collapse
Affiliation(s)
- M G Yakubovskaya
- Carcinogenesis Institute, Cancer Research Centre, Russian Academy of Medical Sciences, Moscow, Russia.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Abstract
BACKGROUND Alternative DNA conformations are of particular interest as potential signals to mark important sites on the genome. The structural variability of CA microsatellites is particularly pronounced; these are repetitive poly(CA). poly(TG) DNA sequences spread in all eukaryotic genomes as tracts of up to 60 base pairs long. Many in vitro studies have shown that the structure of poly(CA). poly(TG) can vary markedly from the classical right handed DNA double helix and adopt diverse alternative conformations. Here we have studied the mechanism of formation and the structure of an alternative DNA structure, named Form X, which was observed previously by polyacrylamide gel electrophoresis of DNA fragments containing a tract of the CA microsatellite poly(CA). poly(TG) but had not yet been characterized. RESULTS Formation of Form X was found to occur upon reassociation of the strands of a DNA fragment containing a tract of poly(CA). poly(TG), in a process strongly stimulated by the nuclear proteins HMG1 and HMG2. By inserting Form X into DNA minicircles, we show that the DNA strands do not run fully side by side but instead form a DNA knot. When present in a closed DNA molecule, Form X becomes resistant to heating to 100 degrees C and to alkaline pH. CONCLUSIONS Our data strongly support a model of Form X consisting in a DNA loop at the base of which the two DNA duplexes cross, with one of the strands of one duplex passing between the strands of the other duplex, and reciprocally, to form a semicatenated DNA junction also called a DNA hemicatenane.
Collapse
Affiliation(s)
- Claire Gaillard
- Institut Jacques Monod, 2 Place Jussieu, 75251 Paris 05, France
| | | |
Collapse
|
23
|
Zammatteo N, Jeanmart L, Hamels S, Courtois S, Louette P, Hevesi L, Remacle J. Comparison between different strategies of covalent attachment of DNA to glass surfaces to build DNA microarrays. Anal Biochem 2000; 280:143-50. [PMID: 10805532 DOI: 10.1006/abio.2000.4515] [Citation(s) in RCA: 252] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
DNA microarray is a powerful tool allowing simultaneous detection of many different target molecules present in a sample. The efficiency of the array depends mainly on the sequence of the capture probes and the way they are attached to the support. The coupling procedure must be quick, covalent, and reproducible in order to be compatible with automatic spotting devices dispensing tiny drops of liquids on the surface. We compared several coupling strategies currently used to covalently graft DNA onto a glass surface. The results indicate that fixation of aminated DNA to an aldehyde-modified surface is a choice method to build DNA microarrays. Both the coupling procedure and the hybridization efficiency have been optimized. The detection limit of human cytomegalovirus target DNA amplicons on such DNA microarrays has been estimated to be 0.01 nM by fluorescent detection.
Collapse
Affiliation(s)
- N Zammatteo
- Laboratoire de Biochimie Cellulaire, Namur, Belgium.
| | | | | | | | | | | | | |
Collapse
|
24
|
Abstract
We have previously observed that double-stranded DNA fragments containing a tract of the tandemly repeated sequence poly(CA). poly(TG) can associate in vitro to form stable complexes of low electrophoretic mobility, which are recognized with high specificity by proteins HMG1 and HMG2. The formation of such complexes has since been observed to depend on interactions of DNA with polypropylene surfaces, with the suggestion that the formation of low mobility complexes might be the result of strand dissociation followed by misaligned reassociation of the repetitive sequences. The data presented here show that at high ionic strength the interactions of DNA with polypropylene are sufficiently strong for DNA to remain bound to the polypropylene surface, which suggests that DNA might also be involved in interactions with hydrophobic molecules in vivo. Under such conditions, low-mobility complexes are found only in the material adsorbed to the polypropylene surface, and all DNA fragments are able to form low-mobility structures, whether or not they contain repetitive sequences. Preventing the separation of strands by ligating hairpin loop oligonucleotides at both ends of the fragments does not prevent the formation of low-mobility complexes. Our results suggest two different pathways for the formation of complexes. In the first, dissociation is followed by misaligned reassociation of repetitive sequences, yielding duplexes with single-stranded end regions that associate to form multimeric complexes. In the second, repetitive as well as nonrepetitive DNA molecules bound to polypropylene adopt a conformation with locally unwound regions, which allows interactions between neighboring duplexes adsorbed on the surface, resulting in the formation of low-mobility complexes.
Collapse
Affiliation(s)
- C Gaillard
- Institut Jacques Monod, 2 place Jussieu, 75251 Paris 05, France
| | | | | | | |
Collapse
|
25
|
Abstract
We demonstrate that DNA sediments in the presence of millimolar concentrations of zinc or related metal cations and that EDTA entirely dissolves the sediment. The sedimentation is promoted by alkaline pH but the pH dependence is abolished by submillimolar concentrations of phosphate anions. We suspect that the metal cations generate sedimenting particles of insoluble hydroxides or phosphates for which DNA has a strong affinity. The events involved in DNA-metal phosphate co-sedimentation are similar to the processes that enable calcium phosphate-assisted transfection. Hence, work with even submillimolar concentrations of zinc and most other metal cations, which many DNA-binding proteins need for their activities, requires care to avoid the sedimentation of DNA. Literature reporting about zinc effects on DNA is discussed from the point of view of the present results.
Collapse
Affiliation(s)
- E Kejnovsky
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-61265 Brno, Czech Republic
| | | |
Collapse
|
26
|
Pearson CE, Wang YH, Griffith JD, Sinden RR. Structural analysis of slipped-strand DNA (S-DNA) formed in (CTG)n. (CAG)n repeats from the myotonic dystrophy locus. Nucleic Acids Res 1998; 26:816-23. [PMID: 9443975 PMCID: PMC147324 DOI: 10.1093/nar/26.3.816] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The mechanism of disease-associated trinucleotide repeat length variation may involve slippage of the triplet-containing strand at the replication fork, generating a slipped-strand DNA structure. We recently reported formation in vitro of slipped-strand DNA (S-DNA) structures when DNAs containing triplet repeat blocks of myotonic dystrophy or fragile X diseases were melted and allowed to reanneal to form duplexes. Here additional evidence is presented that is consistent with the existence of S-DNA structures. We demonstrate that S-DNA structures can form between two complementary strands containing equal numbers of repeats. In addition, we show that both the propensity for S-DNA formation and the structural complexity of S-DNAs formed increase with increasing repeat length. S-DNA structures were also analyzed by electron microscopy, confirming that the two strands are slipped out of register with respect to each other and confirming the structural polymorphism expected within long tracts of trinucleotide repeats. For (CTG)50.(CAG)50 two distinct populations of slipped structures have been identified: those involving </=10 repeats per slippage, which appear as bent/kinked DNA molecules, and those involving >10 repeats, which have multiple loops or hairpins indicative of complex alternative DNA secondary structures.
Collapse
Affiliation(s)
- C E Pearson
- Center for Genome Research, Institute of Biosciences and Technology, Department of Biochemistry and Biophysics, Texas A&M University, Houston, TX 77030-3303, USA.
| | | | | | | |
Collapse
|
27
|
|
28
|
Abstract
Recent developments in the rapid sequencing, mapping, and analysis of DNA rely on the specific binding of DNA to specially treated surfaces. We show here that specific binding of DNA via its unmodified extremities can be achieved on a great variety of surfaces by a judicious choice of the pH. On hydrophobic surfaces the best binding efficiency is reached at a pH of approximately 5.5. At that pH a approximately 40-kbp DNA is 10 times more likely to bind by an extremity than by a midsegment. A model is proposed to account for the differential adsorption of the molecule extremities and midsection as a function of pH. The pH-dependent specific binding can be used to align anchored DNA molecules by a receding meniscus, a process called molecular combing. The resulting properties of the combed molecules will be discussed.
Collapse
Affiliation(s)
- J F Allemand
- LPS, ENS, URA D 1306 CNRS, associé aux universitié Paris VI, France
| | | | | | | | | |
Collapse
|
29
|
Abstract
The potential of guanine-rich oligodeoxyribonucleotides (oligos) as nucleic acid drugs is increasingly being investigated, for example, as aptamers against heparin-binding proteins and as purine-motif triplex-forming oligos. However, G-rich oligos can be very polymorphic under physiological conditions, often with the resulting structures possessing vastly different functional capabilities. To better understand the intrinsic oligo parameters that affect their structure, we used nondenaturing gel electrophoresis to investigate a series of G-rich oligos derived from the sequence 5'-TGGGTGGGGTGGGGTGGGT for their abilities to self-associate through G-quartet formation. From these studies the following observations could be made: (1) oligos containing four clusters of three or more contiguous Gs readily associated intramolecularly but did not associate intermolecularly; (2) intermolecular dimerization was the preferred mode of interaction when one of the oligos contained only two G clusters; and (3) T-rich extensions promoted multimerization of oligos into still higher-order species.
Collapse
Affiliation(s)
- A J Cheng
- Department of Tumor Biology, University of Texas, M.D. Anderson Anderson Cancer Center, Houston 77030, USA
| | | |
Collapse
|
30
|
Abstract
We observed that DNA fragments in room temperature solution undergo low levels of denaturation in the presence of certain types of polypropylene tube surfaces. If the fragments contain (GT)n.(CA)n or (GA)n.(CT)n sequences, multimeric complexes are also formed. This surface activity is inhibited by addition of micromolar concentrations of an oligodeoxyribonucleotide of arbitrary sequence to the tube prior to adding the double-stranded DNA. The reaction was not observed in tubes made of borosilicate glass or in polypropylene-based tubes designed to have low-binding properties. In the case of the DNA fragments that form surfaced-induced multimers, similar complexes can be obtained by denaturation and renaturation of the fragment ("induced" association) without regard to the type of tube surface. However, induced association requires the presence of magnesium ions or polyethylene glycol (or concentration by evaporation) for efficient formation of complexes, whereas surface-dependent dissociation has no such requirements. This difference in buffer requirement suggests that association as well as denaturation takes place on the surface. We suggest models for the formation and structure of these complexes based on surface-dependent denaturation followed by misaligned renaturation of repeated sequences and intermolecular pairing of unpaired regions. This denaturation and complex formation may be important for the interpretation of protein-DNA binding experiments and might be related to hydrophobic interactions of DNA in vivo.
Collapse
Affiliation(s)
- B P Belotserkovskii
- Cell and Molecular Biology Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, California 94025, USA
| | | |
Collapse
|
31
|
|
32
|
Abstract
Site-specific recombination in Saccharomyces cerevisiae was used to generate non-replicative DNA rings containing yeast telomeric sequences. In topoisomerase mutants expressing Escherichia coli topoisomerase I, the rings adopted a novel DNA topology consistent with the ability of yeast telomeric DNA to block or retard the axial rotation of DNA. DNA fragments bearing portions of the terminal repeat sequence C1-3 A/TG1-3 were both necessary and sufficient to create a barrier to DNA rotation. Synthetic oligonucleotide sequences containing Rap1p binding sites, a well represented motif in naturally occurring C1-3A arrays, also conferred immobilization; mutant Rap1p binding sites and telomeric sequences from other organisms were not sufficient. DNA anchoring was diminished by addition of competing telomeric sequences, implicating a role for an as yet unidentified limiting trans-acting factor. Though Rap1p is a likely protein constituent of the DNA anchor, deletion of the non-essential C-terminal domain did not affect the topology of telomeric DNA rings. Similarly, disruption of SIR2, SIR3 and SIR4, genes which influence a variety of telomere functions in yeast, also had no effect. We propose that telomeric DNA supports the formation of a SIR-independent macromolecular protein-DNA assembly that hinders the motion of DNA because of its linkage to an insoluble nuclear structure. Potential roles for DNA anchoring in telomere biology are discussed.
Collapse
Affiliation(s)
- A Mirabella
- Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
| | | |
Collapse
|