The intercalating drugs possess a planar aromatic chromophore unit by which they insert between DNA bases causing the distortion of classical B-DNA form. The planar tricyclic structure of anthraquinones belongs to the group of chromophore units and enables anthraquinones to bind to DNA by intercalating mode. The interactions of simple derivatives of anthraquinone, quinizarin (1,4-dihydroxyanthraquinone) and danthron (1,8-dihydroxyanthraquinone), with negatively supercoiled and linear DNA were investigated using a combination of the electrophoretic methods, fluorescence spectrophotometry and single molecule technique an atomic force microscopy. The detection of the topological change of negatively supercoiled plasmid DNA, unwinding of negatively supercoiled DNA, corresponding to appearance of DNA topoisomers with the low superhelicity and an increase of the contour length of linear DNA in the presence of quinizarin and danthron indicate the binding of both anthraquinones to DNA by intercalating mode.
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http://dx.doi.org/10.1016/j.bbrc.2014.01.007 | DOI Listing |
Unlabelled: Molecular crowding influences DNA mechanics and DNA - protein interactions and is ubiquitous in living cells. Quantifying the effects of molecular crowding on DNA supercoiling is essential to relating experiments to DNA supercoiling. We use single molecule magnetic tweezers to study DNA supercoiling in the presence of dehydrating or crowding co-solutes.
View Article and Find Full Text PDFMethods Mol Biol
December 2024
DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain.
DNA supercoiling in biological systems can occur via three mechanisms. The first is by the activity of DNA topoisomerases, such as DNA gyrases, that can increase or reduce the linking number of relaxed DNA (Lk). The second is via DNA translocation motors, such as RNA and DNA polymerases, that produce twin supercoiled DNA domains: one positively supercoiled in front and one negatively supercoiled behind.
View Article and Find Full Text PDFbioRxiv
December 2024
Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
The obligate intracellular bacterial pathogen, (Ct), has a distinct DNA topoisomerase I (TopA) with a C-terminal domain (CTD) homologous to eukaryotic SWIB domains. Despite the lack of sequence similarity at the CTDs between TopA (CtTopA) and TopA (EcTopA), full-length CtTopA removed negative DNA supercoils and complemented the growth defect of an mutant. We demonstrated that CtTopA is less processive in DNA relaxation than EcTopA in dose-response and time course studies.
View Article and Find Full Text PDFSci Adv
December 2024
Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, 2629HZ, Netherlands.
Eukaryotes carry three types of structural maintenance of chromosome (SMC) protein complexes, condensin, cohesin, and SMC5/6, which are ATP-dependent motor proteins that remodel the genome via DNA loop extrusion (LE). SMCs modulate DNA supercoiling but remains incompletely understood how this is achieved. Using a single-molecule magnetic tweezers assay that directly measures how much twist is induced by individual SMCs in each LE step, we demonstrate that all three SMC complexes induce the same large negative twist (i.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
December 2024
Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
Type II topoisomerase DNA gyrase transduces the energy of ATP hydrolysis into the negative supercoiling of DNA. The postulated catalytic mechanism involves stabilization of a chiral DNA loop followed by the passage of the T-segment through the temporarily cleaved G-segment resulting in sign inversion. The molecular basis for this is poorly understood as the chiral loop has never been directly observed.
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