Normal function and abnormal aggregation of transactivation response (TAR) DNA/RNA-binding protein 43 kDa (TDP-43) are directly associated with the lethal genetic diseases: cystic fibrosis, amyotrophic lateral sclerosis (ALS), and frontotemporal lobar degeneration (FTLD). The binding of TDP-43 to single-stranded DNA (ssDNA) or RNA is involved in transcriptional repression, regulation of RNA splicing, and RNA stabilization. Equilibrium dissociation constants () of TDP-43 and ssDNA or RNA have been determined using various methods; however, methods that can measure with high sensitivity in a short time using a small amount of TDP-43 in solution would be advantageous. Here, in order to determine the of TDP-43 and fluorescence-labeled ssDNA as well as the binding stoichiometry, we use fluorescence correlation spectroscopy (FCS), which detects the slowed diffusion of molecular interactions in solution with single-molecule sensitivity, in addition to electrophoretic mobility shift assay (EMSA). Using tandem affinity chromatography of TDP-43 dually tagged with glutathione-S-transferase and poly-histidine tags, highly purified protein was obtained. FCS successfully detected specific interaction between purified TDP-43 and TG ssDNA repeats, with a in the nanomolar range. The of the TDP-43 mutant was not different from the wild type, although mutant oligomers, which did not bind ssDNA, were observed. Analysis of the fluorescence brightness per dimerized TDP-43/ssDNA complex was used to evaluate their binding stoichiometry. The results suggest that an assay combining FCS and EMSA can precisely analyze ssDNA recognition mechanisms, and that FCS may be applied for the rapid and quantitative determination of the interaction strength between TDP-43 and ssDNA or RNA. These methods will aid in the elucidation of the substrate recognition mechanism of ALS- and FTLD-associated variants of TDP-43.
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http://dx.doi.org/10.1016/j.bbrep.2018.03.009 | DOI Listing |
Nat Commun
January 2025
Developmental Therapeutics Branch & Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA.
Type IA topoisomerases (TopoIAs) are present in all living organisms. They resolve DNA/RNA catenanes, knots and supercoils by breaking and rejoining single-stranded DNA/RNA segments and allowing the passage of another nucleic acid segment through the break. Topoisomerase III-β (TOP3B), the only RNA topoisomerase in metazoans, promotes R-loop disassembly and translation of mRNAs.
View Article and Find Full Text PDFMikrochim Acta
January 2025
Key Laboratory of Synthetic and Natural Functional Molecule, College of Chemistry and Materials Science, Northwest University, Xi'an, 710127, People's Republic of China.
A biosensor based on solid-state nanochannels of anodic aluminum oxide (AAO) membrane for both electrochemical and naked-eye detection of microRNA-31 (MiR-31) is proposed. For this purpose, MoS nanosheets, which possess different adsorption capabilities to single-stranded and double-stranded nucleic acids, are deposited onto the top surface of the AAO membrane. Moreover, multi-functional DNA nanostructure have been designed by linking a G-rich sequence for folding to a G-quadruplex at three vertices and a complementary sequence of MiR-31 at the other one vertex of a DNA tetrahedron.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2025
Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 00 Brno, Czech Republic.
Molecular dynamics (MD) simulations are an important and well-established tool for investigating RNA structural dynamics, but their accuracy relies heavily on the quality of the employed force field (). In this work, we present a comprehensive evaluation of widely used pair-additive and polarizable RNA s using the challenging UUCG tetraloop (TL) benchmark system. Extensive standard MD simulations, initiated from the NMR structure of the 14-mer UUCG TL, revealed that most s did not maintain the native state, instead favoring alternative loop conformations.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States.
Direct translocation of RNA with secondary structures using single-molecule electrophoresis through protein nanopores shows significant fluctuations in the measured ionic current, in contrast to unstructured single-stranded RNA or DNA. We developed a multiscale model combining the oxRNA model for RNA with the 3-dimensional Poisson-Nernst-Planck formalism for electric fields within protein pores, aiming to map RNA conformations to ionic currents as RNA translocates through three protein nanopores: α-hemolysin, CsgG, and MspA. Our findings reveal three distinct stages of translocation (pseudoknot, melting, and molten globule) based on contact maps and current values.
View Article and Find Full Text PDFAlternative Lengthening of Telomeres (ALT) is a homologous recombination-dependent telomere elongation mechanism utilized by at least 10-15% of all cancers. Here we identified that the DNA topoisomerase, TOP3A is enriched at the telomeres of ALT cells but not at the telomeres of telomerase-positive (Tel) cancer cells. We demonstrate that TOP3A stabilizes the shelterin protein TERF2 in ALT cancer cell lines but not in Tel cells and that long non-coding telomere transcribed RNA (TERRA) enrichment at telomeres depends upon TOP3A.
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