15 research outputs found
Small molecule-based detection of non-canonical RNA G-quadruplex structures that modulate protein translation
Tandem repeats of guanine-rich sequences in RNA often form thermodynamically stable four-stranded RNA structures. Such RNA G-quadruplexes have long been considered to be linked to essential biological processes, yet their physiological significance in cells remains unclear. Here, we report a approach that permits the detection of RNA G-quadruplex structures that modulate protein translation in mammalian cells. The approach combines antibody arrays and RGB-1, a small molecule that selectively stabilizes RNA G-quadruplex structures. Analysis of the protein and mRNA products of 84 cancer-related human genes identified Nectin-4 and CapG as G-quadruplex-controlled genes whose mRNAs harbor non-canonical G-quadruplex structures on their 5ā²UTR region. Further investigations revealed that the RNA G-quadruplex of CapG exhibits a structural polymorphism, suggesting a possible mechanism that ensures the translation repression in a KCl concentration range of 25ā100 mM. The approach described in the present study sets the stage for further discoveries of RNA G-quadruplexes
Biological Safety Evaluation and Surface Modification of Biocompatible Tiā15Zrā4Nb Alloy
We performed biological safety evaluation tests of three TiāZr alloys under accelerated extraction condition. We also conducted histopathological analysis of long-term implantation of pure V, Al, Ni, Zr, Nb, and Ta metals as well as NiāTi and high-V-containing Tiā15Vā3Alā3Sn alloys in rats. The effect of the dental implant (screw) shape on morphometrical parameters was investigated using rabbits. Moreover, we examined the maximum pullout properties of grit-blasted TiāZr alloys after their implantation in rabbits. The biological safety evaluation tests of three TiāZr alloys (Tiā15Zrā4Nb, Tiā15Zrā4Nbā1Ta, and Tiā15Zrā4Nbā4Ta) showed no adverse (negative) effects of either normal or accelerated extraction. No bone was formed around the pure V and Ni implants. The Al, Zr, Nb, and NiāTi implants were surrounded by new bone. The new bone formed around TiāNi and high-V-containing Ti alloys tended to be thinner than that formed around TiāZr and Tiā6Alā4V alloys. The rate of bone formation on the threaded portion in the Tiā15Zrā4Nbā4Ta dental implant was the same as that on a smooth surface. The maximum pullout loads of the grit- and shot-blasted TiāZr alloys increased linearly with implantation period in rabbits. The pullout load of grit-blasted TiāZr alloy rods was higher than that of shot-blasted ones. The surface roughness (Ra) and area ratio of residual Al2O3 particles of the Tiā15Zrā4Nb alloy surface grit-blasted with Al2O3 particles were the same as those of the grit-blasted Alloclassic stem surface. It was clarified that the grit-blasted Tiā15Zrā4Nb alloy could be used for artificial hip joint stems
RNA-based cooperative protein labeling that permits direct monitoring of the intracellular concentration change of an endogenous protein
Imaging the dynamics of proteins in living cells is a powerful means for understanding cellular functions at a deeper level. Here, we report a versatile method for spatiotemporal imaging of specific endogenous proteins in living mammalian cells. The method employs a bifunctional aptamer capable of selective protein recognition and fluorescent probe-binding, which is induced only when the aptamer specifically binds to its target protein. An aptamer for Ī²-actin protein preferentially recognizes its monomer forms over filamentous forms, resulting in selective G-actin staining in both fixed and living cells. Through actin-drug treatment, the method permitted direct monitoring of the intracellular concentration change of endogenous G-actin. This protein-labeling method, which is highly selective and non-covalent, provides rich insights into the study of spatiotemporal protein dynamics in living cells
A Small Molecule That Represses Translation of GāQuadruplex-Containing mRNA
The G-quadruplexes
form highly stable nucleic acid structures,
which are implicated in various biological processes in both DNA and
RNA. Although DNA G-quadruplexes have been studied in great detail,
biological roles of RNA G-quadruplexes have received less attention.
Here, a screening of a chemical library permitted identification of
a small-molecule tool that binds selectively to RNA G-quadruplex structures.
The polyaromatic molecule, RGB-1, stabilizes RNA G-quadruplex, but
not DNA versions or other RNA structures. RGB-1 intensified the G-quadruplex-mediated
inhibition of RNA translation in mammalian cells, decreased expression
of the <i>NRAS</i> proto-oncogene in breast cancer cells,
and permitted identification of a novel sequence that forms G-quadruplex
in <i>NRAS</i> mRNA. RGB-1 may serve as a unique tool for
understanding cellular roles of RNA G-quadruplex structures