"kissing Complex" Or "kissing loop"

Translation regulation commonly involves the 5'-m7GpppN cap which binds the initiation factor 4E bound to recruit the other initiation factors and the small ribosomal subunit. Yet some viruses, such as the Blackcurrant Reversion virus (BRV), have no 5'-cap but are still able to translate using alternative mechanisms such as 3' cap independent translation enhancers (3' CITE). The 3' CITEs in BRV's bipartite genome are predicted to work like 4E by recruiting initiation factors and bringing them to the 5' end for initiation of translation though a 5'-3' RNA kissing interaction, called the kissing-loop interaction sequence (KIS)...

High-resolution structural studies are essential for understanding the folding and function of diverse RNAs. Herein, we present a nanoarchitectural engineering strategy for efficient structural determination of RNA-only structures using single-particle cryogenic electron microscopy (cryo-EM). This strategy-ROCK (RNA oligomerization-enabled cryo-EM via installing kissing loops)-involves installing kissing-loop sequences onto the functionally nonessential stems of RNAs for homomeric self-assembly into closed rings with multiplied molecular weights and mitigated structural flexibility...

RNA fibers are a class of biomaterials that can be assembled using HIV-like kissing loop interactions. Because of the programmability of molecular design and low immunorecognition, these structures present an interesting opportunity to solve problems in nanobiotechnology and synthetic biology. However, the experimental tools to fully characterize and discriminate among different fiber structures in solution are limited. Herein, we utilize solid-state nanopore experiments and Brownian dynamics simulations to characterize and distinguish several RNA fiber structures that differ in their degrees of branching...

Canonical eukaryotic mRNA translation requires 5'cap recognition by initiation factor 4E (eIF4E). In contrast, many positive-strand RNA virus genomes lack a 5'cap and promote translation by non-canonical mechanisms. Among plant viruses, PTEs are a major class of cap-independent translation enhancers located in/near the 3'UTR that recruit eIF4E to greatly enhance viral translation. Previous work proposed a single form of PTE characterized by a Y-shaped secondary structure with two terminal stem-loops (SL1 and SL2) atop a supporting stem containing a large, G-rich asymmetric loop that forms an essential pseudoknot (PK) involving C/U residues located between SL1 and SL2...

DNA nanotechnology marvels the scientific world with its capabilities to design, engineer, and demonstrate nanoscale shapes. This review is a condensed version walking the reader through the structural developments in the field over the past 40 years starting from the basic design rules of the double-stranded building block to the most recent advancements in self-assembled hierarchically achieved structures to date. It builds off from the fundamental motivation of building 3-dimensional (3D) lattice structures of tunable cavities going all the way up to artificial nanorobots fighting cancer...

The ongoing COVID-19 pandemic highlights the necessity for a more fundamental understanding of the coronavirus life cycle. The causative agent of the disease, SARS-CoV-2, is being studied extensively from a structural standpoint in order to gain insight into key molecular mechanisms required for its survival. Contained within the untranslated regions of the SARS-CoV-2 genome are various conserved stem-loop elements that are believed to function in RNA replication, viral protein translation, and discontinuous transcription...

Riboswitches are regulatory RNA elements that undergo functionally important allosteric conformational switching upon binding of specific ligands. The here investigated guanidine-II riboswitch binds the small cation guanidinium and forms a kissing loop-loop interaction between its P1 and P2 hairpins. We investigate the structural changes to support previous studies regarding the binding mechanism. as previously published experimental data of the complete aptamer domain containing both linker-connected P1 and P2 hairpins are missing...

We describe an efficient method to condense RNAs into tightly packed RNA nanoparticles (RNPs) for biomedical applications without hydrophobic or cationic agents. We embedded kissing loops and siRNA in the RNAs to constrain the size of RNPs to ca. 100 nm, making them suitable not only for cellular uptake but also for passive tumor accumulation. The resulting RNPs were efficiently internalized into cells and downregulated the target gene of siRNAs. When intravenously injected into tumor-bearing mice, RNPs could also accumulate in the tumor...

Accurate prediction of RNA structure and folding stability has a far-reaching impact on our understanding of RNA functions. Here we develop Vfold2D-MC, a new physics-based model, to predict RNA structure and folding thermodynamics from the sequence. The model employs virtual bond-based coarse-graining of RNA backbone conformation and generates RNA conformations through Monte Carlo sampling of the bond angles and torsional angles of the virtual bonds. Using a coarse-grained statistical potential derived from the known structures, we assign each conformation with a statistical weight...

Single-particle cryogenic electron microscopy (cryo-EM) has become a standard technique for determining protein structures at atomic resolution1-3 . However, cryo-EM studies of protein-free RNA are in their early days. The Tetrahymena thermophila group I self-splicing intron was the first ribozyme to be discovered and has been a prominent model system for the study of RNA catalysis and structure-function relationships4 , but its full structure remains unknown. Here we report cryo-EM structures of the full-length Tetrahymena ribozyme in substrate-free and bound states at a resolution of 3...

Elucidating the structure of RNA and RNA ensembles is essential to understand biological functions. In this work, we explored the previously uncharted reactivity of bis-chloropiperidines (B-CePs) towards RNA. We characterized at the molecular level the different adducts induced by the fast reacting compound B-CeP 1 with RNA. Following an approach based on solution thermal melting coupled with ESI mass spectrometry (STHEM-ESI), we proved the ability of B-CePs to induce inter-molecular cross-links between guanines in double stranded RNA...

Biosensors are of interest for the quantitative detection of small molecules (metabolites, drugs and contaminants for instance). To this end, fluorescence is a widely used technique that is easily associated to aptamers. Light-up aptamers constitute a particular class of oligonucleotides that, specifically induce fluorescence emission when binding to cognate fluorogenic ligands such as malachite green (MG). We engineered a dual aptasensor for theophylline (Th) based on the combination of switching hairpin aptamers specific for MG on the one hand and for Th on the other hand, hence their names: malaswitch (Msw) and theoswitch (Thsw)...

The experimental construction of a double-stranded DNA microcircle of only 42 base pairs entailed a great deal of ingenuity and hard work. However, figuring out the three-dimensional structures of intermediates and the final product can be particularly baffling. Using a combination of model building and unrestrained molecular dynamics simulations in explicit solvent we have characterized the different DNA structures involved along the process. Our 3D models of the single-stranded DNA molecules provide atomic insight into the recognition event that must take place for the DNA bases in the cohesive tail of the hairpin to pair with their complementary bases in the single-stranded loops of the dumbbell...

Cobalamin riboswitch is a cis-regulatory element widely found in the 5'-UTRs of the vitamin B12-associated genes in bacteria, resulting in modulation and production of a particular protein. Thermoanaerobacter tengcongensis ( Tte ) AdoCbl riboswitches are the largest of the known riboswitches with 210 nucleotides, partially due to its long peripheral P6-extension, which enable high affinity of AdoCbl. Two structural elements, T-loop/T-looplike motif and kissing loop are key to the global folding of the RNA. While the structure of the Tte AdoCbl riboswitch complex is known, we still do not understand the structure and conformation before AdoCbl ligand recognition...

Ligand binding and temperature play important roles in riboswitch RNAs' structures and functions. However, most studies focused on studying structural dynamics or gene-regulation function of riboswitches from the aspect of ligand, instead of temperature. Here we combined NMR, ITC, stopped-flow and in vivo assays to investigate the ligand-triggered switch of adenine riboswitch from 10 to 45°C. Our results demonstrated that at single-nucleotide resolution, structural regions sensed ligand and temperature diversely...

In virtue of the inherent molecular recognition and programmability, DNA has recently become the most promising for high-performance biosensors. The rationally engineered nucleic acid architecture will be very advantageous to hybridization efficiency, specificity, and sensitivity. Herein, a robust and split-mode photoelectrochemical (PEC) biosensor for miRNA-196a was developed based on an entropy-driven tetrahedral DNA (EDTD) amplifier coupled with superparamagnetic nanostructures. The DNA tetrahedron structure features in rigidity and structural stability that contribute to obtain precise identification units and specific orientations, improving the hybridization efficiency, sensitivity, and selectivity of the as-designed PEC biosensor...

The capsid protein of dengue virus strain 2 (DENV2C) promotes nucleic acid structural rearrangements using chaperone activity. However, the role of DENV2C during the interaction of RNA elements in the conserved 5' untranslated region (5'UTR) to the 3' untranslated region (3'UTR) is still unclear. Thus, we investigated the effect of DENV2C on the annealing mechanism of two RNA hairpin elements from the 5'UTR to their complementary sequences during (+)/(-) ds-RNAformation and (+) RNA circularization. DENV2C was found to switch the annealing pathway for RNA elements involved in (+)/(-) ds-RNA formation, but not for RNA elements related to (+) RNA circularization...

Wine killer yeasts such as killer strains of Torulaspora delbrueckii and Saccharomyces cerevisiae contain helper large-size (4.6 kb) dsRNA viruses (V-LA) required for the stable maintenance and replication of killer medium-size dsRNA viruses (V-M) which bear the genes that encode for the killer toxin. The genome of the new V-LA dsRNA from the T. delbrueckii Kbarr1 killer yeast (TdV-LAbarr1) was characterized by high-throughput sequencing (HTS). The canonical genome of TdV-LAbarr1 shares a high sequence identity and similar genome organization with its Saccharomyces counterparts...

When electrosprayed from typical native MS solution conditions, RNA hairpins and kissing complexes acquire charge states at which they get significantly more compact in the gas phase than their initial structure in solution. Here we also show the limits of using force field molecular dynamics to interpret the gas-phase structures of nucleic acid complexes in the gas phase, as the predicted CCS distributions do not fully match the experimental ones. We suggest that higher-level calculation levels should be used in the future...

The unique G3:U70 base pair in the acceptor stem of tRNAAla has been shown to be a critical recognition site by alanyl-tRNA synthetase (AlaRS). The base pair resides on one of the arms of the L-shaped structure of tRNA (minihelix) and the genetic code has likely evolved from a primordial tRNA-aaRS (aminoacyl-tRNA synthetase) system. In terms of the evolution of tRNA, incorporation of a G:U base pair in the structure would be important. Here, we found that two independent short hairpin RNAs change their conformation through kissing-loop interactions, finally forming a minihelix-like structure, in which the G3:U70 base pair, is incorporated...