Nejvíce citovaný článek - PubMed ID 20660477
G-quadruplexes are noncanonical nucleic acid structures formed by stacked guanosine tetrads. Despite their functional and structural diversity, a single consensus model is typically used to describe sequences with the potential to form G-quadruplex structures. We are interested in developing more specific sequence models for G-quadruplexes. In previous work, we functionally characterized each sequence in a 496-member library of variants of a monomeric reference G-quadruplex for the ability to bind GTP, promote a model peroxidase reaction, generate intrinsic fluorescence, and to form multimers. Here we used NMR to obtain a broad overview of the structural features of this library. After determining the 1H NMR spectrum of each of these 496 sequences, spectra were sorted into multiple classes, most of which could be rationalized based on mutational patterns in the primary sequence. A more detailed screen using representative sequences provided additional information about spectral classes, and confirmed that the classes determined based on analysis of 1H NMR spectra are correlated with functional categories identified in previous studies. These results provide new insights into the surprising structural diversity of this library. They also show how NMR can be used to identify classes of sequences with distinct mutational signatures and functions.
- Klíčová slova
- DNA, G-quadruplex, Multimeric structures, NMR,
- MeSH
- G-kvadruplexy * MeSH
- guanosintrifosfát chemie metabolismus MeSH
- magnetická rezonanční spektroskopie metody MeSH
- mutace MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- guanosintrifosfát MeSH
G-quadruplexes (G4s) formed within RNA are emerging as promising targets for therapeutic intervention in cancer, neurodegenerative disorders and infectious diseases. Sequences containing a succession of short GG blocks, or uneven G-tract lengths unable to form three-tetrad G4s (GG motifs), are overwhelmingly more frequent than canonical motifs involving multiple GGG blocks. We recently showed that DNA is not able to form stable two-tetrad intramolecular parallel G4s. Whether RNA GG motifs can form intramolecular G4s under physiological conditions and play regulatory roles remains a burning question. In this study, we performed a systematic analysis and experimental evaluation of a number of biologically important RNA regions involving RNA GG motifs. We show that most of these motifs do not form stable intramolecular G4s but need to dimerize to form stable G4 structures. The strong tendency of RNA GG motif G4s to associate may participate in RNA-based aggregation under conditions of cellular stress.
- MeSH
- dimerizace MeSH
- G-kvadruplexy * MeSH
- genetická transkripce MeSH
- lidé MeSH
- nukleotidové motivy * MeSH
- RNA * chemie metabolismus genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- RNA * MeSH
Metal ions are essential components for the survival of living organisms. For most species, intracellular and extracellular ionic conditions differ significantly. As G-quadruplexes (G4s) are ion-dependent structures, changes in the [Na+]/[K+] ratio may affect the folding of genomic G4s. More than 11000 putative G4 sequences in the human genome (hg19) contain at least two runs of three continuous cytosines, and these mixed G/C-rich sequences may form a quadruplex or a competing hairpin structure based on G-C base pairing. In this study, we examine how the [Na+]/[K+] ratio influences the structures of G/C-rich sequences. The natural G4 structure with a 9-nt long central loop, CEBwt, was chosen as a model sequence, and the loop bases were gradually replaced by cytosines. The series of CEB mutations revealed that the presence of cytosines in G4 loops does not prevent G4 folding or decrease G4 stability but increases the probability of forming a competing structure, either a hairpin or an intermolecular duplex. Slow conversion to the quadruplex in vitro (in a potassium-rich buffer) and cells was demonstrated by NMR. 'Shape-shifting' sequences may respond to [Na+]/[K+] changes with delayed kinetics.
G-quadruplexes are four-stranded nucleic acid structures occurring in the genomes of all living organisms and viruses. It is increasingly evident that these structures play important molecular roles; generally, by modulating gene expression and overall genome integrity. For a long period, G-quadruplexes have been studied specifically in the context of human promoters, telomeres, and associated diseases (cancers, neurological disorders). Several of the proteins for binding G-quadruplexes are known, providing promising targets for influencing G-quadruplex-related processes in organisms. Nonetheless, in plants, only a small number of G-quadruplex binding proteins have been described to date. Thus, we aimed to bioinformatically inspect the available protein sequences to find the best protein candidates with the potential to bind G-quadruplexes. Two similar glycine and arginine-rich G-quadruplex-binding motifs were described in humans. The first is the so-called "RGG motif"-RRGDGRRRGGGGRGQGGRGRGGGFKG, and the second (which has been recently described) is known as the "NIQI motif"-RGRGRGRGGGSGGSGGRGRG. Using this general knowledge, we searched for plant proteins containing the above mentioned motifs, using two independent approaches (BLASTp and FIMO scanning), and revealed many proteins containing the G4-binding motif(s). Our research also revealed the core proteins involved in G4 folding and resolving in green plants, algae, and the key plant model organism, Arabidopsis thaliana. The discovered protein candidates were annotated using STRINGdb and sorted by their molecular and physiological roles in simple schemes. Our results point to the significant role of G4-binding proteins in the regulation of gene expression in plants.
- Klíčová slova
- G-quadruplex folding, G-quadruplex resolving, G-quadruplex-binding proteins, NIQI, RGG motif, regulation of gene expression,
- Publikační typ
- časopisecké články MeSH
G-quadruplexes have long been perceived as rare and physiologically unimportant nucleic acid structures. However, several studies have revealed their importance in molecular processes, suggesting their possible role in replication and gene expression regulation. Pathways involving G-quadruplexes are intensively studied, especially in the context of human diseases, while their involvement in gene expression regulation in plants remains largely unexplored. Here, we conducted a bioinformatic study and performed a complex circular dichroism measurement to identify a stable G-quadruplex in the gene RPB1, coding for the RNA polymerase II large subunit. We found that this G-quadruplex-forming locus is highly evolutionarily conserved amongst plants sensu lato (Archaeplastida) that share a common ancestor more than one billion years old. Finally, we discussed a new hypothesis regarding G-quadruplexes interacting with UV light in plants to potentially form an additional layer of the regulatory network.
- Klíčová slova
- UV light, circular dichroism, evolution, nucleic acids, plant science,
- MeSH
- Arabidopsis chemie genetika účinky záření MeSH
- cirkulární dichroismus MeSH
- fylogeneze MeSH
- G-kvadruplexy * účinky záření MeSH
- Glaucophyta chemie genetika účinky záření MeSH
- molekulární evoluce MeSH
- regulace genové exprese u rostlin genetika MeSH
- Rhodophyta chemie genetika účinky záření MeSH
- RNA-polymerasa II chemie genetika MeSH
- rostlinné proteiny chemie genetika účinky záření MeSH
- rostliny chemie genetika účinky záření MeSH
- sekvence aminokyselin MeSH
- sekvenční seřazení MeSH
- ultrafialové záření MeSH
- výpočetní biologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- RNA-polymerasa II MeSH
- rostlinné proteiny MeSH
The importance of gene expression regulation in viruses based upon G-quadruplex may point to its potential utilization in therapeutic targeting. Here, we present analyses as to the occurrence of putative G-quadruplex-forming sequences (PQS) in all reference viral dsDNA genomes and evaluate their dependence on PQS occurrence in host organisms using the G4Hunter tool. PQS frequencies differ across host taxa without regard to GC content. The overlay of PQS with annotated regions reveals the localization of PQS in specific regions. While abundance in some, such as repeat regions, is shared by all groups, others are unique. There is abundance within introns of Eukaryota-infecting viruses, but depletion of PQS in introns of bacteria-infecting viruses. We reveal a significant positive correlation between PQS frequencies in dsDNA viruses and corresponding hosts from archaea, bacteria, and eukaryotes. A strong relationship between PQS in a virus and its host indicates their close coevolution and evolutionarily reciprocal mimicking of genome organization.
- Klíčová slova
- G-quadruplex, G4Hunter, bioinformatics, coevolution, dsDNA, host, virus,
- MeSH
- Archaea virologie MeSH
- Bacteria virologie MeSH
- DNA genetika MeSH
- G-kvadruplexy * MeSH
- genom virový * MeSH
- genom MeSH
- lidé MeSH
- regulace genové exprese MeSH
- virové proteiny genetika MeSH
- viry genetika MeSH
- výpočetní biologie metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- DNA MeSH
- virové proteiny MeSH
Recently, we reported an inhibitory effect of guanine substitutions on the conformational switch from antiparallel to parallel quadruplexes (G4) induced by dehydrating agents. As a possible cause, we proposed a difference in the sensitivity of parallel and antiparallel quadruplexes to the guanine substitutions in the resulting thermodynamic stability. Reports on the influence of guanine substitutions on the biophysical properties of intramolecular parallel quadruplexes are rare. Moreover, such reports are often complicated by the multimerisation tendencies of parallel quadruplexes. To address this incomplete knowledge, we employed circular dichroism spectroscopy (CD), both as stopped-flow-assisted fast kinetics measurements and end-point measurements, accompanied by thermodynamic analyses, based on UV absorption melting profiles, and electrophoretic methods. We showed that parallel quadruplexes are significantly more sensitive towards guanine substitutions than antiparallel ones. Furthermore, guanine-substituted variants, which in principle might correspond to native genomic sequences, distinctly differ in their biophysical properties, indicating that the four guanines in each tetrad of parallel quadruplexes are not equal. In addition, we were able to distinguish by CD an intramolecular G4 from intermolecular ones resulting from multimerisation mediated by terminal tetrad association, but not from intermolecular G4s formed due to inter-strand Hoogsteen hydrogen bond formation. In conclusion, our study indicates significant variability in parallel quadruplex structures, otherwise disregarded without detailed experimental analysis.
- Klíčová slova
- DNA secondary structure, circular dichroism, multimerisation, parallel guanine quadruplex, stopped-flow,
- MeSH
- cirkulární dichroismus MeSH
- DNA chemie genetika MeSH
- G-kvadruplexy MeSH
- guanin chemie MeSH
- konformace nukleové kyseliny MeSH
- molekulární modely MeSH
- substituce aminokyselin * MeSH
- termodynamika MeSH
- vodíková vazba MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- DNA MeSH
- guanin MeSH
Non-canonical nucleic acid structures play important roles in the regulation of molecular processes. Considering the importance of the ongoing coronavirus crisis, we decided to evaluate genomes of all coronaviruses sequenced to date (stated more broadly, the order Nidovirales) to determine if they contain non-canonical nucleic acid structures. We discovered much evidence of putative G-quadruplex sites and even much more of inverted repeats (IRs) loci, which in fact are ubiquitous along the whole genomic sequence and indicate a possible mechanism for genomic RNA packaging. The most notable enrichment of IRs was found inside 5'UTR for IRs of size 12+ nucleotides, and the most notable enrichment of putative quadruplex sites (PQSs) was located before 3'UTR, inside 5'UTR, and before mRNA. This indicates crucial regulatory roles for both IRs and PQSs. Moreover, we found multiple G-quadruplex binding motifs in human proteins having potential for binding of SARS-CoV-2 RNA. Non-canonical nucleic acids structures in Nidovirales and in novel SARS-CoV-2 are therefore promising druggable structures that can be targeted and utilized in the future.
- Klíčová slova
- G-quadruplex, RNA, coronavirus, genome, inverted repeats,
- Publikační typ
- časopisecké články MeSH
G-quadruplexes are noncanonical nucleic acid structures formed from stacked guanine tetrads. They are frequently used as building blocks and functional elements in fields such as synthetic biology and also thought to play widespread biological roles. G-quadruplexes are often studied as monomers, but can also form a variety of higher-order structures. This increases the structural and functional diversity of G-quadruplexes, and recent evidence suggests that it could also be biologically important. In this review, we describe the types of multimeric topologies adopted by G-quadruplexes and highlight what is known about their sequence requirements. We also summarize the limited information available about potential biological roles of multimeric G-quadruplexes and suggest new approaches that could facilitate future studies of these structures.
- Klíčová slova
- DNA:RNA hybrid, G-quadruplex, R-loop, dimer, multimer, oligomer, promoter, telomere, tetramer,
- MeSH
- DNA chemie MeSH
- G-kvadruplexy * MeSH
- konformace nukleové kyseliny * MeSH
- molekulární modely MeSH
- molekulární struktura MeSH
- RNA chemie MeSH
- telomery MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- DNA MeSH
- RNA MeSH
Peptides presented on major histocompatibility (MHC) class I molecules form an essential part of the immune system's capacity to detect virus-infected or transformed cells. Earlier works have shown that pioneer translation peptides (PTPs) for the MHC class I pathway are as efficiently produced from introns as from exons, or from mRNAs targeted for the nonsense-mediated decay pathway. The production of PTPs is a target for viral immune evasion but the underlying molecular mechanisms that govern this non-canonical translation are unknown. Here, we have used different approaches to show how events taking place on the nascent transcript control the synthesis of PTPs and full-length proteins. By controlling the subcellular interaction between the G-quadruplex structure (G4) of a gly-ala encoding mRNA and nucleolin (NCL) and by interfering with mRNA maturation using multiple approaches, we demonstrate that antigenic peptides derive from a nuclear non-canonical translation event that is independently regulated from the synthesis of full-length proteins. Moreover, we show that G4 are exploited to control mRNA localization and translation by distinguishable mechanisms that are targets for viral immune evasion.
- MeSH
- antigeny genetika imunologie MeSH
- buněčné jádro genetika imunologie MeSH
- G-kvadruplexy MeSH
- imunitní únik genetika imunologie MeSH
- lidé MeSH
- messenger RNA genetika imunologie MeSH
- MHC antigeny I. třídy genetika imunologie MeSH
- nonsense mediated mRNA decay genetika imunologie MeSH
- peptidy genetika imunologie MeSH
- proteosyntéza genetika imunologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- antigeny MeSH
- messenger RNA MeSH
- MHC antigeny I. třídy MeSH
- peptidy MeSH
