Search

International audience; LARP4A belongs to the ancient RNA-binding protein superfamily of La-related proteins (LARPs). In humans, it acts mainly by stabilizing mRNAs, enhancing translation and controlling polyA lengths of heterologous mRNAs. These activities are known to implicate its association with mRNA, protein partners and translating ribosomes, albeit molecular details are missing. Here, we characterize the direct interaction between LARP4A, oligoA RNA and the MLLE domain of the PolyA-binding protein (PABP). Our study shows that LARP4A-oligoA association entails novel RNA recognition features involving the N-terminal region of the protein that exists in a semi-disordered state and lacks any recognizable RNA-binding motif. Against expectations, we show that the La module, the conserved RNA-binding unit across LARPs, is not the principal determinant for oligoA interaction, only contributing to binding to a limited degree. Furthermore, the variant PABP-interacting motif 2 (PAM2w) featured in the N-terminal region of LARP4A was found to be important for both RNA and PABP recognition, revealing a new role for this proteinprotein binding motif. Our analysis demonstrates the mutual exclusive nature of the PAM2w-mediated interactions, thereby unveiling a tantalizing interplay between LARP4A, polyA and PABP.

We report the case of a man affected by polymicrobial endocarditis developed on a St. Jude Medical Riata lead with a malfunction because of the outsourcing of conductors. The patient was treated with antibiotic targeted therapy and showed different bacteria at the blood cultures and then underwent transvenous leads extraction. Vegetations were highlighted on the caval, atrial, and ventricular tracts of the Riata lead, but the cultures were all negative. The externalization of Riata lead may cause the malfunction but it could also promote bacterial colonies and vegetations. In conclusion, looking for early signs of infection is mandatory during Riata leads follow-up checks.

This dissertation can be divided in two parts. In the first part, my efforts have been focused on the study of the Gquadruplex structures. In chapter one, I describe the unusual arrangement of the DNA to form the G-quadruplex structures and their biological role, underlying the reason why in the last period a lot of research groups focused their studies on this topic. In chapter two, after a brief introduction of the first molecules capable to bind the G-quadruplex (Distamicyn A and its derivates), I describe the new organic molecule capable to interact with the DNA quadruplex, which I have discovered applying some innovative approaches during my PhD. In the second part of this thesis I introduce the research conducted in the laboratory of Dr. Maria R. Conte at the King’s College of London. In this stimulating environment I started studying the structure of the protein LARP4 and its interaction with a poly (A) RNA using the NMR. In the course of my research I have learnt the techniques allowing to do the transformation, the expression and the purification of the protein. A summary presentation of the techniques I have applied is reported in the second part in chapter five.

Background: Elderly patients are at high risk of both ischaemic and bleeding events, and the low body weight is considered a risk factor for major bleeding in atrial fibrillation (AF) patients on anticoagulation therapy. The aim of our study was to compare the safety and effectiveness of non-vitamin K antagonist oral anticoagulants (NOACs) versus well-controlled vitamin-K antagonists (VKA) therapy among AF patients aged >75 years and with a body weight

International audience; Human LARP4A belongs to a superfamily of RNA binding proteins called La-related proteins (LARPs). Whilst being a positive regulator of protein synthesis and a promoter of mRNA stability, LARP4A also controls cell morphology and motility in human breast and prostate cancer cells. All LARPs share a characteristic RNA binding unit named the La-module, which despite a high level of primary structure conservation exhibits a great versatility in RNA target selection. Human LARP4A La-module is the most divergent compared with other LARPs and its RNA recognition properties have only recently started to be revealed. Given the key role of LARP4A protein in cancer cell biology, we have initiated a complete NMR characterisation of its La-module and here we report the assignment of 1 H, 15 N and 13 C resonances resulting from our studies.

The chemical synthesis and 1H NMR analysis of a novel bicyclic uridine derivative, with a 18-crown-6 ether moiety fused at the ribose 2- and 3-positions, as first example of a hitherto unknown class of ribose-modified nucleosides, are here described. NMR-based conformational analysis studies showed for the modified nucleoside a marked preference for an N-type sugar puckering and the nucleobase in the anti conformation, with the uracil favouring the coordination of a sodium ion hosted in the crown ether.

Targeting of DNA secondary structures, such as G-quadruplexes, is now considered an appealing opportunity for drug intervention in anticancer therapy. So far, efforts made in the discovery of chemotypes able to target G-quadruplexes mainly succeeded in the identification of a number of polyaromatic compounds featuring end-stacking binding properties. Against this general trend, we were persuaded that the G-quadruplex grooves can recognize molecular entities with better drug-like and selectivity properties. From this idea, a set of small molecules was identified and the structural features responsible for G-quadruplex recognition were delineated. These compounds were demonstrated to have enhanced affinity and selectivity for the G-quadruplex over the duplex structure. Their ability to induce selective DNA damage at telomeric level and to induction of apoptosis and senescence on tumor cells is herein experimentally proven. © 2012 American Chemical Society.

The growing amount of literature about G-quadruplex DNA clearly demonstrates that such a structure is no longer viewed as just a biophysical strangeness but it is instead being considered as an important target for the treatment of various human disorders such as cancers or venous thrombosis. In this scenario, with the aim of finding brand new molecular scaffolds able to interact with the groove of the DNA quadruplex [d(TGGGGT)] 4, we recently performed a successful structure-based virtual screening (VS) campaign. As a result, six molecules were found to be somehow groove binders. Herein, we report the results of novel NMR titration experiments of these VS-derived ligands with modified quadruplexes, namely [d(TGG BrGGT)] 4 and [d(TGGGG BrT)] 4. The novel NMR spectroscopy experiments combined with molecular modelling studies, allow for a more detailed picture of the interaction between each binder and the quadruplex DNA. Noteworthy, isothermal titration calorimetry (ITC) measurements on the above-mentioned compounds revealed that 2, 4, and 6 besides their relatively small dimensions bind the DNA quadruplex [d(TGGGGT)] 4 with higher affinity than distamycin A, to the best of our knowledge, the most potent groove binder identified thus far. © 2011 Elsevier Masson SAS. All rights reserved.

The perception of odor and flavor of food is a complicated physiological and psychological process that cannot be explained by simple models. Quantitative descriptive analysis is a technique used to describe sensory features. Nevertheless, the availability of a number of instrumental techniques has opened up the possibility to calibrate the sensory perception. In this frame, we have tested the potentiality of nuclear magnetic resonance spectroscopy as a predictive tool to measure sensory descriptors. In particular, we have used an NMR metabolomic approach that allowed us to differentiate the analyzed samples based on their chemical composition. We were able to correlate the NMR metabolomic fingerprints recorded for canned tomato samples to the sensory descriptors bitterness, sweetness, sourness, saltiness, tomato and metal taste, redness, and density, suggesting that NMR might be a very useful tool for the characterization of sensory features of tomatoes.

The study of DNA G-quadruplex stabilizers has enjoyed a great momentum in the late years due to their application as anticancer agents. The recognition of the grooves of these structural motifs is expected to result in a higher degree of selectivity over other DNA structures. Therefore, to achieve an enhanced knowledge on the structural and conformational requisites for quadruplex groove recognition, distamycin A, the only compound for which a pure groove binding has been proven, has been chemically modified. Surprisingly, structural and thermodynamic studies revealed that the absence of Coulombic interactions results in an unprecedented binding position in which both the groove and the 3' end of the DNA are occupied. This further contribution adds another piece to the so far elusive puzzle of the recognition between ligands and DNA quadruplexes and will serve as a platform for a rational design of new groove binders.

G-quadruplex DNA (G4-DNA) structures are four-stranded helical DNA (or RNA) structures, comprising stacks of G-tetrads, which are the outcome of planar association of four guanines in a cyclic Hoogsteen hydrogen-bonding arrangement. In the last decade the number of publications where CD spectroscopy has been used to study G4-DNAs, is extremely high. However, with very few exceptions, these investigations use an empirical interpretation of CD spectra. In this interpretation two basic types of CD spectra have been associated to a single specific difference in the features of the strand folding, i.e. the relative orientation of the strands, "parallel" (all strands have the same 5′ to 3′ orientation) or "antiparallel". Different examples taken from the literature where the empirical interpretation is not followed or is meaningless are presented and discussed. Furthermore, the case of quadruplexes formed by monomeric guanosine derivatives, where there is no strand connecting the adjacent quartets and the definition parallel/antiparallel strands cannot apply, will be discussed. The different spectral features observed for different G-quadruplexes is rationalised in terms of chromophores responsible for the electronic transitions. A simplified exciton coupling approach or more refined QM calculations allow to interpret the different CD features in terms of different stacking orientation (head-to-tail, head-to-head, tail-to-tail) between adjacent G-quartets irrespectively of the relative orientation of the stands (parallel/antiparallel). © 2010 The Royal Society of Chemistry.

(Figure Presented) In the past decade, DNA G-quadruplexes have come into the limelight thanks to their biological implications and to their potential druggability in anticancer therapy. In particular, it has been found that small molecules that stabilize G-quadruplex structures are effective inhibitors of telomerase which plays a critical role in tumorigenesis. So far, the quadruplex groove recognition, which is expected to give a higher degree of selectivity over the other DNA structures, has been demonstrated for very few compounds. Thus with the aim of detecting new and structurally diverse groove binders, a structure-based virtual screening campaign has been performed using the X-ray structure of the [d(TGGGGT)]4 quadruplex. Remarkable results were achieved, and six brand new different molecular entities have been found to interact with the groove through NMR experiments. The reported results will certainly stimulate further studies aimed at the design and optimization of new quadruplex-specific groove binders to be applied as anticancer agents and for other diseases. © 2009 American Chemical Society.