Ball and stick model of nucleic acid.

<p>Ball and stick model of various types of nucleic acid helical forms, showing base inclination angle axis (solid red line); diameter of groove (dashed blue line).</p

The secondary structure and refined structure of the RNA construct 5´ r(UUGGGCCAGCAGCAGGUCC)₂.

<p>A. The secondary structure of oligonucleotide r(C<u>A</u>G) repeat duplex model that allowed crystal growth. B. The global structure of the RNA including the electron density map at 1.0 σ C. The electron density map of non-canonical A-A pairs at 1.0σ. D. The backbone structure of the RNA construct.</p

Structural Insights Reveal the Dynamics of the Repeating r(CAG) Transcript Found in Huntington’s Disease (HD) and Spinocerebellar Ataxias (SCAs)

<div><p>In humans, neurodegenerative disorders such as Huntington’s disease (HD) and many spinocerebellar ataxias (SCAs) have been found to be associated with CAG trinucleotide repeat expansion. An important RNA-mediated mechanism that causes these diseases involves the binding of the splicing regulator protein MBNL1 (Muscleblind-like 1 protein) to expanded r(C<b><u>A</u></b>G) repeats. Moreover, mutant huntingtin protein translated from expanded r(C<b><u>A</u></b>G) also yields toxic effects. To discern the role of mutant RNA in these diseases, it is essential to gather information about its structure. Detailed insight into the different structures and conformations adopted by these mutant transcripts is vital for developing therapeutics targeting them. Here, we report the crystal structure of an RNA model with a r(C<b><u>A</u></b>G) motif, which is complemented by an NMR-based solution structure obtained from restrained Molecular Dynamics (rMD) simulation studies. Crystal structure data of the RNA model resolved at 2.3 Å reveals non-canonical pairing of adenine in 5´-CAG/3´-GAC motif samples in different <i>syn</i> and <i>anti</i> conformations. The overall RNA structure has helical parameters intermediate to the A- and B-forms of nucleic acids due to the global widening of major grooves and base-pair preferences near internal AA loops. The comprehension of structural behaviour by studying the spectral features and the dynamics also supports the flexible nature of the r(C<b><u>A</u></b>G) motif.</p></div

Three dimensional structure of the 1x1 nucleotide AA internal loop and its closing base pairs for RNA construct 5´ r(UUGGGCCAGCAGCAGGUCC)₂.

<p>Each of the loop closing pairs has geometry consistent with that of Watson-Crick GC base pairs. The distance values (in Å) are labeled for hydrogen bonds (dashed lines); the C1´-C1´ distances (solid lines).</p

Lowest energy conformation of 5´ r(CCGCAGCGG)_2.

<p>A. The lowest energy conformation of CAG motif obtained after rMD simulation of 5´ r(CCGC<u>A</u>GCGG)_<b>2</b>. B. Ensemble of ten lowest energy structures of 5´ r(CCGC<u>A</u>GCGG)_<b>2</b> obtained after rMD simulation. C. Ensemble of ten lowest energy structures of AA pairs of 5´ r(CCGC<u>A</u>GCGG)_<b>2</b> obtained after rMD simulation.</p

Front. Mol. Biosci.

Nanodomains are dynamic membrane subcompartments, enriched in specific lipid, and protein components that act as functional platforms to manage an abundance of cellular processes. The remorin protein of plants is a well-established nanodomain marker and widely serves as a paradigm to study nanodomain clustering. Located at the inner leaflet of the plasma membrane, remorins perform essential functions during signaling. Using deuteriumand phosphorus solid-state NMR, we inquire on themolecular determinants of the lipid-protein and protein-protein interactions driving nanodomain clustering. By monitoring thermotropism properties, lipid acyl chain order and membrane thickness, we report the effects of phosphoinositides and sterols on the interaction of various remorin peptides and protein constructs with the membrane. We probed several critical residues involved in this interaction and the involvement of the coiled-coil homo-oligomerisation domain into the formation of remorin nanodomains. We trace the essential role of the pH in nanodomain clustering based on anionic lipids such as phosphoinositides. Our results reveal a complex interplay between specific remorin residues and domains, the environmental pH and their resulting effects on the lipid dynamics for phosphoinositide-enriched membranes.Facteurs cellulaires recrutés par les potyvirus pour leur transport intercellulaire : de nouvelles sources de résistance des plantes

Nanodomain Clustering of the Plant Protein Remorin by Solid-State NMR

International audienceNanodomains are dynamic membrane subcompartments, enriched in specific lipid, and protein components that act as functional platforms to manage an abundance of cellular processes. The remorin protein of plants is a well-established nanodomain marker and widely serves as a paradigm to study nanodomain clustering. Located at the inner leaflet of the plasma membrane, remorins perform essential functions during signaling. Using deuterium and phosphorus solid-state NMR, we inquire on the molecular determinants of the lipid-protein and protein-protein interactions driving nanodomain clustering. By monitoring thermotropism properties, lipid acyl chain order and membrane thickness, we report the effects of phosphoinositides and sterols on the interaction of various remorin peptides and protein constructs with the membrane. We probed several critical residues involved in this interaction and the involvement of the coiled-coil homo-oligomerisation domain into the formation of remorin nanodomains. We trace the essential role of the pH in nanodomain clustering based on anionic lipids such as phosphoinositides. Our results reveal a complex interplay between specific remorin residues and domains, the environmental pH and their resulting effects on the lipid dynamics for phosphoinositide-enriched membranes.Les nanodomaines sont des sous-compartiments membranaires dynamiques, enrichis en lipides spécifiques et en composants protéiques qui servent de plateformes fonctionnelles pour gérer une abondance de processus cellulaires. La protéine remorine des plantes est un marqueur de nanodomaines bien établi et sert largement de paradigme pour l'étude des grappes de nanodomaines. Situés au niveau de la foliole interne de la membrane plasmique, les remorines remplissent des fonctions essentielles lors de la signalisation. En utilisant la RMN à l'état solide du deutérium et du phosphore, nous étudions les déterminants moléculaires des interactions lipide-protéine et protéine-protéine à l'origine des amas de nanodomaines. En surveillant les propriétés du thermotropisme, l'ordre de la chaîne acyle lipidique et l'épaisseur de la membrane, nous rapportons les effets des phosphoinositides et des stérols sur l'interaction de divers peptides et constructions protéiques de remorine avec la membrane. Nous avons étudié plusieurs résidus critiques impliqués dans cette interaction et l'implication du domaine de l'homo-oligomérisation à bobine enroulée dans la formation des nanodomaines remoriniques. Nous retraçons le rôle essentiel du pH dans la formation de grappes de nanodomaines à base de lipides anioniques tels que les phosphoinositides. Nos résultats révèlent une interaction complexe entre les résidus et les domaines spécifiques des remorines, le pH environnemental et leurs effets sur la dynamique lipidique des membranes enrichies en phosphoinositides