Conformational proofreading of distant 40S ribosomal subunit maturation events by a long-range communication mechanism

Eukaryotic ribosomes are synthesized in a hierarchical process driven by a plethora of assembly factors, but how maturation events at physically distant sites on pre- ribosomes are coordinated is poorly understood. Using functional analyses and cryo- EM, we show that ribosomal protein Rps20 orchestrates communication between two multi-step maturation events across the pre-40S subunit. Our study reveals that during pre-40S maturation, formation of essential contacts between Rps20 and Rps3 permits assembly factor Ltv1 to recruit the Hrr25 kinase, thereby promoting Ltv1 phosphorylation. In parallel, a deeply buried Rps20 loop reaches to the opposite pre- 40S side, where it stimulates Rio2 ATPase activity. Both cascades converge to the final maturation steps releasing Rio2 and phosphorylated Ltv1. We propose that conformational proofreading exerted via Rps20 constitutes a checkpoint permitting assembly factor release and progression of pre-40S maturation only after completion of all earlier maturation steps

Ribosomal 60S-subunit production: the final scene

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Maturation of pre‐40S particles in yeast and humans

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La nature des interactions entre substances humiques et tensio-actifs cationiques révèle l'organisation moléculaire de la matière humique

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Complexes of humic acid with cationic surfactants support the supramolecular view of extracted humic matter

International audienceThe structural organization of extracted humic matter, polymeric or supramolecular, has been a long-standing controversial issue. In this paper, we show that the interaction between a reference humic material, the Suwannee River Humic Acid (SRHA), and a homologous series of cationic surfactants (n-alkyl trimethyl ammonium chloride) provides key insights to resolve the controversy. By combining measurements of turbidity, electrophoretic mobility, surface tension, and cryogenic transmission electron microscopy, we show that (i) the binding of cationic surfactant to the anionic humic acid is initially triggered by electrostatic interactions; (ii) the contrasting evolution of turbidity-surfactant concentration curves implies that the surfactant alkyl chain interacts with the hydrophobic moieties of humic matter from very low concentrations of surfactant; (iii) a drastic restructuring of humic matter occurs upon surfactant binding, which brings out supplementary anionic humic sites; (iv) in the presence of C12 cationic surfactant, SRHA spontaneously forms stable nanoscale unilamellar vesicles, which, in addition to the high surface activity of complexes, could be of interest in the remediation of oil-contaminated environments; (v) the sequence of molecular structures obtained from SRHA with increasing amounts of C12-cationic surfactant-humic-rich vesicles, aggregates, surfactant-rich vesicles-bears striking similarities with the phase behaviour of aqueous mixtures of anionic and cationic surfactants, thus supporting the supramolecular view of humic structure

Probing the organization of fulvic acid using a cationic surfactant

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The Rio1p ATPase hinders premature entry into translation of late pre-40S pre-ribosomal particles

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Characterization of the lipid envelope of exosome encapsulated HEV particles protected from the immune response

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