Final Pre-40S Maturation Depends on the Functional Integrity of the 60S Subunit Ribosomal Protein L3

Ribosomal protein L3 is an evolutionarily conserved protein that participates in the assembly of early pre-60S particles. We report that the rpl3[W255C] allele, which affects the affinity and function of translation elongation factors, impairs cytoplasmic maturation of 20S pre-rRNA. This was not seen for other mutations in or depletion of L3 or other 60S ribosomal proteins. Surprisingly, pre-40S particles containing 20S pre-rRNA form translation-competent 80S ribosomes, and translation inhibition partially suppresses 20S pre-rRNA accumulation. The GTP-dependent translation initiation factor Fun12 (yeast eIF5B) shows similar in vivo binding to ribosomal particles from wild-type and rpl3[W255C] cells. However, the GTPase activity of eIF5B failed to stimulate processing of 20S pre-rRNA when assayed with ribosomal particles purified from rpl3[W255C] cells. We conclude that L3 plays an important role in the function of eIF5B in stimulating 3′ end processing of 18S rRNA in the context of 80S ribosomes that have not yet engaged in translation. These findings indicate that the correct conformation of the GTPase activation region is assessed in a quality control step during maturation of cytoplasmic pre-ribosomal particles

Proposal of the French Society of Vascular Medicine for the prevention, diagnosis and treatment of venous thromboembolic disease in outpatients with COVID-19

International audienceThe proposal is intended to help physicians treating patients with COVID-19 for the diagnosis, treatment and prevention of venous thromboembolic disease either when leaving the hospital or treated as outpatients.This document is a synthesis of opinions of a working group from the French Society of Vascular Medicine (SFMV) composed of private practice and hospital-based physicians. This proposal is based on a limited level of evidence. This proposal is likely to evolve with the knowledge of the disease

The kinase activity of human Rio1 is required for final steps of cytoplasmic maturation of 40S subunits

hRio1 is an atypical protein kinase of the conserved RIO family. Depletion of hRio1 affects the last step of 18S rRNA maturation and causes defects in recycling of trans-acting factors from pre-40S subunits in the cytoplasm. The kinase activity of hRio1 is essential for recycling of the endonuclease hNob1 and its binding partner hDim2 from pre-40S

Dissection of Dom34–Hbs1 reveals independent functions in two RNA quality control pathways

International audienceEukaryotic cells have several quality control pathways that rely on translation to detect and degrade defective RNAs. Dom34 and Hbs1 are two proteins that are related to translation termination factors and are involved in no-go decay (NGD) and nonfunctional 18S ribosomal RNA (rRNA) decay (18S NRD) pathways that eliminate RNAs that cause strong ribosomal stalls. Here we present the structure of Hbs1 with and without GDP and a low-resolution model of the Dom34-Hbs1 complex. This complex mimics complexes of the elongation factor and transfer RNA or of the translation termination factors eRF1 and eRF3, supporting the idea that it binds to the ribosomal A-site. We show that nucleotide binding by Hbs1 is essential for NGD and 18S NRD. Mutations in Hbs1 that disrupted the interaction between Dom34 and Hbs1 strongly impaired NGD but had almost no effect on 18S NRD. Hence, NGD and 18S NRD could be genetically uncoupled, suggesting that mRNA and rRNA in a stalled translation complex may not always be degraded simultaneously