Biology subjects

Henry, Y.

Publications and source records attributed to Henry, Y..

5 recordsLinked to original sources

bioRxiv2026

A bifunctional H/ACA snoRNP mediates both pseudouridylation and rRNA scaffolding during ribosome assembly

The early steps of eukaryotic large ribosomal subunit assembly remain poorly understood due to the structural flexibility of pre-60S intermediates, whose rRNA is extensively modified by small nucleolar RNPs (snoRNPs). Some snoRNPs, however, lack any modification function and instead scaffold ribosome assembly through largely unknown mechanisms. Here, we show that the H/ACA snoRNP snR37 integrates both modifying and scaffolding roles. Biochemical and structural analyses reveal a canonical H/ACA core that pseudouridylates a conserved uridine in the A site of the peptidyl transferase center, the catalytic heart of the 60S subunit. Additional RNA helices recruit non-core proteins, the Upa1-Upa2 heterodimer and Rbp95, which mediate stable snR37 association with pre-60S complexes. These proteins cooperate with the Npa1 rRNA chaperone complex to link four rRNA domains, thereby structurally organizing early pre-60S intermediates and promoting proper formation of the PTC. This dual organization establishes a paradigm for snoRNPs combining rRNA modification and scaffolding functions.

biochemistry↗

bioRxiv2024

Methylparaben dampens virulence and transmissibility of the Drosophila pathogen Pseudomonas entomophila

In the last 20 years, Pseudomonas entomophila (Pe) has emerged as a model to explore insect immunity to bacterial intestinal pathogens. Laboratory studies evidenced multiple detrimental effects of Pe on Drosophila melanogaster. However, these effects require that the bacteria are ingested in extremely high concentrations of 1010 - 1011 CFU per mL (OD600 20 - 200), questioning the relevance of this pathogen in nature. Here, we tested whether the need for such high doses may be due to protective effects of the food preservative methylparaben (Nipagin), a standard ingredient of artificial Drosophila diets. While significant mortality in flies fed diet containing standard methylparaben concentration required doses of >1010 CFU per mL, when methylparaben was absent we could observe mortality using 500,000x lower doses. Consistent with these results, we demonstrated strong bactericidal properties of methylparaben on Pe in vitro. In the absence of methylparaben even the smallest inocula (105 CFU per mL) led to high bacterial loads (106 CFU per fly) after several days, indicating the ability of Pe to grow and overcome the flies defenses. We also demonstrate that in the absence of methylparaben, infected flies could easily transmit the pathogen to other adults and to offspring, resulting in high mortality and thus highlighting the potential of Pe as a pathogen of Drosophila in nature. Our study also underscores that careful consideration should be given to food additives used in standard diets in laboratory research on host-pathogen interaction. ImportanceAccurate characterization of pathogen infections requires appropriate experimental methodologies. Infections of insects with Pe are frequently studied using fruit flies as a model organism, with laboratory cultures typically maintained on artificial media containing various food preservatives. In this study, we show that one commonly used preservative, methylparaben, significantly influences the outcome of oral infections with Pe. We found that minimal infection doses, far below the standards of the field, could be still lethal to flies raised on media without methylparaben. This increased virulence was also associated with increased transmission of the pathogen, both from infected adult flies to their offspring and to uninfected adults. Our findings show how subtle variations in experimental conditions can profoundly affect how we perceive pathogenic threats.

immunology↗

bioRxiv2022

The Ribosome Maturation Factor Rea1 utilizes nucleotide independent and ATP hydrolysis driven Linker remodelling for the removal of ribosome assembly factors

The ribosome maturation factor Rea1 (or Midasin) catalyses the removal of assembly factors from large ribosomal subunit precursors to promote their export from the nucleus to the cytosol. Rea1 consists of nearly 5000 amino-acid residues and belongs to the AAA+ protein family. It consists of a ring of six AAA+ domains from which the {approx} 1700 amino-acid residue linker emerges that is subdivided into stem, middle and top domains. A flexible and unstructured D/E rich region connects the linker top to a MIDAS (metal ion dependent adhesion site) domain, which is able to bind the assembly factor substrates. Despite its key importance for ribosome maturation, the Rea1 mechanism driving assembly factor removal is still poorly understood. Here we demonstrate that the Rea1 linker is essential for assembly factor removal. It rotates and swings towards the AAA+ ring following a complex remodelling scheme involving nucleotide independent as well as nucleotide dependent steps. ATP-hydrolysis is required to engage the linker with the AAA+ ring and ultimately with the AAA+ ring docked MIDAS domain. The interaction between the linker top and the MIDAS domain allows force transmission for assembly factor removal.

biochemistry↗

bioRxiv2022

The transcriptomic signature of physiological trade-offs caused by larval overcrowding in Drosophila melanogaster

Intraspecific competition at the larval stage is an important ecological factor affecting life-history, adaptation and evolutionary trajectory in holometabolous insects. However, the molecular pathways and physiological trade-offs underpinning these ecological processes are poorly characterised. We reared Drosophila melanogaster at three egg densities (5, 60 and 300 eggs/ml) and sequenced the transcriptomes of pooled third-instar larvae. We also examined emergence time, egg-to-adult viability, adult mass and adult sex-ratio at each density. Medium crowding had minor detrimental effects on adult phenotypes compared to low density and yielded 24 differentially expressed genes (DEGs) including several chitinase enzymes. In contrast, high crowding had substantial detrimental effects on adult phenotypes and yielded 2107 DEGs. Among these, upregulated gene sets were enriched in sugar, steroid and amino acid metabolism as well as DNA replication pathways, whereas downregulated gene sets were enriched in ABC transporters, Taurine, Toll/Imd signalling and P450 xenobiotics metabolism pathways. Overall, our findings show that larval overcrowding has a large consistent effect on several molecular pathways (i.e., core responses) with few pathways displaying density-specific regulation (i.e., idiosyncratic responses). This provides important insights into how holometabolous insects respond to intraspecific competition during development.

ecology↗

bioRxiv2020

RIOK2 phosphorylation by RSK promotes synthesis of the human small ribosomal subunit

Ribosome biogenesis lies at the nexus of various signaling pathways coordinating protein synthesis with cell growth and proliferation. This process is regulated by well-described transcriptional mechanisms, but a growing body of evidence indicates that other levels of regulation exist. Here we show that the Ras/mitogen-activated protein kinase (MAPK) pathway stimulates post-transcriptional stages of human ribosome synthesis. We identify RIOK2, a pre-40S particle assembly factor, as a new target of the MAPK-activated kinase RSK. RIOK2 phosphorylation by RSK promotes cytoplasmic maturation of late pre-40S particles, which is required for optimal protein synthesis and cell proliferation. RIOK2 phosphorylation facilitates its release from pre-40S particles and its nuclear re-import, prior to completion of small ribosomal subunits. Our results bring a detailed mechanistic link between the Ras/MAPK pathway and the maturation of human pre-40S particles, which open a hitherto poorly explored area of ribosome biogenesis.

molecular biology↗