Biology subjects

Plisson-Chastang, C.

Publications and source records attributed to Plisson-Chastang, C..

8 recordsLinked to original sources

bioRxiv2026

CDC25B couples ribosome biogenesis to cell cycle kinetics to promote spinal cord neurogenesis

During neurogenesis, neural progenitors undergo a tightly regulated transition from proliferation to differentiation, which requires precise coordination between cell cycle progression and molecular reprogramming. Although the role of CDC25B is well established in promoting G2/M transition through CDK1 activation, we previously showed that it is both necessary and sufficient to trigger neural progenitor differentiation, via CDK-dependent and CDK-independent mechanisms. However, the molecular networks underlying this neurogenic activity remain poorly understood. Here, using a gain-of-function approach in the chicken spinal cord combined with bulk RNA sequencing, we show that CDC25B overexpression upregulates transcripts encoding ribosomal proteins and enhances ribosome biogenesis (RiBi) in neural progenitors. Consistent with these findings, during normal development, RiBi increases in neurogenic progenitor domains expressing CDC25B. Notably, the increase in RiBi is not associated with an increase in translation in neural progenitors. Instead, it is followed by an increase in mTORC1 activity in neuronal precursors and subsequently by a rise in the global translation rate in differentiating neurons. Moreover, increasing mTORC1 activity is sufficient to trigger a premature transition of neuronal precursors to the next step of differentiation. Altogether, our data support a model in which CDC25B coordinates cell cycle progression with RiBi in neurogenic progenitors, thereby initiating a program that culminates in translation in differentiating neurons.

developmental biology↗

bioRxiv2026

The R2T(P) complex orchestrates the SHQ1 driven early steps of box H/ACA snoRNP maturation

The chaperones RuvBL1 and RuvBL2 are members of the AAA+ ATPase family and participate in diverse cellular processes, including DNA repair, transcriptional regulation, and assembly of macromolecular complexes such as snoRNPs. The biogenesis of box H/ACA snoRNPs additionally requires the assembly factor SHQ1. These protein-RNA complexes are essential for ribosome biogenesis and telomerase stability and are linked to diseases such as dyskeratosis congenita and cancer. Despite detailed knowledge of mature complexes, their assembly mechanisms and how they can be modulated remain unclear. We characterize a trimeric interaction between SHQ1 and RuvBL1:RuvBL2, providing insight into early maturation of the protein-only precursor of box H/ACA snoRNPs. SHQ1 binds the flexible domain II of RuvBL1:RuvBL2, corresponding to the dodecamerization interface, suggesting disruption of this interface and promotion of hexamer formation. We further purified a complex containing RuvBL1:RuvBL2, SHQ1, and DKC1, the catalytic component of H/ACA snoRNPs and a client of SHQ1. This demonstrates that SHQ1 and DKC1 can simultaneously associate with RuvBL1:RuvBL2, potentially facilitating DKC1 release and subsequent snoRNA binding. Additionally, we identified a direct interaction between SHQ1 and RPAP3, a co-chaperone of RuvBL1:RuvBL2 (within the R2TP). Hence, RPAP3 may be responsible for recruiting SHQ1:DKC1 to hexameric RuvBL1:RuvBL2 and/or assist in the AAA+ mediated dissociation of the dimer. Since SHQ1 shares a domain with PIH1D1, an integral member of the R2TP complex, our findings suggest that early H/ACA snoRNP maturation may involve the R2T instead of the previously proposed R2TP complex.

biophysics↗

bioRxiv2025

Organelle distribution and protein translation defects in radial glia cells with mutations in Eml1

Cerebral cortical development is a finely regulated process, depending on key neuronal progenitors, giving rise to post-mitotic neurons that migrate to superficial regions in the developing brain. Disruptions can give rise to severe cortical malformations that are associated with intellectual disability and intractable epilepsy. Mutations in EML1/Eml1, coding for a microtubule (MT)-associated protein, lead to subcortical heterotopia (SH) in both humans and mice. In developing mutant mouse brains, ectopic apical radial glia (aRG) progenitors were found outside the normal proliferative ventricular zone (VZ). The normal role of Eml1 in these cells remains to be precisely determined. Using proteomics and imaging approaches, we compared brain tissue from control and mutant mice and identified microtubule and organelle dysregulation. Eml1 influences the trafficking of organelles to different compartments of aRG, where they may be involved in local functions. Thus, we find that mitochondrial and polysome distribution are altered in mutant conditions. Indeed, Eml1 interacts with translational machinery, and an overall downregulation of translation is observed when analysing the translatome of Eml1 mutant aRG. Paradoxically, an upregulation of translation-related mRNAs is also observed. These new data uncover an unprecedented function of Eml1, as well as associating novel subcellular patho-mechanisms with severe heterotopia formation.

neuroscience↗

bioRxiv2025

Translatome and translation dynamics analysis of a RiboCancer cell line panel reveals that leukemia-associated Rps15 mutations rewire translation through codon-specific tRNA accommodation defects.

Deletions and point mutations targeting ribosomal proteins (RPs) have been identified in cancer. Yet, their role in translational dysregulation remains poorly understood. We performed an integrated genome-wide translatome analysis (proteome, Ribo-seq and total RNA-seq) as well as RiboMethSeq on an isogenic cell line library modeling the most recurrent RP defects in cancer (Rpl5+/-, Rpl11+/-, Rpl22+/-, Rpl22-/-, Rpl10 R98S, Rps15 P131S and Rps15 H137Y). RP knock-out had minimal effects on translation, whereas RP point mutations induced a significant number of translation efficiency changes, affecting up to 10% of expressed genes in Rps15 mutants associated with Chronic Lymphocytic Leukemia (CLL). Cryo-electron microscopy and biochemical analyses revealed that the Rps15 mutations destabilize the C-terminal Rps15 domain, affecting the translation elongation cycle dynamics, and deregulating accommodation of aminoacylated tRNAs at the ribosomal A-site. Using Ribo-seq and translation reporter assays, we show that this accommodation defect shows codon specificity, explaining the reduced translation efficiency of genes enriched for these codons in Rps15 mutant cells, such as histones. Notably, genes with reduced translation efficiency in Rps15 mutated cells were enriched for transcriptional regulators such as transcription factor Runx3, resulting in downregulation of Runx3 target genes involved in immune regulation. Altogether, this study provides a comparative map of the translational rewiring driven by the most frequent somatic RP mutations. We provide unprecedented mechanistic insights in the translation defects induced by CLL-associated Rps15 mutations, and reveal an unappreciated cross-talk between translational and transcriptional dysregulation in these RP mutant cells. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/687986v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cd2846org.highwire.dtl.DTLVardef@10f3c49org.highwire.dtl.DTLVardef@13f1595org.highwire.dtl.DTLVardef@a212df_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

R2TP-like Quaternary Chaperones: a comprehensive overview to understand the dynamic R2SP complex

The human R2SP complex belongs to the R2TP-like quaternary chaperone family and consists of RUVBL1, RUVBL2, SPAG1 and PIH1D2. R2SP is crucial for the correct assembly of motile cilia (SPAG1 null mutations cause Primary Ciliary Dyskinesia) and the organization of the synaptic zone. RUVBL1/2 ATPases are the powerhouse of this molecular machinery, while SPAG1 and PIH1D2 would be adaptors that interact with specific clients to promote their quaternary assembly. Despite these functional data, little is known about the structure of R2SP and the precise mode of action of these R2TP-like complexes. We have combined biochemical and structural approaches (NMR, structural mass spectrometry and cryo-EM) to investigate the 3D organization of the human R2SP complex, its mode of assembly and ATPase activity. Our study reveals a three-dimensional structure similar to that of the canonical R2TP complex, but also highlights differences in the mode of action of its RUVBL1/2 ATPase core as well as the binding of its adaptors SPAG1 and PIH1D2.

biophysics↗

bioRxiv2024

SURF2 is a MDM2 antagonist in triggering the nucleolar stress response

Cancer cells are addicted to strong ribosome production to sustain their proliferation rate. Many chemotherapies impede ribosome production which is perceived by cells as "nucleolar stress" (NS), triggering p53-dependent and independent response pathways leading to cell cycle arrest and/or apoptosis. The 5S RNP particle, a sub-ribosomal particle, is instrumental to NS response. Upon ribosome assembly defects, the 5S RNP accumulate as free form. This free form is able to sequester and inhibit MDM2, thus promoting p53 stabilization. To investigate how cancer cells can resist to NS, we purified free-5S RNP and uncovered a new interaction partner, SURF2. Functional characterization of SURF2 shows that its depletion increases cellular sensitivity to NS, while its overexpression promotes their resistance to it. Consistently, SURF2 expression level negatively correlates with the overall survival in adrenocortical and head and neck squamous cell carcinomas. Our data demonstrate that SURF2 buffers free-5S RNP particles, and can modulate their activity. SURF2 regulates NS responses, and is a key player in both ribosomopathies and oncogenic mechanisms.

cell biology↗

bioRxiv2021

Probing small ribosomal subunit RNA helix 45 acetylation across eukaryotic evolution

NAT10 is an essential enzyme that catalyzes the formation of N4-acetylcytidine (ac4C) in eukaryotic transfer RNA (tRNA) and 18S ribosomal RNA (rRNA). Recent studies in human cells suggested that rRNA acetylation is dependent on SNORD13, a non-canonical box C/D small nucleolar RNA (SNORD) predicted to base-pair with 18S rRNA via two antisense elements. However, the selectivity of SNORD13-dependent cytidine acetylation and its relationship to NAT10s essential function in pre-rRNA processing remain to be defined. Here, we used CRISPR-Cas9 genome editing to formally demonstrate that SNORD13 is required for acetylation of a single cytidine residue of human and zebrafish 18S rRNA. In-depth characterization revealed that SNORD13-dependent ac4C is dispensable for yeast or human cell growth, ribosome biogenesis, translation, and the development of multicellular metazoan model organisms. This loss of function analysis inspired a cross-evolutionary survey of the eukaryotic rRNA acetylation machinery that led to the characterization of many novel SNORD13 genes in phylogenetically-distant metazoans and more deeply rooted photosynthetic organisms. This includes an atypical SNORD13-like RNA in D. melanogaster which appears to guide ac4C to 18S rRNA helix 45 despite lacking one of the two rRNA antisense elements. Finally, we discover that C. elegans 18S rRNA is not acetylated despite the presence of an essential NAT10 homolog. Altogether, our findings shed light on the molecular mechanisms underlying SNORD13-mediated rRNA acetylation across the eukaryotic tree of life and raise new questions regarding the biological function and evolutionary persistence of this highly conserved rRNA base modification.

molecular biology↗

bioRxiv2020

The final step of 40S ribosomal subunit maturation is controlled by a dual key lock

Preventing premature interaction of preribosomes with the translation apparatus is essential to translation accuracy. Hence, the final maturation step releasing functional 40S ribosomal subunits, namely processing of the 18S ribosomal RNA 3 end, is safeguarded by protein DIM2, which both interacts with the endoribonuclease NOB1 and masks the rRNA cleavage site. To elucidate the control mechanism that unlocks NOB1 activity, we performed cryo-EM analysis of late human pre-40S particles purified using a catalytically-inactive form of ATPase RIO1. These structures, together with in vivo and in vitro functional analyses, support a model in which ATP-loaded RIO1 cooperates with ribosomal protein RPS26/eS26 to displace DIM2 from the 18S rRNA 3 end, thereby triggering final cleavage by NOB1; release of ADP then leads to RIO1 dissociation from the 40S subunit. This dual key lock mechanism requiring RIO1 and RPS26 guarantees the precise timing of pre-40S particle conversion into translation-competent ribosomal subunits.

molecular biology↗