Biology subjects

Henras, A.

Publications and source records attributed to Henras, A..

7 recordsLinked to original sources

bioRxiv2024

A novel family of lncRNAs relate facioscapulohumeral muscular dystrophy to nucleolar architecture and protein synthesis rate

Facioscapulohumeral muscular dystrophy (FSHD) is a hereditary myopathy linked to deletions of the tandemly arrayed D4Z4 macrosatellite repeats at human chromosome 4q35. These deletions accompany local chromatin changes and the anomalous expression of nearby transcripts FRG2A, DBET, and D4Z4. We discovered that FRG2A is one member of a family of long non-coding RNAs (lncRNAs) expressed at elevated levels in skeletal muscle cells with distinct amounts detected in individual patients. We found that FRG2A lncRNA preferentially associates with rDNA sequences and centromeres and promotes the three-dimensional association of centromeres with the nucleolar periphery in FSHD cells. Furthermore, we demonstrate that the elevated FRG2A expression in cells from FSHD patients reduces rDNA transcription and global protein synthesis. Our results frame an entirely unanticipated new disease model in which elevated lncRNAs levels mediated by deletions of D4Z4 macrosatellite repeats leads to a diminished protein synthesis capacity, thereby contributing to muscle wasting.

molecular biology↗

bioRxiv2023

Ribosomal RNA synthesis by RNA polymerase I is regulated by premature termination of transcription.

The RNA polymerase I (Pol I) enzyme that synthesizes large rRNA precursors, exhibits high rate of pauses during elongation, indicative of a discontinuous process. We show here that Premature Termination of Transcription (PTT) by Pol I is a critical regulatory step limiting rRNA production in vivo. The Pol I mutant, SuperPol (RPA135-F301S), produces 1.5-fold more rRNA than the wild type (WT). Combined CRAC and rRNA analysis link increased rRNA production in SuperPol to reduced PTT, resulting in shifting polymerase distribution toward the 3 end of rDNA genes. In vitro, SuperPol shows reduced nascent transcript cleavage, associated with more efficient transcript elongation after pauses, to the detriment of transcriptional fidelity. Notably, SuperPol is resistant to BMH-21, a drug impairing Pol I elongation and inducing proteasome-mediated degradation of Pol I subunits. Compared to WT, SuperPol maintains subunit stability and sustains high transcription levels upon BMH-21 treatment. These comparative results show that PTT is alleviated in SuperPol while it is stimulated by BMH-21 in WT Pol I.

molecular biology↗

bioRxiv2023

EEF2-inactivating toxins engage the NLRP1 inflammasome and promote epithelial barrier disruption upon Pseudomonas infection

The intracellular inflammasome complex have been implicated in the maladaptive tissue damage and inflammation observed in chronic Pseudomonas aeruginosa infection. Human airway and corneal epithelial cells, which are critically altered during chronic infections mediated by P. aeruginosa, specifically express the inflammasome sensor NLRP1. Here, together with a companion study, we report that the NLRP1 inflammasome detects Exotoxin A (EXOA), a ribotoxin released by P. aeruginosa Type 2 Secretion System (T2SS) during chronic infection. Mechanistically, EXOA-driven Eukaryotic Elongation Factor 2 (EEF2) ribosylation and covalent inactivation promotes ribotoxic stress and subsequent NLRP1 inflammasome activation, a process shared with other EEF2-inactivating toxins, Diphtheria Toxin and Cholix Toxin. Biochemically, irreversible EEF2 inactivation triggers ribosome stress-associated kinases ZAK- and P38-dependent NLRP1 phosphorylation and subsequent proteasome-driven functional degradation. Finally, Cystic Fibrosis cells from patients exhibit exacerbated P38 activity and hypersensitivity to EXOA-induced ribotoxic stress-dependent NLRP1 inflammasome activation, a process inhibited by the use of ZAK inhibitors. Altogether, our results show the importance of P. aeruginosa virulence factor EXOA at promoting NLRP1-dependent epithelial damage and identify ZAK as a critical sensor of virulence-inactivated EEF2. KEY POINTSO_LIP. aeruginosa induces NLRP1-dependent pyroptosis in human corneal and nasal epithelial cells C_LIO_LIP. aeruginosa Exotoxin A (EXOA) and other EEF2-inactivating bacterial exotoxins activate the human NLRP1 inflammasome C_LIO_LIEEF2 inactivation promotes ribotoxic stress response and ZAK kinase-dependent NLRP1 inflammasome activation. C_LIO_LIBronchial epithelial cells from Cystic Fibrosis patients show extreme sensitivity to ribotoxic stress-dependent NLRP1 inflammasome activation in response to Exotoxin A C_LIO_LIP38 and ZAK inhibition protects Cystic Fibrosis epithelial cell from EXOA-induced pyroptosis C_LI

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↗

bioRxiv2021

Long non-coding RNA Neat1 is a key translational regulator in hypoxia.

Internal ribosome entry sites (IRESs) drive translation initiation during stress. In response to hypoxia, (lymph)angiogenic factors responsible for tissue revascularization in ischemic diseases are induced by the IRES-dependent mechanism. Here we searched for IRES trans-acting factors (ITAFs) active in early hypoxia in mouse cardiomyocytes. Using knock-down and proteomics approaches, we show a link between a stressed-induced nuclear body, the paraspeckle, and IRES-dependent translation. Furthermore, smiFISH experiments demonstrate the recruitment of IRES-containing mRNA into paraspeckle during hypoxia. Our data reveal that the long non-coding RNA Neat1, an essential paraspeckle component, is a key translational regulator, active on IRESs of (lymph)angiogenic and cardioprotective factor mRNAs. In addition, paraspeckle proteins p54nrb and PSPC1 as well as nucleolin and Rps2, two p54nrb-interacting proteins identified by mass spectrometry, are ITAFs for IRES subgroups. Paraspeckle thus appears as a platform to recruit IRES-containing mRNAs and possibly host IRESome assembly. Polysome PCR array shows that Neat1 isoforms regulate IRES-dependent translation and, more widely, translation of mRNAs involved in stress response. HighlightsO_LIParaspeckle formation correlates with activation of translation via internal ribosome entry sites (IRES) in mouse hypoxic cardiomyocytes as well as in tumoral cells. C_LIO_LIThe long non-coding RNA Neat1, an essential paraspeckle component, is a key translational regulator of (lymph)angiogenic and cardioprotective factor expression in this process. C_LIO_LIIRES-containing mRNA is recruited into paraspeckles during hypoxia. C_LIO_LIParaspeckle proteins p54nrb and PSPC1 as well as two p54nrb-interacting proteins, nucleolin and RPS2, contribute to this process. C_LIO_LIParaspeckle appears as a platform for IRESome formation in the nucleus. C_LIO_LIThe Neat1 isoforms widely regulate the translation of mRNAs containing IRESs and of genes involved in the stress response. C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/430272v2_ufig1.gif" ALT="Figure 1"> View larger version (98K): org.highwire.dtl.DTLVardef@1741648org.highwire.dtl.DTLVardef@62e741org.highwire.dtl.DTLVardef@13c86a8org.highwire.dtl.DTLVardef@acae63_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

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↗

bioRxiv2018

Vasohibin1, a new IRES trans-acting factor for sequential induction of angiogenic factors in hypoxia

Hypoxia, a major inducer of angiogenesis, is known to trigger major changes of gene expression at the transcriptional level. Furthermore, global protein synthesis is blocked while internal ribosome entry sites (IRES) allow specific mRNAs to be translated. Here we report the transcriptome and translatome signatures of (lymph)angiogenic genes in hypoxic HL-1 cardiomyocytes: most genes are not induced at the transcriptome-, but at the translatome level, including all IRES-containing mRNAs. Our data reveal activation of (lymph)angiogenic mRNA IRESs in early hypoxia. We identify vasohibin1 (VASH1) as an IRES trans-acting factor (ITAF) able to activate FGF1 and VEGFD IRESs in hypoxia while it inhibits several IRESs in normoxia. Thus this new ITAF may have opposite effects on IRES activities. These data suggest a generalized process of IRES-dependent translational induction of (lymph)angiogenic growth factors expression in early hypoxia, whose pathophysiological relevance is to trigger formation of new functional vessels in ischemic heart. VASH1 is not always required, indicating that the IRESome composition is variable, thus allowing subgroups of IRESs to be activated under the control of different ITAFs.

cell biology↗