Biology subjects

LE HIR, H.

Publications and source records attributed to LE HIR, H..

3 recordsLinked to original sources

bioRxiv2025

Chemical inhibition of Exon Junction Complex assembly impairs mRNA localization and neural stem cells ciliogenesis

The Exon Junction Complex (EJC) is formed by the essential eIF4A3, MAGOH and Y14 core proteins. It is universally deposited during splicing at exon-exon junctions. The EJC is known to impact almost every post-transcriptional regulatory step throughout the life of mRNAs including their modifications, splicing, decay and trafficking. Its dysregulation leads to neurodevelopmental pathologies. Here we show that EJC-i, a compound known to block the ATPase activity of eIF4A3, inhibits de novo EJC assembly. EJC-i and targeted knockdown of either eIF4A3 or Y14 core EJC subunits lead to very similar phenotypes by impacting the destiny of mRNAs due to alterations in alternative splicing, nonsense-mediated mRNA decay, genome-wide m6A methylation and proper intracellular addressing of specific transcripts, in particular to the centrosome. Both EJC impairment methods disrupt the centrosome function that might be responsible for mitotic arrest at prometaphase. As a small molecule that readily diffuses into cells, EJC-i is a particularly attractive easy to use and versatile tool to investigate EJC functions in live cells or whole organism that are not prone to genetic manipulation. Indeed, this property was used to disrupt ciliogenesis in primary neural stem cells.

molecular biology↗

bioRxiv2025

Mapping interactions within the NMD decapping complex reveals how Upf1 recruits Dcp2 onto mRNA targets

Upf1 RNA helicase is a pivotal factor in the conserved nonsense-mediated mRNA decay (NMD) process. Upf1 is responsible for coordinating the recognition of premature termination codons (PTC) in a translation-dependent manner and subsequently triggering mRNA degradation. Multiple factors assist Upf1 during these two consecutive steps. In Saccharomyces cerevisiae, Upf2 and Upf3 associated to Upf1 (Upf1-2/3) contribute to PTC recognition but are absent from the Upf1-decapping complex that includes Nmd4, Ebs1, Dcp1, and Dcp2. Despite their importance for NMD, the organization and dynamics of these Upf1-containing complexes remains unclear. Here, we show how distinct domains of Upf1 make direct contacts with Dcp1/Dcp2, Nmd4 and Ebs1 using recombinant proteins. These proteins also bind to each other forming an extended network of interactions within the Upf1-decapping complex. Dcp2 and Upf2 are shown to compete for the same binding site in the Upf1 N-terminal CH domain. This finding accounts for the isolation of two mutually exclusive Upf1-containing complexes from cell lysates. Furthermore, we show how Nmd4-assisted recruitment of Upf1 promotes the anchoring of the decapping protein to the mRNA.

biochemistry↗

bioRxiv2020

Exon Junction Complex dependent mRNA localization is linked to centrosome organization during ciliogenesis

Exon junction complexes (EJC) mark untranslated spliced mRNAs and are crucial for the mRNA lifecycle. An imbalance in EJC dosage alters mouse neural stem cell (mNSC) division and is linked to human neurodevelopmental disorders. In quiescent mNSC and immortalized human retinal pigment epithelial (RPE1) cells, centrioles form a basal body for ciliogenesis. Here, we report that EJCs accumulate at basal bodies of mNSC or RPE1 cells and decline when these cells differentiate or resume growth. A high-throughput smFISH screen identifies two transcripts accumulating at centrosomes in quiescent cells, NIN and BICD2. In contrast to BICD2, the localization of NIN transcripts is EJC-dependent. NIN mRNA encodes a core component of centrosomes required for microtubule nucleation and anchoring. We find that EJC down-regulation impairs both pericentriolar material organization and ciliogenesis. An EJC-dependent mRNA trafficking towards centrosome and basal bodies might contribute to proper mNSC division and brain development.

cell biology↗