Many of the most highly conserved elements in the human genome are "poison exons," alternatively spliced exons that contain premature termination codons and permit post-transcriptional regulation of mRNA abundance through induction of nonsense-mediated mRNA decay (NMD). Poison exons are widely assumed to be highly conserved due to their presumed importance for organismal fitness, but this functional importance has never been tested in the context of a whole organism. Here, we report that a poison exon in Smndc1 is conserved across mammals and plants and plays a molecular autoregulatory function in both kingdoms. We generated mouse and A. thaliana models lacking this poison exon to find its loss leads to deregulation of SMNDC1 protein levels, pervasive alterations in mRNA processing, and organismal size restriction. Together, these models demonstrate the importance of poison exons for both molecular and organismal phenotypes that likely explain their extraordinary conservation.
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http://dx.doi.org/10.1371/journal.pgen.1011363 | DOI Listing |
EMBO J
January 2025
Newcastle University Biosciences Institute (NUBI), Central Parkway, Newcastle University, NE1 3BZ, Newcastle upon Tyne, UK.
The cellular concentrations of splicing factors (SFs) are critical for controlling alternative splicing. Most serine and arginine-enriched (SR) protein SFs regulate their own concentration via a homeostatic feedback mechanism that involves regulation of inclusion of non-coding 'poison exons' (PEs) that target transcripts for nonsense-mediated decay. The importance of SR protein PE splicing during animal development is largely unknown despite PE ultra-conservation across animal genomes.
View Article and Find Full Text PDFNAR Genom Bioinform
December 2024
Center for Molecular and Cellular Biology, Skolkovo Institute of Science and Technology, Bolshoy Bulvar, 30, 121205, Moscow, Russia.
Eukaryotic cells express a large number of transcripts from a single gene due to alternative splicing. Despite hundreds of thousands of splice isoforms being annotated in databases, it has been reported that the current exon catalogs remain incomplete. At the same time, introns of human protein-coding (PC) genes contain a large number of evolutionarily conserved elements with unknown function.
View Article and Find Full Text PDFJ Neurosci
November 2024
Department of Human Genetics, The University of Chicago, Chicago, IL 60637, USA
How master splicing regulators crosstalk with each other and to what extent transcription regulators are differentially spliced remain unclear in the developing brain. Here, cell-type-specific RNA-Seq analyses of the developing neocortex uncover variable expression of the Rbfox1/2/3 genes and enriched splicing events in transcription regulators, altering protein isoforms or inducing nonsense-mediated mRNA decay. Transient expression of Rbfox proteins in radial glial progenitors induces neuronal splicing events preferentially in transcription regulators such as and Surprisingly, Rbfox proteins promote the inclusion of a mammal-specific alternative exon and a previously undescribed poison exon in Simultaneous ablation of in the neocortex downregulates neuronal isoforms and disrupts radial neuronal migration.
View Article and Find Full Text PDFChem Biol Drug Des
October 2024
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Splicing modulation by a small compound offers therapeutic potential for diseases caused by splicing abnormality. However, only a few classes of compounds that can modulate splicing have been identified. We previously identified BAY61-3606, a multiple kinase inhibitor, as a compound that relaxes the splicing fidelity at the 3' splice site recognition.
View Article and Find Full Text PDFRNA
December 2024
Department of Biochemistry, University of California, Riverside, California 92521, USA
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