Oral Presentation Australasian RNA Biology and Biotechnology Association 2025 Conference

The innate immune sensor MDA5 guards against infection by surveying cellular RNA homeostasis (130549)

Natalia G Sampaio 1 2 3 , Linden J Gearing+ 1 2 , Antonio Dias Junior+ 3 , Lise Chauveau+ 4 , Valerie Odon+ 3 , Chiara Cursi+ 3 , Alice Mayer+ 3 , Madara Ratnadiwakara+ 2 5 , Minna-Liisa Änkö+ 2 5 6 , Paul J Hertzog+ 1 2 , Jan Rehwinkel* 3
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  2. Department of Molecular and Translational Sciences, Southern Clinical School, Monash University, Clayton, VIC, Australia
  3. Medical Research Council Human Immunology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
  4. RNA viruses and metabolism team, Institut de Recherche en Infectiologie de Montpellier , Montpellier, France
  5. Centre for Cancer Research, Hudson Institute of Medical Research, Clayton, VIC, Australia
  6. Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland

MDA5 is an innate immune RNA sensor that detects infection with a range of viruses and other pathogens. Activation of MDA5 drives a robust inflammatory interferon response to protect against infection. MDA5’s RNA agonists are not well defined. We used single-nucleotide resolution crosslinking and immunoprecipitation (iCLIP) to study its ligands. Surprisingly, upon infection with SARS-CoV-2 or encephalomyocarditis virus, MDA5 bound overwhelmingly to cellular RNAs. Many binding sites were intronic and proximal to Alu elements and to potentially base-paired structures. Concomitantly, cytoplasmic levels of intron-containing unspliced transcripts increased in infected cells and displayed enrichment of MDA5 iCLIP peaks. Moreover, overexpression of a splicing factor abrogated MDA5 activation. Finally, when depleted of viral sequences, RNA extracted from infected cells still stimulated MDA5. Taken together, we propose that MDA5 surveys RNA processing fidelity and detects infections by sensing perturbations of posttranscriptional events such as splicing, establishing a paradigm of innate immune ‘guarding’ for RNA sensors.

 

* Corresponding authors: natalia.sampaio@hudson.org.au; jan.rehwinkel@imm.ox.ac.uk

+ Equal contribution