Science Bite (3 minute oral presentation with PPT in live session and poster) - Students and ECRs only Lorne Infection and Immunity 2023

MDA5 guards against infection by surveying cellular RNA homeostasis (#65)

Natalia Sampaio 1 2 3 , Liden J Gearing 1 2 , Antonio G Dias Junior 3 , Lise Chauveau 4 , Valerie Odon 3 , Chiara Cursi 3 , Alice Mayer 3 , Madara Ratnadiwakara 5 , Minna-Liisa Anko 6 , Paul J Hertzog 1 2 , Jan Rehwinkel 3
  1. 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 a range of viruses. MDA5’s RNA agonists are not well defined. We used individual-nucleotide resolution crosslinking and immunoprecipitation (iCLIP) to study its ligands. Surprisingly, upon infection with SARS-CoV-2 or encephalomyocarditis virus (EMCV), MDA5 bound overwhelmingly to cellular RNAs. Many binding sites were intronic and proximal to Alu elements. MDA5-bound RNA was enriched in Poly(A) and Poly(U) motifs, some of which may form double-stranded RNA. In SARS-CoV-2 and EMCV-infected cells, cytoplasmic levels of intron-containing unspliced transcripts were increased, suggesting dysregulation of splicing. Concomitantly, MDA5 iCLIP peaks were enriched in introns accumulating in the cytoplasm of infected cells. Moreover, rescue of splicing abrogated MDA5 activation. Finally, when depleted of viral RNA, RNA extracted from infected cells still stimulated MDA5. Taken together, MDA5 surveys RNA processing fidelity and detects splicing perturbation during infection, establishing a paradigm of innate immune ‘guarding’ for RNA sensors.