2. Academic Validation
  3. AKT constitutes a signal-promoted alternative exon-junction complex that regulates nonsense-mediated mRNA decay

AKT constitutes a signal-promoted alternative exon-junction complex that regulates nonsense-mediated mRNA decay

  • Mol Cell. 2022 Aug 4;82(15):2779-2796.e10. doi: 10.1016/j.molcel.2022.05.013.
Hana Cho 1,  Elizabeth T Abshire 1,  Maximilian W Popp 1,  Christoph Pröschel 2,  Joshua L Schwartz 3,  Gene W Yeo 3,  Lynne E Maquat 4
Affiliations

Affiliations

  • 1 Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA.
  • 2 Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Stem Cell and Regenerative Medicine Institute, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA.
  • 3 Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA; Stem Cell Program, University of California, San Diego, La Jolla, CA, USA; Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA, USA.
  • 4 Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA. Electronic address: lynne_maquat@urmc.rochester.edu.
PMID: 35675814 DOI: 10.1016/j.molcel.2022.05.013
Abstract

Despite a long appreciation for the role of nonsense-mediated mRNA decay (NMD) in destroying faulty, disease-causing mRNAs and maintaining normal, physiologic mRNA abundance, additional effectors that regulate NMD activity in mammalian cells continue to be identified. Here, we describe a haploid-cell genetic screen for NMD effectors that has unexpectedly identified 13 proteins constituting the Akt signaling pathway. We show that Akt supersedes UPF2 in exon-junction complexes (EJCs) that are devoid of RNPS1 but contain CASC3, defining an unanticipated insulin-stimulated EJC. Without altering UPF1 RNA binding or ATPase activity, AKT-mediated phosphorylation of the UPF1 CH domain at T151 augments UPF1 helicase activity, which is critical for NMD and also decreases the dependence of helicase activity on ATP. We demonstrate that upregulation of Akt signaling contributes to the hyperactivation of NMD that typifies Fragile X syndrome, as exemplified using FMR1-KO neural stem cells derived from induced pluripotent stem cells.

Keywords

AKT signaling; Fragile X syndrome; UPF1 helicase and RNA-binding activities; UPF1 phosphorylation; afuresertib; alternative exon-junction complexes; human haploid-cell screen; insulin; nonsense-mediated mRNA decay.

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