ADAR1 Safeguards MET by Suppressing ER Stress Through RNA Editing in Promoting Reprogramming

Abstract

RNA chemical modifications are intricately linked to transcriptome structural and functional diversity. Whereas somatic cell reprogramming involves a profound rewiring of epigenetic and transcriptomic landscapes, how RNA modifications contribute to overriding somatic cell identity is incompletely understood. Here we demonstrate that loss of Adenosine-to-Inosine (A-to-I) editing of RNA by ADAR1 hampers mesenchymal-to-epithelial transition (MET) and impedes induced pluripotent stem cell (iPSC) formation. Absence of RNA editing leads to aberrant innate immune response (IIR) expression programs, which unleash endoplasmic reticulum (ER) stress and hinder epithelial fate acquisition. Using chemical and genetic approaches, we show a dual role for A-to-I editing in preventing MDA5-dependent activation of ER stress and ensuring proper double strand RNA (dsRNA) compartmentalization for PERK activation. Thus, our study establishes a critical role for A-to-I RNA modification in cell fate transitions during reprogramming, which delineates a novel regulatory layer underlying MET control for efficient reprogramming.

Keywords: RNA A-to-I editing, ADAR1, somatic cell reprogramming, iPSC, pluripotency, MET, ER stress, UPR, innate immune response, Subcellular Localization