A reduction in A-to-I RNA editing by ADAR disrupts Pumilio-mediated inhibition of MAPK signaling to drive intestinal stem cell aging.

Aging impairs intestinal stem cell (ISC) function, disrupting epithelial homeostasis and regenerative repair. Loss of ISC quiescence promotes intestinal dysfunction and contributes to organismal aging. Here, we report an epitranscriptomic mechanism through which a decrease in adenosine-to-inosine (A-to-I) RNA editing by the adenosine deaminase ADAR in ISCs during aging disrupts a conserved signaling axis that maintains ISC quiescence. In Drosophila melanogaster, ISC-specific loss of dADAR triggered hyperproliferation and tissue aging, whereas dADAR overexpression reduced age-related gut dysfunction and extended life span. Intestinal injury induced a decrease in dADAR, which was necessary for tissue regeneration, and in the zinc finger protein dZn72D, which stabilized dADAR to support intestinal homeostasis during aging. dADAR edited transcripts encoding the RNA binding protein Pumilio (dPUM) to generate an isoform that inhibited translation of two components of the mitogen-activated protein kinase (MAPK), dEGFR and dERK, thereby maintaining ISC quiescence. The abundance of ADAR2 and of the dZn72D ortholog ZFR decreased in human colonic crypts with aging and in mouse colon after injury, suggesting that attenuation of ADAR activity may play a conserved role in ISC aging and in facilitating colonic regeneration. Our work identifies a conserved mechanism of epitranscriptomic regulation that safeguards tissues and the decay of ADAR-mediated RNA editing as a form of age-related epigenetic information loss that disrupts ISC homeostasis.