Derepression of transposable elements enhances interferon beta signaling and stem/progenitor cell activity after proton irradiation

Abstract

SummaryThe release and subsequent detection of nucleic acids into the cytoplasm constitute a hallmark of the radiation-induced DNA damage response. However, different radiation types, such as photons and protons, may elicit distinct DNA damage responses, uniquely influencing normal stem cell activity and tissue regeneration. Here, we show that proton irradiation leads to enhanced derepression of transposable elements (TEs) with consequent activation of salivary gland stem/progenitor cells. This response is mediated by a pronounced loss of heterochromatin regulators and accumulation of cytoplasmic TE-derived dsRNA, resulting in upregulation of RIG-I and augmented interferon-beta (IFN-β) signaling. Single cell RNA sequencing (scRNA-seq) and TE dynamics analyses corroborate these findings, specifically in a subpopulation ofSox9-expressing stem/progenitor cells with increased INF-β response. These data reveal that the presence of TE-derived IFN-β in the microenvironment of irradiated organoids increases stem/progenitor cell activity and organoid growth, pointing to advantages of proton therapy over photon-based radiotherapy.