Mitochondrial RNA degradation regulates differentiation, stemness, and immune sensitivity in acute myeloid leukemia.

Eukaryotic cells have separate genomes in the nucleus and mitochondria. Mitochondrial DNA is transcribed bi-directionally to generate mitochondrial RNA (mtRNA) and dsRNA as a by-product of this transcription. We demonstrate that mtRNA transcription and degradation are increased in AML (Acute Myeloid Leukemia) cells and stem cells resulting in higher rates of mtRNA turnover. We discover that the mitochondrial degradosome, SUV3 and PNPase, is upregulated in AML cells and stem cells and functionally important for degradation of mtRNA and mitochondrial dsRNA (double stranded RNA) in AML. Depleting SUV3 or PNPase impairs mtRNA degradation and promotes the accumulation of dsRNA. dsRNA that accumulates after depleting SUV3 or PNPase, stimulates IFN-I signaling that induces AML differentiation, decreases stemness and increases sensitivity to immune-mediating cytotoxicity. Thus, this work highlights mitochondrial RNA regulation in AML and identifies a mechanism by which mtRNA turnover influences AML differentiation, stem cell function, and immune sensitization.