New Insights into Mitochondrial–Nuclear Interactions Revealed through Analysis of Small RNAs

Mitochondrial sequence variants affect phenotypic function, often through interaction with the nuclear genome. These "mitonuclear" interactions have been linked both to evolutionary processes and human health. The study of these interactions has focused on mechanisms regulating communication between mitochondrial and nuclear proteins; the role of mitochondrial (mt) RNAs has received little attention. Here, we show that small mt-RNAs bind to the nuclear protein Argonaute 2, and that nuclear miRNAs bind to mt-mRNAs. We identify one small mt-RNA that binds to Argonaute 2 in human tissues whose expression and sequence remain unchanged across vertebrates. Although analyses of CLEAR-CLIP sequencing data sets of human and mouse did not reveal consistent interactions between small mt-RNAs and nuclear mRNAs, we found that MT-ND4 and MT-ATP6 mRNAs are bound by different nuclear miRNAs in humans and mice. Our work homes in on previously unknown interactions between nuclear and small mt-RNAs, which may play key roles in intergenomic communication.