Box C/D Small Nucleolar Ribonucleoproteins Regulate Mitochondrial Surveillance and Innate Immunity

Monitoring of mitochondrial functions is crucial for organismal survival. This task is performed by mitochondrial surveillance or quality control pathways, which are activated by signals originating from mitochondria and relayed to the nucleus (retrograde response) to start the transcription of protective genes. In Caenorhabditis elegans , several systems exist, including the UPR ^mt , MAPK ^mt , and the ESRE pathway. These pathways are highly conserved and their loss results in compromised survival following mitochondrial stress.

In this study, we found a novel interaction between the box C/D snoRNA core proteins (snoRNPs) and mitochondrial surveillance and innate immunity pathways. We showed that C/D snoRNPs are required for the full expressions of UPR ^mt and ESRE upon stress. Meanwhile, we found that the loss of C/D snoRNPs increased immune responses. Understanding the “molecular switch” mechanisms of interplay between these pathways may be important for understanding of multifactorial processes, including response to infection or aging.