Two conserved transcription factors and a histone deubiquitinase regulate the mitochondrial unfolded protein response and longevity interacting with insulin signalling

The mitochondrial prohibitin (PHB) complex is critical to mitochondrial function. Depletion of PHB has opposite effects on ageing, shortening lifespan in wild-type worms while extending the lifespan of metabolically compromised animals, including insulin/IGF-1 receptor daf-2(e1370) mutants. PHB loss strongly induces the mitochondrial unfolded protein response (UPRmt) to maintain mitochondrial homeostasis, but this response is attenuated in daf-2 mutants. To uncover new regulators of this differential PHB-mediated stress response, as well as mechanisms behind the opposite longevity outcomes of PHB depletion, we carry out the first genome-wide double RNAi screen in C. elegans. We identify two transcription factors, ZNF-622 and TLF-1, and the histone deubiquitinase USP-48 as modulators of the UPRmt and longevity interacting with insulin signalling. We further show that USP-48 interacts with DVE-1 to regulate the UPRmt mostly independently of ATFS-1 through deubiquitylation of histone H2B. Collectively, this study proves the feasibility of double RNAi genetic screens and underlines the importance of epigenetic regulation in mitochondrial stress mediated longevity. *Sergio Gordillo-García and Jesús Fernandez-Abascal contributed equally.