The transcriptional co-activator PGC-1α is a key regulator of mitochondrial function and muscle fiber specification in the skeletal muscle.The E3 ubiquitin ligase RNF34 ubiquitinates PGC-1α and negatively regulates mammalian brown fat cell metabolism.However,the functional importance of RNF34 in the skeletal muscle and its impact on energy metabolism remain unknown.The Drosophila PGC-1 homolog dPGC-1 and its mammalian counterparts have conserved functions in mitochondria and insulin signaling.Here,we showed that the Drosophila RNF34 (dRNF34) ubiquitinates the Drosophila PGC-1α(dPGC-1) and promotes its degradation in HEK293T cells by immunoprecipitation and weste blot analysis.This allows us to use Drosophila as a powerful model system to study the physiological role of RNF34 in mitochondrial function and metabolism.In the in vivo studies,by separately expressing two independent UAS-dRNF34 RNAi transgenes driven by the muscle-specific 24B-Gal4 driver,we found that knockdown of dRNF34 specifically in muscle promotes mitochondrial biogenesis,improves negative geotaxis,extends climbing time to exhaustion in moderate aged flies and counteracts high-fat-diet-induced high triglyceride content.Furthermore,we showed that knockdown of dPGC-1 reversed the effects of the dRNF34 knockdown phenotypes described above.Our results reveal that dRNF34 plays an important role in regulating mitochondrial biogenesis in muscle and lipid metabolism through dPGC-1.Thus,inhibition of RNF34 activity provides a potential novel therapeutic strategy for the treatment of agerelated muscle dysfunction.