GTPBP8 and osteosarcoma: To confirm GTPBP8 mitochondrial subcellular localization (as it has not yet been annotated in the human MitoCarta3.0 dataset), we performed immunofluorescence imaging of human 143B osteosarcoma (HOS) cells transiently expressing a C-terminal FLAG-tagged GTPBP8 cDNA construct (GTPBP8::FLAG) (Supplementary Fig. 1B).