Mpf1 is a novel factor that affects the dual distribution of tail-anchored proteins between mitochondria and peroxisomes

Over half of cellular proteins must target upon their translation to distinct cellular compartments to function. Whereas considerable progress has been made in our understanding of targeting to individual organelles, we know truly little about how proteins distribute their targeting between two, or more, destinations - a process called dual/multiple targeting. In this study, we shine mechanistic insight into the process of dual targeting of proteins between the yeast mitochondria and peroxisomes. We performed a high throughput systematic microscopy screen in which we visualized the location of the model tail-anchored (TA) proteins Fis1 and Gem1 on the background of mutants in all yeast genes. This screen identified three proteins, whose absence resulted in a higher portion of the TA proteins in peroxisomes: the two paralogues Tom70, Tom71, as well as the uncharacterized gene YNL144C that we renamed mitochondria peroxisomes factor 1 (Mpf1). We characterized Mpf1 to be an unstable protein that associated with the cytosolic face of the mitochondrial outer membrane. Furthermore, our study uncovers a unique contribution of Tom71 for the regulation of the dual targeting and reveals a link between TOM70/71 and the quantity of transcripts of MPF1. Collectively, our study revealed, for the first-time, factors that influence the dual targeting of proteins between mitochondria and peroxisomes.