Spatial coordination of cytosolic and mitochondrial translation

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Project Summary: Mitochondria are critical for cells with high energy demand. Mitochondrial ATP synthase completes the final step of ATP production. Mutations in ATP synthase cause a range of diseases, including Schizophrenia, and heart failure. Thus, the basic biology of ATP synthase is important for health and disease. The subunits of the ATP synthase are encoded by the nuclear and mitochondrial genome. A unique challenge of assembling the ATP synthase is to coordinate the gene expressions from dual genetic origins. Recent studies showed that cytosolic and mitochondrial translation are temporally synchronized to maintain the stoichiometry of the ATP synthase subunits (Couvillion, M.T., et al. Nature, 2016; Soto, I, et al. Genome Biology, 2022). However, the underlying mechanism of the cross-compartment communication remains largely unknown. I aim to fill in the knowledge gap in this proposed study. Using single-molecule fluorescent in situ hybridization (smFISH) in yeast, I imaged the mRNAs of a nuclear-encoded subunit, ATP2, and a mitochondrial-encoded subunit, ATP6/8. I discovered that the ATP2 and ATP6/8 mRNA co-localized on the mitochondrial network. Based on this observation, I hypothesize that the cytosolic and mitochondrial translation co-localize on opposite sides of the mitochondrial double membrane, thereby promoting the assembly of the ATP synthase. In Aim 1, I propose to determine how the ATP2 mRNAs co-translationally associate with mitochondria. In Aim 2, I will define the spatial coordination between the cytosolic and mitochondrial mRNAs in yeast and cultured neurons. In Aim 3, I shall identify the regulating proteins and dissect the underlying mechanism of the cross-compartment co-localization. This study will uncover a novel mechanism by which cells spatially coordinate the nuclear and mitochondrial gene expressions during mitochondrial biogenesis. My PhD training with Dr. Peter Walter prepared me with the skills in organelle biology, yeast cell biology, and biochemistry. My postdoctoral training with Dr. Robert Singer equipped me with the expertise in single-molecule imaging. These complementary skills give me the unique opportunity to conduct this proposed study. During the K99 phase, Dr. Singer will help me develop the skills to image mRNAs in yeast and cultured neurons. Extending my research from yeast to neurons will increase the impact of my future research. Dr. Michael Rout (Co-Mentor) will provide the expertise to identify the proteins that bind to the co-localizing mRNAs. Dr. Liza Pon (Co-Mentor), Dr. Thomas Fox (Consultant), and Dr. Christof Osman (Collaborator) form my mitochondrial mentoring team. Their diverse background will allow me to acquire the knowledge and skills of different aspects of mitochondria. This study will open opportunities to study the spatial regulation of mitochondrial gene expression. It will serve as a foundation for an independent research program in my future laboratory.