Synchronized translation programs across compartments during mitochondrial biogenesis

Abstract

Oxidative phosphorylation (OXPHOS) is fundamental for life. OXPHOS complexes pose a unique challenge for the cell, because their subunits are encoded on two different genomes, the nuclear genome and the mitochondrial genome. Genomic approaches designed to study nuclear/cytosolic and bacterial gene expression have not been broadly applied to the mitochondrial system; thus the co-regulation of OXPHOS genes remains largely unexplored. Here we globally monitored mitochondrial and nuclear gene expression processes in Saccharomyces cerevisiae during mitochondrial biogenesis, when OXPHOS complexes are synthesized. Nuclear- and mitochondrial-encoded OXPHOS transcript levels do not increase concordantly. Instead, we observe that mitochondrial and cytosolic translation are rapidly and dynamically regulated in a strikingly synchronous fashion. Furthermore, the coordinated translation programs are controlled unidirectionally through the intricate and dynamic control of cytosolic translation. Thus the nuclear genome carefully directs the coordination of mitochondrial and cytosolic translation to orchestrate the timely synthesis of each OXPHOS complex, representing an unappreciated regulatory layer shaping the mitochondrial proteome. Our whole-cell genomic profiling approach establishes a foundation for global gene regulatory studies of mitochondrial biology.