Suborganellar Localization of Mitochondrial Proteins and Transcripts in Human Cells

Mitochondria have complex ultrastructure which includes continuous subcompartments, such as matrix, intermembrane space, and two membranes, as well as focal structures, such as nucleoids, RNA granules, and mitoribosomes. Comprehensive studies of the spatial distribution of proteins and RNAs inside the mitochondria are necessary to understand organellar gene expression processes and macromolecule targeting pathways. Here we give examples of distribution analysis of mitochondrial proteins and transcripts by conventional microscopy and the super-resolution technique 3D STORM. We provide detailed protocols and discuss limitations of immunolabeling of mitochondrial proteins and newly synthesized mitochondrial RNAs by bromouridine incorporation and single-molecule RNA FISH in hepatocarcinoma cells.