Hemono, M. | bioRxiv Science

bioRxiv2022

FRIENDLY (FMT) is an RNA binding protein associated with cytosolic ribosomes at the mitochondrial surface

The spatial organization of protein synthesis in the eukaryotic cell is essential for maintaining the integrity of the proteome and the functioning of the cell. Translation on free polysomes or on ribosomes associated with the endoplasmic reticulum has been studied for a long time. More recent data have revealed selective translation of mRNAs in other compartments, in particular at the surface of mitochondria. Although these processes have been described in many organisms, in particular in plants, the mRNA targeting and localized translation mechanisms remain poorly understood. Here, the Arabidopsis thaliana Friendly (FMT) protein is shown to be a cytosolic RNA binding protein that associates with cytosolic ribosomes at the surface of mitochondria. Its knockdown delays seedling development and causes mitochondrial clustering. The mutation also disrupts the mitochondrial proteome and the localization of nuclear transcripts on the surface of mitochondria. These data indicate that FMT participates in the localization of mRNAs and their translation at the surface of mitochondria.

plant biology↗

bioRxiv2021

CLUH interactome reveals an association to SPAG5 and a proximity to the translation of mitochondrial protein

Mitochondria require thousands of proteins to fulfil their essential function in energy production and other fundamental biological processes. These proteins are mostly encoded by the nuclear genome, translated in the cytoplasm before being imported into the organelle. RNA binding proteins (RBPs) are central players in the regulation of this process by affecting mRNA translation, stability or localization. CLUH is an RBP recognizing specifically mRNAs coding for mitochondrial proteins, but its precise molecular function and interacting partners remain undiscovered in mammals. Here we reveal for the first time CLUH interactome in mammalian cells. Using both co-IP and BioID proximity-labeling approaches, we identify novel molecular partners interacting stably or transiently with CLUH in HCT116 cells and mouse embryonic stem cells. We reveal a stable RNA-independent interaction of CLUH with itself and with SPAG5 in cytosolic granular structures. More importantly, we uncover an unexpected proximity of CLUH to mitochondrial proteins and their cognate mRNAs in the cytosol. Additionally, our data highlight the importance of CLUH TPR domain for its interactions with both proteins and mRNAs. Overall, through the analysis of CLUH interactome, our study sheds a new light on CLUH molecular function by highlighting its association to the translation and subcellular localization of some mRNAs coding for mitochondrial proteins.

molecular biology↗