EOLA1, a novel mitochondria-localized protein critical for heart functions via regulating mitochondrial translation

Mitochondria has its own mRNA translation system, which is mediated by mitochondria-specific protein synthesis machinery – 'mitoribosomes'. Dysregulation of mitochondrial translation disrupts the metabolic homeostasis and has been implicated in pathologies including metabolic syndromes, neurological disorders and cardiac diseases. Here, we identify that EOLA1 (Endothelium and lymphocyte associated ASCH domain 1) as a novel mitochondrial protein and exclusively localizes to mitochondria matrix. We further show that knockout of EOLA1 dramatically affects mitochondrial translation and subsequently the oxidative phosphorylation in mammalian cells. Mechanistically, EOLA1 interacts with mt-rRNA (mitochondrial ribosomal RNA) and EFTU, which maintains the translation elongation of mitochondrial mRNAs. Importantly, we generated a Eola1 knocked-out mice model and found that heart functions are obviously abnormal upon depletion of EOLA1 homolog in mouse, implying that EOLA1 are important for proper functions of heart via regulating mitochondrial translation. Taken together, our work demonstrates that EOLA1 is a novel regulator for mt-RNA and mitochondrial translation. Overall design: To systematically identify novel molecules involved in the regulation of mitochondrial function, an unbiased positive screening was performed in a cancer cell model using a CRISPRi/Cas9 library. Secondly, considering that EOLA1's ASCH domain likely binds with RNA2, we decided to identify the RNAs targeted by EOLA1 via UV-RIP-seq. We found that EOLA1 protein abundantly interacts with 12S mt-rRNA, which is the RNA component of mitochondrial mt-SSUs.