A Newly Identified Protein Regulates Translation in Mammalian Mitochondria

Abstract

Mitochondria are responsible for providing 90% of the energy in eukaryotic organisms by oxidative phosphorylation (OXPHOS). Mitochondrially encoded components of OXPHOS complexes are all essential and synthesized by a specialized translation system containing 55S ribosomes in mitochondria. In the reevaluation of mitochondrial ribosomal proteins (MRPs) and ribosome‐interacting proteins, we identified Gadd45GIP1 as a bona fide component in purified 55S ribosomes. Here, we report Gadd45GIP1 association with the large subunit of mammalian mitochondrial ribosomes and its role in the regulation of mitochondrial protein synthesis. In siRNA knock‐down studies, reduced expression of Gadd45GIP1 decreased de novo synthesis of the 13 mitochondrially encoded proteins of OXPHOS complexes in vivo. This indicates that the Gadd45GIP1 is an essential member of the mitochondrial ribosome, and its specific role in protein synthesis is currently under investigation.Supported by NIH grant R01GM071034 (E.C.K.)