MTERF4 regulates translation by targeting the methyltransferase NSUN4 to the mammalian mitochondrial ribosome.

Precise control of mitochondrial DNA gene expression is critical for regulation of oxidative phosphorylation capacity in mammals. The MTERF protein family plays a key role in this process, and its members have been implicated in regulation of transcription initiation and site-specific transcription termination. We now demonstrate that a member of this family, MTERF4, directly controls mitochondrial ribosomal biogenesis and translation. MTERF4 forms a stoichiometric complex with the ribosomal RNA methyltransferase NSUN4 and is necessary for recruitment of this factor to the large ribosomal subunit. Loss of MTERF4 leads to defective ribosomal assembly and a drastic reduction in translation. Our results thus show that MTERF4 is an important regulator of translation in mammalian mitochondria.