MTERF4 (mitochondrial transcription termination factor 4) is a critical regulator of mitochondrial ribosome biogenesis and translation. The protein functions as a scaffold that recruits the RNA methyltransferase NSUN4 to the large mitochondrial ribosomal subunit (39S) 1, facilitating essential rRNA modifications required for ribosome assembly 2. MTERF4 contains structurally repeated MTERF-motifs forming a nucleic acid binding domain that creates an RNA binding path for both MTERF4 and NSUN4 1, and mutations disrupting this complex formation impair mitochondrial ribosome biogenesis 3. MTERF4 regulates expression of mitochondrial DNA-encoded respiratory chain proteins by controlling mitochondrial translation 4. In brown adipocytes, MTERF4 is essential for oxidative phosphorylation complex assembly and thermogenic capacity; MTERF4 deficiency impairs complex I, III, and IV assembly and reduces respiratory capacity 4. Beyond thermogenesis, MTERF4 dysfunction is implicated in neurodegenerative diseases: knockdown worsens MPP⁺-induced mitochondrial dysfunction in Parkinson's disease models 5, and MTERF4 overexpression promotes amyloidogenic APP processing in Alzheimer's disease models 6. These findings establish MTERF4 as a key regulator of mitochondrial protein synthesis with relevance to metabolic and neurodegenerative diseases.