MRPL12 is a component of the 39S subunit of mammalian mitochondrial ribosomes, and is encoded by a nuclear gene. The protein forms a homodimer, localizes predominantly to mitochondria and binds to the large mitochondrial ribosomal subunit. It is required for CycD/Cdk4- induced cell growth. In addition, forming a ribosomal stalk with MRPL7, MRPL12 is required for the recruitment of translation elongation factors Tu and G to the large ribosomal subunit . It also a part of a novel regulatory mechanism that coordinates mitochondrial transcription with translation and/or ribosome biogenesis during human mitochondrial gene expression.