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. 2020 May 28;21(11):3820. doi: 10.3390/ijms21113820

Figure 2.

Figure 2

Models of coordination of human mitochondrial and cytosolic translation programs during OXPHOS assembly. Mitochondrial translation exhibits plasticity in coordination with nuclear gene expression by three possible translational regulatory systems identified in humans. (A) MITRAC15 binds to MT-ND2 in a complex with mitoribosome to promote its translation and assembly into CI. ACAD9, a CI assembly factor encoded by the nuclear genome, associates ND2 polypeptides specifically downstream of MITRAC15 for assembly of the ND2 subunit into CI. (B) C12orf62 and MITRAC12 act specifically on mitoribosomes translating MT-CO1 mRNA and as members of the early COX1 assembly intermediates to promote MT-CO1 translation. The nuclear-encoded COX4 subunit of CIV post-translationally facilitates completion of CIV assembly by binding to the C12orf62/MITRAC12/nascent COX1 protein complex. (C) The translational activator TACO1 is hypothesized to bind 5′ end of mtDNA-encoded MT-CO1 mRNA for the induction of nascent COX1 synthesis to be assembled into CIV. Abbreviations are as follows: SSU: small ribosomal subunit, LSU: large ribosomal subunit, mt-SSU: mitochondrial small ribosomal subunit, mt-LSU: mitochondrial large ribosomal subunit, TACO1: translational activator of cytochrome c oxidase I, COX1: cytochrome c oxidase subunit 1, COX4: cytochrome c oxidase subunit 4, C12orf62: cytochrome c oxidase assembly protein COX14, MITRAC12: mitochondrial translation regulation assembly intermediate of cytochrome c oxidase protein of 12 kDa, ACAD9: Acyl-CoA dehydrogenase family member 9, MITRAC15: mitochondrial translation regulation assembly intermediate of cytochrome c oxidase protein of 15 kDa.