What limits the allotopic expression of nucleus-encoded mitochondrial genes? The case of the chimeric Cox3 and Atp6 genes

Mitochondrion. 2011 Jan;11(1):147-54. doi: 10.1016/j.mito.2010.09.003. Epub 2010 Sep 18.


Allotopic expression is potentially a gene therapy for mtDNA-related diseases. Some OXPHOS proteins like ATP6 (subunit a of complex V) and COX3 (subunit III of complex IV) that are typically mtDNA-encoded, are naturally nucleus-encoded in the alga Chlamydomonas reinhardtii. The mitochondrial proteins whose genes have been relocated to the nucleus exhibit long mitochondrial targeting sequences ranging from 100 to 140 residues and a diminished overall mean hydrophobicity when compared with their mtDNA-encoded counterparts. We explored the allotopic expression of the human gene products COX3 and ATP6 that were re-designed for mitochondrial import by emulating the structural properties of the corresponding algal proteins. In vivo and in vitro data in homoplasmic human mutant cells carrying either a T8993G mutation in the mitochondrial atp6 gene or a 15bp deletion in the mtDNA-encoded cox3 gene suggest that these human mitochondrial proteins re-designed for nuclear expression are targeted to the mitochondria, but fail to functionally integrate into their corresponding OXPHOS complexes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cell Nucleus / enzymology*
  • Cell Nucleus / genetics
  • Chlamydomonas reinhardtii / enzymology*
  • Chlamydomonas reinhardtii / genetics
  • Cricetinae
  • Cricetulus
  • DNA, Mitochondrial / genetics
  • Electron Transport Complex IV / genetics
  • Electron Transport Complex IV / metabolism*
  • Genes, Mitochondrial*
  • Genetic Therapy / methods
  • Humans
  • Microscopy, Fluorescence
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Mitochondria / metabolism
  • Mitochondrial Proton-Translocating ATPases / genetics
  • Mitochondrial Proton-Translocating ATPases / metabolism*
  • Mutation
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism*


  • DNA, Mitochondrial
  • MT-ATP6 protein, human
  • Recombinant Fusion Proteins
  • Electron Transport Complex IV
  • Mitochondrial Proton-Translocating ATPases