What limits the allotopic expression of nucleus-encoded mitochondrial genes? The case of the chimeric Cox3 and Atp6 genes.
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.
Figueroa-Martínez
Francisco
F
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México DF, Mexico.
Vázquez-Acevedo
Miriam
M
Cortés-Hernández
Paulina
P
García-Trejo
José J
JJ
Davidson
Edgar
E
King
Michael P
MP
González-Halphen
Diego
D
D000818:Animals; D016466:CHO Cells; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics; D006224:Cricetinae; D003412:Cricetulus; D004272:DNA, Mitochondrial / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D050259:Genes, Mitochondrial; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*
D004272:DNA, Mitochondrial; C501005:MT-ATP6 protein, human; D011993:Recombinant Fusion Proteins; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases