Mitochondrial gene therapy: an arena for the biomedical use of inteins.

Mitochondrial DNA (mtDNA) mutations underlie many rare diseases and might also contribute to human ageing. Gene therapy is a tempting future possibility for intervening in mitochondriopathies. Expression of the 13 mtDNA-encoded proteins from nuclear transgenes (allotopic expression) might be the most effective gene-therapy strategy. Its only confirmed difficulty is the extreme hydrophobicity of these proteins, which prevents their import into mitochondria from the cytosol. Inteins (self-splicing 'protein introns') might offer a solution to this problem: their insertion into such transgenes could greatly reduce the encoded proteins' hydrophobicity, enabling import, with post-import excision restoring the natural amino acid sequence.