Search

Human mitochondria contain their own genome, mtDNA. This small molecule encodes 24 RNA species and 13 polypeptides, which are essential components of the mitochondrial respiratory chain. The mitochondrial genome is present in hundreds or thousands of copies in each cell and is believed to turnover throughout the life of the cell. Defects of the mitochondrial genome (mtDNA) cause a variety of multisystemic disorders routinely affecting the muscle and nervous system. There is currently no effective treatment for patients with defects of the mitochondrial genome. In many patients, defective cells harbour two sub-populations of mtDNA (a situation termed heteroplasmy), one being normal, the other containing the pathogenic mutation. The mutated copy is often recessive, with biochemical and clinical defects only becoming apparent when the levels of mutated mtDNA outweigh the normal copies. It has therefore been postulated that by selectively preventing replication of the mutated mtDNA, the normal copy will propagate, restoring biochemical function. The search has therefore been on during recent years to identify an antigenomic molecule that will fulfil this criterion. Following evidence that peptide nucleic acids could selectively inhibit replication of templates carrying a known pathogenic mtDNA mutation in vitro, we report on the progress of this approach and the various modifications that are now being used to improve the efficacy of PNA-based antigenomic inhibition. [ABSTRACT FROM AUTHOR]

Although the precise mechanisms of the aging process remain poorly understood, a plausible theory for cellular dysfunction and deterioration during aging involves mitochondria (1, 2). The major function of mitochondria is to generate energy for cellular processes in the form of ATP by oxidative phosphorylation. Mitochondria contain their own DNA (mtDNA), a small 16.5 kb circular molecule that encodes 13 essential polypeptides of the mitochondrial respiratory chain, as well as 2 rRNAs and 22 tRNAs required for intramitochondrial protein synthesis (3). The mitochondrial respiratory chain is a series of five, multisubunit protein complexes located within the inner mitochondrial membrane. The first four of these (complexes I-IV) reoxidize reduced cofactors (NADH and FADH2) generated by the oxidation of foodstuffs, thereby generating an electrochemical gradient across the inner mitochondrial membrane which is harnessed by the fifth complex, the ATP synthetase, to drive the formation of ATP. [ABSTRACT FROM AUTHOR]