Mitochondrial DNA and RNA Polymerases

Abstract

AbstractMitochondria are vital to cellular activities, both cell growth and programmed death. The organelle contains its own DNA, which codes for a subset of genes oxidative phosphorylation electron transfer chain that couples oxidation–reduction reactions with ATP synthesis. Maintenance of mitochondrial DNA (mtDNA) requires a designated group of proteins that are nuclear encoded and transported to mitochondria. Both DNA and RNA polymerases have bacteriophage origins but have clearly deviated from their ancestors and have combined features of prokaryotic and eukaryotic enzymes. Mitochondrial DNA polymerase, Pol γ performs all DNA synthesis activities in replication and repair. Mammalian Pol γ holoenzyme consists of a catalytic subunit Pol γA and an accessory subunit Pol γB that regulates all activities of the catalytic subunit. Mitochondrial DNA replication and transcription are intimately related, as the mitochondrial transcription machinery provides transcripts for RNA primers for mtDNA replication as well as gene expression. Human mitochondrial DNA and RNA polymerases are adverse reaction targets for antiviral reagents against HIV and hepatitis viruses, and human Pol γ mutations have been implicated in multisystem clinical disorders. Studies of mitochondrial polymerases are therefore of immediate human health importance.KeywordsDNA polymerase gammamtDNA replication and repairantiretroviral drug toxicityMitochondrial RNA transcription