Transcription and its regulation in mammalian and human mitochondria

In eukaryotic cells mitochondria are the primary source of ATP, which is generated by oxidative phosphorylation. In humans and mammals these organelles contain their own maternally-inherited genome. Defects in mitochondrial gene expression result in a number of human diseases and contribute to aging. Transcription of mitochondrial genes is carried out by unique transcription machinery comprised of a single subunit bacteriophage T7-like mitochondrial RNA polymerase, together with several nuclear-encoded transcription factors. Mitochondrial transcription (and as a consequence oxidative phosphorylation) may be regulated by transcription initiation and termination factors, and by changes in ATP levels in response to alterations of the cell's metabolic demands. Recent data suggest that transcription in mitochondria is also coordinated with other crucial processes such as DNA replication and translation, indicating the importance of studies of molecular mechanisms of mitochondrial gene expression in these organelles.