The transcription machinery in mammalian mitochondria.

Initiation of transcription at mitochondrial promoters in mammalian cells requires the simultaneous presence of a monomeric mitochondrial RNA polymerase, mitochondrial transcription factor A, and either transcription factor B1 or B2. We here review recent progress in our understanding of how these basal factors cooperate in the initiation and regulation of mitochondrial transcription. We describe the evolutionary origin of individual transcription factors and discuss how these phylogenetic relationships may facilitate a molecular understanding of the mitochondrial transcription machinery.