Low levels of mitochondrial transcription factor A in mitochondrial DNA depletion.

Low levels of mitochondrial transcription factor A (mtTFA) were found in muscle fibers with mitochondrial DNA (mtDNA) depletion in a child with fatal mitochondrial myopathy and also in a human cell line lacking mtDNA. High levels of this transcriptional activator were found in muscle fibers with mtDNA accumulation in two patients with single mtDNA deletions. This is the first example of a nuclear gene product that varies with the levels of mtDNA in humans. Since transcription is required for the replication of mtDNA, it is possible that mtTFA may be involved in the regulation of mtDNA replication.