Replication-transcription switch in human mitochondria

http://www.sciencemag.org/content/347/6221/548.full

Karen Agaronyan, Yaroslav I. Morozov, Michael Anikin and Dmitry Temiakov

Mitochondrial DNA (mtDNA) replication coincides with transcription in both time and space. As such, there is potential for collisions between the separate machineries of these processes to cause detrimental effects. This study elucidates the mechanisms of decision making, between transcription and replication. The authors investigate the effects of human transcription elongation factor (TEFM) binding to mitochondrial RNA polymerase (mtRNAP). The authors suggest that mtRNAP initiates replication of mtDNA when unbound to TEFM,  by transcribing short 120nt replication primers and then falling off of the mtDNA. However, when bound to TEFM, mtRNAP transcribes the entire heavy strand, ready for translation into protein. Thus, TEFM behaves as a molecular switch, toggling between replication and transcription of mtDNA, suggesting they are mutually exclusive processes.