The circular DNA of human mitochondria must be both replicated and transcribed. For transcription, the RNA polymerase ‘train’ requires a protein called TEFM. This drawings shows how TEFM acts as a ‘cowcatcher’ that deflects obstacles from secondary structures in the RNA – like a steam locomotive breaking through a barricade. Replication, on the other hand, occurs in the absence of TEFM, when transcription terminates prematurely generating primers for replication.
Check out the two Cell papers by Hauke Hillen from the Cramer Lab and the Temiakov lab here and here!
