A study on the human mitochondrial RNA polymerase activity points to existence of a transcription factor B-like protein

In the present work, the RNA polymerase activity of the human mitochondrial RNA polymerase mature protein (h-mtRPOLin) is shown, and its molecular activity calculated (2.1 +/- 0.9 min(-1)). An activity analysis of h-mtRPOLm and deleted versions of it has demonstrated that the entire recombinant protein is required for this activity. In addition, h-mtRPOLm alone or in presence of the known mitochondrial transcription factors (human mitochondrial transcription factor A and/or human mitochondrial transcription termination factor) is not able to initiate transcription from the specific human mitochondrial promoters pointing to the existence of a human mitochondrial transcription factor B-like protein. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.