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Mammalian transcription factor A is a core component of the mitochondrial transcription machinery

Journal article
Authors Yonghong Shi
Anke Dierckx
Paulina Wanrooij
Sjoerd Wanrooij
N. G. Larsson
Marcus Wilhelmsson
Maria Falkenberg
Claes M Gustafsson
Published in Proceedings of the National Academy of Science of the United States of America
Volume 109
Issue 41
Pages 16510-16515
ISSN 0027-8424
Publication year 2012
Published at Institute of Biomedicine, Department of Medical Biochemistry and Cell Biology
Pages 16510-16515
Language en
Subject categories Biophysical chemistry, Spectroscopy, Biochemistry, Molecular biology


Transcription factor A (TFAM) functions as a DNA packaging factor in mammalian mitochondria. TFAM also binds sequence-specifically to sites immediately upstream of mitochondrial promoters, but there are conflicting data regarding its role as a core component of the mitochondrial transcription machinery. We here demonstrate that TFAM is required for transcription in mitochondrial extracts as well as in a reconstituted in vitro transcription system. The absolute requirement of TFAM can be relaxed by conditions that allow DNA breathing, i.e., low salt concentrations or negatively supercoiled DNA templates. The situation is thus very similar to that described in nuclear RNA polymerase II-dependent transcription, in which the free energy of supercoiling can circumvent the need for a subset of basal transcription factors at specific promoters. In agreement with these observations, we demonstrate that TFAM has the capacity to induce negative supercoils in DNA, and, using the recently developed nucleobase analog FRET-pair tC(O)-tC(nitro), we find that TFAM distorts significantly the DNA structure. Our findings differ from recent observations reporting that TFAM is not a core component of the mitochondrial transcription machinery. Instead, our findings support a model in which TFAM is absolutely required to recruit the transcription machinery during initiation of transcription.

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