Nucleic Acids Research Advance Access originally published online on September 15, 2009
Nucleic Acids Research 2009 37(20):6765-6783; doi:10.1093/nar/gkp750
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Nucleic Acids Research, 2009, Vol. 37, No. 20 6765-6783
© The Author(s) 2009. Published by Oxford University Press.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Genome Integrity, Repair and Replication |
Biophysical characterizations of human mitochondrial transcription factor A and its binding to tumor suppressor p53
1MRC Centre for Protein Engineering, Medical Research Council, Hills Road, Cambridge CB2 0QH, UK and 2Xi’an JiaoTong-Liverpool University, 111 Ren Ai Road, Dushu Lake Higher Education Town, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China
*To whom correspondence should be addressed. Tel: +44 1223 402137; Fax: +44 1223 402140; Email: arf25{at}cam.ac.uk
Received July 20, 2009. Revised August 24, 2009. Accepted August 25, 2009.
Human mitochondrial transcription factor A (TFAM) is a multi-functional protein, involved in different aspects of maintaining mitochondrial genome integrity. In this report, we characterized TFAM and its interaction with tumor suppressor p53 using various biophysical methods. DNA-free TFAM is a thermally unstable protein that is in equilibrium between monomers and dimers. Self-association of TFAM is modulated by its basic C-terminal tail. The DNA-binding ability of TFAM is mainly contributed by its first HMG-box, while the second HMG-box has low-DNA-binding capability. We also obtained backbone resonance assignments from the NMR spectra of both HMG-boxes of TFAM. TFAM binds primarily to the N-terminal transactivation domain of p53, with a Kd of 1.95 ± 0.19 µM. The C-terminal regulatory domain of p53 provides a secondary binding site for TFAM. The TFAM–p53-binding interface involves both TAD1 and TAD2 sub-domains of p53. Helices 
1 and 2 of the HMG-box constitute the main p53-binding region. Since both TFAM and p53 binds preferentially to distorted DNA, the TFAM–p53 interaction is implicated in DNA damage and repair. In addition, the DNA-binding mechanism of TFAM and biological relevance of the TFAM–p53 interaction are discussed.