Nucleic Acids Research Advance Access originally published online on November 26, 2007
Nucleic Acids Research 2008 36(2):393-403; doi:10.1093/nar/gkm1025
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2008, Vol. 36, No. 2 393-403
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
The N-terminal domain of TWINKLE contributes to single-stranded DNA binding and DNA helicase activities
1Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm and 2Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
*To whom correspondence should be addressed. Tel: +46 8 58583730; Fax: +46 8 779 5383; Email: maria.falkenberg{at}ki.se
Received March 5, 2007. Revised October 4, 2007. Accepted October 29, 2007.
The TWINKLE protein is a hexameric DNA helicase required for replication of mitochondrial DNA. TWINKLE displays striking sequence similarity to the bacteriophage T7 gene 4 protein (gp4), which is a bi-functional primase-helicase required at the phage DNA replication fork. The N-terminal domain of human TWINKLE contains some of the characteristic sequence motifs found in the N-terminal primase domain of the T7 gp4, but other important motifs are missing. TWINKLE is not an active primase in vitro and the functional role of the N-terminal region has remained elusive. In this report, we demonstrate that the N-terminal part of TWINKLE is required for efficient binding to single-stranded DNA. Truncations of this region reduce DNA helicase activity and mitochondrial DNA replisome processivity. We also find that the gp4 and TWINKLE are functionally distinct. In contrast to the phage protein, TWINKLE binds to double-stranded DNA. Moreover, TWINKLE forms stable hexamers even in the absence of Mg2+ or NTPs, which suggests that an accessory protein, a helicase loader, is needed for loading of TWINKLE onto the circular mtDNA genome.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Goffart, H. M. Cooper, H. Tyynismaa, S. Wanrooij, A. Suomalainen, and J. N. Spelbrink Twinkle mutations associated with autosomal dominant progressive external ophthalmoplegia lead to impaired helicase function and in vivo mtDNA replication stalling Hum. Mol. Genet., January 15, 2009; 18(2): 328 - 340. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. H. Hakonen, S. Goffart, S. Marjavaara, A. Paetau, H. Cooper, K. Mattila, M. Lampinen, A. Sajantila, T. Lonnqvist, J. N. Spelbrink, et al. Infantile-onset spinocerebellar ataxia and mitochondrial recessive ataxia syndrome are associated with neuronal complex I defect and mtDNA depletion Hum. Mol. Genet., December 1, 2008; 17(23): 3822 - 3835. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Matsushima, C. L. Farr, L. Fan, and L. S. Kaguni Physiological and Biochemical Defects in Carboxyl-terminal Mutants of Mitochondrial DNA Helicase J. Biol. Chem., August 29, 2008; 283(35): 23964 - 23971. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Wanrooij, J. M. Fuste, G. Farge, Y. Shi, C. M. Gustafsson, and M. Falkenberg Human mitochondrial RNA polymerase primes lagging-strand DNA synthesis in vitro PNAS, August 12, 2008; 105(32): 11122 - 11127. [Abstract] [Full Text] [PDF]
|
|