Replication of mitochondrial DNA occurs by strand displacement with alternative light-strand origins, not via a strand-coupled mechanism

  1. Timothy A. Brown1,2,6,
  2. Ciro Cecconi3,
  3. Ariana N. Tkachuk1,2,
  4. Carlos Bustamante4, and
  5. David A. Clayton1,5
  1. 1Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA; 2National Institutes of Health, Guest, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892, USA; 3Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; 4Howard Hughes Medical Institute, Department of Molecular and Cell Biology and Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA

Abstract

The established strand-displacement model for mammalian mitochondrial DNA (mtDNA) replication has recently been questioned in light of new data using two-dimensional (2D) agarose gel electrophoresis. It has been proposed that a synchronous, strand-coupled mode of replication occurs in tissues, thereby casting doubt on the general validity of the “orthodox,” or strand-displacement model. We have examined mtDNA replicative intermediates from mouse liver using atomic force microscopy and 2D agarose gel electrophoresis in order to resolve this issue. The data provide evidence for only the orthodox, strand-displacement mode of replication and reveal the presence of additional, alternative origins of lagging light-strand mtDNA synthesis. The conditions used for 2D agarose gel analysis are favorable for branch migration of asymmetrically replicating nascent strands. These data reconcile the original displacement mode of replication with the data obtained from 2D gel analyses.

Keywords

Footnotes

  • Supplemental material is available at http://www.genesdev.org.

  • Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1352105.

  • Corresponding authors.

  • ↵5 E-MAIL clayton{at}hhmi.org; FAX (301) 215-8828.

  • ↵6 E-MAIL brownt{at}hhmi.org; FAX (301) 496-0190.

    • Accepted August 15, 2005.
    • Received July 6, 2005.
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  1. doi: 10.1101/gad.1352105 Genes & Dev. 2005. 19: 2466-2476 Copyright © 2005, by Cold Spring Harbor Laboratory Press

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