Human heart mitochondrial DNA is organized in complex catenated networks containing abundant four-way junctions and replication forks.

TitleHuman heart mitochondrial DNA is organized in complex catenated networks containing abundant four-way junctions and replication forks.
Publication TypeJournal Article
Year of Publication2009
AuthorsPohjoismäki, JLO, Goffart, S, Tyynismaa, H, Willcox, S, Ide, T, Kang, D, Suomalainen, A, Karhunen, PJ, Griffith, JD, Holt, IJ, Jacobs, HT
JournalJ Biol Chem
Volume284
Issue32
Pagination21446-57
Date Published2009 Aug 07
ISSN0021-9258
KeywordsAdult, Aged, Animals, Brain, Child, Preschool, DNA, Mitochondrial, Female, Heart, Humans, Male, Mice, Mice, Transgenic, Middle Aged, Nucleic Acid Conformation, Rabbits, Species Specificity, Swine, Tissue Distribution
Abstract

Analysis of human heart mitochondrial DNA (mtDNA) by electron microscopy and agarose gel electrophoresis revealed a complete absence of the -type replication intermediates seen abundantly in mtDNA from all other tissues. Instead only Y- and X-junctional forms were detected after restriction digestion. Uncut heart mtDNA was organized in tangled complexes of up to 20 or more genome equivalents, which could be resolved to genomic monomers, dimers, and linear fragments by treatment with the decatenating enzyme topoisomerase IV plus the cruciform-cutting T7 endonuclease I. Human and mouse brain also contained a population of such mtDNA forms, which were absent, however, from mouse, rabbit, or pig heart. Overexpression in transgenic mice of two proteins involved in mtDNA replication, namely human mitochondrial transcription factor A or the mouse Twinkle DNA helicase, generated abundant four-way junctions in mtDNA of heart, brain, and skeletal muscle. The organization of mtDNA of human heart as well as of mouse and human brain in complex junctional networks replicating via a presumed non- mechanism is unprecedented in mammals.

DOI10.1074/jbc.M109.016600
Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M109.016600
PubMed ID19525233
PubMed Central IDPMC2755869
Grant ListMC_U105663140 / / Medical Research Council / United Kingdom
R01 GM031819 / GM / NIGMS NIH HHS / United States
GM31819 / GM / NIGMS NIH HHS / United States
/ / Medical Research Council / United Kingdom