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Nucleic Acids Res. 2013 Jun;41(11):5837-50. doi: 10.1093/nar/gkt196. Epub 2013 Apr 16.

Mitochondrial DNA replication proceeds via a 'bootlace' mechanism involving the incorporation of processed transcripts.

Author information

1
MRC-Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK.

Abstract

The observation that long tracts of RNA are associated with replicating molecules of mitochondrial DNA (mtDNA) suggests that the mitochondrial genome of mammals is copied by an unorthodox mechanism. Here we show that these RNA-containing species are present in living cells and tissue, based on interstrand cross-linking. Using DNA synthesis in organello, we demonstrate that isolated mitochondria incorporate radiolabeled RNA precursors, as well as DNA precursors, into replicating DNA molecules. RNA-containing replication intermediates are chased into mature mtDNA, to which they are thus in precursor-product relationship. While a DNA chain terminator rapidly blocks the labeling of mitochondrial replication intermediates, an RNA chain terminator does not. Furthermore, processed L-strand transcripts can be recovered from gel-extracted mtDNA replication intermediates. Therefore, instead of concurrent DNA and RNA synthesis, respectively, on the leading and lagging strands, preformed processed RNA is incorporated as a provisional lagging strand during mtDNA replication. These findings indicate that RITOLS is a physiological mechanism of mtDNA replication, and that it involves a 'bootlace' mechanism, in which processed transcripts are successively hybridized to the lagging-strand template, as the replication fork advances.

PMID:
23595151
PMCID:
PMC3675460
DOI:
10.1093/nar/gkt196
[Indexed for MEDLINE]
Free PMC Article

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