Discovery of a major D-loop replication origin reveals two modes of human mtDNA synthesis

Science. 2004 Dec 17;306(5704):2098-101. doi: 10.1126/science.1102077.


Mammalian mitochondrial DNA (mtDNA) replication has long been considered to occur by asymmetric synthesis of the two strands, starting at the multiple origins of the strand-displacement loop (D-loop). We report the discovery of a major replication origin at position 57 in the D-loop of several human cell lines (HeLa, A549, and 143B.TK-) and immortalized lymphocytes. The nascent chains starting at this origin, in contrast to those initiated at the previously described origins, do not terminate prematurely at the 3' end of the D-loop but proceed well beyond this control point, behaving as "true" replicating strands. This origin is mainly responsible for mtDNA maintenance under steady-state conditions, whereas mtDNA synthesis from the formerly identified D-loop origins may be more important for recovery after mtDNA depletion and for accelerating mtDNA replication in response to physiological demands.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Cell Line, Tumor
  • DNA Primers / metabolism
  • DNA Probes
  • DNA Replication*
  • DNA, Mitochondrial / biosynthesis*
  • DNA, Mitochondrial / chemistry
  • DNA, Mitochondrial / metabolism
  • DNA-Directed DNA Polymerase / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Ethidium / pharmacology
  • HeLa Cells
  • Humans
  • Lymphocytes / metabolism
  • Nucleic Acid Conformation
  • Polymerase Chain Reaction
  • Replication Origin*


  • DNA Primers
  • DNA Probes
  • DNA, Mitochondrial
  • Tli polymerase
  • DNA-Directed DNA Polymerase
  • Ethidium