title: Discovery of a major D-loop replication origin reveals two modes of human mtDNA synthesis.
abstract: 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.
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fish
authors.forename: Nicola
authors.initials: N
authors.lastname: Raule
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Attardi
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D017931:DNA Primers / Q000378:metabolism; D015342:DNA Probes; D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004996:Ethidium / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism; D009690:Nucleic Acid Conformation; D016133:Polymerase Chain Reaction; D018741:Replication Origin
chemical_list: D017931:DNA Primers; D015342:DNA Probes; D004272:DNA, Mitochondrial; C070331:Tli polymerase; D004259:DNA-Directed DNA Polymerase; D004996:Ethidium