Intermediates in the replication of kinetoplast DNA minicircles

P. A. Kitchin, V. A. Klein, P. T. Englund

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Kinetoplast DNA of Crithidia fasciculata and other trypanosomatids is in the form of a network of thousands of minicircles and a few dozen maxicircles. Minicircles replicate as free molecules after release from the network, and their progeny subsequently reattach to the network (Englund, P.T. (1979) J. Biol. Chem 254, 4895-4900). The minicircles just released from the network are covalently closed and apparently completely relaxed. After Cairns-type (θ) replication, the two minicircle progeny have different structures. One has a nascent H (heavy) strand which initially is in the form of 20-110 nucleotide fragments that are separated by gaps (Kitchin, P.A., Klein, V.A., Fein, B.I., and Englund, P.T. (1984) J. Biol. Chem. 259, 15532-15539). The other initially has a full-size (2.5 kilobase) nascent L (light) strand. During the time between formation of these progeny molecules and network reattachment, the nascent L strand is nicked (or gapped) and nascent H strand is partially repaired. Therefore, both progeny, at the time of reattachment, have several nicks (or gaps) in their nascent strand. Minicircle progeny with a nascent L strand reattach to the network quickly, whereas those with a nascent H strand reattach more slowly. Once reattached to the network, the nicks or gaps in the minicircles are repaired until finally covalent closure occurs.

Original languageEnglish (US)
Pages (from-to)3844-3851
Number of pages8
JournalJournal of Biological Chemistry
Issue number6
StatePublished - 1985

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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