DNA replication-dependent formation of joint DNA molecules in Physarum polycephalum

Mol Cell. 2001 May;7(5):971-80. doi: 10.1016/s1097-2765(01)00237-4.


Two-dimensional neutral/neutral agarose gel electrophoresis is used extensively to localize replication origins. This method resolves DNA structures containing replication forks. It also detects X-shaped recombination intermediates in meiotic cells, in the form of a typical vertical spike. Intriguingly, such a spike of joint DNA molecules is often detectable in replicating DNA from mitotic cells. Here, we used naturally synchronous DNA samples from Physarum polycephalum to demonstrate that postreplicative, DNA replication-dependent X-shaped DNA molecules are formed between sister chromatids. These molecules have physical properties reminiscent of Holliday junctions. Our results demonstrate frequent interactions between sister chromatids during a normal cell cycle and suggest a novel phase during DNA replication consisting of transient, joint DNA molecules formed on newly replicated DNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Cycle / genetics
  • Chromatids / ultrastructure
  • DNA / ultrastructure*
  • DNA Replication / genetics*
  • Electrophoresis, Gel, Two-Dimensional
  • Hydroxyurea / pharmacology
  • Kinetics
  • Magnesium / pharmacology
  • Physarum polycephalum / genetics*
  • Replication Origin
  • S Phase / genetics
  • Temperature


  • DNA
  • Magnesium
  • Hydroxyurea