A pathway for mitotic chromosome formation

Science. 2018 Feb 9;359(6376):eaao6135. doi: 10.1126/science.aao6135. Epub 2018 Jan 18.


Mitotic chromosomes fold as compact arrays of chromatin loops. To identify the pathway of mitotic chromosome formation, we combined imaging and Hi-C analysis of synchronous DT40 cell cultures with polymer simulations. Here we show that in prophase, the interphase organization is rapidly lost in a condensin-dependent manner, and arrays of consecutive 60-kilobase (kb) loops are formed. During prometaphase, ~80-kb inner loops are nested within ~400-kb outer loops. The loop array acquires a helical arrangement with consecutive loops emanating from a central "spiral staircase" condensin scaffold. The size of helical turns progressively increases to ~12 megabases during prometaphase. Acute depletion of condensin I or II shows that nested loops form by differential action of the two condensins, whereas condensin II is required for helical winding.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Animals
  • Cell Line
  • Chromosomes / chemistry*
  • Chromosomes / genetics*
  • Computational Biology
  • DNA-Binding Proteins / metabolism
  • Genomics
  • Interphase
  • Mitosis*
  • Multiprotein Complexes / metabolism
  • Prometaphase
  • Prophase
  • Xenopus laevis


  • DNA-Binding Proteins
  • Multiprotein Complexes
  • condensin complexes
  • Adenosine Triphosphatases