Fig. 5. Distinct roles for condensin I and II in mitotic chromosome formation.

(A) Genome-wide curves of contact frequency P(s) vs genomic distance s, normalized to unity at s=100 kb. The curves are P(s) derived from Hi-C data obtained from CAP-H2-depleted (left panel) and CAP-H-depleted cells (right panel), at t = 7–60 minutes after release from G₂ arrest. Dashed line indicates P(s) = s^−0.5. (B) Overlayed P(s) curves of WT, CAP-H-and CAP-H2-depleted chromosomes show independent contributions of two condensin complexes to short- and long-distance contacts. (C) Polymer models of CAP-H2 (top) and CAP-H (bottom) depleted chromosomes. Top: depletion of CAP-H2 is modeled via removal of outer loops and relaxation of the helix.. Bottom: depletion of CAP-H is modeled via removal of the inner loops, while preserving the helical arrangement of the scaffold. Condensin II loop anchors are shown in red, condensin I loop anchors are shown in blue. (D) P(s) derived from late prometaphase CAP-H2 depletion Hi-C experiments (red line) and the three best fitting polymer models (grayscale lines). The average loop size and linear density of loops along the chromosome axis are indicated. (E) The average loop size and linear DNA density of the 3 best-fitting models of CAP-H2-depleted chromosomes at different time points. (F) P(s) derived from late prometaphase CAP-H depletion Hi-C experiments (blue line) and the best fitting polymer models with and without nested inner loops (grayscale lines). The average size of outer and inner loops, the length of a helix turn in Mb and the helical pitch are indicated. (G) The best fitting P(s) predictions by the staircase coarse grained model for late prometaphase CAP-H depletion Hi-C experiments at t = 30 minutes after release of G₂ arrest (gray lines; experimental P(s): red lines. Top: loop size is 200 kb, bottom: loop size is 400 kb.