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Fig. 3 Cohesin forms fountains via loop extrusion. (A) Example Hi-C snapshot of left-directed fountain in control, SMC-3-, and WAPL-1-depletion conditions. (From top to bottom rows) The observed balanced matrix, distance-decay normalized observed-over-expected matrix, and insulation score using 30 kb window and 500 bp step. Black lines indicate the condition (control of depletions); red lines, the condition minus the control; and the purple vertical line, identified fountain origins. (B) Example Hi-C snapshot of right-directed fountain. (C) Cartoon trajectory of left-directed fountain (A) arising from two-sided loop-extruding factor reeling in DNA faster on the left than right side. (D) Contact probability, P(s), as a function of linear genomic separation between pairs of loci, s (top), and its log-derivative, the slopes of P(s) in log-space (bottom), are plotted for three conditions in different colors. The inferred average loop size for cohesin in unperturbed state (red) and the extended average loop size for cohesin in WAPL-1 depletion (blue) are annotated. (E) On-diagonal pileup of observed-over-expected matrix centered at the fountain origins grouped into four quantiles based on the fountain strength.