Figure 10:

Conformation of legs produced by active loop extrusion. A) Schematic of legs, each with genomic length $g_{leg}(t)\sim {\left(v_{ex}t\right)}^{1/D}$ and mean square size $<r_{leg}^2(t)>\sim {\left(v_{ex}t\right)}^{2/D}$. The left-hand schematic shows the initial chromatin conformation with fractal dimension $D$ at the time of cohesin binding. The right-hand schematic shows leg extension at time $t$. B) Mean square distance between cohesin and a locus $s_{c,out}$ away outside of its extruded loop at different times after binding (solid lines) compared to $<r_0^2\left(s_{c,out}+v_{ex}t\right)>$, the unperturbed mean squared sizes of sections with genomic lengths $s_{c,out}+v_{ex}t$ (dashed lines), from hybrid MD—MC simulations of single cohesins actively extruding a relaxed polymer chain $(D\approx 2)$ with $v_{ex}\approx 0.3\mathrm{k}\mathrm{b}\mathrm{p}$ per ${\tau }_0(\kappa \approx 0.15)$. The solid black line is the predicted limiting behavior for full polymer extension. The solid green curve is the unperturbed mean square sizes of sections with genomic length $s_{c,out}$. The dashed green line is the predicted scaling behavior of these unperturbed sizes without extrusion.