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. Author manuscript; available in PMC: 2016 Oct 7.
Published in final edited form as: FEBS Lett. 2015 Sep 10;589(20 0 0):3031–3036. doi: 10.1016/j.febslet.2015.09.004

Figure 2.

Figure 2

Mechanistic ensembles based on loop extrusion can explain interphase and metaphase chromosomal organization. Left: In a model of loop extrusion, Loop Extruding Factors (LEFs) bind to chromatin and extrude a progressively larger loop [52]. Top: In interphase, a TAD organization can be achieved with a low density of LEFs that stall at boundary elements, potentially inwards-oriented CTCF sites [55]. Bottom: In metaphase, a homogeneous contact map with a slowly-decaying contact probability in agreement with experimental Hi-C maps can be achieved via loop extrusion as well. However, in this case the density of LEFs is higher and boundary elements are no longer present. In this case, LEFs extrude all available chromatin fiber, and form an array of consecutive loops [20].