Dynamics of CTCF- and cohesin-mediated chromatin looping revealed by live-cell imaging.

Gabriele, Michele, Hugo B Brandão, Simon Grosse-Holz, Asmita Jha, Gina M Dailey, Claudia Cattoglio, Tsung-Han S Hsieh, Leonid Mirny, Christoph Zechner, and Anders S Hansen. 2022. “Dynamics of CTCF- and Cohesin-Mediated Chromatin Looping Revealed by Live-Cell Imaging.”. Science (New York, N.Y.) 376 (6592): 496-501.

Abstract

Animal genomes are folded into loops and topologically associating domains (TADs) by CTCF and loop-extruding cohesins, but the live dynamics of loop formation and stability remain unknown. Here, we directly visualized chromatin looping at the Fbn2 TAD in mouse embryonic stem cells using super-resolution live-cell imaging and quantified looping dynamics by Bayesian inference. Unexpectedly, the Fbn2 loop was both rare and dynamic, with a looped fraction of approximately 3 to 6.5% and a median loop lifetime of approximately 10 to 30 minutes. Our results establish that the Fbn2 TAD is highly dynamic, and about 92% of the time, cohesin-extruded loops exist within the TAD without bridging both CTCF boundaries. This suggests that single CTCF boundaries, rather than the fully CTCF-CTCF looped state, may be the primary regulators of functional interactions.

Last updated on 06/23/2023
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