The interplay between asymmetric and symmetric DNA loop extrusion
- Massachusetts Institute of Technology, United States
Abstract
Chromosome compaction is essential for reliable transmission of genetic information. Experiments suggest that ~ 1000-fold compaction is driven by condensin complexes that extrude chromatin loops, i.e., progressively collect chromatin fiber from one or both sides of the complex to form a growing loop. Theory indicates that symmetric two-sided loop extrusion can achieve such compaction, but recent single-molecule studies (Golfier et al., 2020) observed diverse dynamics of condensins that perform one-sided, symmetric two-sided, and asymmetric two-sided extrusion. We use simulations and theory to determine how these molecular properties lead to chromosome compaction. High compaction can be achieved if even a small fraction of condensins have two essential properties: a long residence time and the ability to perform two-sided (not necessarily symmetric) extrusion. In mixtures of condensins I and II, coupling two-sided extrusion and stable chromatin binding by condensin II promotes compaction. These results provide missing connections between single-molecule observations and chromosome-scale organization.
Data availability
Software used to perform simulations is publicly and freely available at https://github.com/mirnylab/one_sided_extrusion/tree/master/mitotic. Data analyzed from single-molecule experiments was previously published as part of Golfier et al. eLife 9:e53885 (2020).
Article and author information
Author details
Funding
National Institutes of Health (U54DK107980)
- Edward J Banigan
- Leonid A Mirny
National Institutes of Health (U54CA193419)
- Edward J Banigan
- Leonid A Mirny
National Institutes of Health (GM114190)
- Edward J Banigan
- Leonid A Mirny
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Banigan & Mirny
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The interplay between asymmetric and symmetric DNA loop extrusion
eLife 9:e63528.
https://doi.org/10.7554/eLife.63528
