Limits of Chromosome Compaction by Loop-Extruding Motors
During mitosis, human chromosomes are linearly compacted about 1000-fold by loop-extruding motors. Recent experiments have shown that condensins extrude DNA loops but in a "one-sided" manner. This contrasts with existing models, which predict that symmetric, "two-sided" loop extr...
| Main Authors: | , |
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| Other Authors: | , |
| Format: | Article |
| Language: | English |
| Published: |
American Physical Society (APS),
2020-07-23T16:11:02Z.
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| Subjects: | |
| Online Access: | Get fulltext |
| Summary: | During mitosis, human chromosomes are linearly compacted about 1000-fold by loop-extruding motors. Recent experiments have shown that condensins extrude DNA loops but in a "one-sided" manner. This contrasts with existing models, which predict that symmetric, "two-sided" loop extrusion accounts for mitotic chromosome compaction. We explore whether one-sided extrusion, as it is currently seen in experiments, can compact chromosomes by developing a mean-field theoretical model for polymer compaction by motors that actively extrude loops and dynamically turnover. The model establishes a stringent upper bound of only about tenfold for compaction by strictly one-sided extrusion. We confirm this result with stochastic simulations. Thus, strictly one-sided extrusion as it has been observed so far cannot be the sole mechanism of chromosome compaction. However, as shown by the model, other two-sided or effectively two-sided mechanisms can achieve sufficient compaction. NSF Physics of Living Systems (Grant 15049420) National Institutes of Health (Grant GM114190) National Institutes of Health (Grant DK107980) |
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