2019 EJRNL PP EDWARD J. BANIGAN 1.pdf
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Terbatas Ratnasari
» ITB
Terbatas Ratnasari
» ITB
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.