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Pathways of DNA unlinking: A story of stepwise simplification.

Abstract:
In Escherichia coli DNA replication yields interlinked chromosomes. Controlling topological changes associated with replication and returning the newly replicated chromosomes to an unlinked monomeric state is essential to cell survival. In the absence of the topoisomerase topoIV, the site-specific recombination complex XerCD- dif-FtsK can remove replication links by local reconnection. We previously showed mathematically that there is a unique minimal pathway of unlinking replication links by reconnection while stepwise reducing the topological complexity. However, the possibility that reconnection preserves or increases topological complexity is biologically plausible. In this case, are there other unlinking pathways? Which is the most probable? We consider these questions in an analytical and numerical study of minimal unlinking pathways. We use a Markov Chain Monte Carlo algorithm with Multiple Markov Chain sampling to model local reconnection on 491 different substrate topologies, 166 knots and 325 links, and distinguish between pathways connecting a total of 881 different topologies. We conclude that the minimal pathway of unlinking replication links that was found under more stringent assumptions is the most probable. We also present exact results on unlinking a 6-crossing replication link. These results point to a general process of topology simplification by local reconnection, with applications going beyond DNA.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1038/s41598-017-12172-2

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Grant:
099204/Z/12Z
200782/Z/16/Z


Publisher:
Nature Research
Journal:
Scientific Reports More from this journal
Volume:
7
Issue:
1
Article number:
12420
Publication date:
2017-09-29
Acceptance date:
2017-09-01
DOI:
EISSN:
2045-2322
Pmid:
28963549


Language:
English
Keywords:
Pubs id:
pubs:732958
UUID:
uuid:e6920738-0682-432a-95ac-e745e564b7e7
Local pid:
pubs:732958
Source identifiers:
732958
Deposit date:
2019-07-03

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