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Title: DNA catenation along native budding yeast chromosomes
Author: Mariezcurrena Antón, A.
ISNI:       0000 0004 8498 515X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Despite the discovery of the double helical structure of DNA in 1953 by Watson and Crick, there are still many aspects of DNA topology that are not well understood. DNA catenation arises as a consequence of replication and results in the physical interlinking between replicated sister chromatids. Catenanes must be resolved prior to chromosome segregation; failure to do so can result in chromosome segregation errors and consequent aneuploidy. Type II topoisomerases, a highly conserved and essential class of enzymes, are the main decatenases in the cell. When and where catenation arises along authentic eukaryotic chromosomes, where it persists, and when and where it is resolved, is poorly understood. This is mainly due to the technical difficulties of visualizing intertwines between linear DNA molecules. We describe here our attempt to study catenation of native budding yeast chromosomes by looping out segments of linear chromosomes as DNA circles. We used site-specific recombination to excise chromosomal regions of 8 to 18 kb. The topoisomer pattern produced circular monomers that were accompanied by slower migrating bands whose behaviour is consistent with that of catenanes. They appear during DNA replication, and are resolved by topoisomerase II treatment in vitro. We find catenanes at replication termination regions and cohesin binding sites, where catenanes are expected to arise and persist, but not to a greater extent than elsewhere in the genome. We propose that once formed, catenanes distribute freely along chromosomes. Moreover, we provide evidence for precatenane formation, as DNA intertwinings between loop outs during replication elongation but before termination are detected. This approach allows us to provide previously inaccessible insight into the topology of eukaryotic chromosomes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available