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44403
Topoisomerase
Description
Mind Map on Topoisomerase, created by jessica.woodward on 12/04/2013.
Mind Map by
jessica.woodward
, updated more than 1 year ago
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jessica.woodward
about 11 years ago
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Resource summary
Topoisomerase
Immunodepletion and antibody blocking showed topo II activity required for chr. assembly and condensation
once condensation completed, topo II no longer required - blocking had no effect
Topo II molecules easily extracted from chr. under MILD conditions
Morphology of chr. well preserved
mAb, MPM-2 (recognizes mitosis-specific phosphoproteins) resistant to the same treatment
Localization: Immunofluorescence showed topo II uniformly distributed throughout condensed chr. NOT just axis
Chr. organization and axial structures are maintained after topo II extraction
=> topo II doesn't play a scaffolding role in the structural maintenance of mitotic chromosomes
chr. scaffold = framework structure of nonhistone proteins that organize chromatin loops in mitotic chromosomes
Topo II = enzyme that catalyzes strand passing of double stranded DNA
Type II topoisomerases cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP.
Topo II required for the individualization of chromosomes in vertebrates, and for disentangling replicated sister chromosomes in all oganisms
All eukaryotic cells have at least one type II topoisomerase
Vertebrates have 2 isoforms: topo IIa and topo IIb, with distinct localization patterns in vivo
During mitosis, topo IIa is enriched on chromosomes, whereas topo IIb is mostly cytoplasmic
Topo I
13S condensin (I) is able to introduce +ve supercoils into a closed circular DNA with the help of bacterial/eukaryotic topo I
reaction is ATP dependent
supercoiling
Topo II
Right-handed knots into circular nicked plasmids
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