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SUMMARY:DNA nanoscopy to decipher the hierarchical nature of chromosomes -
  Dr Kirti Prakash\, Dept. of Paediatrics\, University of Cambridge
DTSTART:20190712T143000Z
DTEND:20190712T151000Z
UID:TALK127078@talks.cam.ac.uk
CONTACT:Paula Bibby
DESCRIPTION:DNA is a long polymer with a double-helix geometry. A helix is
  probably the most refined structure by which two polymers may couple and 
 provide a pairing mechanism for maximally effective replication. The helix
  then wraps around octamers of histone proteins to form nucleosomes in a f
 ascinating beads-on-a-string structure. At the final order of compaction\,
  DNA organises itself into globules called chromosome territories.\n\nSome
  outstanding questions in the chromosome biology are: how do 10-nm “bead
 -on-a-strings” nucleosomes fold into 1000-nm size chromosome territories
 ? Are there intermediary chromatin domains? If so\, of what size and shape
 ? And how do they regulate chromatin folding? Does 30-nm chromatin fibre e
 xist? Are chromosomes territories coacervates? \n\nWe have developed a new
  method to image DNA in high-resolution and found at least three distinct 
 orders of chromatin states: 30-60 nm (active phase)\, 120-150 nm (represse
 d phase) and 250-500 nm (inactive phase). These domains are organised in p
 eriodic and symmetric compartments\, indicating the spatial organisation o
 f active and inactive regions of the genome. Moreover\, we found that\, un
 der stress\, chromatin dynamically remodels and adapts to hollow\, condens
 ed ring and rod-like configurations\, which reverse back to the original s
 tructure when stress conditions cease.\n\nHere\, I propose an alternative 
 classification of higher-order states of DNA based on domain sizes and top
 ological shapes. I also examine the biophysical aspects of DNA condensatio
 n and the role of sequence information (both nucleic and protein) in drivi
 ng the reversible folding of DNA.
LOCATION:Marjory Stephenson Seminar Room\, Hopkins Building\, Dept of Bioc
 hemistry
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