This week's main colloquium will be held by Dr. Robert Young of Rutgers University (and App State Alumni). Dr. Young will be giving a talk on "The Twists and Turns of Circular DNA: Biophysical Implications of Protein-DNA Interactions." See this link for access to the zoom meeting. All are welcome to join and learn from this talk!
Abstract: Small extrachrosomal circles of DNA found in eukaryotic cells are associated with a range of functionalities including targeted drug delivery and proliferation of cancer cells. Binding of proteins to the minicircles produces localized distortions that must be alleviated along the neighbouring unbound regions causing the DNA to coil upon itself. DNA minicircles adopt a variety of topoisomers that depend on how writhed and twisted the strands are once the ends are covalently bonded. This talk focuses on a well-studied set of nucleosome-bound circles of lengths less tha 500-bp, where ~140-bp of DNA wraps in a left-handed superhelical pathway about an assembly of eight histone proteins forming a minichromosome. New research from our laboratory shows unexpectedly wide variations in local twist along nucleosomal DNA (in red), This talk will showcase the work done on how the internal twist of nucleosomal DNA influences the global configurations of minicircles of varying lengths obtained by either reducing the size of the minichromosome or by simulating the breathing of the nucleosomal DNA. This is done using a meso-scale approach in calculating the optimized elastic energy of the minichromosomes at the base-pair step level with the nucleosomal DNA constrained to pathways found from well resolved structures.