MCELLBI 110 Lecture Notes - Lecture 2: Conformational Change, Nucleosome, Histone H2B
24 Feb 2021
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Lecture #2: the scope of the problem, dna must be compacted approximately 10^6 fold. Human mitochondrial genome: circle, 0. 04% of the size of chromosome 21, protein coding genes, trna. Imposing a writhe, the crossing of double helix over itself. N terminus of each histone is unstructured and projects outward from nucleosome: tails are stretched outside the dna, histone n-termini, euphemistically called histone tails . Dna loop emerges from the lumen of the condensing ring: other hypotheses though. Advances in optical imaging allow dna enzymology at the single molecule level. Single molecule assay for the visualization of condesin mediated dna looping: biotin, biotinylated nucleotides added to ends of dna molecule, protein that has binding sites for biotin binds to dna or end of the slide, so tacks the. Topological constraints: bacterial chromosomes and plasmids are circular. How the loops are formed: a. growing loops is stabilized as cohesion rings encounter two ctcf binding motifs pointing into the loop, b.
