Fully wrapped lifetime of nucleosome

Value 0.25 sec
Organism Eukaryotes
Reference Li G, Levitus M, Bustamante C, Widom J. Rapid spontaneous accessibility of nucleosomal DNA. Nat Struct Mol Biol. 2005 Jan12(1):46-53.PubMed ID15580276
Method Studies using fluorescence resonance energy transfer (FRET) reveal that site exposure involves large increases in separation between a fluorescence donor on one end of the nucleosomal DNA and a fluorescence acceptor on the histone core, implying that site exposure occurs by progressive unwrapping of the nucleosomal DNA starting from one end of the nucleosome. A second approach is based on fluorescence correlation spectroscopy (FCS) of small numbers of nucleosomes at a time, diffusing freely in dilute solution.
Comments The opening rate constant (k12) of approximately 4 s-1 corresponds to a lifetime in the fully wrapped state (tau wrapped) = 1/k12 250 ms. Nucleosomes in solution look like those imaged by crystallography only for very short periods of time, < <1 s, before undergoing a large-scale spontaneous unwrapping event.
Entered by Uri M
ID 103090