Disruption of reconstituted nucleosomes. The effect of particle concentration, MgCl2 and KCl concentration, the histone tails, and temperature.

We find that reconstituted nucleosome cores containing specific DNA sequences dissociate on dilution. This disruption of histone-DNA contacts leading to the release of free DNA is facilitated by the presence of the core histone tails, MgCl2 (5 mM), KCl (60 mM), and temperatures above 0 degree C. Under reaction conditions that are commonly used to assess trans-acting factor access to nucleosomal DNA, histone-DNA contacts are on the threshold of instability. We demonstrate how dilution of reconstituted nucleosomes containing a TATA box can facilitate TBP access to DNA.