Mechanism of nucleosome disruption and octamer transfer by the chicken SWI/SNF-like complex

We had recently characterized SLC, a SWI/SNF-like chromatin remodelling activity, from chicken liver. The SLC efficiently disrupts nucleosomes, transfers histone octamers from nucleosomal substrates onto acceptor DNA, and slides histone octamers along DNA. Here, we present evidence that SLC is indeed a SWI/SNF homologue, and it disrupts nucleosomes by inducing extensive dynamic helical distortions in the nucleosomal DNA. Both the nucleosome disruption and octamer transfer functions are indifferent to nucleosomal histone tails. We further show that the nucleosome disruption precedes the octamer transfer and that the latter requires continuous presence of ATP. Based on these observations, we propose that a disrupted nucleosome is not a spontaneous substrate for octamer transfer; rather the nucleosome disruption and the octamer transfer are two temporally successive, ATP-dependent events during nucleosome remodelling by SLC in vitro.