The SWI/SNF complex creates loop domains in DNA and polynucleosome arrays and can disrupt DNA-histone contacts within these domains

To understand the mechanisms by which the chromatin-remodeling SWI/SNF comp lex interacts with DNA and alters nucleosome organization, we have imaged t he SWI/SNF complex with both naked DNA and nucleosomal arrays by using ener gy-filtered microscopy. By making,STP-independent contacts with DNA at mult iple sites on its surface, SWI/SNF creates Loops, bringing otherwise-distan t sites into close proximity, In the presence of ATP, SWI/SNF action leads to the disruption of nucleosomes within domains that appear to be topologic ally constrained by the complex, The data indicate that the action of one S WI/SNF complex on an array of nucleosomes can lead to the formation of a re gion where multiple nucleosomes are disrupted. Importantly, nucleosome disr uption hy SWI/SNF results in a loss of DNA content from the nucleosomes. Th is indicates a mechanism by which SWI/SNF unwraps part of the nucleosomal D NA.