The ATP-dependent chromatin remodeling complex SWI/SNF regulates transcription 
and has been implicated in promoter nucleosome eviction. Efficient nucleosome 
disassembly by SWI/SNF alone in biochemical assays, however, has not been 
directly observed. Employing a model system of dinucleosomes rather than 
mononucleosomes, we demonstrate that remodeling leads to ordered and efficient 
disassembly of one of the two nucleosomes. An H2A/H2B dimer is first rapidly 
displaced, and then, in a slower reaction, an entire histone octamer is lost. 
Nucleosome disassembly by SWI/SNF did not require additional factors such as 
chaperones or acceptors of histones. Observations in single molecules as well as 
bulk measurement suggest that a key intermediate in this process is one in which 
a nucleosome is moved toward the adjacent nucleosome. SWI/SNF recruited by the 
transcriptional activator Gal4-VP16 preferentially mobilizes the proximal 
nucleosome and destabilizes the adjacent nucleosome.