SWI/SNF Has Intrinsic Nucleosome Disassembly Activity that Is Dependent on Adjacent Nucleosomes

SummaryThe 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.

Graphical AbstractFigure optionsDownload high-quality image (150 K)Download as PowerPoint slideHighlights▸ SWI/SNF efficiently disassembles nucleosomes in the absence of histone acceptors ▸ Nucleosome disassembly by SWI/SNF requires two adjacent nucleosomes ▸ Disassembly is a two-step process with first removal of an H2A/H2B dimer ▸ SWI/SNF mobilizes nucleosomes away from sites bound by transcription factor