SWI/SNF has intrinsic nucleosome disassembly activity that is dependent on adjacent nucleosomes.
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.
Dechassa
Mekonnen Lemma
ML
Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901-4413, USA.
Sabri
Abdellah
A
Pondugula
Santhi
S
Kassabov
Stefan R
SR
Chatterjee
Nilanjana
N
Kladde
Michael P
MP
Bartholomew
Blaine
B
D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D002874:Chromosome Mapping; D008958:Models, Molecular; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
D002868:Chromosomal Proteins, Non-Histone; D009707:Nucleosomes; C445179:SWI-SNF-B chromatin-remodeling complex; D014157:Transcription Factors