Chromatin remodeling by ISW2 and SWI/SNF requires DNA translocation inside the nucleosome.
Chromatin-remodeling complexes regulate access to nucleosomal DNA by mobilizing nucleosomes in an ATP-dependent manner. In this study, we find that chromatin remodeling by SWI/SNF and ISW2 involves DNA translocation inside nucleosomes two helical turns from the dyad axis at superhelical location-2. DNA translocation at this internal position does not require the propagation of a DNA twist from the site of translocation to the entry/exit sites for nucleosome movement. Nucleosomes are moved in 9- to 11- or approximately 50-base-pair increments by ISW2 or SWI/SNF, respectively, presumably through the formation of DNA loops on the nucleosome surface. Remodeling by ISW2 but not SWI/SNF requires DNA torsional strain near the site of translocation, which may work in conjunction with conformational changes of ISW2 to promote nucleosome movement on DNA. The difference in step size of nucleosome movement by SWI/SNF and ISW2 demonstrates how SWI/SNF may be more disruptive to nucleosome structure than ISW2.
Zofall
Martin
M
Department of Biochemistry and Molecular Biology, 1245 Lincoln Drive Neckers 229, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-4413, USA.
Persinger
Jim
J
Kassabov
Stefan R
SR
Bartholomew
Blaine
B
D021581:Active Transport, Cell Nucleus; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000378:metabolism; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; C086468:ISWI protein; D046911:Macromolecular Substances; D009707:Nucleosomes; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000251:Adenosine Triphosphatases