A 'loop recapture' mechanism for ACF-dependent nucleosome remodeling.
The ATPase ISWI is the molecular motor of several nucleosome remodeling complexes including ACF. We analyzed the ACF-nucleosome interactions and determined the characteristics of ACF-dependent nucleosome remodeling. In contrast to ISWI, ACF interacts symmetrically with DNA entry sites of the nucleosome. Two-color fluorescence cross-correlation spectroscopy measurements show that ACF can bind four DNA duplexes simultaneously in a complex that contains two Acf1 and ISWI molecules. Using bead-bound nucleosomal substrates, nucleosome movement by mechanisms involving DNA twisting was excluded. Furthermore, an ACF-dependent local detachment of DNA from the nucleosome was demonstrated in a novel assay based on the preferred intercalation of ethidium bromide to free DNA. The findings suggest a loop recapture mechanism in which ACF introduces a DNA loop at the nucleosomal entry site that propagates over the histone octamer surface and leads to nucleosome repositioning.
Strohner
Ralf
R
Adolf-Butenandt-Institut, Molekularbiologie, Schillerstrasse 44, 80336 München, Germany.
Wachsmuth
Malte
M
Dachauer
Karoline
K
Mazurkiewicz
Jacek
J
Hochstatter
Julia
J
Rippe
Karsten
K
Längst
Gernot
G
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D042002:Chromatin Assembly and Disassembly / Q000502:physiology*; D004247:DNA / Q000378:metabolism*; D018983:DNA Footprinting; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004996:Ethidium; D006657:Histones / Q000378:metabolism; D008957:Models, Genetic; D009707:Nucleosomes / Q000378:metabolism* / Q000502:physiology; D016133:Polymerase Chain Reaction; D013050:Spectrometry, Fluorescence; D014157:Transcription Factors / Q000378:metabolism*
C120419:Acf protein, Drosophila; D029721:Drosophila Proteins; D006657:Histones; D009707:Nucleosomes; D014157:Transcription Factors; D004247:DNA; D000251:Adenosine Triphosphatases; D004996:Ethidium