Article
- The EMBO Journal (2004) 23, 2092 - 2104
- doi:10.1038/sj.emboj.7600220
Published online: 6 May 2004
Subject Category:
Topography of the ISW2–nucleosome complex: insights into nucleosome spacing and chromatin remodeling
Mohamedi N Kagalwala, Benjamin J Glaus, Weiwei Dang, Martin Zofall and Blaine Bartholomew
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL, USA
Correspondence to:
Blaine Bartholomew, Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, 1245 Lincoln Dr., Neckers Bldg, Room 229, Carbondale, IL 62901-4413, USA. Tel.: +1 618 453 6437; Fax: +1 618 453 6440; E-mail: bbartholomew@siumed.edu
Received 9 September 2003; Accepted 5 April 2004
Abstract
Linker DNA was found to be critical for the specific docking of ISW2 with nucleosomes as shown by mapping the physical contacts of ISW2 with nucleosomes at base-pair resolution. Hydroxyl radical footprinting revealed that ISW2 not only extensively interacts with the linker DNA, but also approaches the nucleosome from the side perpendicular to the axis of the DNA superhelix and contacts two disparate sites on the nucleosomal DNA from opposite sides of the superhelix. The topography of the ISW2–nucleosome was further delineated by finding which of the ISW2 subunits are proximal to specific sites within the linker and nucleosomal DNA regions by site-directed DNA photoaffinity labeling. Although ISW2 was shown to contact 
63 bp of linker DNA, a minimum of 20 bp of linker DNA was required for stable binding of ISW2 to nucleosomes. The remaining 43 bp of flanking linker DNA promoted more efficient binding under competitive binding conditions and was functionally important for enhanced sliding of nucleosomes when ISW2 was significantly limiting.
Keywords:
- chromatin,
- chromatin remodeling,
- ISW2,
- ISWI,
- nucleosome
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