Generation and Interconversion of Multiple Distinct Nucleosomal States as a Mechanism for Catalyzing Chromatin Fluidity

• Published in: Molecular cell Vol. 8; no. 6; pp. 1219 - 1230
• Main Authors: Narlikar, Geeta J., Phelan, Michael L., Kingston, Robert E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2001
• Subjects: Adenosine Triphosphate - metabolism; Animals; Binding Sites; Catalysis; Cell Line; Chromatin - chemistry; Chromatin - genetics; Chromatin - metabolism; Deoxyribonuclease I - metabolism; Deoxyribonucleases, Type II Site-Specific - metabolism; DNA - chemistry; DNA - genetics; DNA - metabolism; DNA Helicases; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Gene Expression Regulation; GroEL protein; HeLa Cells; Humans; Hydrolysis; Kinetics; Macromolecular Substances; Models, Genetic; Molecular Chaperones - chemistry; Molecular Chaperones - metabolism; Molecular Conformation; Nuclear Proteins - metabolism; Nuclease Protection Assays; Nucleosomes - chemistry; Nucleosomes - genetics; Nucleosomes - metabolism; Protein Subunits; SWI/SNF complex; Thermodynamics; Transcription Factors - chemistry; Transcription Factors - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/S1097-2765(01)00412-9

We have dissected the steps in nucleosome remodeling by BRG1, the ATPase subunit of human SWI/SNF. BRG1-catalyzed DNA exposure is not enhanced by the proximity of the site to the ends of nucleosomal DNA, suggesting that the mechanism involves more than peeling or sliding of the DNA. Comparison of DNA exposure at specific sites with overall changes in the path of DNA implies that BRG1 generates multiple distinct remodeled structures and continuously interconverts them. These characteristics are shared by the entire SWI/SNF complex and have parallels, as well as interesting differences, with the activities of GroEL and Hsp70 protein chaperones. The chaperone-like activity of SWI/SNF is expected to create multiple opportunities for the binding of distinct regulatory factors, providing one mechanism by which SWI/SNF family complexes can contribute to both activation and repression of transcription.