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Published on: February 10, 2022
Inverted factor access and slow reversion characterize SWI/SNF-altered nucleosome dimers
Natalia P Ulyanova1, Gavin R Schnitzler
1Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
The Journal of Biological Chemistry
|November 24, 2006
Summary
Human SWI/SNF (hSWI/SNF) remodeling complexes alter nucleosome structures, forming dimers and altosomes. These altered forms exhibit unique DNA accessibility profiles and influence transcription factor binding, impacting gene regulation.
Area of Science:
- Chromatin biology
- Molecular genetics
- Biochemistry
Background:
- The human SWI/SNF (hSWI/SNF) complex is crucial for gene regulation through ATP-dependent chromatin remodeling.
- Previous studies demonstrated hSWI/SNF's ability to generate structurally altered nucleosome dimers from mononucleosomes.
- Recent findings indicated hSWI/SNF also produces structurally altered dinucleosomes, termed altosomes, from polynucleosomal templates.
Purpose of the Study:
- To propose a unified model for hSWI/SNF-generated nucleosome products (dimers and altosomes).
- To investigate the DNA accessibility within these altered nucleosome structures for transcription factors.
- To explore the reciprocal influence between hSWI/SNF products and transcription factor binding.
Main Methods:
- Biophysical characterization of nucleosome structures and dynamics.
- Analysis of DNA accessibility using biochemical assays.
- Investigating transcription factor interactions with altered nucleosomes.
Main Results:
- Dinucleosomes (altosomes) and dimers generated by hSWI/SNF revert to normal nucleosomes at comparable rates.
- Altered dimers can be cleaved into particles resembling mononucleosomes.
- DNA accessibility in altered dimers is highest in the middle and lowest at the ends, contrasting with normal mononucleosomes.
- Transcription factor binding affects the equilibrium between normal nucleosomes and hSWI/SNF-generated dimers.
Conclusions:
- A single model can explain the formation and properties of both hSWI/SNF-altered dimers and altosomes.
- The distinct DNA accessibility profile of altered dimers has significant implications for transcription factor access.
- Transcription factors and hSWI/SNF products engage in a dynamic interplay that influences chromatin structure and gene expression.
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