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Transitions between in situ and isolated chromatin
P J Giannasca1, R A Horowitz, C L Woodcock
1Department of Biology, University of Massachusetts, Amherst 01003.
Journal of Cell Science
|June 1, 1993
Summary
Chromatin isolation from nuclei involves structural changes. Refolding after isolation does not fully restore the native higher-order structure, challenging existing models of genome architecture.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Chromatin, the complex of DNA and proteins, forms higher-order structures within eukaryotic nuclei.
- Understanding chromatin's native state and structural transitions is crucial for comprehending genome organization and function.
Purpose of the Study:
- To investigate the structural changes chromatin undergoes upon isolation from nuclei.
- To determine if isolated chromatin refolds to its native higher-order structure.
- To re-evaluate the proposed native state of bulk eukaryotic genome chromatin.
Main Methods:
- Isolation of starfish sperm chromatin from nuclei.
- Analysis of chromatin fiber structure in solution and within the nucleus.
- Comparison of higher-order structure before and after isolation and refolding.
Main Results:
- Chromatin isolation involves a transition to an extended nucleosomal arrangement.
- Isolated chromatin fibers are wider than native nuclear fibers, indicating incomplete refolding.
- The refolding process does not fully regenerate the native higher-order structure.
Conclusions:
- The mechanism of chromatin isolation involves structural unfolding.
- Refolding of isolated chromatin does not replicate the native higher-order structure.
- The concept of a defined chromatin fiber architecture for the bulk genome in its native state requires reconsideration.