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Alterations in nucleosome core structure in linker histone-depleted chromatin
S I Usachenko1, I M Gavin, S G Bavykin
1W. A. Engelhardt Institute of Molecular Biology, Academy of Sciences of Russia, Vavilova, 32, 117984 Moscow B-334, Russia.
The Journal of Biological Chemistry
|February 16, 1996
Summary
Chromatin structure changes when linker histone H1 is removed, altering histone-DNA contacts within nucleosomes. This "stretched nucleosome" conformation may occur during chromatin activation and is reversible.
Area of Science:
- Molecular Biology
- Epigenetics
- Chromatin Structure
Background:
- Histone-DNA contacts are similar in condensed and active chromatin.
- Differences in histone-DNA contact strength were previously unexplained.
- Histone H1's role in chromatin condensation is known.
Purpose of the Study:
- To investigate the cause of differing histone-DNA contact strengths.
- To identify conformational changes in the nucleosomal core.
- To understand the implications of these changes for chromatin activation.
Main Methods:
- Comparative analysis of histone-DNA contacts in various chromatin states.
- Examination of nucleosomal core conformation in linker histone-depleted versus folded chromatin.
- Investigating the reversibility of nucleosome structural alterations.
Main Results:
- Nucleosomal cores in linker histone-depleted chromatin exhibit a distinct conformational state.
- This state, termed the "stretched nucleosome," shows altered histone H4 and H2A/H2B contacts.
- The stretched nucleosome conformation is a general feature of unfolded, linker histone-depleted chromatin and is reversible.
Conclusions:
- Nucleosome conformation changes due to linker DNA stretching during chromatin unfolding.
- This structural alteration is independent of chromatin source and histone variants studied.
- The "stretched nucleosome" may play a role in chromatin activation processes.