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The Nucleosome Core Particle

The Nucleosome Core Particle

Nucleosomes are the DNA-histone complex, where the DNA strand is wound around the histone core. The histone core is an octamer containing two copies of H2A, H2B, H3, and H4 histone proteins.
Nucleosomes, paradoxically, perform two opposite functions simultaneously. On the one hand, their primary aim is to protect the delicate DNA strands from physical damage and help achieve a higher compaction ratio. On the other hand, they must allow polymerase enzymes to access histone-bound DNA during...

The Nucleosome Core Particle

The Nucleosome Core Particle

Nucleosomes are the DNA-histone complex, where the DNA strand is wound around the histone core. The histone core is an octamer containing two copies of H2A, H2B, H3, and H4 histone proteins.
The paradox
Nucleosomes, paradoxically, perform two opposite functions simultaneously. On the one hand, their main responsibility is to protect the delicate DNA strands from physical damage and help achieve a higher compaction ratio. While on the other hand, they must allow polymerase enzymes to access DNA...

Nucleosome Remodeling

Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA inaccessible to DNA binding proteins such as DNA polymerase and RNA polymerase. Hence, the fundamental problem is to ensure access to DNA when appropriate, despite the compact and protective chromatin structure.
Nucleosome remodeling complex
Eukaryotic cells have specialized enzymes called ATP-dependent nucleosome remodeling enzymes. These enzymes...

Histone Modification

Histone Modification

The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational modifications such as acetylation, methylation, phosphorylation, and ubiquitination. Particular combinations of these modifications form “histone codes” that influence the chromatin folding and tissue-specific gene expression.
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...

Histone Modification

Histone Modification

The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational modifications such as acetylation, methylation, phosphorylation, and ubiquitination. Particular combinations of these modifications form “histone codes” that influence the chromatin folding and tissue-specific gene expression.
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...

The Nucleosome

The Nucleosome

Human DNA is almost two meters long. However, it is compressed inside a tiny nucleus measuring only a few microns in diameter. To make this degree of compaction possible, DNA is organized into several sequential levels so that it can fit into such a tiny space. The most compact form of DNA is a chromosome that can be seen under a microscope in a dividing cell.
In a chromosome, DNA is wound twice around a protein complex called a histone octamer core, which consists of 8 histone proteins. This...

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Related Experiment Video

Updated: May 18, 2026

Reconstitution of Nucleosomes with Differentially Isotope-labeled Sister Histones

Reconstitution of Nucleosomes with Differentially Isotope-labeled Sister Histones

Published on: March 26, 2017

Asymmetrically modified nucleosomes.

Philipp Voigt¹, Gary LeRoy, William J Drury

¹Howard Hughes Medical Institute, New York University School of Medicine, Department of Biochemistry, New York, NY 10016, USA.

|October 2, 2012

Summary

This summary is machine-generated.

Nucleosomes can be modified on histone copies symmetrically or asymmetrically. This asymmetry influences gene regulation and chromatin states, revealing new insights into epigenetic mechanisms.

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Reconstitution of Nucleosomes with Differentially Isotope-labeled Sister Histones

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Area of Science:

Epigenetics and Molecular Biology
Chromatin Biology
Gene Regulation

Background:

Mononucleosomes, the fundamental units of chromatin, consist of core histones, and their posttranslational modifications are crucial for chromatin-dependent processes.
The precise in vivo modification status of individual histone copies within a nucleosome remains largely undetermined.

Purpose of the Study:

To investigate whether histone copies within a nucleosome are identically modified in vivo.
To explore the functional implications of symmetric versus asymmetric histone modifications.

Main Methods:

Analysis of nucleosomes from embryonic stem cells, fibroblasts, and cancer cells.
Utilizing techniques to detect histone H3 lysine 27 di/trimethylation (H3K27me2/3) and H4K20me1.
Investigating bivalent histone modifications, including H3K4me3, H3K36me3, and H3K27me3, using direct physical evidence.

Main Results:

Nucleosomes exhibit both symmetrically and asymmetrically modified populations for H3K27me2/3 and H4K20me1.
Direct evidence for bivalent nucleosomes with distinct modifications (H3K4me3/H3K36me3 and H3K27me3) on opposite H3 tails was found.
Bivalency at target genes resolved upon differentiation of embryonic stem cells.
Polycomb repressive complex 2-mediated H3K27 methylation was inhibited by symmetrically placed H3K4me3 or H3K36me3, but not by asymmetric placement.

Conclusions:

Asymmetric histone modifications may establish diverse functional nucleosome states.
A mechanism for incorporating bivalent features into nucleosomes is proposed.
Histone modification asymmetry plays a role in regulating gene expression and chromatin function.