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Epichromatin and chromomeres: a 'fuzzy' perspective
1Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, 716 Stevens Avenue, Portland, ME 04103, USA dolins@une.edu.
Open Biology
|June 8, 2018
Summary
Epichromatin and chromomeres, key chromatin structures, were identified using specific antibodies. Unstructured histone tails, through multivalent binding, stabilize these structures, forming the
Area of Science:
- Cell Biology
- Molecular Biology
- Chromatin Structure
Background:
- Epichromatin and chromomeres are distinct chromatin regions observed at the nuclear periphery and on mitotic chromosomes.
- The precise molecular interactions stabilizing these structures remain incompletely understood.
Purpose of the Study:
- To investigate the structural and molecular basis of epichromatin and chromomere organization.
- To explore the role of histone intrinsically disordered peptide regions (IDPRs) in chromatin stability.
Main Methods:
- Immunostaining using a bivalent anti-nucleosome antibody (mAb PL2-6) to identify epichromatin.
- Immunostaining with monovalent Fab fragments of mAb PL2-6 to identify chromomeres.
- Analysis of histone tail structures and their potential interactions.
Main Results:
- Epichromatin and chromomeres were visualized, revealing exposed nucleosome epitopes.
- Histone tails, particularly histone H1 tails, are implicated in stabilizing chromomeres through multivalent interactions.
- The nucleosome acidic patch is a likely target for the anti-nucleosome antibody.
Conclusions:
- The 'unstructured stability' hypothesis proposes that collective weak interactions of histone IDPRs stabilize chromatin structures like epichromatin and chromomeres.
- These interactions are analogous to antibody avidity, highlighting the importance of multivalency in chromatin organization.
- Cationic histone tails may mediate interactions with anionic components of the nuclear envelope.
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02:32Position-effect Variegation
In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.
01:01Euchromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions take up more dye, appearing darker, while the less-compact areas take up less dye and appear lighter. Based on the compaction level, chromatins are classified into two primary forms – euchromatin and heterochromatin.
Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...
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02:35Chromatin Position Affects Gene Expression
Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the nucleus greatly influences access to genetic information. Generally, the nucleus' periphery is considered transcriptionally repressive, while the cell's interior is considered a transcriptionally active area.
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02:38Heterochromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions that take up more dye are called heterochromatin. Heterochromatin is further classified into two forms – constitutive heterochromatin and facultative heterochromatin.
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01:01Euchromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions take up more dye, appearing darker, while the less-compact areas take up less dye and appear lighter. Based on the compaction level, chromatins are classified into two primary forms – euchromatin and heterochromatin.
Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...
Euchromatin is the less dense region of the chromatin and stains lighter. Euchromatin contains histone H3 extensively...
02:38Heterochromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions that take up more dye are called heterochromatin. Heterochromatin is further classified into two forms – constitutive heterochromatin and facultative heterochromatin.
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...