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06:53
Quantification of γH2AX Foci in Response to Ionising Radiation
Published on: April 7, 2010
Chromatin decondensed by acetylation shows an elevated radiation response
Z Nackerdien1, J Michie, L Böhm
1Department of Radiotherapy, Faculty of Medicine, University of Stellenbosch, Tygerberg, Republic of South Africa.
Radiation Research
|February 1, 1989
Summary
Sodium butyrate treatment increases cell radiosensitivity by relaxing chromatin structure, making DNA more accessible to radiation damage. This suggests DNA packing significantly influences cellular radiation sensitivity.
Area of Science:
- Cellular and Molecular Radiobiology
- Chromatin Structure and DNA Damage
Background:
- Sodium butyrate is known to induce hyperacetylation of histones, leading to chromatin relaxation.
- Chromatin condensation is hypothesized to play a role in cellular resistance to DNA damage.
Purpose of the Study:
- To investigate the effect of sodium butyrate-induced chromatin relaxation on the radiosensitivity of V-79 Chinese hamster lung fibroblasts.
- To determine the impact of DNA accessibility within acetylated chromatin on radiation-induced DNA strand breaks.
Main Methods:
- V-79 cells were treated with sodium butyrate and subsequently exposed to 60Co gamma irradiation.
- Cell survival was assessed using a colony assay.
- Isolated control and acetylated chromatin were irradiated, and DNA single-strand breaks were quantified using alkaline sucrose density centrifugation.
Main Results:
- Cells treated with sodium butyrate exhibited 1.3-1.4 times higher radiosensitivity compared to control cells.
- Irradiation of isolated acetylated chromatin resulted in a higher frequency of DNA single-strand breaks (2.0 +/- 0.3 per 10 Gy/10^8 Da) compared to control chromatin (0.9 +/- 0.03 per 10 Gy/10^8 Da).
Conclusions:
- Chromatin relaxation, induced by sodium butyrate, enhances cellular radiosensitivity.
- Increased DNA accessibility in acetylated chromatin leads to a greater number of radiation-induced DNA strand breaks.
- DNA packing and accessibility within chromatin are critical determinants of cellular radiosensitivity.
Related Concept Videos
00:58DNA Packaging
Overview
02:25Spreading of Chromatin Modifications
The histone proteins in the nucleosomes are post-translationally modified (PTM) to increase or decrease access to DNA. The commonly observed PTMs are methylation, acetylation, phosphorylation, and ubiquitination of lysine amino acids in the histone H3 tail region. These histone modifications have specific meaning for the cell. Hence, they are called "histone code". The protein complex involved in histone modification is termed as "reader-writer" complex.
Writers
The writer is an enzyme that can...
Writers
The writer is an enzyme that can...
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...
02:35Chromatin 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.
Topologically Associated Domains (TADs)
The 3-dimensional positioning of chromatin in the nucleus influences the timing and level of...
Topologically Associated Domains (TADs)
The 3-dimensional positioning of chromatin in the nucleus influences the timing and level of...
02:05Duplication of Chromatin Structure
The process of chromosome duplication during cell division requires genome-wide disruption and re-assembly of chromatin. The chromatin structure must be accurately inherited, reassembled, and maintained in the daughter cells to ensure lineage propagation.
The basic unit of the chromatin is the nucleosome, consisting of DNA wrapped around octameric histone proteins and short stretches of linker DNA separating individual nucleosomes. The histone proteins within the nucleosome have their...
The basic unit of the chromatin is the nucleosome, consisting of DNA wrapped around octameric histone proteins and short stretches of linker DNA separating individual nucleosomes. The histone proteins within the nucleosome have their...
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...