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Mapping Absolute DNA Density in Cell Nuclei using Single-molecule Localization Microscopy
Published on: November 11, 2025
CHROMOSIN, A DESOXYRIBOSE NUCLEOPROTEIN COMPLEX OF THE CELL NUCLEUS
1Laboratories of The Rockefeller Institute for Medical Research and the Department of Zoology, Columbia University, New York.
The Journal of General Physiology
|October 30, 2009
Summary
Researchers isolated a chromosin, a nuclear complex of desoxyribose nucleic acid and proteins, from various cells. This chromosin is active in bacterial transformation, suggesting its components play a role in genetic material.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- The nucleus of eukaryotic and prokaryotic cells contains complex structures involved in genetic material organization and function.
- Previous research on nuclear components has yielded varying views on the presence and role of histones in different cell types.
Purpose of the Study:
- To isolate and characterize a desoxyribose nucleoprotein complex, termed chromosin, from diverse cell sources.
- To investigate the composition and properties of chromosin, including its protein and nucleic acid components.
- To assess the biological activity of chromosin, specifically its role in bacterial transformation.
Main Methods:
- Isolation of chromosin from animal, plant, and bacterial cells, with precautions to ensure nuclear origin and avoid cytoplasmic contamination.
- Chemical analysis to identify desoxyribose nucleic acid, histone, and non-histone proteins within the chromosin complex.
- Extraction using varying concentrations of NaCl (1 M and 0.02 M) to study the dissociation and depolymerization of chromosin components.
- Testing the biological activity of chromosin from Type III pneumococcus in bacterial transformation experiments.
Main Results:
- Chromosin was successfully prepared from a wide range of cells, confirming its nuclear origin and absence of ribose nucleoproteins.
- A typical chromosin comprises desoxyribose nucleic acid, histone, and non-histone protein, with distinct tryptophane content differentiating the proteins.
- Chromosin isolated from Type III pneumococcus demonstrated activity in transforming pneumococcus cultures, indicating a potential role in genetic transfer.
- Dissociation of nucleic acid and histone components occurred in 1 M NaCl, while partial depolymerization of nucleic acid was observed in 0.02 M NaCl.
Conclusions:
- Histones are present in most animal cells and some plant and bacterial cells, challenging previous assumptions.
- Chromosin represents a complex extracted from chromatin, not a discrete chemical compound, and its structure is altered during extraction.
- The biological activity of chromosin in bacterial transformation suggests its components are integral to genetic material and function.
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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...
02:21Chromatin Packaging
Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 meters of DNA. How is such a long DNA strand packed inside a nucleus measuring only 10 - 20 microns in diameter?
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order structures.
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order structures.
01:32Chromatin Packaging
Each human somatic cell contains 6 billion base pairs of DNA. Each base pair is 0.34 nm long, meaning each diploid cell contains a staggering 2 meters of DNA. This long DNA strand is packed inside a nucleus measuring only 10-20 microns in diameter with the help of specialized DNA-binding proteins called histones. Together they form a compact DNA-protein complex called chromatin. The chromatin is further compacted into higher-order structures. The highest level of compaction is achieved during...
02:21Chromatin Packaging
Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 meters of DNA. How is such a long DNA strand packed inside a nucleus measuring only 10 - 20 microns in diameter?
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order structures.
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order structures.
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...
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...