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DNA condensation refers to the process of compacting DNA molecules in vitro or in vivo. [1] Mechanistic details of DNA packing are essential for its functioning in the process of gene regulation in living systems. Condensed DNA often has surprising properties, which one would not predict from classical concepts of dilute solutions.
In the latter experiments, the activity of individual condensin complexes on DNA was visualized by real-time fluorescence imaging, revealing that condensin I indeed is a fast loop-extruding motor and that a single condensin I complex can extrude 1,500 bp of DNA per second in a strictly ATP-dependent manner.
In biology the term 'condensation' is used much more broadly and can also refer to liquid–liquid phase separation to form colloidal emulsions or liquid crystals within cells, and liquid–solid phase separation to form gels, [1] sols, or suspensions within cells as well as liquid-to-solid phase transitions such as DNA condensation during ...
Acetylation removes the positive charge on the histones, thereby decreasing the interaction of the N termini of histones with the negatively charged phosphate groups of DNA. As a consequence, the condensed chromatin is transformed into a more relaxed structure that is associated with greater levels of gene transcription. This relaxation can be ...
DNA damage process occurs within the condition of chromatin, and the constantly changing chromatin environment has a large effect on it. [28] Accessing and repairing the damaged cell of DNA, the genome condenses into chromatin and repairing it through modifying the histone residues.
Heterochromatin is a tightly packed form of DNA or condensed DNA, which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes.
The nucleosome is the basic unit of DNA condensation and consists of a DNA double helix bound to an octamer of core histones (2 dimers of H2A and H2B, and an H3/H4 tetramer). About 147 base pairs of DNA coil around 1 octamer, and ~20 base pairs are sequestered by the addition of the linker histone (H1), and various length of "linker" DNA (~0 ...
Such modifications affect the binding affinity between histones and DNA, and thus loosening or tightening the condensed DNA wrapped around histones, e.g., Methylation of specific lysine residues in H3 and H4 causes further condensation of DNA around histones, and thereby prevents binding of transcription factors to the DNA that lead to gene ...