nukleosomin

Nucleosomin is a protein that plays a crucial role in the structural organization of chromatin, the complex of DNA and protein found in the nucleus of eukaryotic cells. First identified in the slime mold *Physarum polycephalum*, nucleosomin has since been found in various organisms, including humans, where it is known as histone H2A, H2B, H3, and H4. These histones form the core of nucleosomes, the fundamental repeating units of chromatin.

Nucleosomes consist of approximately 147 base pairs of DNA wrapped around an octamer of histone proteins—two copies each of H2A, H2B, H3, and H4. The nucleosomal core particle is stabilized by interactions between the histones and the DNA, as well as histone-histone contacts. The spacing between nucleosomes is regulated by linker histones, such as H1, which further compact chromatin into higher-order structures.

The function of nucleosomin extends beyond simple DNA packaging. Histone modifications, including acetylation, methylation, phosphorylation, and ubiquitination, influence chromatin accessibility, gene expression, and DNA repair. For example, acetylation of histones typically loosens chromatin structure, promoting transcription, while methylation can either activate or repress gene expression depending on the specific residue modified.

In addition to its role in chromatin structure, nucleosomin is involved in DNA replication, repair, and the maintenance of genomic integrity. Mutations or dysregulation in histone proteins have been linked to various diseases, including cancers, where altered chromatin remodeling can lead to uncontrolled cell proliferation or genomic instability.

Research on nucleosomin continues to expand our understanding of epigenetic regulation, which governs how genetic information is accessed and utilized by the cell without changing the underlying DNA sequence. Studies in model organisms and human cells have provided insights into how nucleosomal organization contributes to cellular identity, development, and disease.