Histonok

Histonok is a term encountered in some non-English scientific texts as an alternative transliteration or inflected form of histones, the protein components around which DNA wraps to form chromatin. In English-language biology, the standard term is histone (plural histones). When used, histonok refers to the same protein family, typically including the core histones H2A, H2B, H3 and H4, which assemble into a histone octamer around which about 146 base pairs of DNA are wrapped to form a nucleosome. The linker histone H1 associates with the DNA between nucleosomes to help stabilize higher-order chromatin structure.

Roles and functions of histones include packaging DNA into compact, organized chromatin and regulating access to genetic information. They influence processes such as transcription, DNA replication, repair, and chromatin remodeling. The N-terminal tails of histones are subject to post-translational modifications, such as acetylation, methylation, phosphorylation and ubiquitination, which create epigenetic marks that help control gene expression without changing the DNA sequence. Enzymes such as histone acetyltransferases (HATs), deacetylases (HDACs), methyltransferases (HMTs) and demethylases dynamically regulate these marks.

Variant histones and histone chaperones add further complexity. Variants like H2A.Z, H3.3 and CENP-A can replace canonical histones at specific genomic regions, influencing stability and function. Histones and their modifications play essential roles in development, differentiation and genome integrity; dysregulation of histone-related processes is linked to diseases, including cancer and congenital disorders.

History notes that histones were first isolated in the late 19th to early 20th century, and the term derives from Greek for tissue. Modern work characterized nucleosome structure and the broad spectrum of histone modifications that regulate chromatin dynamics.