Kromaatinmuunnos

Kromaatinmuunnos (chromatin modification) refers to the chemical and structural changes that occur to chromatin, the complex of DNA and histone proteins that packages genetic material within the nucleus of eukaryotic cells. These modifications regulate chromatin accessibility and, consequently, gene expression without altering the underlying DNA sequence. Major types of kromaatinmuunnos include covalent modifications of histone tails—such as acetylation, methylation, phosphorylation, ubiquitination, sumoylation and ADP‑ribosylation—as well as DNA methylation and the incorporation of histone variants. Histone acetylation, catalyzed by histone acetyltransferases, generally loosens chromatin structure and promotes transcription. In contrast, histone deacetylases remove acetyl groups, leading to chromatin compaction and transcriptional repression. Histone methylation can either activate or silence genes depending on the specific lysine or arginine residue and the degree of methylation. DNA methylation at CpG islands is typically associated with long‑term gene silencing and is mediated by DNA methyltransferases.

The dynamic balance of these modifications is maintained by opposing enzyme families and is essential for development, cellular differentiation, DNA repair, and the maintenance of genomic stability. Dysregulation of kromaatinmuunnos is linked to numerous diseases, including cancer, neurodegenerative disorders and metabolic syndromes. Targeting chromatin-modifying enzymes has become a therapeutic strategy; drugs such as histone deacetylase inhibitors and DNA methyltransferase inhibitors are already approved for certain cancers. Research into kromaatinmuunnos continues to uncover novel regulatory mechanisms and potential clinical applications.