Histonmódosítások

Histonmódosítások, also known as histone modifications, are crucial epigenetic mechanisms that regulate gene expression without altering the underlying DNA sequence. These modifications occur primarily on the N-terminal tails of histone proteins, which are the fundamental building blocks of chromatin, the complex of DNA and proteins that forms chromosomes. Histones act like spools around which DNA is wound, and their modifications can alter the accessibility of the DNA to transcription machinery.

Common histone modifications include acetylation, methylation, phosphorylation, and ubiquitination. Histone acetylation, typically associated with gene activation, involves the addition of an acetyl group to lysine residues, neutralizing their positive charge and loosening the chromatin structure. Conversely, histone methylation can either activate or repress gene expression depending on the specific residue and the number of methyl groups added. Histone phosphorylation and ubiquitination also play roles in chromatin structure and function, influencing processes like DNA repair and replication.

These modifications are dynamically regulated by enzymes that add them (writers) and enzymes that remove them (erasers). The pattern of histone modifications on a particular region of DNA constitutes the "histone code," which is interpreted by specific proteins to dictate downstream cellular responses. Aberrant histone modification patterns are implicated in various diseases, including cancer, and are therefore targets for therapeutic interventions. Understanding histone modifications is essential for comprehending gene regulation and its implications in health and disease.