histonkoden
Histonkoden, or the histone code, refers to the proposed set of covalent post-translational modifications on histone proteins that regulate chromatin structure and gene expression. In eukaryotic cells, histones H2A, H2B, H3, and H4 carry modifications on their tail regions, including methylation, acetylation, phosphorylation, ubiquitination, and sumoylation. The histone code hypothesis suggests that specific combinations of these marks create binding sites for reader proteins that recruit chromatin modifiers and transcriptional machinery, thereby influencing transcriptional outcomes. Enzymes act as writers to add marks, erasers to remove them, and readers to interpret them.
Common marks include H3K4me3 at active promoters; H3K27ac at active enhancers; H3K36me3 along transcribed gene bodies;
The histone code framework has driven extensive genome-wide mapping and proteomic studies and is central to
Research approaches include chromatin immunoprecipitation followed by sequencing (ChIP-seq), mass spectrometry of histone tails, and newer