Histone methylation

Methylation events that weaken chemical attractions between histone tails and DNA increase transcription because they enable the DNA to uncoil from nucleosomes so that transcription factor proteins and RNA polymerase can access the DNA. This process is critical for the regulation of gene expression that allows different cells to express different genes. Histone methylation, as a mechanism for modifying chromatin structure is associated with stimulation of neural pathways known to be important for formation of long-term memories and learning. Histone methylation is crucial for almost all phases of animal embryonic development. Animal models have shown methylation and other epigenetic regulation mechanisms to be associated with conditions of aging, neurodegenerative diseases, and intellectual disability (Rubinstein–Taybi syndrome, X-linked intellectual disability). Misregulation of H3K4, H3K27, and H4K20 are associated with cancers. This modification alters the properties of the nucleosome and affects its interactions with other proteins, particularly in regards to gene transcription processes. The fundamental unit of chromatin, called a nucleosome, contains DNA wound around a protein octamer.