[Investigation of histone H3 methylation during long term memory formation].

Histone H3 posttranslational modifications play important role in chromatin remodeling and are involved in gene expression regulation during long term memory formation. If acetylation and phosphorylation of histones has been intensively studied for several years, the role of methylation during learning is only under establishment. Histone methylation is an interesting subject, since it can both activate and repress gene expression. By using food avoidance behavior of mollusk Helix as a model, we analyzed lysine 4 histone H3 tri-methylation (H3K4) and lysine 9 H3 di-methylation (H3K9), which induces and represses genes correspondingly. We showed that there was a significant increase in histone H3 methylation at lysine 4 and lysine 9 in Helix central nervous system upon consolidation of long term memory. Data obtained show the involvement of histone methylation to the epigenetic mechanisms of long-term memory formation in mollusk Helix on transcription repression and activation levels. Beside this, induction ofH3 methylation at lysine 9 can reflect influence of inhibitory processes, playing an important role in central nervous system functioning.