Epigenetic memory restoration and maintenance after cell division

Nucleosomes, composed of histones, pack chromatin and make genes less available for transcription. Methylation of some histone positions is associated with repression of transcription and epigenetic silencing of some genes. After cell division during the cell cycle, maintenance of expression patterns requires restoration of those epigenetic marks after DNA replication in the G2 phase. Jiang and Berger show that trimethylation of H3.1 is restored early in G2 and remains stable in G1, and that this rapid restoration is specific to plants. Furthermore, proteins of the Polycomb complex are involved in the deposition and maintenance of the trimethylation marks, so have an important role on epigenetic silencing memory in response to the environment and potentially allowing for developmental plasticity. (Summary by Gaby Auge) Science 10.1126/science.aan4965