Histone

Gene

Cell biology

EZH2

Biology

Epigenetics

DNA methylation

Heterochromatin protein 1

Gene silencing

Epigenomics

Genetics

Chromatin

Histone methylation

Heterochromatin

Constitutive heterochromatin

Gene expression

Current Opinion in Genetics & Development

Compacted, transcriptionally repressed chromatin, referred to as heterochromatin, represents a major fraction of the higher eukaryotic genome and exerts pivotal functions of silencing repetitive elements, maintenance of genome stability, and control of gene expression. Among the different histone post-translational modifications (PTMs) associated with heterochromatin, tri-methylation of lysine 9 on histone H3 (H3K9me3) is gaining increased attention. Besides its known role in repressing repetitive elements and non-coding portions of the genome, recent observations indicate H3K9me3 as an important player in silencing lineage-inappropriate genes. The ability of H3K9me3 to influence cell identity challenges the original concept of H3K9me3-marked heterochromatin as mainly a constitutive type of chromatin and provides a further level of understanding of how to modulate cell fate control. Here, we summarize the role of H3K9me3 marked heterochromatin and its dynamics in establishing and maintaining cellular identity.

Role of H3K9me3 heterochromatin in cell identity establishment and maintenance