Recognition of H3K9 methylation by GLP is required for efficient establishment of H3K9 methylation, rapid target gene repression, and mouse viability

Abstract

GLP and G9a are major H3K9 dimethylases and are essential for mouse early embryonic development. GLP and G9a both harbor ankyrin repeat domains that are capable of binding H3K9 methylation. However, the functional significance of their recognition of H3K9 methylation is unknown. Here, we report that the histone methyltransferase activities of GLP and G9a are stimulated by neighboring nucleosomes that are premethylated at H3K9. These stimulation events function in cis and are dependent on the H3K9 methylation binding activities of ankyrin repeat domains of GLP and G9a. Disruption of the H3K9 methylation-binding activity of GLP in mice causes growth retardation of embryos, ossification defects of calvaria, and postnatal lethality due to starvation of the pups. In mouse embryonic stem cells (ESCs) harboring a mutant GLP that lacks H3K9me1-binding activity, critical pluripotent genes, including Oct4 and Nanog, display inefficient establishment of H3K9me2 and delayed gene silencing during differentiation. Collectively, our study reveals a new activation mechanism for GLP and G9a that plays an important role in ESC differentiation and mouse viability.

The expanding role of the Ehmt2/G9a complex in neurodevelopment

“…When the Ehmt1 Ank repeat domains are inactivated by mutation, the Ehmt1/2 complex is no longer able to bind effectively to monomethylated H3K9. 24 However, when the SET domain of Ehmt1 is inactivated by mutation embryos are viable and survive to adulthood, 25 in contrast to Ehmt2 SET mutations, which are embryonic lethal. 26 This data implies that Ehmt1 plays a particularly important role in recruiting the complex to monomethylated sites, whereas Ehmt2 is required for the methyltransferase activity.…”

EHMT2 directs DNA methylation for efficient gene silencing in mouse embryos

“…5G). To extend these findings, we analyzed ChIP-seq profiles of H3K9me1/2 in ESCs (Liu et al 2015) and also performed H3K9me2 ChIP-seq in E8.5 embryos. According to the ChIP-seq data, HMRs are marked by H3K9 mono-and dimethylation in ESCs and E8.5 embryos, but the enrichment for these marks is only slightly higher than that of the surrounding sequences (Fig.…”

“…GSE46545) (Mozzetta et al 2014), H3K9me1/2 in ESCs (GEO accession no. GSE54412) (Liu et al 2015), H3K4me2 in ESCs (GEO accession no. GSE30203) (Stadler et al 2011), and H3K9me2 in E8.5 embryos (this study).…”

Sound of silence: the properties and functions of repressive Lys methyltransferases

“…Interestingly, these ankyrin domains were shown to possess a methyl-Lysbinding module that allows binding to H3K9me1 and H3K9me2 marks, independently of SET domains 14 . Binding to H3K9me2 by GLP through its ankyrin domains stimulates its activity on the neighbouring nucleosomes and is required for the establishment of H3K9 methylation in vivo 15 .…”