TWIST1 methylation by SETD6 selectively antagonizes LINC-PINT expression in Glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and aggressive malignant brain tumor among adults, which is characterized by high invasion, migration and proliferation abilities. One important process that contributes to the invasiveness of GBM is the epithelial to mesenchymal transition (EMT). EMT is regulated by a set of defined transcription factors which tightly regulate this process, among them is the basic helix-loop-helix family member, TWIST1. Here we show that TWIST1 is methylated on lysine-33 at chromatin by SETD6, a methyltransferase with expression levels correlating with poor survival in GBM patients. RNA-seq analysis in U251 GBM cells suggested that both SETD6 and TWIST1 regulate cell adhesion and migration processes. We further show that TWIST1 methylation attenuates the expression of the long-non-coding RNA, LINC-PINT, thereby suppressing EMT in GBM. Mechanistically, TWIST1 methylation represses the transcription of LINC-PINT by increasing the occupancy of EZH2 and the catalysis of the repressive H3K27me3 mark at the LINC-PINT locus. Under un-methylated conditions, TWIST1 dissociates from the LINC-PINT locus, allowing the expression of LINC-PINT which leads to increased cell adhesion and decreased cell migration. Together, our findings unravel a new mechanistic dimension for selective expression of LINC-PINT mediated by TWIST1 methylation.

Genetic and epigenetic regulation of zebrafish intestinal development

Many regulatory pathways are conserved in the zebrafish intestine compared to mammals, rendering it a strong model to study intestinal development. However, the (epi)genetic regulation of zebrafish intestinal development remains largely uncharacterized. We performed RNA-sequencing and chromatin immunoprecipitation (ChIP)-sequencing for activating (H3K4me3) and repressive (H3K27me3) chromatin marks on isolated intestines at 5, 7, and 9 days post-fertilization (dpf), during which zebrafish transit from yolk dependence to external feeding. RNA-sequencing showed the enrichment of metabolic maintenance genes at all time points and a significant increase in lipid metabolism between 5 and 9 dpf. A strong correlation was observed between gene expression and presence of chromatin marks on gene promoters; H3K4me3-marked genes were expressed higher than H3K27m3-marked genes. Next, we studied a key epigenetic player, Enhancer of zeste homolog 2 (Ezh2). Ezh2 places the repressive H3K27me3 mark on the genome and is highly conserved in vertebrates. We used the nonsense mutant allele ezh2(hu5670) to study the effect of ezh2 loss on intestinal development. These mutants survived gastrulation and died around 11 dpf, showing severe morphological defects in the intestine and liver, accompanied by decreased intestinal (fabp2) and hepatic (fabp10a) marker expressions. Our results suggest that Ezh2 is essential for proper intestinal tissue maintenance and overall survival.

MSK1 triggers the expression of the INK4AB/ARF locus in oncogene-induced senescence

The tumor suppressor proteins p15INK4B, p16INK4A, and p14ARF, encoded by the INK4AB/ARF locus, are crucial regulators of cellular senescence. The locus is epigenetically silenced by the repressive Polycomb complexes in growing cells but is activated in response to oncogenic stress. Here we show that the mitogen- and stress-activated kinase (MSK1) is up-regulated after RAF1 oncogenic stress and that the phosphorylated (activated) form of MSK1 is significantly increased in the nucleus and recruited to the INK4AB/ARF locus. We show that MSK1 mediates histone H3S28 phosphorylation at the INK4AB/ARF locus and contributes to the rapid transcriptional activation of p15INK4B and p16INK4A in human cells despite the presence of the repressive H3K27me3 mark. Furthermore, we show that upon MSK1 depletion in oncogenic RAF1-expressing cells, H3S28ph presence at the INK4 locus and p15INK4B and p16INK4A expression are reduced. Finally, we show that H3S28-MSK–dependent phosphorylation functions in response to RAF1 signaling and that ERK and p38α contribute to MSK1 activation in oncogene-induced senescence.

Dietary resistant starch type 4-derived butyrate attenuates nuclear factor-kappa-B1 through modulation of histone H3 trimethylation at lysine 27

A fermentation product of RS4, butyrate, attenuates proinflammatory NFκB1 through an enrichment of the repressive H3K27me3 mark, suggesting a potential role of dietary RS4 in immunometabolic health management.

Ezh2 Requires PHF1 To Efficiently Catalyze H3 Lysine 27 Trimethylation In Vivo

ABSTRACT The mammalian Polycomblike protein PHF1 was previously shown to interact with the Polycomb group (PcG) protein Ezh2, a histone methyltransferase whose activity is pivotal in sustaining gene repression during development and in adulthood. As Ezh2 is active only when part of the Polycomb Repressive Complexes (PRC2-PRC4), we examined the functional role of its interaction with PHF1. Chromatin immunoprecipitation experiments revealed that PHF1 resides along with Ezh2 at Ezh2-regulated genes such as the HoxA loci and the non-Hox MYT1 and WNT1 genes. Knockdown of PHF1 or of Ezh2 led to up-regulated HoxA gene expression. Interestingly, depletion of PHF1 did correlate with reduced occupancy of Bmi-1, a PRC1 component. As expected, knockdown of Ezh2 led to reduced levels of its catalytic products H3K27me2/H3K27me3. However, reduced levels of PHF1 also led to decreased global levels of H3K27me3. Notably, the levels of H3K27me3 decreased while those of H3K27me2 increased at the up-regulated HoxA loci tested. Consistent with this, the addition of PHF1 specifically stimulated the ability of Ezh2 to catalyze H3K27me3 but not H3K27me1/H3K27me2 in vitro. We conclude that PHF1 modulates the activity of Ezh2 in favor of the repressive H3K27me3 mark. Thus, we propose that PHF1 is a determinant in PcG-mediated gene repression.