Impact of OGT deregulation on EZH2 target genes FOXA1 and FOXC1 expression in breast cancer cells

Abstract

Enhancer of zest homolog 2 (EZH2) is a histone methyltransferase which plays a crucial role in cancer progression by regulation of genes involved in cellular processes such as proliferation, invasion and self-renewal. Activity and biological function of EZH2 are regulated by posttranslational modifications. It is suggested that EZH2 stability may be regulated by O-GlcNAc transferase (OGT), which is an enzyme catalyzing the addition of GlcNAc moieties to target proteins. In this study, we determined the impact of OGT on expression of EZH2 target genes FOXA1 and FOXC1, that are involved in breast cancer progression. The results of chromatin immunoprecipitation experiments showed that both EZH2 and OGT are targeted to the promoter regions of FOXA1 and FOXC1 and knockdown of EZH2 or OGT affects expression of studied genes in breast non-malignant (MCF10A) and cancer cells (MCF7, T47D and MDA-MB-231). The results showed that OGT silencing affects EZH2 binding to FOXC1 promoter but the effect is cell-context dependent. Despite the slight decrease in EZH2 protein level in cells with OGT depletion, EZH2 binding to FOXC1 was increased. Moreover, OGT binding to promoter regions of FOXA1 and FOXC1 was increased in cells with knockdown of EZH2. Increased expression of FOXA1 and FOXC1 in cells with OGT deregulation was associated with increased acetylation level of histone H3. The results suggest that OGT is involved in regulation of FOXA1 and FOXC1 expression but its role is not associated with regulation of EZH2 protein stability.

A novel SIRT6 activator ameliorates neuroinflammation and ischemic brain injury via EZH2/FOXC1 axis

“…SIRT6 is a kind of deacetylase that regulates the transcription of its target genes by interacting with various transcription factors 39 . Accumulating studies found that the acetylation of EZH2 enhances its capacity in regulating FOXC1 28 , 40 . To determine whether MDL-811 could regulate EZH2 acetylation under our experimental conditions, we assessed the levels of acetylated EZH2 by immunoprecipitation.…”

O-linked N-acetylglucosamine transferase (OGT) regulates pancreatic α-cell function in mice

“…For example, FOXA1 and FOXA2, both of which play an important role in α-cell glucagon biosynthesis and secretion ( 28 ), are O-GlcNAc modified by OGT in cancer cells, and this modification is important for the stability of the protein ( 29 ). Moreover, OGT has been shown to directly bind to the promoter of FOXA1 to regulate its expression levels ( 30 ). In the current study, we show that FOXA2 mRNA and protein levels were reduced in α-cell line with OGT inhibition.…”

Post-translational modifications of PRC2: signals directing its activity

“…Accordingly, EZH2 O-GlcNAcylation does not affect PRC2 assembly but occurs at the N-terminal region, including the S73, S76, S84, S87 and T313 sites, which may regulate the stability of the isolated EZH2, while O-GlcNAcylation of EZH2 at S729 is required for the methyltransferase activity of PRC2 to catalyse H3K27me2/3 [ 154 , 155 ]. Another study revealed that O-GlcNAcylation of EZH2 affects its binding to the promoter regions of FOXA1/C1 (Forkhead box protein A1/C1), suggesting that EZH2 O-GlcNAcylation might affect the targeting of PRC2 to chromatin [ 156 ]. Overall, these observations suggest that O-GlcNAcylation of EZH2 may regulate the catalytic activity and genomic targeting of PRC2.…”