STAT3-driven transcription depends upon the dimethylation of K49 by EZH2

Abstract

Several transcription factors, including p53, NF-κB, and STAT3, are modified by the same enzymes that also modify histones, with important functional consequences. We have identified a previously unrecognized dimethylation of K49 of STAT3 that is crucial for the expression of many IL-6-dependent genes, catalyzed by the histone-modifying enzyme enhancer of zeste homolog 2 (EZH2). Loss of EZH2 is protumorigenic in leukemias, but its overexpression is protumorigenic in solid cancers. Connecting EZH2 to a functionally important methylation of STAT3, which is constitutively activated in many tumors, may help reveal the basis of the opposing roles of EZH2 in liquid and solid tumors and also may identify novel therapeutic opportunities.posttranslational modification | histone methyltransferase | gene expression S TAT3 is activated in 70% of all solid and hematological tumors (1, 2), where it stimulates proliferation, survival, angiogenesis, invasion, and tumor-promoting inflammation. Recently, STAT3 also was found to have an important role in maintaining cancer stem cells, both in vitro and in mouse tumor models, indicating that it is integrally involved in tumor initiation, progression, and maintenance (3). IL-6-induced constitutive activation of STAT3 was observed in neoplastic gastric tissue and is positively correlated with tumor progression (4), and the expression of tyrosine-phosphorylated STAT3 is associated with poor prognosis in colorectal cancer, independent of the mutation status of MSI, CIMP, BRAF, or KRAS (5). The STAT3 gene is rarely mutated in cancer but rather is activated by members of the IL-6 family of cytokines, receptor tyrosine kinases, mutated JAKs, or oncogenic cellular tyrosine kinases, such as SRC (6). Because STAT3 is constitutively activated during disease progression and metastasis, it is a promising therapeutic target. Even though transcription factors are difficult drug targets, accumulating evidence for the crucial roles of posttranslational modifications of transcription factors in mediating target gene expression provides an opportunity to develop drugs against the modifying enzymes rather than against the transcription factors themselves.STAT3 is activated primarily by phosphorylation of Y705 (7) and secondarily by phosphorylation of S727 (8). The acetylation of STAT3 at K685 (9, 10) has been shown recently to have little or no effect on IL-6-dependent gene expression (11). Ray et al. (12) reported that IL-6-induced gene expression requires p300-mediated acetylation of K49 and K87 and that monoubiquitination at K97 is a key mediator of BRD4-dependent gene expression (13). Like NF-κB and p53, STAT3 is reversibly methylated on lysine residues by histone-modifying enzymes, with important functional consequences (14). Furthermore, STAT3 is known to be di-or trimethylated on K140 or K180 by the histone methyltransferase SET9 (SET domain containing lysine methyltransferase 9) or EZH2 (enhancer of zeste homolog 2), respectively (15, 16). Here we show that IL-6-dependent, previously unident...

Histone H3 Serine 28 Is Essential for Efficient Polycomb-Mediated Gene Repression in Drosophila

“…Of note, some other Ezh2 substrates can be methylated despite the lack of a ''KS'' module. These include K26 of mouse histone H1 variant H1e, K49 of STAT3, and K116 of Jarid2 (Dasgupta et al, 2015;Kuzmichev et al, 2004;Sanulli et al, 2015), where the lysine residue is followed by an alanine, glutamate, and phenylalanine, respectively. Moreover, the link between peptide sequence and enzymology of Ezh2 was shown to differ in non-histone substrates (Lee et al, 2012).…”

The impact of melatonin and carbon ion irradiation on cancer stem cells

“…EZH2-STAT3 interaction is noticeable in GSCs and necessary for GSC clonogenic growth [49][50][51]. Co-immunoprecipitation experiments were carried out to define the effect of melatonin treatment on EZH2-STAT3 interaction in GSCs.…”

Mutation Spectra of Histone Methyltransferases With Canonical SET Domains and EZH2-Targeted Therapy

“…The C-terminal SET domain is involved in the methylation of H3K27 [58] and nonhistone proteins, such as GATA4 at K300 [69] and STAT3 at K49 and K180 [70,71]. Wild-type EZH2 and the Y641F/N EZH2 mutant preferentially methylate H3K27me0 and H3K27me2, respectively; however, the A677G and A687V EZH2 mutants nonspecifically methylate H3K27me0, H3K27me1 and H3K27me2.…”

“…EZH2-dependent STAT3 methylation at K49 is necessary for IL-6-induced STAT3 signaling in colon cancer cells [70], whereas EZH2-dependent STAT3 methylation at K180 is necessary for AKT-induced STAT3 signaling in glioblastoma stem cells [71]. Proteomic analyses on the substrates of EZH2 methyltransferase using MS will contribute to the elucidation of complex EZH2 functions in various cell contexts.…”