Project description:BackgroundEnhancer of zeste homologue 2 (EZH2), the core member of polycomb repressive complex 2 (PRC2), has multiple splicing modes and performs various physiological functions. However, function and mechanism of alternative splicing at Ezh2 exon 3 in reproduction are unknown.MethodsWe generated Ezh2Long and Ezh2Short mouse models with different point mutations at the Ezh2 exon 3 alternative splicing site, and each mutant mouse model expressed either the long or the short isoform of Ezh2. We examined mutant mouse fertility and oocyte development to assess the function of Ezh2 alternative splicing at exon 3 in the reproductive system.ResultsWe found that Ezh2Long female mice had normal fertility. However, Ezh2Short female mice had significantly decreased fertility and obstructed oogenesis, with compromised mitochondrial function in Ezh2Short oocytes. Interestingly, increased EZH2 protein abundance and accumulated H3K27me3 were observed in Ezh2Short oocytes.ConclusionsOur results demonstrate that correct Ezh2 alternative splicing at exon 3 is important for mouse oogenesis.
Project description:The responses of macrophages to lipopolysaccharide (LPS) might determine the direction of clinical manifestations of sepsis, which is the immune response against severe infection. Meanwhile, the enhancer of zeste homologue 2 (Ezh2), a histone lysine methyltransferase of epigenetic regulation, might interfere with LPS response. With a single LPS stimulation, Ezh2 null(Ezh2flox/flox; LysM-Crecre/−) macrophages demonstrated lower supernatant TNF-α than Ezh2 control (Ezh2fl/fl; LysM-Cre−/−), perhaps due to an upregulation of Socs3, which is a suppressor of cytokine signaling 3, due to the loss of the Ezh2 gene. In LPS tolerance, Ezh2 null macrophages indicated higher supernatant TNF-α and IL-6 than the control, supporting an impact of the loss of the Ezh2 inhibitory gene. In parallel, Ezh2 null mice demonstrated lower serum TNF-α and IL-6 than the control mice after an LPS injection, indicating a less severe LPS-induced hyper-inflammation in Ezh2 null mice. In conclusion, an absence of Ezh2 in macrophages resulted in less severe LPS-induced inflammation, as indicated by low serum cytokines, with less severe LPS tolerance, as demonstrated by higher cytokine production, partly through the upregulated Socs3.
Project description:Overexpression of EZH2 in estrogen receptor negative (ER-) breast cancer promotes metastasis. EZH2 has been mainly studied as the catalytic component of the Polycomb Repressive Complex 2 (PRC2) that mediates gene repression by trimethylating histone H3 at lysine 27 (H3K27me3). However, how EZH2 drives metastasis despite the low H3K27me3 levels observed in ER- breast cancer is unknown. We have shown that in human invasive carcinomas and distant metastases, cytoplasmic EZH2 phosphorylated at T367 is significantly associated with ER- disease and low H3K27me3 levels. Here, we explore the interactome of EZH2 and of a phosphodeficient mutant EZH2_T367A. We identified novel interactors of EZH2, and identified interactions that are dependent on the phosphorylation and cellular localization of EZH2 that may play a role in EZH2 dependent metastatic progression.
Project description:The Enhancer of Zeste 2 Polycomb Repressive Complex 2 Subunit (EZH2) is an essential epigenetic modifier able to methylate lysine 27 on histone H3 (H3K27) to induce chromatin compaction, protein complex recruitment and ultimately transcriptional repression. Hematologic malignancies, including Diffuse Large B cell lymphoma (DLBCL) and Acute myeloid leukemia (AML) have shown a high EZH2-mutation frequency (>20%) associated with poor clinical outcomes. Particularly, two distinct oncogenic mutations, so-called gain-of-function (Y641F and A677G) and loss-of-function (H689A and F667I) are found in the catalytic domain of EZH2. In this study, a comprehensive multi-omics approach was employed to characterize downstream effects of H3K27me3 deposition driven by EZH2 mutations. Human embryonic kidney cells (HEK293T) were transfected to generate three stable EZH2 mutants: EZH2(Y641F), EZH2(A677G), and EZH2(H689A/F667I), which were validated via immunoblotting and DIA-MS-based histone profiling assay. The histone profiling assay demonstrated a significant increase of approximately two-fold in H3.1/H3.3K27me3 for Y641F EZH2 mutant. There was a modest increase in the combinatorial PTMs H3.1/H3.3K27me3K36me1 and a significant depletion in H3.1 and H3.3 K27me2. The most depleted peptide was H3.3K27me2K36me2. For the A677G EZH2 mutant, the assay demonstrated an enrichment on H3.1/H3.3K27me3, combinatorial K27me3K36me1 and a slight increase in K27me1 and K18ac but only on H3.1. The most depleted peptide was H3.3K27me2K36me2. The H689A/F667I cell line has the most alterations in global histone PTMs. The most highly enriched were H3.1/H3.3K36me2, H3.1K9me3 and H3.3K36me1. The most depleted modifications were H3.1K23ac and H3.1K27me3.
Project description:Cohesin, a trimeric complex that establishes sister chromatid cohesion, has additional roles in chromatin organization and transcription. We report that among those roles is the regulation of alternative splicing through direct interactions and in situ colocalization with splicing factors. Degradation of cohesin results in marked changes in splicing, independent of its effects on transcription. Introduction of a single cohesin point mutation in embryonic stem cells alters splicing patterns, demonstrating causality. In primary human acute myeloid leukemia, mutations in cohesin are highly correlated with distinct patterns of alternative splicing. Cohesin also directly interacts with BRD4, another splicing regulator, to generate a pattern of splicing that is distinct from either factor alone, documenting their functional interaction. These findings identify a role for cohesin in regulating alternative splicing in both normal and leukemic cells and provide insights into the role of cohesin mutations in human disease.
Project description:Aging has many effects on female reproductive system, among which declined oocyte quality and impaired embryo developmental potential are the most important factors affecting female fertility. However, the mechanisms of oocyte aging have not yet been fully understood due to the complex and multifactorial nature of this physiological process. Here, we selected normal reproductively aging female mice as research object and constructed protein expression profile of metaphase II (MII) oocytes from three age groups. A total of 187 differentially expressed (DE) proteins were identified, and bioinformatics analysis showed that these DE proteins were highly enriched in the RNA splicing. Next, RNA-seq was performed on 2-cell embryos from these three age groups, splicing analysis showed that there were a total of 1375 differentially spliced genes (DSGs) and 2363 differentially spliced events (DSEs). DSGs in the reproductive aging groups versus the younger group were enriched in biological processes related to DNA damage repair/response. Binding motif analysis suggested PUF60 may be the core splicing factor that causes the decline of the developmental potential of oocytes in reproductive aging mice, and changing the splicing pattern of its potential downstream DSG Cdk9 could partially mimic phenotypes in the reproductive aging groups. Taken together, our study suggested the abnormal expression of splicing regulation protein in aging MII oocytes will affect the splicing of nascent RNA after zygotic genome activation in 2-cell embryos, leading to the production of abnormally spliced transcripts of some key genes associated with DNA damage repair/response, thus affected the developmental potential of aged oocytes.
Project description:To demonstrated that EZH2 regulates human erythropoiesis in a stage-specific, dual-function manner by catalyzing histone and non-histone methylation,We performed RNA-seq and ChIP-seq.
Project description:Titin, a sarcomeric protein expressed primarily in striated muscles, is responsible for maintaining the structure and biomechanical properties of muscle cells. Cardiac titin undergoes developmental size reduction from 3.7 megadaltons in neonates to primarily 2.97 megadaltons in the adult. This size reduction results from gradually increased exon skipping between exons 50 and 219 of titin mRNA. Our previous study reported that Rbm20 is the splicing factor responsible for this process. In this work, we investigated its molecular mechanism. We demonstrate that Rbm20 mediates exon skipping by binding to titin pre-mRNA to repress the splicing of some regions; the exons/introns in these Rbm20-repressed regions are ultimately skipped. Rbm20 was also found to mediate intron retention and exon shuffling. The two Rbm20 speckles found in nuclei from muscle tissues were identified as aggregates of Rbm20 protein on the partially processed titin pre-mRNAs. Cooperative repression and alternative 3' splice site selection were found to be used by Rbm20 to skip different subsets of titin exons, and the splicing pathway selected depended on the ratio of Rbm20 to other splicing factors that vary with tissue type and developmental age.
Project description:Leucine-rich repeat (LRR) domains are evolutionarily conserved in proteins that function in development and immunity. Here we report strict exonic modularity of LRR domains of several human gene families, which is a precondition for alternative splicing (AS). We provide evidence for AS of LRR domain within several Nod-like receptors, most prominently the inflammasome sensor NLRP3. Human NLRP3, but not mouse NLRP3, is expressed as two major isoforms, the full-length variant and a variant lacking exon 5. Moreover, NLRP3 AS is stochastically regulated, with NLRP3 ∆ exon 5 lacking the interaction surface for NEK7 and hence loss of activity. Our data thus reveals unexpected regulatory roles of AS through differential utilization of LRRs modules in vertebrate innate immunity.