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The N 6 -methyladenosine (m 6 A) modification influences various mRNA metabolic events and tumorigenesis, however, its functions in nonsense-mediated mRNA decay (NMD) and whether NMD detects induced carcinogenesis pathways remain undefined. Here, we showed that the m 6 A methyltransferase METTL3 sustained its oncogenic role by modulating NMD of splicing factors and alternative splicing isoform switches in glioblastoma (GBM). Methylated RNA immunoprecipitation-seq (MeRIP-seq) analyses showed that m 6 A modification peaks were enriched at metabolic pathwayrelated transcripts in glioma stem cells (GSC) compared with neural progenitor cells. In addition, the clinical aggressiveness of malignant gliomas was associated with elevated expression of METTL3. Furthermore, silencing METTL3 or overexpressing dominant-negative mutant METTL3 suppressed the growth and self-renewal of GSCs. Integrated transcriptome and MeRIP-seq analyses revealed that downregulating the expression of METTL3 decreased m 6 A modification levels of serineand arginine-rich splicing factors (SRSF), which led to YTHDC1-dependent NMD of SRSF transcripts and decreased SRSF protein expression. Reduced expression of SRSFs led to larger changes in alternative splicing isoform switches. Importantly, the phenotypes mediated by METTL3 deficiency could be rescued by downregulating BCL-X or NCOR2 isoforms. Overall, these results establish a novel function of m 6 A in modulating NMD and uncover the mechanism by which METTL3 promotes GBM tumor growth and progression.Significance: These findings establish the oncogenic role of m 6 A writer METTL3 in glioblastoma stem cells.

Although somatic cell reprogramming to generate inducible pluripotent stem cells (iPSCs) is associated with profound epigenetic changes, the roles and mechanisms of epigenetic factors in this process remain poorly understood. Here we identify Jmjd3 as a potent negative regulator of reprogramming. Jmjd3-deficient MEFs produced significantly more iPSC colonies than did wild-type cells, while ectopic expression of Jmjd3 markedly inhibited reprogramming. We show that the inhibitory effects of Jmjd3 are produced through both histone demethylase-dependent and -independent pathways. The latter pathway is entirely novel and involves Jmjd3 targeting of PHF20 for ubiquitination and degradation via recruitment of an E3 ligase, Trim26. Importantly, PHF20-deficient MEFs could not be converted to fully reprogrammed iPSCs, even with knockdown of Jmjd3, Ink4a or p21, indicating that this protein exerts predominant effects on reprogramming. Our findings demonstrate a previously unrecognized role of Jmjd3 in cellular reprogramming and provide molecular insight into the mechanisms by which the Jmjd3-PHF20 axis controls this process.

CD-based host–guest supramolecular hydrogels and their potential biomedical application.

Epigenetic factors have been implicated in the regulation of CD4+ T cell differentiation. Jmjd3 plays a role in many biological processes, but its in vivo function in T cell differentiation remains unknown. Here, we report that Jmjd3 ablation promotes CD4+ T cell differentiation into Th2 and Th17 cells in the small intestine and colon, and inhibits T cell differentiation into Th1 cells under different cytokine-polarizing conditions and in a Th1-dependent colitis model. Jmjd3 deficiency also restrains the plasticity of the conversion of Th2, Th17 or Treg cells to Th1 cells. The skewing of T cell differentiation is concomitant with changes in the expression of key transcription factors and cytokines. H3K27me3 and H3K4me3 levels in Jmjd3-deficient cells are correlated with altered gene expression through interactions with specific transcription factors. Our results identify Jmjd3 as an epigenetic factor in T cell differentiation via changes in histone methylation and target gene expression.

N6-methyladenosine (m6A) is the most prevalent internal RNA modification, especially within eukaryotic messenger RNAs (mRNAs). m6A modifications of RNA regulate splicing, translocation, stability, and translation into proteins. m6A modifications are catalyzed by RNA methyltransferases, such as METTL3, METTL14, and WTAP (writers); the modifications are removed by the demethylases fat mass and obesity-associated protein (FTO) and ALKBH5 (ALKB homolog 5) (erasers); and the modifications are recognized by m6A-binding proteins, such as YTHDF domain-containing proteins and IGF2BPs (readers). Abnormal changes in the m6A levels of these genes are closely related to tumor occurrence and development. In this paper, we review the role of m6A in human cancer and summarize its prospective applications in cancer.

The human mixed-lineage leukemia 5 (MLL5) protein mediates hematopoietic cell homeostasis, cell cycle, and survival; however, the molecular basis underlying MLL5 activities remains unknown. Here, we show that MLL5 is recruited to gene-rich euchromatic regions via the interaction of its plant homeodomain finger with the histone mark H3K4me3. The 1.48-Å resolution crystal structure of MLL5 plant homeodomain in complex with the H3K4me3 peptide reveals a noncanonical binding mechanism, whereby K4me3 is recognized through a single aromatic residue and an aspartate. The binding induces a unique His-Asp swapping rearrangement mediated by a C-terminal α-helix. Phosphorylation of H3T3 and H3T6 abrogates the association with H3K4me3 in vitro and in vivo, releasing MLL5 from chromatin in mitosis. This regulatory switch is conserved in the Drosophila ortholog of MLL5, UpSET, and suggests the developmental control for targeting of H3K4me3. Together, our findings provide first insights into the molecular basis for the recruitment, exclusion, and regulation of MLL5 at chromatin.T he mixed-lineage leukemia 5 (MLL5) protein was initially identified as a candidate tumor suppressor and more recently has been shown to play a critical role in hematopoiesis and lymphopoiesis (1). The MLL5 gene-containing region of chromosome 7 is frequently deleted in patients with hematological disorders, including acute myeloid and therapy-induced leukemias and myeloid dysplastic syndrome (MDS). Depletion of Mll5 in mice causes mild postnatal lethality, with some of the surviving animals showing retarded growth, male sterility, and decreased size of thymus, spleen, and lymph nodes (2-4). Genetic analyses of these Mll5 deficiencies reveals a 30% decrease in the number of hematopoietic stem cells (HSC) and progenitors, defects in HSC self-renewal mechanisms, and impaired myeloid differentiation (2-4). In addition to being an essential mediator of HSC homeostasis, MLL5 has been implicated in cytokinesis, the DNA damage response, and genome maintenance (5-7). Overexpression and knockdown of MLL5 both induce cell cycle arrest at various phases, suggesting a versatile function of MLL5 throughout the cell cycle (5).MLL5 belongs to the MLL family of methyltransferases that regulate gene expression during developmental processes. These enzymes catalyze the addition of methyl groups to the e-amino moiety of lysine and are highly specific for lysine 4 of histone H3. Along with MLL5, also known as a lysine methyltransferase 2E (KMT2E), the MLL family contains MLL1-4, SET1A, and SET1B (KMT2A-KMT2D, KMT2F, and KMT2G, respectively) (8). Full-length MLL5 is ∼200 kDa and is evolutionarily distant from the more canonical and better-characterized members of this family. Unlike the other multimodular MLL proteins, MLL5 consists of only two conserved motifs near the N terminus, a plant homeodomain (PHD) finger, followed by a catalytic Su(var)3-9, enhancer of zeste, trithorax (SET) domain. A long, ∼1,000-residue C-terminal region of MLL5 displays no apparent homology to...

IntroductionSecondary osteoporosis is common in systemic lupus erythematosus and leads to a reduction in quality of life due to fragility fractures, even in patients with improvement of the primary disorder. Systemic transplantation of mesenchymal stem cells could ameliorate bone loss and autoimmune disorders in a MRL/lpr mouse systemic lupus erythematosus model, but the detailed therapeutic mechanism of bone regeneration is not fully understood. In this study, we transplanted human bone marrow mesenchymal stem cells (BMMSCs) and stem cells from exfoliated deciduous teeth (SHED) into MRL/lpr mice and explored their therapeutic mechanisms in secondary osteoporotic disorders of the systemic lupus erythematosus model mice.MethodsThe effects of systemic human mesenchymal stem cell transplantation on bone loss of MRL/lpr mice were analyzed in vivo and ex vivo. After systemic human mesenchymal stem cell transplantation, recipient BMMSC functions of MRL/lpr mice were assessed for aspects of stemness, osteogenesis and osteoclastogenesis, and a series of co-culture experiments under osteogenic or osteoclastogenic inductions were performed to examine the efficacy of interleukin (IL)-17-impaired recipient BMMSCs in the bone marrow of MRL/lpr mice.ResultsSystemic transplantation of human BMMSCs and SHED recovered the reduction in bone density and structure in MRL/lpr mice. To explore the mechanism, we found that impaired recipient BMMSCs mediated the negative bone metabolic turnover by enhanced osteoclastogenesis and suppressed osteoblastogenesis in secondary osteoporosis of MRL/lpr mice. Moreover, IL-17-dependent hyperimmune conditions in the recipient bone marrow of MRL/lpr mice damaged recipient BMMSCs to suppress osteoblast capacity and accelerate osteoclast induction. To overcome the abnormal bone metabolism, systemic transplantation of human BMMSCs and SHED into MRL/lpr mice improved the functionally impaired recipient BMMSCs through IL-17 suppression in the recipient bone marrow and then maintained a regular positive bone metabolism via the balance of osteoblasts and osteoclasts.ConclusionsThese findings indicate that IL-17 and recipient BMMSCs might be a therapeutic target for secondary osteoporosis in systemic lupus erythematosus.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0091-4) contains supplementary material, which is available to authorized users.