Jiang et al. generated Dpy30 conditional knockout mice to determine what role Dpy30 and its associated H3K4 methylation may play in the fate determination of tissue-specific stem cells such as HSCs.

Alternative splicing of pre-mRNAs significantly contributes to the complexity of gene expression in higher organisms, but the regulation of the splice site selection remains incompletely understood. We have previously demonstrated that a chromatin-associated protein, AKAP95, has a remarkable activity in enhancing chromatin transcription. In this study, we show that AKAP95 interacts with many factors involved in transcription and RNA processing, including selective groups of hnRNP proteins, through its N-terminal region, and directly regulates pre-mRNA splicing. AKAP95 binds preferentially to proximal intronic regions on pre-mRNAs in human transcriptome, and this binding requires its zinc-finger domains. By selectively coordinating with hnRNP H/F and U proteins, AKAP95 appears to mainly promote the inclusion of many exons in the genome. AKAP95 also directly interacts with itself. Taken together, our results establish AKAP95 as a mostly positive regulator of pre-mRNA splicing and a possible integrator of transcription and splicing regulation.

• DPY30 is important for the proliferation and proper differentiation of human hematopoietic progenitor cells.• dpy30 and efficient H3K4 methylation are essential for the normal hematopoiesis of zebrafish.Epigenetic mechanisms, including histone modifications, have emerged as important factors influencing cell fate determination. The functional role of H3K4 methylation, however, remains largely unclear in the maintenance and differentiation of hematopoietic stem cells (HSCs)/hematopoietic progenitor cells (HPCs). Here we show that DPY30, a shared core subunit of the SET1/MLL family methyltransferase complexes and a facilitator of their H3K4 methylation activity, is important for ex vivo proliferation and differentiation of human CD34 1 HPCs. DPY30 promotes HPC proliferation by directly regulating the expression of genes critical for cell proliferation. Interestingly, while DPY30 knockdown in HPCs impaired their differentiation into the myelomonocytic lineage, it potently promoted hemoglobin production and affected the kinetics of their differentiation into the erythroid lineage. In an in vivo model, we show that morpholino-mediated dpy30 knockdown resulted in severe defects in the development of the zebrafish hematopoietic system, which could be partially rescued by coinjection of dpy30 messenger RNA. Taken together, our results establish a critical role of DPY30 in the proliferation and appropriate differentiation of hematopoietic progenitor cells and in animal hematopoiesis. Finally, we also demonstrate a crucial role of DPY30 in the growth of several MLL1-fusion-mediated leukemia cell lines. (Blood. 2014;124(13):2025-2033 IntroductionThe maintenance, proliferation, and differentiation of stem and progenitor cells are ultimately controlled at the level of gene expression, which is closely tied to the global and local epigenetic status in the cell. A paradigm for such epigenetic control of gene expression is shown by 2 well-established antagonistic histone modifications: H3K27 methylation, catalyzed by the Polycomb group complexes, and H3K4 methylation, mainly catalyzed by the Trithorax group complexes.1 Although H3K27 methylation is generally associated with gene repression, H3K4 methylation is prevalently associated with gene activation. 2,3 Roles for Polycomb group complexes and H3K27 methylation have been extensively studied in both embryonic stem cells (ESCs) 4-6 and hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs). 7-15On the other hand, the functional roles for H3K4 methylation in the maintenance and differentiation of stem and progenitor cells remain largely unclear.The SET1/MLL family complexes are the most notable H3K4 methyltransferases in mammals. They are composed of either SET1A, SET1B, MLL1, MLL2, MLL3, or MLL4 as the catalytic subunit, and WDR5, RBBP5, ASH2L, and DPY30 as integral core subunits that are required for the full methylation activity of these complexes. 2,[16][17][18][19] The functional roles of the SET1/MLL complexes are especially pertinent to the hemato...

While the genomic binding of MYC protein correlates with active epigenetic marks on chromatin, it remains largely unclear how major epigenetic mechanisms functionally impact the tumorigenic potential of MYC. Here, we show that, compared with the catalytic subunits, the core subunits, including DPY30, of the major H3K4 methyltransferase complexes were frequently amplified in human cancers and selectively upregulated in Burkitt lymphoma. We show that DPY30 promoted the expression of endogenous MYC and was also functionally important for efficient binding of MYC to its genomic targets by regulating chromatin accessibility. Dpy30 heterozygosity did not affect normal animal physiology including lifespan, but significantly suppressed Myc-driven lymphomagenesis, as cells failed to combat oncogene-triggered apoptosis as a result of insufficient epigenetic modulation and expression of a subset of antiapoptotic genes. Dpy30 reduction also greatly impeded MYC-dependent cellular transformation, without affecting normal cell growth. These results suggest that MYC hijacks a major epigenetic pathway - H3K4 methylation - to facilitate its molecular activity in target binding and to coordinate its oncogenic program for efficient tumorigenesis, meanwhile creating "epigenetic vulnerability." DPY30 and the H3K4 methylation pathway are thus potential epigenetic targets for treating certain MYC-driven cancers.

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