Edited by Xiao-Fan WangDifferentiation of human embryonic stem cells into mesendoderm (ME) is directed by extrinsic signals and intrinsic epigenetic modifications. However, the dynamics of these epigenetic modifications and the mechanisms by which extrinsic signals regulate the epigenetic modifications during the initiation of ME differentiation remain elusive. In this study, we report that levels of histone H3 Lys-27 trimethylation (H3K27me3) decrease during ME initiation, which is essential for subsequent differentiation induced by the combined effects of activin and Wnt signaling. Furthermore, we demonstrate that activin mediates the H3K27me3 decrease via the Smad2-mediated reduction of EZH2 protein level. Our results suggest a two-step process of ME initiation: first, epigenetic priming via removal of H3K27me3 marks and, second, transcription activation. Our findings demonstrate a critical role of H3K27me3 priming and a direct interaction between extrinsic signals and epigenetic modifications during ME initiation.
SummaryCellular responses to transforming growth factor β (TGF-β) depend on cell context. Here, we explored how TGF-β/nodal signaling crosstalks with the epigenome to promote mesendodermal differentiation. We find that expression of a group of mesendodermal genes depends on both TRIM33 and nodal signaling in embryoid bodies (EBs) but not in embryonic stem cells (ESCs). Only in EBs, TRIM33 binds these genes in the presence of expanded H3K18ac marks. Furthermore, the H3K18ac landscape at mesendodermal genes promotes TRIM33 recruitment. We reveal that HDAC1 binds to active gene promoters and interferes with TRIM33 recruitment to mesendodermal gene promoters. However, the TRIM33-interacting protein p300 deposits H3K18ac and further enhances TRIM33 recruitment. ATAC-seq data demonstrate that TRIM33 primes mesendodermal genes for activation by maintaining chromatin accessibility at their regulatory regions. Altogether, our study suggests that HDAC1 and p300 are key factors linking the epigenome through TRIM33 to the cell context-dependent nodal response during mesendodermal differentiation.
In this paper, we are aimed to search the Pareto front of multi-objective optimal reactive power dispatch by the primal dual interior point method. In the front part are the introductions of optimal reactive power dispatch model, the concepts of Pareto optimum solution and Pareto front, and the primal dual interior point method. In the rear part, the process of searching Pareto front will be presented, followed by the case study which consists of three cases. By conducting case study, we concludes that the primal dual interior point method performs effectively as well as efficiently in searching the Pareto front of multi-objective optimal reactive power dispatch.Index Terms--optimal reactive power dispatch, multiobjective nonlinear programming, Pareto front, Pareto optimum solution, primal dual interior point method I.
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