MLL-fusion proteins, AF9 and ENL, play an essential role in the recruitment of DOT1L and the H3K79 hypermethylation of MLL target genes, which is pivotal for leukemogenesis. Blocking these interactions may represent a novel therapeutic approach for MLL-rearranged leukemia. Based on the 7 mer DOT1L peptide, a class of peptidomimetics was designed. Compound with modified middle residues, achieved significantly improved binding affinities to AF9 and ENL, with K values of 15 nM and 57 nM, respectively. Importantly, recognizes and binds to the cellular AF9 protein and effectively inhibits the AF9-DOT1L interactions in cells. Modifications of the N- and C-termini of resulted in with 2-fold improved binding affinity to AF9 and much decreased peptidic characteristics. Our study provides a proof-of-concept for development of nonpeptidic compounds to inhibit DOT1L activity by targeting its recruitment and the interactions between DOT1L and MLL-oncofusion proteins AF9 and ENL.

Abnormal migration and proliferation of vascular smooth muscle cells (VSMCs) are the pathological basis of hyperplasia during vein graft disease. It remains unknown if circular RNAs (circRNAs) are involved in vein graft disease. In the present study, a rat vein graft model was constructed by the "cuff" technique, and whole transcriptome deep sequencing was applied to identify differential circRNAs in the grafted vein compared to the control. We identified a novel circRNA, named circTET3, whose structure was verified by Sanger sequencing and RNase R digestion. CircTET3 was increased in the grafted vein and stably located in the cytoplasm as detected by fluorescence in situ hybridization. Knockdown of circTET3 suppressed VSMC migration by acting as an endogenous miR-351-5p sponge detected by RNA pull-down and dual-luciferase reporter assays. PTPN1 was the targeted gene due to the competitive binding of circTET3 to miR-351-5p. This regulatory pathway may serve as a potential therapeutic avenue against intimal hyperplasia in vein graft disease.

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Dendritic cells (DCs) have crucial roles in immune‐related diseases. However, it is difficult to explore DCs because of their rareness and heterogeneity. Although previous studies had been performed to detect the phenotypic characteristics of DC populations, the functional diversity has been ignored. Using a combination of flow cytometry, single‐cell quantitative PCR, and bioinformatic analysis, we depicted the DC panorama with not only phenotypic but also functional markers. Functional classification of DCs in mouse lymphoid tissue (spleen) and nonlymphoid tissue (liver) was performed. The results revealed that expression of macrophage scavenger receptor 1 (MSR1) and C–C motif chemokine receptors (CCR)1, CCR2, and CCR4 were elevated in liver DCs, suggesting increased lipid uptake and migration abilities. The enriched expression of costimulatory molecule CD80, TLR9, and TLR adaptor MYD88 in spleen DCs indicated a more‐mature phenotype, enhanced pathogen recognition, and T‐cell stimulation abilities. Furthermore, we compared DCs in the atherosclerotic mouse models with healthy controls. In addition to the quantitative increase in DCs in the liver and spleen of the apolipoprotein E‐knockout (ApoE−/−) mice, the functional expression patterns of the DCs also changed at the single‐cell level. These results promote our understanding of the participation of DCs in inflammatory diseases and have potential applications in DC clinical assessment.—Shi, Q., Zhuang, F., Liu, J.‐T., Li, N., Chen, Y.‐X., Su, X.‐B., Yao, A.‐H., Yao, Q.‐P., Han, Y., Li, S.‐S., Qi, Y.‐X., Jiang, Z.‐L. Single‐cell analyses reveal functional classification of dendritic cells and their potential roles in inflammatory disease. FASEB J. 33, 3784–3794 (2019). http://www.fasebj.org

On the basis of a previously identified DOT1L peptide mimetic (compound 3), a series of novel peptide mimetics were designed and synthesized. These compounds can potently bind to AF9 and ENL either in cell-free binding assays or in leukemia cells, and selectively inhibit the growth of leukemia cells containing mixed lineage leukemia (MLL) fusion proteins. The most potent compound 12 exhibited comparable anticancer cellular activities to those of EPZ5676, a clinical stage enzymatic inhibitor of DOT1L in several leukemia cell lines containing MLL fusion proteins. Mechanism studies for compound 12 indicated that it did not affect the global methylation of H3K79 catalyzed by DOT1L but could effectively suppress the methylation of H3K79 at MLL fusion proteins targeted genes and inhibit the expressions of these genes. Our studies thus demonstrated that inhibiting the protein–protein interactions between DOT1L and MLL fusion proteins is a potentially effective strategy for the treatment of MLL rearranged leukemias.