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Mixed lineage leukemia 1 (MLL1), a histone H3 lysine 4 (H3K4) methyltransferase, exerts its enzymatic activity by interacting with menin and other proteins. It is unclear whether inhibition of the MLL1‐menin interaction influences epithelial‐mesenchymal transition (EMT), renal fibroblast activation, and renal fibrosis. In this study, we investigated the effect of disrupting MLL1‐menin interaction on those events and mechanisms involved in a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO), in cultured mouse proximal tubular cells and renal interstitial fibroblasts. Injury to the kidney increased the expression of MLL1 and menin and H3K4 monomethylation (H3K4me1); MLL1 and menin were expressed in renal epithelial cells and renal interstitial fibroblasts. Inhibition of the MLL1‐menin interaction by MI‐503 administration or siRNA‐mediated silencing of MLL1 attenuated UUO‐induced renal fibrosis, and reduced expression of α‐smooth muscle actin (α‐SMA) and fibronectin. These treatments also inhibited UUO‐induced expression of transcription factors Snail and Twist and transforming growth factor β1 (TGF‐β1) while expression of E‐cadherin was preserved. Moreover, treatment with MI‐503 and transfection with either MLL siRNA or menin siRNA inhibited TGF‐β1‐induced upregulation of α‐SMA, fibronectin and Snail, phosphorylation of Smad3 and AKT, and downregulation of E‐cadherin in cultured renal epithelial cells. Finally, MI‐503 was effective in abrogating serum or TGFβ1‐induced transformation of renal interstitial fibroblasts to myofibroblasts in vitro. Taken together, these results suggest that targeting disruption of the MLL1‐menin interaction attenuates renal fibrosis through inhibition of partial EMT and renal fibroblast activation. [ABSTRACT FROM AUTHOR]

Objective To establish a novel approach for diagnosing endometriosis (EM) in patients with impaired endometrial receptivity. Method Mixed lineage leukemia 1 (MLL1) and enhancer of zeste homolog 2 (EZH2) levels were analyzed. The MLL1:EZH2 ratio in identifying impaired endometrial receptivity has been established and validated. Results In normal endometrial tissue, the MLL1:EZH2 ratio increased significantly in the midsecretory phase, compared with that in the proliferative phase. In the midsecretory phase, the MLL1:EZH2 ratio in endometrial tissues and uterine secretions accurately identifies patients with EM who have impaired endometrial receptivity. In the validation group, the sensitivity and specificity of the MLL1:EZH2 ratio in the uterine secretions of the midsecretory phase, in diagnosing patients EM who have impaired endometrial receptivity, were 100% and 96.55%, respectively. Conclusions The MLL1:EZH2 ratio in uterine secretions of the midsecretory phase may serve as a marker to diagnose EM in patients with impaired endometrial receptivity. [ABSTRACT FROM AUTHOR]

Mixed lineage leukemia 1 (MLL1, also known as MLL or KMT2A) is an important transcription factor and histone-H3 lysine-4 (H3K4) methyltransferase. It is a master regulator for transcription of important genes (e.g., Hox genes) for embryonic development and hematopoiesis. However, it is largely dispensable in matured cells. Dysregulation of MLL1 leads to overexpression of certain Hox genes and eventually leukemia initiation. Chromosome translocations involving MLL1 cause ~ 75% of acute leukemia in infants and 5–10% in children and adults with a poor prognosis. Targeted therapeutics against oncogenic fusion MLL1 (onco-MLL1) are therefore needed. Onco-MLL1 consists of the N-terminal DNA-interacting domains of MLL1 fused with one of > 70 fusion partners, among which transcription cofactors AF4, AF9 and its paralog ENL, and ELL are the most frequent. Wild-type (WT)- and onco-MLL1 involve numerous protein–protein interactions (PPI), which play critical roles in regulating gene expression in normal physiology and leukemia. Moreover, WT-MLL1 has been found to be essential for MLL1-rearranged (MLL1-r) leukemia. Rigorous studies of such PPIs have been performed and much progress has been achieved in understanding their structures, structure–function relationships and the mechanisms for activating gene transcription as well as leukemic transformation. Inhibition of several critical PPIs by peptides, peptidomimetic or small-molecule compounds has been explored as a therapeutic approach for MLL1-r leukemia. This review summarizes the biological functions, biochemistry, structure and inhibition of the critical PPIs involving MLL1 and its fusion partner proteins. In addition, challenges and perspectives of drug discovery targeting these PPIs for the treatment of MLL1-r leukemia are discussed. [ABSTRACT FROM AUTHOR]

The aberrant histone methylation patterns contribute to the pathogenesis of endometriosis (EM). Mixed lineage leukemia 1 (MLL1), a histone methyltransferase, is crucial for gene expression by catalyzing the trimethylation of histone 3 lysine 4 (H3K4me3) in gene promoter. This study aimed to explore whether MLL1 is involved in EM-related infertility. The expressions of MLL1 and H3K4me3 were analyzed in the eutopic endometria from EM women with infertility (n = 22) and the normal endometria from EM-free women (n = 22). Mouse EM model was established. The MLL1 and H3K4me3 expression patterns in mice endometria of early pregnancy were also investigated. Immortalized human endometrial stromal cells (iESCs) were cultured and underwent in vitro decidualization. The chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) was performed to find the target gene of MLL1 during decidual process. Results showed that both MLL1 and H3K4me3 decreased in the euto pic endometrium from EM patients compared to that in the normal endometrium. Du ring early pregnancy and the decidual process, MLL1 and H3K4me3 were significantly upregulated in stromal cells. ChIP-seq and ChIP-qPCR found that the cytochrome c oxidase subunit 4I 2 (COX4I2) was directly targeted by MLL1. The dominance of COX4I2-containing enzyme induced the expression of hypoxia-inducible factor-2a (HIF-2a), whose expression in the periimplantation endometrium is essential for embryo implantation. Further results showed that MLL1 was directly regulated by progesterone (P4) - P4 rece ptors (PRs). Our study proved that MLL1 was involved in EM-related infertility, which may provide a novel approach to treat the nonreceptive endometrium in EM patients. [ABSTRACT FROM AUTHOR]

Summary The nucleoporin 98 gene ( NUP98 ) is fused to a variety of partner genes in multiple hematopoietic malignancies. Here, we demonstrate that NUP98 fusion proteins, including NUP98-HOXA9 (NHA9), NUP98-HOXD13 (NHD13), NUP98-NSD1, NUP98-PHF23, and NUP98-TOP1 physically interact with mixed lineage leukemia 1 (MLL1) and the non-specific lethal (NSL) histone-modifying complexes. Chromatin immunoprecipitation sequencing illustrates that NHA9 and MLL1 co-localize on chromatin and are found associated with Hox gene promoter regions. Furthermore, MLL1 is required for the proliferation of NHA9 cells in vitro and in vivo. Inactivation of MLL1 leads to decreased expression of genes bound by NHA9 and MLL1 and reverses a gene expression signature found in NUP98 -rearranged human leukemias. Our data reveal a molecular dependency on MLL1 function in NUP98-fusion-driven leukemogenesis. [ABSTRACT FROM AUTHOR]

• MLL1, TLR4, and TRIF are highly expressed in RA. • MLL1 enriches H3K4me3 in TLR4 promoter region to increase TLR4 expression in RA. • MLL1 silencing blocks the TRIF/NF-κB signaling pathway by reducing TLR4 in RA. • MLL1 silencing inhibits RA-FLS migration and invasion. • This study proposes a theoretical basis for the treatment of RA. Rheumatoid arthritis (RA) is the most common inflammatory arthritis and is a major cause of disability. Interestingly, the histone methyltransferase mixed-lineage leukemia 1 (MLL1) has been linked to many inflammation-related diseases. Moreover, toll-like receptor 4 (TLR4) has been reported to induce migration and invasion in RA-fibroblast-like synoviocytes (FLSs). This study intended to delineate the functional relevance of MLL1 in RA progression, which implicates the regulation of TLR4. First, clinical synovial tissues were collected from RA patients and patients with severe joint trauma to isolate FLSs. We identified highly expressed MLL1 and TLR4 in synovial tissues of RA patients, and the expression of them was positively correlated in RA-FLSs. More importantly, silencing of MLL1 and TLR4 resulted in suppressed migration and invasion of RA-FLSs, accompanied by reduced inflammation. Additionally, mechanistic investigations showed that MLL1 upregulated TLR4 expression by inducing H3K4me3 in the promoter region of TLR4. Functional assays revealed that overexpression of MLL1 activated the TRIF/NF-κB signaling pathway, resulting in accelerated migration and invasion, and inflammation of RA-FLSs in vitro. TLR4 knockdown could compromise the effects of MLL1 overexpression. The in vivo assays in a collagen-induced arthritis rat model validated the in vitro findings. Taken together, histone methyltransferase MLL1 induces TLR4 expression by mediating H3K4me3 in the TLR4 promoter, thus activating the TRIF/NF-κB signaling pathway, which thereby promotes the migration and invasion of RA-FLSs and ultimately exacerbates the progression of RA. [ABSTRACT FROM AUTHOR]