MI-2

MI-2 is a Menin-MLL inhibitor with IC50 value of 0.45 μM [1].

Mixed-lineage leukemia (MLL) is a common target of chromosomal translocations in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). The leukemogenic activity of MLL fusion proteins is dependent on their direct interaction with menin, which is a tumor suppressor that directly controls cell growth in endocrine organs [1].

MI-2 is a Menin-MLL inhibitor. MI-2 bound to the wild-type menin but didn’t bind M278K and Y323K menin mutants. In HEK293 cells transfected with Flag-MLL-AF9, MI-2 effectively inhibited the menin-MLL-AF9 interaction without affecting the expression level of menin and MLL-AF9. In mouse bone marrow cells (BMC) transduced with MLL-AF9 and MLL-ENL, MI-2 blocked proliferation of BMC with GI50 value of about 5 μM. Also, MI-2 inhibited colony formation in BMC transduced with MLL-AF9. In a series of human MLL leukemia cell lines, MI-2 significantly inhibited translocation in a dose dependant way [1].

Reference:
[1].  Grembecka J, He S, Shi A, et al. Menin-MLL inhibitors reverse oncogenic activity of MLL fusion proteins in leukemia. Nat Chem Biol, 2012, 8(3): 277-284.

Mi-2/NuRD chromatin remodeling complexes regulate B and T-lymphocyte development and function.[Pubmed:25123281]

Immunol Rev. 2014 Sep;261(1):126-40.

MI-2/nucleosomal remodeling and deacetylase (NuRD) complexes are important epigenetic regulators of chromatin structure and gene expression. MI-2/NuRD complexes are an assemblage of proteins that combine key epigenetic regulators necessary for (i) histone deacetylation and demethylation, (ii) binding to methylated DNA, (iii) mobilization of nucleosomes, and (iv) recruitment of additional regulatory proteins. Depending on their context in chromatin, MI-2/NuRD complexes either activate or repress gene transcription. In this regard, they are important regulators of hematopoiesis and lymphopoiesis. MI-2/NuRD complexes maintain pools of hematopoietic stem cells. Specifically, components of these complexes control multiple stages of B-cell development by regulating B-cell specific transcription. With one set of components, they inhibit terminal differentiation of germinal center B cells into plasma B cells. They also mediate gene repression together with Blimp-1 during plasma cell differentiation. In cooperation with Ikaros, MI-2/NuRD complexes also play important roles in T-cell development, including CD4 versus CD8 fate decisions and peripheral T-cell responses. Dysregulation of NuRD during lymphopoiesis promotes leukemogenesis. Here, we review general properties of MI-2/NuRD complexes and focus on their functions in gene regulation and development of lymphocytes.

Enzyme-linked immunosorbent assays for detection of anti-transcriptional intermediary factor-1 gamma and anti-Mi-2 autoantibodies in dermatomyositis.[Pubmed:27693019]

J Dermatol Sci. 2016 Dec;84(3):272-281.

BACKGROUND: Autoantibodies against transcriptional intermediary factor 1 (TIF1) and MI-2 are selectively detected in patients with dermatomyositis (DM). To measure these antibodies readily, the development of reliable ELISA systems has been needed. OBJECTIVE: This study aimed to establish enzyme-linked immunosorbent assays (ELISAs) for anti-TIF1gamma and anti-MI-2beta antibodies (Abs) and to assess their utility. METHODS: Serum samples were obtained from 104 patients with classic DM, 68 with clinically amyopathic DM (CADM) and 70 with polymyositis, who were followed up at 8 medical centers across Japan. Serum samples from 190 patients with other connective tissue diseases (CTDs) and 123 healthy individuals were also assessed. Serum antibody levels were examined by ELISAs coated with full-length TIF1gamma or MI-2beta proteins produced by a baculovirus expression system. To assess the cross-reactivity, partial-length MI-2beta proteins with or without mutations were produced and examined for reactivity. RESULTS: When compared with immunoprecipitation assay, anti-TIF1gamma Ab ELISA showed 100% sensitivity and 100% specificity, while anti-MI-2beta Ab ELISA showed 100% sensitivity and 99.6% specificity. Anti-TIF1gamma Ab was positive in 30 (28.8%) with classic DM and 4 (5.9%) with CADM, whereas 14 (13.5%) with classic DM, but none with CADM, were positive for anti-MI-2beta Ab. Of 30 anti-TIF1gamma Ab-positive DM patients, 23 (67.6%) had malignancy. Anti-MI-2beta Ab-positive serum samples exhibited modest cross-reactivity with the TIF1gamma protein due to the homologous amino acid sequence containing cysteines in their plant homeodomains. CONCLUSION: The current study demonstrates the utility of newly established ELISAs for anti-TIF1gamma and anti-MI-2beta Abs, which can serve as easier detection systems for routine testing.

LincRNA-Cox2 modulates TNF-alpha-induced transcription of Il12b gene in intestinal epithelial cells through regulation of Mi-2/NuRD-mediated epigenetic histone modifications.[Pubmed:26578685]

FASEB J. 2016 Mar;30(3):1187-97.

Long intergenic noncoding RNAs (lincRNAs) can regulate the transcription of inflammatory genes and thus may represent a new group of inflammatory mediators with a potential pathogenic role in inflammatory diseases. Here, our genome-wide transcriptomic data show that TNF-alpha stimulation caused up-regulation of 171 lincRNAs and down-regulation of 196 lincRNAs in murine intestinal epithelial cells in culture. One of the up-regulated lincRNAs, lincRNA-Cox2, is an early-responsive lincRNA induced by TNF-alpha through activation of the NF-kB signaling pathway. Knockdown of lincRNA-Cox2 resulted in reprogramming of the gene expression profile in intestinal epithelial cells in response to TNF-alpha stimulation. Specifically, lincRNA-Cox2 silencing significantly (P < 0.05) enhanced the transcription of Il12b, a secondary late-responsive gene induced by TNF-alpha. Mechanistically, lincRNA-Cox2 promoted the recruitment of the MI-2/nucleosome remodeling and deacetylase (MI-2/NuRD) repressor complex to the Il12b promoter region. Recruitment of the MI-2/NuRD complex was associated with decreased H3K27 acetylation and increased H3K27 dimethylation at the Il12b promoter region, which might contribute to Il12b trans-suppression by lincRNA-Cox2. Thus, our data demonstrate a novel mechanism of epigenetic modulation by lincRNA-Cox2 on Il12b transcription, supporting an important role for lincRNAs in the regulation of intestinal epithelial inflammatory responses.

Toxoplasma Effector Recruits the Mi-2/NuRD Complex to Repress STAT1 Transcription and Block IFN-gamma-Dependent Gene Expression.[Pubmed:27414498]

Cell Host Microbe. 2016 Jul 13;20(1):72-82.

Interferon gamma (IFN-gamma) is an essential mediator of host defense against intracellular pathogens, including the protozoan parasite Toxoplasma gondii. However, prior T. gondii infection blocks IFN-gamma-dependent gene transcription, despite the downstream transcriptional activator STAT1 being activated and bound to cognate nuclear promoters. We identify the parasite effector that blocks STAT1-dependent transcription and show it is associated with recruitment of the MI-2 nucleosome remodeling and deacetylase (NuRD) complex, a chromatin-modifying repressor. This secreted effector, toxoplasma inhibitor of STAT1-dependent transcription (TgIST), translocates to the host cell nucleus, where it recruits MI-2/NuRD to STAT1-dependent promoters, resulting in altered chromatin and blocked transcription. TgIST is conserved across strains, underlying their shared ability to block IFN-gamma-dependent transcription. TgIST deletion results in increased parasite clearance in IFN-gamma-activated cells and reduced mouse virulence, which is restored in IFN-gamma-receptor-deficient mice. These findings demonstrate the importance of both IFN-gamma responses and the ability of pathogens to counteract these defenses.