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  • MDR1 mediated chemoresistance: BMI1 and TIP60 in action. 27295567

    Chemotherapy-induced emergence of drug resistant cells is frequently observed and is exemplified by the expression of family of drug resistance proteins including, multidrug resistance protein 1 (MDR1). However, a concise mechanism for chemotherapy-induced MDR1 expression is unclear. Mechanistically, mutational selection, epigenetic alteration, activation of the Wnt pathway or impaired p53 function have been implicated. The present study describes that the surviving fraction of cisplatin resistant cells co- upregulate MDR1, BMI1 and acetyl transferase activity of TIP60. Using complementary gain and loss of function approaches, we demonstrate that the expression of MDR1 is positively regulated by BMI1, a stem-cell factor classically known as a transcriptional repressor. Our study establishes a functional interaction between TIP60 and BMI-1 resulting in upregulation of MDR1 expression. Chromatin immunoprecipitation (ChIP) assays further establish that the proximal MDR1 promoter responds to cisplatin in a BMI1 dependent manner. BMI1 interacts with a cluster of E-box elements on the MDR1 promoter and recruits TIP60 resulting in acetylation of histone H2A and H3. Collectively, our data establish a hitherto unknown liaison among MDR1, BMI1 and TIP60 and provide mechanistic insights into cisplatin-induced MDR1 expression resulting in acquired cross-resistance against paclitaxel, doxorubicin and likely other drugs. In conclusion, our results advocate utilizing anti-BMI1 strategies to alleviate acquired resistance to chemotherapy.
    Tipo de documento:
    Referencia
    Referencia del producto:
    17-371
    Nombre del producto:
    EZ-ChIP™

  • Single nucleosome ChIPs identify an extensive switch of acetyl marks on cell cycle promoters. 20505338

    Histones are modified by different post-translational modifications which are marks of peculiar chromatin functions. We previously evaluated histone methylations of G1/S and G2/M cell-cycle promoters at the single nucleosome level; here we report an analysis of acetylation marks, including some for which essentially nothing is known. In general, our data confirm the presence of H3/H4, but not H2A/H2B, in active core promoters. H3K14ac and H3K27ac are associated with active promoters, while H3K9ac and H3K18ac are more ambiguous, being also found under repression. Acetylation of H3K36, H3K79 and H2BK120, all residues involved in positive function through methylations or monoubiquitination, were found on repressed genes. H2Bub was present only on transcribed areas, and absent on core promoters or upstream nucleosomes. KAT2A/KAT2B and subunits of the SAGA and ATAC complexes have differential and dynamic roles: KAT2A-inactivated MEFs show a G1/S block, and KAT2B is important for G2/M. Furthermore, the precision of our analysis allows us to locate some acetylations specifically occurring upstream, downstream or in core promoters. Overall, the switch between methylations-and monoubiquitination-and acetylations on histone Lysines is a general theme on this dynamic group of genes.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-677

  • Modulation of chromatin remodelling induced by the freshwater cyanotoxin cylindrospermopsin in human intestinal caco-2 cells. 24921660

    Cylindrospermopsin (CYN) is a cyanotoxin that has been recognised as an emerging potential public health risk. Although CYN toxicity has been demonstrated, the mechanisms involved have not been fully characterised. To identify some key pathways related to this toxicity, we studied the transcriptomic profile of human intestinal Caco-2 cells exposed to a sub-toxic concentration of CYN (1.6 µM for 24hrs) using a non-targeted approach. CYN was shown to modulate different biological functions which were related to growth arrest (with down-regulation of cdkn1a and uhrf1 genes), and DNA recombination and repair (with up-regulation of aptx and pms2 genes). Our main results reported an increased expression of some histone-modifying enzymes (histone acetyl and methyltransferases MYST1, KAT5 and EHMT2) involved in chromatin remodelling, which is essential for initiating transcription. We also detected greater levels of acetylated histone H2A (Lys5) and dimethylated histone H3 (Lys4), two products of these enzymes. In conclusion, CYN overexpressed proteins involved in DNA damage repair and transcription, including modifications of nucleosomal histones. Our results highlighted some new cell processes induced by CYN.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Heterogeneity of chromatin modifications in testicular spermatocytic seminoma point toward an epigenetically unstable phenotype. 22819380

    Testicular spermatocytic seminoma (SS) is a rare tumor type predominantly found in elderly men. It is thought to originate from spermatogonia and shows cytological and genetic heterogeneity. In this study, we performed for the first time a comprehensive analysis of epigenetic modifications in a series of 36 SS samples. We assessed by immunohistochemistry tumor DNA methylation levels, the expression of methyltransferases DNMT3A, DNMT3B and DNMT3L as well as levels of histone modifications H3K9me2, H3K27me3, H3K4me1, H3K4me2/3, H3K9ac, and H2A.Z. We did not identify any epigenetic marks that matched the pattern of the supposed cell-of-origin, the spermatogonia, and found no correlation between specific marks and the size of the SS cells. The emerging epigenetic picture of SS is a heterogeneous salt-and-pepper-like pattern, with neighboring cells displaying very variable levels of epigenetic marks. We conclude that SS cells display apparent epigenetic heterogeneity and instability, with loss of the organized manner typical for normal germ cell maturation in the adult testis, likely due to the lack of regulatory signals from the absent somatic cell niche.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-689
    Nombre del producto:
    Anti-EZH2 Antibody

  • Efficient organic monoliths prepared by γ-radiation induced polymerization in the evaluation of histone deacetylase inhibitors by capillary(nano)-high performance liquid ... 21561626

    New monolithic HPLC columns were prepared by γ-radiation-triggered polymerization of hexyl methacrylate and ethylene glycol dimethacrylate monomers in the presence of porogenic solvents. Polymerization was carried out directly within capillary (250-200μm I.D.) and nano (100-75μm I.D.) fused-silica tubes yielding highly efficient columns for cap(nano)-LC applications. The columns were applied in the complete separation of core (H2A, H2B, H3, and H4) and linker (H1) histones under gradient elution with UV and/or electrospray ionization (ESI) ion trap mass spectrometry (MS) detections. Large selectivity towards H1, H2A-1, H2A-2, H2B, H3-1, H3-2 and H4 histones and complete separation were obtained within 8min time windows, using fast gradients and very high linear flow velocities, up to 11mm/s for high throughput applications. The method developed was the basis of a simple and efficient protocol for the evaluation of post-translational modifications (PTMs) of histones from NCI-H460 human non-small-cell lung cancer (NSCLC) and HCT-116 human colorectal carcinoma cells. The study was extended to monitoring the level of histone acetylation after inhibition of Histone DeACetylase (HDAC) enzymes with suberoylanilide hydroxamic acid (SAHA), the first HDAC inhibitor approved by the FDA for cancer therapy. Attractive features of our cap(nano)-LC/MS approach are the short analysis time, the minute amount of sample required to complete the whole procedure and the stability of the polymethacrylate-based columns. A lab-made software package ClustMass was ad hoc developed and used to elaborate deconvoluted mass spectral data (aligning, averaging, clustering) and calculate the potency of HDAC inhibitors, expressed through a Relative half maximal Inhibitory Concentration parameter, namely R_IC(50) and an averaged acetylation degree.Copyright © 2011 Elsevier B.V. All rights reserved.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • MOF and H4 K16 acetylation play important roles in DNA damage repair by modulating recruitment of DNA damage repair protein Mdc1. 20837706

    MOF (MYST1) is the major enzyme to catalyze acetylation of histone H4 lysine 16 (K16) and is highly conserved through evolution. Using a conditional knockout mouse model and the derived mouse embryonic fibroblast cell lines, we showed that loss of Mof led to a global reduction of H4 K16 acetylation, severe G(2)/M cell cycle arrest, massive chromosome aberration, and defects in ionizing radiation-induced DNA damage repair. We further showed that although early DNA damage sensing and signaling by ATM were normal in Mof-null cells, the recruitment of repair mediator protein Mdc1 and its downstream signaling proteins 53bp1 and Brca1 to DNA damage foci was completely abolished. Mechanistic studies suggested that Mof-mediated H4 K16 acetylation and an intact acidic pocket on H2A.X were essential for the recruitment of Mdc1. Removal of Mof and its associated proteins phenocopied a charge-neutralizing mutant of H2A.X. Given the well-characterized H4-H2A trans interactions in regulating higher-order chromatin structure, our study revealed a novel chromatin-based mechanism that regulates the DNA damage repair process.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo