Mammalian Su(var) genes in chromatin control Fodor, Barna D; Shukeir, Nicholas; Reuter, Gunter ...
Annual review of cell and developmental biology,
11/2010, Letnik:
26
Journal Article
Recenzirano
Genetic screens in Drosophila have been instrumental in distinguishing approximately 390 loci involved in position effect variegation and heterochromatin stabilization. Most of the identified genes ...so-called Su(var) and E(var) genes are also conserved in mammals, where more than 50 of their gene products are known to localize to constitutive heterochromatin. From these proteins, approximately 12 core heterochromatin components can be inferred. In addition, there are approximately 30 additional Su(var) and 10 E(var) factors that can, under distinct developmental options, interchange with constitutive heterochromatin and participate in the partitioning of the genome into repressed and active chromatin domains. A significant fraction of the Su(var) and E(var) factors are enzymes that respond to environmental and metabolic signals, thereby allowing both the variation and propagation of epigenetic states to a dynamic chromatin template. Moreover, the misregulation of human SU(VAR) and E(VAR) function can advance cancer and many other human diseases including more complex disorders. As such, mammalian Su(var) and E(var) genes and their products provide a rich source of novel targets for diagnosis of and pharmaceutical intervention in many human diseases.
Macrophages are key cell types of the innate immune system regulating host defense, inflammation, tissue homeostasis and cancer. Within this functional spectrum diverse and often opposing phenotypes ...are displayed which are dictated by environmental clues and depend on highly plastic transcriptional programs. Among these the 'classical' (M1) and 'alternative' (M2) macrophage polarization phenotypes are the best characterized. Understanding macrophage polarization in humans may reveal novel therapeutic intervention possibilities for chronic inflammation, wound healing and cancer. Systematic loss of function screening in human primary macrophages is limited due to lack of robust gene delivery methods and limited sample availability. To overcome these hurdles we developed cell-autonomous assays using the THP-1 cell line allowing genetic screens for human macrophage phenotypes. We screened 648 chromatin and signaling regulators with a pooled shRNA library for M1 and M2 polarization modulators. Validation experiments confirmed the primary screening results and identified OGT (O-linked N-acetylglucosamine (GlcNAc) transferase) as a novel mediator of M2 polarization in human macrophages. Our approach offers a possible avenue to utilize comprehensive genetic tools to identify novel candidate genes regulating macrophage polarization in humans.
Fragile X syndrome (FXS) is the most common form of inherited mental retardation, and it is caused in most of cases by epigenetic silencing of the Fmr1 gene. Today, no specific therapy exists for ...FXS, and current treatments are only directed to improve behavioral symptoms. Neuronal progenitors derived from FXS patient induced pluripotent stem cells (iPSCs) represent a unique model to study the disease and develop assays for large-scale drug discovery screens since they conserve the Fmr1 gene silenced within the disease context. We have established a high-content imaging assay to run a large-scale phenotypic screen aimed to identify compounds that reactivate the silenced Fmr1 gene. A set of 50,000 compounds was tested, including modulators of several epigenetic targets. We describe an integrated drug discovery model comprising iPSC generation, culture scale-up, and quality control and screening with a very sensitive high-content imaging assay assisted by single-cell image analysis and multiparametric data analysis based on machine learning algorithms. The screening identified several compounds that induced a weak expression of fragile X mental retardation protein (FMRP) and thus sets the basis for further large-scale screens to find candidate drugs or targets tackling the underlying mechanism of FXS with potential for therapeutic intervention.
Histone lysine trimethyl states represent some of the most robust epigenetic modifications in eukaryotic chromatin. Using a candidate approach, we identified the subgroup of murine Jmjd2 proteins to ...antagonize H3K9me3 at pericentric heterochromatin. H3K27me3 and H4K20me3 marks are not impaired in inducible Jmjd2b-GFP cell lines, but Jmjd2b also reduces H3K36 methylation. Since recombinant Jmjd2b appears as a very poor enzyme, we applied metabolic labeling with heavy methyl groups to demonstrate Jmjd2b-mediated removal of chromosomal H3K9me3 as an active process that occurs well before replication of chromatin. These data reveal that certain members of the jmjC class of hydroxylases can work in a pathway that actively antagonizes a histone lysine trimethyl state.
Posttranslational modifications of histones, such as methylation, regulate chromatin structure and gene expression. Recently, lysine-specific demethylase 1 (LSD1), the first histone demethylase, was ...identified. LSD1 interacts with the androgen receptor and promotes androgen-dependent transcription of target genes by ligand-induced demethylation of mono- and dimethylated histone H3 at Lys 9 (H3K9) only. Here, we identify the Jumonji C (JMJC) domain-containing protein JMJD2C as the first histone tridemethylase regulating androgen receptor function. JMJD2C interacts with androgen receptor in vitro and in vivo. Assembly of ligand-bound androgen receptor and JMJD2C on androgen receptor-target genes results in demethylation of trimethyl H3K9 and in stimulation of androgen receptor-dependent transcription. Conversely, knockdown of JMJD2C inhibits androgen-induced removal of trimethyl H3K9, transcriptional activation and tumour cell proliferation. Importantly, JMJD2C colocalizes with androgen receptor and LSD1 in normal prostate and in prostate carcinomas. JMJD2C and LSD1 interact and both demethylases cooperatively stimulate androgen receptor-dependent gene transcription. In addition, androgen receptor, JMJD2C and LSD1 assemble on chromatin to remove methyl groups from mono, di and trimethylated H3K9. Thus, our data suggest that specific gene regulation requires the assembly and coordinate action of demethylases with distinct substrate specificities.
Canted Cosine Theta layout for accelerator magnets is a very attractive since such magnets can be manufactured and assembled without big tooling, and with a relatively modest number of parts and ...tools. In the frame of European Horizon2020 funds, two collaborations, HITRI plus and I.FAST, are developing a CCT design, of 80 mm free bore, 4 T central dipole field, and 0.4 T/s ramp-rate. This magnet is expected to be the bending element of a gantry, to control the beam delivery in therapy with ions (hadrontherapy). The paper illustrates first a comparison between CCT and more classical cosine theta layout, followed by the comparison between Nb-Ti, Nb 3 Sn, MgB 2 , and HTS tapes coils. Relevant requirement for the magnets of this study is to be operated at low current, to limit the heat generation, in sight of a liquid-free cooling system. The results of the comparison is then applied to the design of two magnet demonstrators. Both adopt a low-losses Nb-Ti rope, consistently with the need for keeping the heat generation as low as possible. The first is a straight combined function dipole-quadrupole, while the second is a curved CCT dipole. The paper concludes with the first manufacturing tests for the CCT formers, for which aluminium -bronze, stainless steel and charged PEEK polymer are being explored as basic material.
A recent laser spectroscopy experiment of three-body pionic helium atoms which was carried out using the 590 MeV ring cyclotron facility of the Paul Scherrer Institute (PSI) is briefly reviewed. The ...charged pion mass may be precisely determined by measuring the transition frequency of the pionic atom and comparing the results with quantum electrodynamics (QED) calculations. The experimental methods used to detect the atomic resonance are described.
Some experimental limits on the annihilation cross sections σann of antiprotons on carbon, palladium, and platinum targets were determined at the previously unexplored kinetic energy region E≈125 ...keV. Information on σann at such low antiproton energies is important in understanding the dynamics of the annihilation process, and provides useful data for models that attempt to describe the matter-antimatter asymmetry in the universe by assuming the existence of islands of antimatter concentration.
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