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Search Results: 1 - 10 of 19846 matches for " Alexander Brehm "
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über die allm hliche Verfestigung der Gedanken beim Drücken von Tasten
Brehm, Alexander
Journal of New Frontiers in Spatial Concepts , 2012,
Abstract: In the Western post-industrial societies, the individual experience is heavily shaped by the day-to-day contact with information and communication technologies. This article argues that everyday experience based on the use of communication technologies leads to a specific adaptation of the human consciousness to the technical environment. The question is discussed, what is the impact of this process on human consciousness.
The dosage-compensation complex in flies and humans
Karim Bouazoune, Michael Korenjak, Alexander Brehm
Genome Biology , 2004, DOI: 10.1186/gb-2004-5-11-352
Abstract: There were many exciting talks presented at the recent EMBL Transcription meeting in Heidelberg that reported recent insights into the role of chromatin-modifying protein complexes in transcriptional regulation, and four captured our interest especially. They all concern work on a ribonucleoprotein complex that has a defined biological role - namely to regulate dosage compensation in flies. This dosage compensation complex (DCC; also referred to as the MSL complex or the 'compensasome') consists of the histone acetyltransferase encoded by males-absent-on-the-first (mof), the male-specific-lethal-encoded, proteins MSL1, MSL2 and MSL3, the Maleless (MLE) helicase and two noncoding RNAs, RNA-on-the-X (roX) 1 and roX2. In addition, it has been suggested that the DCC associates with the JIL1 protein kinase.According to the prevalent model, the DCC is necessary for upregulating gene expression from the single male X chromosome precisely twofold, thus ensuring that male and female flies produce the same amount of X-linked gene products. The DCC, which does not form in females, is believed to facilitate transcription from the hyperactive X. This occurs at least in part through acetylation of histone H4 lysine 16 of the X chromosome, and this acetylation is believed to be catalyzed by the MOF histone acetyltransferase subunit. Immunostaining of the polytene chromosomes has revealed a strong and specific association between the DCC and the male X chromosome; indeed, the DCC 'paints' the X chromosome, but not the autosomes, in its entirety.How does this peculiar localization of the DCC come about? Mutant flies lacking certain subunits of the DCC (but retaining the MSL1 and MSL2 core components) show reduced binding to the male X chromosome. In fact, instead of a chromosome-wide association, DCC binding in the mutants is restricted to 30-55 sites. This and other findings have led to a model whereby the DCC first binds to specialized 'entry sites' on the X from where it 'spreads
The Drosophila methyl-DNA binding protein MBD2/3 interacts with the NuRD complex via p55 and MI-2
Joachim Marhold, Alexander Brehm, Katja Kramer
BMC Molecular Biology , 2004, DOI: 10.1186/1471-2199-5-20
Abstract: The two MBD2/3 isoforms precisely cofractionated with NuRD proteins during gel filtration of extracts derived from early and late embryos. In addition, we demonstrate that MBD2/3 forms multimers, and engages in specific interactions with the p55 and MI-2 subunits of the Drosophila NuRD complex.Our data provide novel insights into the association between Drosophila MBD2/3 and NuRD proteins. Additionally, this work provides a first analysis of the architecture of the Drosophila NuRD complex.Methyl-DNA binding proteins are connecting DNA methylation to transcriptional silencing [1-4]. Up to now, six methyl-DNA binding proteins could be identified in vertebrates [5]. MeCP2, MBD2 and MBD3 can be found in large chromatin complexes containing histone deacetylase activity [1,6,4,3] whereas MBD4 is involved in DNA mismatch-repair [7]. MBD1 has been shown to repress transcription in cell culture [8] and recruits the histone H3-K9 methyltransferase SETDB1 to the chromatin assembly factor CAF-1 during S phase [9]. MBD2, which can bind methylated DNA [6], is a transcriptional repressor recruiting a Nucleosome Remodelling and Deacetylase complex (NuRD) to methylated CpG dinucleotides [6,3], whereas mammalian MBD3, which is not able to bind methylated DNA [10] is an integral component of NuRD [3]. Kaiso, a transcriptional repressor protein, can bind directly to CpG methylated DNA even though it lacks a conserved methyl-DNA binding domain [11]. Kaiso is a component of a subpopulation of MeCP1 complexes that lack MBD2 [11].The Drosophila gene MBD2/3 encodes a protein, which shares high homology to mammalian MBD2 and MBD3 [12,4]. Due to differential splicing, Drosophila MBD2/3 is expressed in two isoforms, the smaller one is lacking part of the putative methyl-DNA binding domain [12-15]. The large isoform is expressed during early development, whereas the small isoform can only be detected during late embryogenesis [14,15]. In insect cells expressing only the small MBD2/3 isoform, th
In-Situ Hydroelectrothermal Deposition of Silicate Layers on Stainless Steel Surfaces  [PDF]
Jaybalan Tamahrajah, Axel Brehm
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.59038
Abstract: The deposition of zeolites on solid support materials is possible by means of electrochemical methods, impregnation processes, as well as in-situ syntheses. Electrochemical deposition of zeolites has been reported as well, however with readily synthesized zeolite structures. Adhesive deposition of zeolites on stainless steel (S316) has been reported. This report investigates the feasibility of the deposition of silicates by in-situ hydroelectrothermal means. The investigation was done in aqueous solutions of pH = 7 to 13 at different temperatures (25°C to 70°C) by linear sweep method. Deposition was done at a saturated H2 atmosphere to ensure prior deposition of thin iron oxide film on the surface and formation of Fe-O-Si-linkages. This was proven by Raman measurement of the samples. Further linear sweep experiments in the presence of silica show monodentate and bidentate Fe-O-Si linkages on the surface, proven by IR-measurements. Presence of dissolved silica was done by UV-Vis with the molybdate yellow method. The best results are achieved at 70°C at pH 13 and ﹣4 mV (vs Ag/AgCl) or 200 mV (vs SHE). Discontinuous homogeneous layers are found on the stainless steel surface observed by SEM, EDX measurements and electrochemical measurements. Layer discontinuties are caused due to low silica concentration at equilibrium hydrothermal conditions, especially in the absence of silicic acid. All results shown are for the best results achieved except for linear sweep measurements and solubility constants of dissolved silica.
Stress-Induced PARP Activation Mediates Recruitment of Drosophila Mi-2 to Promote Heat Shock Gene Expression
Magdalena Murawska,Markus Hassler,Renate Renkawitz-Pohl,Andreas Ladurner,Alexander Brehm
PLOS Genetics , 2011, DOI: 10.1371/journal.pgen.1002206
Abstract: Eukaryotic cells respond to genomic and environmental stresses, such as DNA damage and heat shock (HS), with the synthesis of poly-[ADP-ribose] (PAR) at specific chromatin regions, such as DNA breaks or HS genes, by PAR polymerases (PARP). Little is known about the role of this modification during cellular stress responses. We show here that the nucleosome remodeler dMi-2 is recruited to active HS genes in a PARP–dependent manner. dMi-2 binds PAR suggesting that this physical interaction is important for recruitment. Indeed, a dMi-2 mutant unable to bind PAR does not localise to active HS loci in vivo. We have identified several dMi-2 regions which bind PAR independently in vitro, including the chromodomains and regions near the N-terminus containing motifs rich in K and R residues. Moreover, upon HS gene activation, dMi-2 associates with nascent HS gene transcripts, and its catalytic activity is required for efficient transcription and co-transcriptional RNA processing. RNA and PAR compete for dMi-2 binding in vitro, suggesting a two step process for dMi-2 association with active HS genes: initial recruitment to the locus via PAR interaction, followed by binding to nascent RNA transcripts. We suggest that stress-induced chromatin PARylation serves to rapidly attract factors that are required for an efficient and timely transcriptional response.
LINT, a Novel dL(3)mbt-Containing Complex, Represses Malignant Brain Tumour Signature Genes
Karin Meier,Eve-Lyne Mathieu,Florian Finkernagel,L. Maximilian Reuter,Maren Scharfe,Gunther Doehlemann,Michael Jarek,Alexander Brehm
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002676
Abstract: Mutations in the l(3)mbt tumour suppressor result in overproliferation of Drosophila larval brains. Recently, the derepression of different gene classes in l(3)mbt mutants was shown to be causal for transformation. However, the molecular mechanisms of dL(3)mbt-mediated gene repression are not understood. Here, we identify LINT, the major dL(3)mbt complex of Drosophila. LINT has three core subunits—dL(3)mbt, dCoREST, and dLint-1—and is expressed in cell lines, embryos, and larval brain. Using genome-wide ChIP–Seq analysis, we show that dLint-1 binds close to the TSS of tumour-relevant target genes. Depletion of the LINT core subunits results in derepression of these genes. By contrast, histone deacetylase, histone methylase, and histone demethylase activities are not required to maintain repression. Our results support a direct role of LINT in the repression of brain tumour-relevant target genes by restricting promoter access.
Multiple Aspects of ATP-Dependent Nucleosome Translocation by RSC and Mi-2 Are Directed by the Underlying DNA Sequence
Joke J. F. A. van Vugt, Martijn de Jager, Magdalena Murawska, Alexander Brehm, John van Noort, Colin Logie
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006345
Abstract: Background Chromosome structure, DNA metabolic processes and cell type identity can all be affected by changing the positions of nucleosomes along chromosomal DNA, a reaction that is catalysed by SNF2-type ATP-driven chromatin remodelers. Recently it was suggested that in vivo, more than 50% of the nucleosome positions can be predicted simply by DNA sequence, especially within promoter regions. This seemingly contrasts with remodeler induced nucleosome mobility. The ability of remodeling enzymes to mobilise nucleosomes over short DNA distances is well documented. However, the nucleosome translocation processivity along DNA remains elusive. Furthermore, it is unknown what determines the initial direction of movement and how new nucleosome positions are adopted. Methodology/Principal Findings We have used AFM imaging and high resolution PAGE of mononucleosomes on 600 and 2500 bp DNA molecules to analyze ATP-dependent nucleosome repositioning by native and recombinant SNF2-type enzymes. We report that the underlying DNA sequence can control the initial direction of translocation, translocation distance, as well as the new positions adopted by nucleosomes upon enzymatic mobilization. Within a strong nucleosomal positioning sequence both recombinant Drosophila Mi-2 (CHD-type) and native RSC from yeast (SWI/SNF-type) repositioned the nucleosome at 10 bp intervals, which are intrinsic to the positioning sequence. Furthermore, RSC-catalyzed nucleosome translocation was noticeably more efficient when beyond the influence of this sequence. Interestingly, under limiting ATP conditions RSC preferred to position the nucleosome with 20 bp intervals within the positioning sequence, suggesting that native RSC preferentially translocates nucleosomes with 15 to 25 bp DNA steps. Conclusions/Significance Nucleosome repositioning thus appears to be influenced by both remodeler intrinsic and DNA sequence specific properties that interplay to define ATPase-catalyzed repositioning. Here we propose a successive three-step framework consisting of initiation, translocation and release steps to describe SNF2-type enzyme mediated nucleosome translocation along DNA. This conceptual framework helps resolve the apparent paradox between the high abundance of ATP-dependent remodelers per nucleus and the relative success of sequence-based predictions of nucleosome positioning in vivo.
Online-Beratung bei Kindern und Jugendlichen - ein Erfahrungsbericht von 147 Rat auf Draht“
Ulrike Brehm,Susanne Lindl
E-Beratungsjournal , 2010,
Abstract: 147 Rat auf Draht“ ist als langj hrige Beratungseinrichtung telefonischer Ansprechpartner für Kinder, Jugendliche, junge Erwachsene und deren Bezugspersonen. Seit neun Jahren wird auch Online-Beratung angeboten. Dieser Artikel beschreibt das Onlineangebot und gibt einen beschreibenden überblick über Beratungsthemen und Statistik.
The Drosophila Mi-2 Chromatin-Remodeling Factor Regulates Higher-Order Chromatin Structure and Cohesin Dynamics In Vivo
Barbara Fasulo,Renate Deuring,Magdalena Murawska,Maria Gause,Kristel M. Dorighi,Cheri A. Schaaf,Dale Dorsett,Alexander Brehm,John W. Tamkun
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002878
Abstract: dMi-2 is a highly conserved ATP-dependent chromatin-remodeling factor that regulates transcription and cell fates by altering the structure or positioning of nucleosomes. Here we report an unanticipated role for dMi-2 in the regulation of higher-order chromatin structure in Drosophila. Loss of dMi-2 function causes salivary gland polytene chromosomes to lose their characteristic banding pattern and appear more condensed than normal. Conversely, increased expression of dMi-2 triggers decondensation of polytene chromosomes accompanied by a significant increase in nuclear volume; this effect is relatively rapid and is dependent on the ATPase activity of dMi-2. Live analysis revealed that dMi-2 disrupts interactions between the aligned chromatids of salivary gland polytene chromosomes. dMi-2 and the cohesin complex are enriched at sites of active transcription; fluorescence-recovery after photobleaching (FRAP) assays showed that dMi-2 decreases stable association of cohesin with polytene chromosomes. These findings demonstrate that dMi-2 is an important regulator of both chromosome condensation and cohesin binding in interphase cells.
Differential Expression and Sex Chromosome Association of CHD3/4 and CHD5 during Spermatogenesis
Judith W. Bergs, Nina Neuendorff, Godfried van der Heijden, Evelyne Wassenaar, Peter Rexin, Hans-Peter Els?sser, Roland Moll, Willy M. Baarends, Alexander Brehm
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098203
Abstract: ATP-dependent nucleosome remodelers of the CHD family play important roles in chromatin regulation during development and differentiation. The ubiquitously expressed CHD3 and CHD4 proteins are essential for stem cell function and serve to orchestrate gene expression in different developmental settings. By contrast, the closely related CHD5 is predominantly expressed in neural tissue and its role is believed to be restricted to neural differentiation. Indeed, loss of CHD5 contributes to neuroblastoma. In this study, we first demonstrate that CHD5 is a nucleosome-stimulated ATPase. We then compare CHD3/4 and CHD5 expression in mouse brain and show that CHD5 expression is restricted to a subset of cortical and hippocampal neurons whereas CHD3/4 expression is more widespread. We also uncover high levels of CHD5 expression in testis. CHD5 is transiently expressed in differentiating germ cells. Expression is first detected in nuclei of post-meiotic round spermatids, reaches a maximum in stage VIII spermatids and then falls to undetectable levels in stage IX spermatids. Surprisingly, CHD3/4 and CHD5 show complementary expression patterns during spermatogenesis with CHD3/4 levels progressively decreasing as CHD5 expression increases. In spermatocytes, CHD3/4 localizes to the pseudoautosomal region, the X centromeric region and then spreads into the XY body chromatin. In postmeiotic cells, CHD5 colocalises with macroH2A1.2 in association with centromeres and part of the Y chromosome. The subnuclear localisations of CHD4 and CHD5 suggest specific roles in regulation of sex chromosome chromatin and pericentromeric chromatin structure prior to the histone-protamine switch.
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