16 research outputs found
Epigenetic Regulation of a Murine Retrotransposon by a Dual Histone Modification Mark
Large fractions of eukaryotic genomes contain repetitive sequences of which the vast majority is derived from transposable elements (TEs). In order to inactivate those potentially harmful elements, host organisms silence TEs via methylation of transposon DNA and packaging into chromatin associated with repressive histone marks. The contribution of individual histone modifications in this process is not completely resolved. Therefore, we aimed to define the role of reversible histone acetylation, a modification commonly associated with transcriptional activity, in transcriptional regulation of murine TEs. We surveyed histone acetylation patterns and expression levels of ten different murine TEs in mouse fibroblasts with altered histone acetylation levels, which was achieved via chemical HDAC inhibition with trichostatin A (TSA), or genetic inactivation of the major deacetylase HDAC1. We found that one LTR retrotransposon family encompassing virus-like 30S elements (VL30) showed significant histone H3 hyperacetylation and strong transcriptional activation in response to TSA treatment. Analysis of VL30 transcripts revealed that increased VL30 transcription is due to enhanced expression of a limited number of genomic elements, with one locus being particularly responsive to HDAC inhibition. Importantly, transcriptional induction of VL30 was entirely dependent on the activation of MAP kinase pathways, resulting in serine 10 phosphorylation at histone H3. Stimulation of MAP kinase cascades together with HDAC inhibition led to simultaneous phosphorylation and acetylation (phosphoacetylation) of histone H3 at the VL30 regulatory region. The presence of the phosphoacetylation mark at VL30 LTRs was linked with full transcriptional activation of the mobile element. Our data indicate that the activity of different TEs is controlled by distinct chromatin modifications. We show that activation of a specific mobile element is linked to a dual epigenetic mark and propose a model whereby phosphoacetylation of histone H3 is crucial for full transcriptional activation of VL30 elements
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Multiscale analysis for interacting particles: Relaxation systems and scalar conservation laws
We investigate the derivation of semilinear relaxation systems and scalar conservation laws from a class of stochastic interacting particle systems. These systems are Markov jump processes set on a lattice, they satisfy detailed mass balance (but not detailed balance of momentum), and are equipped with multiple scalings. Using a combination of correlation function methods with compactness and convergence properties of semidiscrete relaxation schemes we prove that, at a mesoscopic scale, the interacting particle system gives rise to a semilinear hyperbolic system of relaxation type, while at a macroscopic scale it yields a scalar conservation law. Rates of convergence are obtained in both scalings
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Contractive relaxation systems and interacting particles for scalar conservation laws
Nous considérons une classe de svstèmes hvperboliques semilinéaires avec relaxation, qui sont contractifS en norme L1 et qui possèdent des régions invariantes. Nous démontrons que, quand le paramètre de relaxation ε tend vers zéro, les solutions du système convergent vers une.solution faible d \u27une loi de conservation, qui satisfait aux conditions d\u27entropie de Kruzhkov. Dans le cas de la dimension un d\u27espace, nous proposons des systèmes de particules avec interaction qui, à l\u27échelle mésoscopique, convergent vers les.systèmes avec relaxation; leur dynamique macroscopique est décrite par les solutions entropiques d\u27une loi de conservation
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Contractive relaxation systems and the scalar multidimensional conservation law
This Article does not have an abstract
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Multiscale analysis for interacting particles: Relaxation systems and scalar conservation laws
We investigate the derivation of semilinear relaxation systems and scalar conservation laws from a class of stochastic interacting particle systems. These systems are Markov jump processes set on a lattice, they satisfy detailed mass balance (but not detailed balance of momentum), and are equipped with multiple scalings. Using a combination of correlation function methods with compactness and convergence properties of semidiscrete relaxation schemes we prove that, at a mesoscopic scale, the interacting particle system gives rise to a semilinear hyperbolic system of relaxation type, while at a macroscopic scale it yields a scalar conservation law. Rates of convergence are obtained in both scalings
Contractive relaxation systems and the scalar multidimensional conservation law
This Article does not have an abstract
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Contractive relaxation systems and interacting particles for scalar conservation laws
Nous considérons une classe de svstèmes hvperboliques semilinéaires avec relaxation, qui sont contractifS en norme L1 et qui possèdent des régions invariantes. Nous démontrons que, quand le paramètre de relaxation ε tend vers zéro, les solutions du système convergent vers une.solution faible d \u27une loi de conservation, qui satisfait aux conditions d\u27entropie de Kruzhkov. Dans le cas de la dimension un d\u27espace, nous proposons des systèmes de particules avec interaction qui, à l\u27échelle mésoscopique, convergent vers les.systèmes avec relaxation; leur dynamique macroscopique est décrite par les solutions entropiques d\u27une loi de conservation