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Noordermeer D.,Research Frontiers
Wiley interdisciplinary reviews. Developmental biology | Year: 2013

Developmentally regulated genes are often controlled by distant enhancers, silencers and insulators, to implement their correct transcriptional programs. In recent years, the development of 3C and derived techniques (4C, 5C, HiC, ChIA-PET, etc.) has confirmed that chromatin looping is an important mechanism for the transfer of regulatory information in mammalian cells. At many developmentally regulated gene loci, transcriptional activation is indeed accompanied by the formation of chromatin loops between genes and distant enhancers. Similarly, dynamic looping between insulator elements and changes in local 3D organization may be observed upon variation in transcriptional activity. Chromatin looping also occurs at silent gene loci, where its function remains less understood. In lineage-committed cells, partial 3D configurations are detected at loci that are activated at later stages. However, these partial configurations usually lack promoter-enhancer loops that accompany transcriptional activation, suggesting they have structural functions. Definitive evidence for a repressive role of chromatin looping is still lacking. Chromatin loops have been reported at repressed loci but, alternatively, they may act as a distraction for active loops. Together, these mechanisms allow fine-tuning of regulatory programs, thus providing further diversity in the transcriptional control of developmentally regulated gene loci. Copyright © 2013 Wiley Periodicals, Inc. Source

A display device comprising a Suspended Particle Device film or other material for controlling the amount of illumination transmitted to an object from one or more light sources to protect the object from degradation by light is described. The display is capable of being dark when the object is not being viewed and being highly transmissive when the object is to be viewed. If desired, the display device may be controlled so as to provide a substantially constant amount of illumination when the object is viewed or intended to be viewed. A method of protecting an object using the display device is also provided.

Nevalainen H.,Research Frontiers | Peterson R.,Research Frontiers
Frontiers in Microbiology | Year: 2014

Hosts used for the production of recombinant proteins are typically high-protein secreting mutant strains that have been selected for a specific purpose, such as efficient production of cellulose-degrading enzymes. Somewhat surprisingly, sequencing of the genomes of a series of mutant strains of the cellulolytic Trichoderma reesei, widely used as an expression host for recombinant gene products, has shed very little light on the nature of changes that boost high-level protein secretion. While it is generally agreed and shown that protein secretion in filamentous fungi occurs mainly through the hyphal tip, there is growing evidence that secretion of proteins also takes place in sub-apical regions. Attempts to increase correct folding and thereby the yields of heterologous proteins in fungal hosts by co-expression of cellular chaperones and foldases have resulted in variable success; underlying reasons have been explored mainly at the transcriptional level. The observed physiological changes in fungal strains experiencing increasing stress through protein overexpression under strong gene promoters also reflect the challenge the host organisms are experiencing. It is evident, that as with other eukaryotes, fungal endoplasmic reticulum is a highly dynamic structure. Considering the above, there is an emerging body of work exploring the use of weaker expression promoters to avoid undue stress. Filamentous fungi have been hailed as candidates for the production of pharmaceutically relevant proteins for therapeutic use. One of the biggest challenges in terms of fungally produced heterologous gene products is their mode of glycosylation; fungi lack the functionally important terminal sialylation of the glycans that occurs in mammalian cells. Finally, exploration of the metabolic pathways and fluxes together with the development of sophisticated fermentation protocols may result in new strategies to produce recombinant proteins in filamentous fungi. © 2014 Nevalainen and Peterson. Source

Thaysen-Andersen M.,Research Frontiers | Packer N.H.,Research Frontiers
Biochimica et Biophysica Acta - Proteins and Proteomics | Year: 2014

Site-specific structural characterization of glycoproteins is important for understanding the exact functional relevance of protein glycosylation. Resulting partly from the multiple layers of structural complexity of the attached glycans, the system-wide site-specific characterization of protein glycosylation, defined as glycoproteomics, is still far from trivial leaving the N- and O-linked glycoproteomes significantly under-defined. However, recent years have seen significant advances in glycoproteomics driven, in part, by the developments of dedicated workflows and efficient sample preparation, including glycopeptide enrichment and prefractionation. In addition, glycoproteomics has benefitted from the continuous performance enhancement and more intelligent use of liquid chromatography and tandem mass spectrometry (LC-MS/MS) instrumentation and a wider selection of specialized software tackling the unique challenges of glycoproteomics data. Together these advances promise more streamlined N- and O-linked glycoproteome analysis. Tangible examples include system-wide glycoproteomics studies detecting thousands of intact glycopeptides from hundreds of glycoproteins from diverse biological samples. With a strict focus on the system-wide site-specific analysis of protein N- and O-linked glycosylation, we review the recent advances in LC-MS/MS based glycoproteomics. The review opens with a more general discussion of experimental designs in glycoproteomics and sample preparation prior to LC-MS/MS based data acquisition. Although many challenges still remain, it becomes clear that glycoproteomics, one of the last frontiers in proteomics, is gradually maturing enabling a wider spectrum of researchers to access this new emerging research discipline. The next milestone in analytical glycobiology is being reached allowing the glycoscientist to address the functional importance of protein glycosylation in a system-wide yet protein-specific manner. © 2013 Elsevier B.V. Source

Schorderet P.,Ecole Polytechnique Federale de Lausanne | Schorderet P.,Research Frontiers | Duboule D.,Ecole Polytechnique Federale de Lausanne | Duboule D.,Research Frontiers | Duboule D.,University of Geneva
PLoS Genetics | Year: 2011

Long non-coding RNAs regulate various biological processes such as dosage compensation, imprinting, and chromatin organization. HOTAIR, a paradigm of this new class of RNAs, is localized within the human HOXC gene cluster and was shown, in human cells, to regulate HOXD genes in trans via the recruitment of Polycomb Repressive Complex 2 (PRC2), followed by the trimethylation of lysine 27 of histone H3. We looked for the presence of Hotair in mice to assess whether this in trans mechanism was conserved, in particular at the developmental stages, when Hoxd genes must be tightly regulated. We show that the cognate mouse Hotair is poorly conserved in sequence; and its absence, along with the deletion of the HoxC cluster, has surprisingly little effect in vivo, neither on the expression pattern or transcription efficiency, nor on the amount of K27me3 coverage of different Hoxd target genes. We conclude that Hotair may have rapidly evolved within mammals and acquired a functional importance in humans that is not easily revealed in mice. Alternatively, redundant or compensatory mechanisms may mask its function when studied under physiological conditions. © 2011 Schorderet, Duboule. Source

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