Insulator

Insulators help separate active chromatin domains from silenced ones. In yeast, gene promoters act as insulators to block the spread of Sir and HP1 mediated silencing while in metazoans most insulators are multipartite autonomous entities. tDNAs are repetitive sequences dispersed throughout the human genome and we now show that some of these tDNAs can function as insulators in human cells. Using computational methods, we identified putative human tDNA insulators. Using silencer blocking, transgene protection ...

... 5, Nos. 4/5, 2008 Copyright © 2008 Inderscience Enterprises Ltd. Analytical simulation of interfacial DNA hybridisation for design of an optimal nanotechnology handheld biosensor Samuel Abiodun Afuwape National University, SOET, San Diego, CA 92123, USA ...

Insulator performance is strongly linked to local installation parameter such as the weather, induced stress, location, pollution etc. Therefore, insulator performance under actual service conditions is hard to be predicted based on laboratory tests, even though such tests may provide valuable hints and directions. Therefore, power utilities, especially these that have part of their network suffering from intense pollution problems, construct open air insulator testing stations in order to gain further insight on insulator performance. There, insulators are stressed under conditions that are as close as possible to the actual service conditions. The parameters usually monitored are the leakage current along with weather conditions. The Greek power, HEDNO, has gained significant experience from constructing and operating TALOS, its own open air test station in a heavily polluted location in the island of Crete. Recently, HEDNO and TALOS participated in a research project focused on the monitoring and diagnosis of polymer based outdoor insulators used in high voltage applications. This paper focuses mainly on the innovations implemented in the test station regarding to the monitoring scheme, setup , hardware and software. These include adopting a variation of the usual leakage current monitoring setup scheme, following a distributed approach for the DAS and using general purpose DAQs equipped with custom made Labview based software.

Insulators or chromatin boundary are DNA elements that organize the genome into discrete regulatory domains by limiting the actions of enhancers and silencers through a “positional-blocking mechanism”. The role of these sequences, both in modulation of the enhancers range of action (enhancer–promoter selectivity) and in the organization of the chromatin in functional domains, is emerging strongly in these last years. There is a great interest in identifying new insulators because deeper knowledge of these elements can help understand how cis-regulatory elements coordinate the expression of the target genes. However, while insulators are critical in gene regulation and genome functioning, only a few have been reported so far. Here, we describe a new insulator sequence that is located in the 5′UTR of the Drosophila retrotransposon ZAM. We have used an “enhancer–blocking assay” to test its effects on the activity of the enhancer in transiently transfected Drosophila S2R+ cell line. Moreover, we show that the new insulator is able to affect significantly the enhancer–promoter interaction in the human cell line HEK293. These results suggest the possibility of employing the ZAM insulator in gene transfer protocols from insects to mammals in order to counteract the transgene positional and genotoxic effects.

Early-life stress (ELS) induces long-lasting changes in gene expression conferring an increased risk for the development of stress-related mental disorders. Glucocorticoid receptors (GR) mediate the negative feedback actions of glucocorticoids (GC) in the paraventricular nucleus (PVN) of the hypothalamus and anterior pituitary and therefore play a key role in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis and the endocrine response to stress. We here show that ELS programs the expression of the GR gene (Nr3c1) by site-specific hypermethylation at the CpG island (CGI) shore in hypothalamic neurons that produce corticotropin-releasing hormone (Crh), thus preventing Crh upregulation under conditions of chronic stress. CpGs mapping to the Nr3c1 CGI shore region are dynamically regulated by ELS and underpin methylation-sensitive control of this region's insulation-like function via Ying Yang 1 (YY1) binding. Our results provide new insight into how a genomic element ...

Conductor-insulator composite films were prepared by cathodic electro-deposition of a dispersion of conductive carbon black and epoxy resin onto tricationic-phosphated galvanized steel panels. The prepared composite films were then characterized regarding their surface ...

In this work, we study the dilution of Spin-On Glass (SOG) in order to obtain high quality SiO2 films at 200° C, with optical and electrical characteristics similar to those of the thermally grown SiO2. For the production of SiO2 films we used 2-propanol and deionized ...

Here, we report the development of a peptide-nucleic acid (PNA)-modified ion-sensitive field-effect transistor (IS-FET)-based biosensor that takes advantage of the change in the surface potential upon hybridization of a negatively charged DNA. PNA was immobilized on a silicon nitride gate insulator by an addition reaction between a maleimide group introduced on the gate surface, the succinimide group of N-(6-maleimidocaproyloxy) succinimide, and the thiol group of the terminal cysteine in PNA. The surface was characterized after each step of the reaction by X-ray photoelectron spectroscopy analysis, and the kinetic analysis of the hybridization events was assessed by surface plasmon resonance. In addition, we measured the -potential before and after PNA-DNA hybridization in the presence of counterions to investigate the change in surface charge density at the surface-solution interface within the order of the Debye length. On the basis of the zeta-potential, the surface charge density, DeltaQ, calculated using the Grahame equation was approximately 4.0 x 10(-3) C/m2 and the estimated number of hybridized molecules was at least 1.7 x 10(11)/cm2. The I-V characteristics revealed that the PNA-DNA duplexes induce a positive shift in the threshold voltage, VT, and a decrease in the saturated drain current, ID. These results demonstrate that direct detection of DNA hybridization should be possible using a PNA-modified IS-FET-based biosensor. PNA is particularly advantageous for this system because it enables highly specific and selective binding at low ionic strength.