Drosophila mini-white model system: new insights into positive position effects and the role of transcriptional terminators and gypsy insulator in transgene shielding

The white gene, which is responsible for eye pigmentation, is widely used to study position effects in Drosophila. As a result of insertion of P-element vectors containing mini-white without enhancers into random chromosomal sites, flies with different eye color phenotypes appear, which is usually explained by the influence of positive/negative regulatory elements located around the insertion site. We found that, in more than 70% of cases when mini-white expression was subject to positive position effects, deletion of the white promoter had no effect on eye pigmentation; in these cases, the transposon was inserted into the transcribed regions of genes. Therefore, transcription through the mini-white gene could be responsible for high levels of its expression in most of chromosomal sites. Consistently with this conclusion, transcriptional terminators proved to be efficient in protecting mini-white expression from positive position effects. On the other hand, the best characterized Drosophila gypsy insulator was poorly effective in terminating transcription and, as a consequence, only partially protected mini-white expression from these effects. Thus, to ensure maximum protection of a transgene from position effects, a perfect boundary/insulator element should combine three activities: to block enhancers, to provide a barrier between active and repressed chromatin, and to terminate transcription

Measurement and application of residual dipolar couplings in biomolecular NMR structure determination

The present work consists of three parts. First, I demonstrate the effectiveness of C12E5/hexanol as an orienting media for the measurement of residual dipolar couplings (RDCs) at low pH and for proteins with the positively charged surfaces, such as carbon storage regulator A at pH 4.5 and catalytic fragment of 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP-CF; theoretical pI 8.99). Second, the structure of the regeneration-induced CNPase homolog was determined based on 15N-1 H, 13C'-13C alpha, and 13Calpha- 1Halpha RDCs measured in Pf1 phage alignment media. Finally, 2D experiments based on the recently introduced SAD-REDOR technique for the measurement of RDCs in proteins were developed. The SAD-REDOR (single-alignment domain rotational-echo double resonance) technique consists of magic angle spinning (MAS) and rotor synchronized radiofrequency pulses applied to the molecule fixed in the polymer-stabilized liquid crystalline media. MAS averages dipolar couplings to zero, while the application of the RF pulses allows selective recovery of chemical shift anisotropy, homonuclear or heteronuclear RDCs. SAD-REDOR can be used to study strongly aligned biomolecules. It allows measurement of both scalar and dipolar couplings in a single sample and control over their magnitudes. Here, I present SAD-IPAP and SAD-HSQC experiments for the measurements of 15N-1 H RDCs in direct and indirect dimensions, respectively, as it is demonstrated for 15N-enriched PSLC ubiquitin

Transposition of Regulatory Elements by P-Element-Mediated Rearrangements in Drosophila melanogaster

Previously we described highly unstable mutations in the yellow locus, induced by the chimeric element and consisting of sequences from a distally located 1A unique genomic region, flanked by identical copies of an internally deleted 1.2-kb P element. Here we show that a sequence, which is part of the yellow 1A region, can be transmitted to the AS-C by successive inversion and reinversion generated by yellow- and AS-C-located P elements. The chimeric element contains a regulatory element from the 1A region that specifically blocks yellow wing and body enhancers and simultaneously stimulates yellow expression in bristles. These results suggest that P-element-generated chimeric elements may play a certain role in rapid changes of regulatory regions of genes during evolution

Mesoporous MXene powders synthesized by acid induced crumpling and their use as Na-ion battery anodes

Manipulating the shapes of, otherwise flat, two-dimensional, 2D, flakes is important in many applications. Herein by simply decreasing the pH of a Ti3C2Tx MXene colloidal suspension, the 2D nanolayers crash out into crumpled flakes, resulting in randomly oriented powders, with a mesoporous architecture. Electrodes made with the latter showed capacities of 250 mAh g−1 at 20 mA g−1 in sodium-ion batteries. The rate performance, 120 mAh g−1 at 500 mA g−1, was also respectable. This acid-induced, reversible, crumpling approach is facile and scalable and could prove important in electrochemical, biological, catalytic, and environmental MXene-based applications

New Properties of Drosophila Fab-7 Insulator

In the Abd-B 3′ cis-regulatory region, which is subdivided into a series of iab domains, boundary elements have previously been detected, including the Fab-7 element providing for the autonomous functioning of the iab-6 and iab-7 cis-regulatory domains. Here, it has been shown that a single copy of the 860-bp Fab-7 insulator effectively blocks the yellow and white enhancers. The eye and testis enhancers can stimulate the white promoter across the pair of Fab-7, which is indicative of a functional interaction between the insulators. Unexpectedly, Fab-7 has proved to lose the enhancer-blocking activity when placed near the white promoter. It seems likely that Fab-7 strengthens the relatively weak white promoter, which leads to the efficient enhancer–promoter interaction and insulator bypass

Mesoporous MXene powders synthesized by acid induced crumpling and their use as Na-ion battery anodes

<p>Manipulating the shapes of, otherwise flat, two-dimensional, 2D, flakes is important in many applications. Herein by simply decreasing the pH of a Ti₃C₂T_x MXene colloidal suspension, the 2D nanolayers crash out into crumpled flakes, resulting in randomly oriented powders, with a mesoporous architecture. Electrodes made with the latter showed capacities of 250 mAh g⁻¹ at 20 mA g⁻¹ in sodium-ion batteries. The rate performance, 120 mAh g⁻¹ at 500 mA g⁻¹, was also respectable. This acid-induced, reversible, crumpling approach is facile and scalable and could prove important in electrochemical, biological, catalytic, and environmental MXene-based applications.</p> <p>By simply decreasing the pH of a Ti₃C₂T_x colloidal suspension, we induce the 2D flakes flocculate into mesoporous crumpled flakes, that we then show can be used as Na-ion battery anodes.</p

Solution Structure of the Carbon Storage Regulator Protein CsrA from Escherichia coli

The carbon storage regulator A (CsrA) is a protein responsible for the repression of a variety of stationary-phase genes in bacteria. In this work, we describe the nuclear magnetic resonance (NMR)-based structure of the CsrA dimer and its RNA-binding properties. CsrA is a dimer of two identical subunits, each composed of five strands, a small α-helix and a flexible C terminus. NMR titration experiments suggest that the β1-β2 and β3-β4 loops and the C-terminal helix are important elements in RNA binding. Even though the β3-β4 loop contains a highly conserved RNA-binding motif, GxxG, typical of KH domains, our structure excludes CsrA from being a member of this protein family, as previously suggested. A mechanism for the recognition of mRNAs downregulated by CsrA is proposed

Chemically Preintercalated Bilayered K_<i>x</i>V₂O₅·<i>n</i>H₂O Nanobelts as a High-Performing Cathode Material for K‑Ion Batteries

Tailoring the structure of the electrode material through chemical insertion of charge-carrying ions emerged as an efficient approach leading to enhanced performance of energy storage devices. Here, we for the first time report the effect of chemically preintercalated K⁺ ions on electrochemical charge storage properties of bilayered vanadium oxide (δ-V₂O₅) as a cathode in nonaqueous K-ion batteries, a low-cost alternative to Li-ion batteries, which is attractive for large-scale energy storage. δ-K_0.42V₂O₅·0.25H₂O with expanded interlayer spacing of 9.65 Å exhibited record high initial discharge capacity of 268 mAh·g^–1 at a current rate of C/50 and 226 mAh·g^–1 at a current rate of C/15. K-preintercalated bilayered vanadium oxide showed capacity retention of 74% after 50 cycles at a constant current of C/15 and 58% capacity retention when the current rate was increased from C/15 to 1C. Analysis of the mechanism of charge storage revealed that diffusion-controlled intercalation dominates over nonfaradaic capacitive contribution. High electrochemical performance of δ-K_0.42V₂O₅·0.25H₂O is attributed to the facilitated diffusion of electrochemically cycled K⁺ ions through well-defined intercalation sites, formed by chemically preintercalated K⁺ ions