Seoul National University

About: Seoul National University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Catalysis. The organization has 65879 authors who have published 138759 publications receiving 3715170 citations. The organization is also known as: SNU & Seoul-dae.

Transferable GaN Layers Grown on ZnO-Coated Graphene Layers for Optoelectronic Devices

Abstract: We fabricated transferable gallium nitride (GaN) thin films and light-emitting diodes (LEDs) using graphene-layered sheets. Heteroepitaxial nitride thin films were grown on graphene layers by using high-density, vertically aligned zinc oxide nanowalls as an intermediate layer. The nitride thin films on graphene layers show excellent optical characteristics at room temperature, such as stimulated emission. As one of the examples for device applications, LEDs that emit strong electroluminescence emission under room illumination were fabricated. Furthermore, the layered structure of a graphene substrate made it possible to easily transfer GaN thin films and GaN-based LEDs onto foreign substrates such as glass, metal, or plastic.

A protective role of nuclear factor-erythroid 2-related factor-2 (Nrf2) in inflammatory disorders

Abstract: Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a key transcription factor that plays a central role in cellular defense against oxidative and electrophilic insults by timely induction of antioxidative and phase-2 detoxifying enzymes and related stress-response proteins. The 5'-flanking regions of genes encoding these cytoprotective proteins contain a specific consensus sequence termed antioxidant response element (ARE) to which Nrf2 binds. Recent studies have demonstrated that Nrf2-ARE signaling is also involved in attenuating inflammation-associated pathogenesis, such as autoimmune diseases, rheumatoid arthritis, asthma, emphysema, gastritis, colitis and atherosclerosis. Thus, disruption or loss of Nrf2 signaling causes enhanced susceptibility not only to oxidative and electrophilic stresses but also to inflammatory tissue injuries. During the early-phase of inflammation-mediated tissue damage, activation of Nrf2-ARE might inhibit the production or expression of pro-inflammatory mediators including cytokines, chemokines, cell adhesion molecules, matrix metalloproteinases, cyclooxygenase-2 and inducible nitric oxide synthase. It is likely that the cytoprotective function of genes targeted by Nrf2 may cooperatively regulate the innate immune response and also repress the induction of pro-inflammatory genes. This review highlights the protective role of Nrf2 in inflammation-mediated disorders with special focus on the inflammatory signaling modulated by this redox-regulated transcription factor.

A knock-out mutation in allene oxide synthase results in male sterility and defective wound signal transduction in Arabidopsis due to a block in jasmonic acid biosynthesis.

Abstract: Recent studies on jasmonic acid (JA) biosynthetic mutants have shown that jasmonates play essential roles in pollen maturation and dehiscence and wound-induced defence against biotic attacks. To better understand the biosynthetic mechanisms of this essential plant hormone, we isolated an Arabidopsis knock-out mutant defective in the JA biosynthetic gene CYP74A (allene oxide synthase, AOS) using reverse genetics screening methods. This enzyme catalyses dehydration of the hydroperoxide to an unstable allene oxide in the JA biosynthetic pathway. Endogenous JA levels, which increase 100-fold 1 h after wounding in wild-type plants, do not increase after wounding in the aos mutant. In addition, the mutant showed severe male sterility due to defects in anther and pollen development. The male-sterile phenotype was completely rescued by exogenous application of methyl jasomonate and by complementation with constitutive expression of the AOS gene. RT-PCR analysis showed that the induction of transcripts for vegetative storage protein and lipoxygenase genes, previously shown to be inducible by wound and jasmonate application in the wild-type, was absent in the aos mutant. In transgenic plants constitutively expressing AOS, wound-induced JA levels were 50-100% higher compared to wild-type plants. Taken together with JA deficiency in the aos mutant, our results show that AOS is critical for the biosynthesis of all biologically active jasmonates. Our results also suggest that AOS expression is limiting JA levels in wounded plants, but that the AOS hydroperoxide substrate levels, controlled by upstream enzymes (lipoxygenase and phospholipase), determine JA levels in unwounded plants.

Genome-wide analysis reveals specificities of Cpf1 endonucleases in human cells

Abstract: Programmable clustered regularly interspaced short palindromic repeats (CRISPR) Cpf1 endonucleases are single-RNA-guided (crRNA) enzymes that recognize thymidine-rich protospacer-adjacent motif (PAM) sequences and produce cohesive double-stranded breaks (DSBs). Genome editing with CRISPR-Cpf1 endonucleases could provide an alternative to CRISPR-Cas9 endonucleases, but the determinants of targeting specificity are not well understood. Using mismatched crRNAs we found that Cpf1 could tolerate single or double mismatches in the 3' PAM-distal region, but not in the 5' PAM-proximal region. Genome-wide analysis of cleavage sites in vitro for eight Cpf1 nucleases using Digenome-seq revealed that there were 6 (LbCpf1) and 12 (AsCpf1) cleavage sites per crRNA in the human genome, fewer than are present for Cas9 nucleases (>90). Most Cpf1 off-target cleavage sites did not produce mutations in cells. We found mismatches in either the 3' PAM-distal region or in the PAM sequence of 12 off-target sites that were validated in vivo. Off-target effects were completely abrogated by using preassembled, recombinant Cpf1 ribonucleoproteins.