Jong-Wha Jung

Structural imprints in vivo decode RNA regulatory mechanisms

Visualizing the physical basis for molecular behaviour inside living cells is a great challenge for biology. RNAs are central to biological regulation, and the ability of RNA to adopt specific structures intimately controls every step of the gene expression program. However, our understanding of physiological RNA structures is limited; current in vivo RNA structure profiles include only two of the four nucleotides that make up RNA. Here we present a novel biochemical approach, in vivo click selective 2′-hydroxyl acylation and profiling experiment (icSHAPE), which enables the first global view, to our knowledge, of RNA secondary structures in living cells for all four bases. icSHAPE of the mouse embryonic stem cell transcriptome versus purified RNA folded in vitro shows that the structural dynamics of RNA in the cellular environment distinguish different classes of RNAs and regulatory elements. Structural signatures at translational start sites and ribosome pause sites are conserved from in vitro conditions, suggesting that these RNA elements are programmed by sequence. In contrast, focal structural rearrangements in vivo reveal precise interfaces of RNA with RNA-binding proteins or RNA-modification sites that are consistent with atomic-resolution structural data. Such dynamic structural footprints enable accurate prediction of RNA–protein interactions and N6-methyladenosine (m6A) modification genome wide. These results open the door for structural genomics of RNA in living cells and reveal key physiological structures controlling gene expression.

A Concise Total Synthesis of (+)‐Tetrabenazine and (+)‐α‐Dihydrotetrabenazine

Highly concise asymmetric total syntheses of (+)-tetrabenazine (1), a drug for the treatment of chorea associated with Huntingtons disease, and of (+)-α-dihydrotetrabenazine (2), an active metabolite of 1, have been accomplished. Our synthetic route features a trans-selective enol etherification, followed by an unprecedented cation-dependent aza-Claisen rearrangement to establish the carbon framework and two stereogenic centers of tetrabenazine. The syntheses consist of seven steps (34 % overall yield) for (+)-2 and eight steps (22 % overall yield) for (+)-1.

First total synthesis and structural confirmation of fluvirucinine A2 via an iterative ring expansion strategy.

The first asymmetric total synthesis of fluvirucinine A(2) has been accomplished. A key feature of the synthesis is an iterative lactam ring expansion to provide rapid access to the 14-membered lactam skeleton and three stereogenic centers. The excellent remote control of the three stereogenic centers relied on stereoselective amidoalkylation followed by an amide-enolate-induced aza-Claisen rearrangement. In addition, the structure of fluvirucinine A(2) has been completely elucidated by our total synthesis.

Design, Synthesis, and Biological Evaluation of Novel Constrained meta-Substituted Phenyl Propanoic Acids as Peroxisome Proliferator-Activated Receptor α and γ Dual Agonists

In an effort to develop dual PPARalpha/gamma activators with improved therapeutic efficacy, a series of diaryl alpha-ethoxy propanoic acid compounds comprising two aryl groups linked by rigid oxime ether or isoxazoline ring were designed and synthesized and their biological activities were examined. Most of the compounds possessing an oxime ether linker were more potent PPARgamma activators than the lead PPARalpha/gamma dual agonist, tesaglitazar in vitro. Compound 18, one of the derivatives with an oxime ether linker, was found to selectively transactivate PPARgamma (EC 50 = 0.028 microM) over PPARalpha (EC 50 = 7.22 microM) in vitro and lower blood glucose in db/ db mice more than muraglitazar after oral treatment for 11 days.

Concise and Enantioselective Total Synthesis of 15-Deoxy-Δ12,14-Prostaglandin J2

The concise and enantioselective synthesis of 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) has been accomplished in 11 steps from a known alcohol. The key step of the synthesis involves an asymmetric Rh-catalyzed cycloisomerization of ene-ynone, followed by an olefin isomerization.

Concise syntheses of (+)-macrosphelides A and B: studies on the macro-ring closure strategy.

Highly concise syntheses of (+)-macrosphelides A and B were accomplished in this study. The key feature of our synthetic route involved the direct three-carbon homologation of the readily available Weinreb amide 6 by the addition of a trans-vinylogous ester anion equivalent and facile construction of the 16-membered macrolide skeleton of macrosphelides via an intramolecular nitrile oxide-olefin cycloaddition. The syntheses of macrosphelides A and B were completed with a 30 and 20% overall yield, respectively. This paper describes the details of our syntheses.

The role of thioredoxin reductase and glutathione reductase in plumbagin-induced, reactive oxygen species-mediated apoptosis in cancer cell lines.

Plumbagin is a secondary metabolite that was first identified in the Plumbago genus of plants. It is a naphthoquinone compound with anti-atherosclerosis, anticancer, anti-inflammatory, antimicrobial, contraceptive, cardiotonic, immunosuppressive, and neuroprotective activities. However, the mechanisms of plumbagins activities are largely unknown. In this study, we examined the effect of plumbagin on HepG2 hepatocellular carcinoma cells as well as LLC lung cancer cells, SiHa cervical carcinoma cells. Plumbagin significantly decreased HepG2 cell viability in a dose-dependent manner. Additionally, treatment with plumbagin significantly increased the Bax/Bcl-2 ratio and caspase-3/7 activity. Using the similarity ensemble approach (SEA)-a state-of-the-art cheminformatic technique-we identified two previously unknown cellular targets of plumbagin: thioredoxin reductase (TrxR) and glutathione reductase (GR). This was then confirmed using protein- and cell-based assays. We found that plumbagin was directly reduced by TrxR, and that this reduction was inhibited by the TrxR inhibitor, sodium aurothiomalate (ATM). Plumbagin also decreased the activity of GR. Plumbagin, and the GR inhibitor sodium arsenite all increased intracellular reactive oxygen species (ROS) levels and this increase was significantly attenuated by pretreatment with the ROS scavenger N-acetyl-cysteine (NAC) in HepG2 cells. Plumbagin increased TrxR-1 and heme oxygenase (HO)-1 expression and pretreatment with NAC significantly attenuated the plumbagin-induced increase of TrxR-1 and HO-1 expression in HepG2 cells, LLC cells and SiHa cells. Pretreatment with NAC significantly prevented the plumbagin-induced decrease in cell viability in these cell types. In conclusion, plumbagin exerted its anticancer effect by directly interacting with TrxR and GR, and thus increasing intracellular ROS levels.

Design, synthesis and insight into the structure-activity relationship of 1,3-disubstituted indazoles as novel HIF-1 inhibitors.

Design, synthesis and insight into the structure-activity relationship (SAR) of 1,3-disubstituted indazoles as novel HIF-1 inhibitors are described. In particular, the substituted furan moiety on indazole skeleton as well as its substitution pattern turns out crucial for the high HIF-1 inhibition.

Design, synthesis and identification of novel colchicine-derived immunosuppressant

Synthesis and biological evaluation of various colchicine analogues through the mixed-lymphocyte reaction (MLR), lymphoproliferation, and inhibitory effects on the inflammatory genes are described. In addition, a new series of immunosuppressive agents developed on the structural basis of colchicine, as well as their structure-activity relationships is reported. The most potent analogue 20a exhibited an excellent immunosuppressive activity on in vivo skin-allograft model, which is comparable to that of cyclosporin A.

Expedient Synthesis of Chiral Homoallylamines via N,O-Acetal TMS Ethers and Its Application

A highly stereoselective and efficient method for the synthesis of optically active homoallylamines was developed. Key features of the method include (1) the utilization of naphthylethylamine as both an excellent chiral auxiliary and the amine source, (2) the 1,3-chiral induction of the N-acyliminium ion with high stereoselectivity and high yield, and (3) facile auxiliary removal under mild conditions to liberate N-Cbz-protected homoallylamines. In addition, the total synthesis of the proposed novel tripeptide containing a β-amino acid has been achieved by applying this method.