Combinatorial synthesis of cholesterol ester transfer protein-mRNA ligands and screening by nondenaturating gel-electrophoresis

RNA, as one of the biomolecules with the most structural and functional diversity, is an attractive therapeutic target.(1) Employing combinatorial chemistry methods, small peptide ligands were found, which bind to a short RNA with important biological functions. A 23-nt RNA oligonucleotide from the cholesterol ester transfer protein mRNA was chosen as a molecular target.(2) A 27-nt RNA oligonucleotide from the human immunodeficiency virus type-1 (HIV-1) TAR RNA was used to control the binding specificity.(3) Tetrapeptide libraries, composed of the amino acids Lys, Tyr, Leu, Ile, and Arg, with and without C- and N-terminal lysines, were synthesized by a combination of combinatorial and divergent solid-phase synthesis. Gel-shift affinity screening was used to extract the peptides with the best RNA binding properties. The peptide Lys-Tyr-Lys-Leu-Tyr-Lys-Cys-NH(2) (1) showing micromolar affinity to its RNA target was characterized with circular dichroism (CD), ultra violet (UV) measurement, and (1)H NMR spectroscopy.     

Targeting RNA with small molecules

Therapeutic targeting of RNA is not as well-developed as with DNA and proteins, and the many structures and functions of RNA suggest that it is an underutilized target. As with DNA, RNA has heterocyclic bases and base pairs with a highly anionic backbone, but as with proteins, RNA can fold into complex tertiary structures that create unique binding pockets for small molecules. Aminoglycoside targeting of ribosomal RNA is a well-known success story, and mRNAs and tRNAs have also served as therapeutic targets as well as model systems for understanding RNA-ligand interactions. The unique, species-specific structures and chemistry involved in splicing and ribozyme activity makes this RNA function an attractive target, and inhibitors of ribozyme activity have been discovered. The numerous serious human diseases caused by RNA viruses highlight the importance of developing new compounds that can target RNA structures in viral genomes. Considerable effort has been directed at finding compounds that target HIV-1 RNAs that control viral replication and frameshifting. As part of these efforts very useful new assays have been developed for small molecule-RNA interactions. The assays have led to the discovery of new inhibitors for different steps in viral replication. The next phase of research in RNA targeting will not only focus on the discovery of new compounds, but also on how to develop small molecules with high affinity and selectively for RNA that can penetrate effectively into a wide array of cell types.     

Synthesis and biological activities of fluorescent acridine-containing HIV-1 nucleocapsid proteins for investigation of nucleic acid-NCp7 interactions

Specific interactions between the 72-amino acid nucleocapsid protein NCp7 of the human immunodeficiency virus, type 1 and the genomic RNA are essential for virus replication. Studies on the mechanism of action of NCp7 require a direct visualization of its complexes with nucleic acids and the determination of binding affinities. To facilitate these investigations, fluorescent NCp7 derivatives were developed by introduction in the NCp7 sequence of a non-natural amino acid, (S)-β-(9-acridinyl)alanine (Aca) obtained by a chiral synthetic method. Three fluorescent NCp7 derivatives were obtained by introducing this amino acid at different positions. As shown by NMR, the three-dimensional structure of NCp7 is not altered by introduction of Aca. The fluorescent peptides were found to be as potent as their precursors in interacting with nucleic acids and in promoting HIV-1 genomic RNA dimerization. Moreover, because of their fluorescent properties, these NCp7s can be used at submicromolar concentrations to directly visualize and quantify protein-nucleic acid interactions in solution or after gel electrophoresis. This could facilitate the development of new antiviral agents aimed at inhibiting the functions of NCp7 and studies on the intracellular traffic of NCp7 within the preintegration complex.     

HIV-1核衣壳蛋白NCp7的功能及其抑制剂研究进展

NCp7在HIV-1生活周期中多个步骤发挥重要的核酸分子伴侣作用。抑制NCp7的功能可阻断HIV-1复制。NCp7含有两个高度保守的锌指结构，对NCp7的功能起决定性作用。锌指结构突变将导致HIV-1丧失感染能力。NCp7抑制剂可望成为下一代不容易产生耐药突变的抗HIV-1药物。本文就NCp7抑制剂目前的研究进展作简略综述。     

Natural-product-library-based screening for discovery of capsid C-terminal domain targeted HIV-1 inhibitors

Antiretroviral therapy (ART) can effectively suppress replication of human immunodeficiency virus type 1 (HIV-1) and limit disease progression. However, ART is unable to eradicate the virus, and the requirement for lifelong treatment may have side effects and may lead to the development of resistance. New approaches to prevent and treat HIV-1 infection should therefore be developed. HIV-1 capsid (CA) protein is an unexploited but attractive target for antiviral drug development. The hydrophobic cavity of the C-terminal domain of CA (CA CTD) has been validated as a potential target for antiviral drugs. Binding of compounds to this conserved non-polar groove in CA CTD allosterically disrupts the CA assembly. This study screened 2080 natural products to identify potential antiviral agents for further development to combat HIV-1 infection. From the primary screen at a fixed concentration of 50 µM, 16 compounds were found to be effective against this target. Six compounds observed in the primary screen were confirmed in dose–response experiments, and were tested against HIV-1-induced cytopathic effects. Two compounds were found to inhibit HIV-1 replication, and the most active compound – rubranol – inhibited viral replication at a moderate micromolar concentration (EC₅₀ = 15.85 μM). The binding modes of rubranol and hirsutanonol to CA CTD were analysed by molecular docking, providing insight for the design of drugs targeting HIV-1 CA. This study reports, for the first time, identification of natural products that showed potential as anti-HIV-1 agents by targeting the conserved hydrophobic cavity of HIV-1 CA CTD.     

Identification of HIV-1 inhibitors targeting the nucleocapsid protein

The HIV-1 nucleocapsid (NC) is a RNA/DNA binding protein encoded within the Gag polyprotein, which is critical for the selection and chaperoning of viral genomic RNA during virion assembly. RNA/DNA binding occurs through a highly conserved zinc-knuckle motif present in NC. Given the necessity of NC-viral RNA/DNA interaction for viral replication, identification of compounds that disrupt the NC-RNA/DNA interaction may have value as an antiviral strategy. To identify small molecules that disrupt NC-viral RNA/DNA binding, a high-throughput fluorescence polarization assay was developed and a library of 14,400 diverse, druglike compounds was screened. Compounds that disrupted NC binding to a fluorescence-labeled DNA tracer were next evaluated by differential scanning fluorimetry to identify compounds that must bind to NC or Gag to impart their effects. Two compounds were identified that inhibited NC-DNA interaction, specifically bound NC with nanomolar affinity, and showed modest anti-HIV-1 activity in ex vivo cell assays.     

Characterisation of inter- and intra-molecular interactions of the dengue virus RNA dependent RNA polymerase as potential drug targets

Our research is directed towards enhancing the understanding of the molecular biology of dengue virus replication with the ultimate goal being to develop novel antiviral strategies based on preventing critical inter- or intra-molecular interactions required for the normal virus life cycle. The viral RNA-dependent RNA polymerase (NS5) and the viral helicase (NS3) interaction offers a possible target for inhibitors to bind and prevent replication. In this study the yeast-two hybrid system was used to show that a small region of NS5 interacts with NS3, and also with the cellular nuclear transport receptor importin-beta. Furthermore, intramolecular interaction between the two putative domains of NS5 can also be detected by the yeast two-hybrid assay. We have also modified the colony lift assay for the beta-galactosidase reporter activity in intact yeast cells which reflects the strength of interaction between two proteins to a microtiter plate format. This assay offers a unique opportunity to screen for small molecule compounds that block physiologically important interactions.     

Derivatives of Salicylic Acid as Inhibitors of YopH in Yersinia pestis

Yersinia pestis causes diseases ranging from gastrointestinal syndromes to bubonic plague and could be misused as a biological weapon. As its protein tyrosine phosphatase YopH has already been demonstrated as a potential drug target, we have developed two series of forty salicylic acid derivatives and found sixteen to have micromolar inhibitory activity. We designed these ligands to have two chemical moieties connected by a flexible hydrocarbon linker to target two pockets in the active site of the protein to achieve binding affinity and selectivity. One moiety possessed the salicylic acid core intending to target the phosphotyrosine-binding pocket. The other moiety contained different chemical fragments meant to target a nearby secondary pocket. The two series of compounds differed by having hydrocarbon linkers with different lengths. Before experimental co-crystal structures are available, we have performed molecular docking to predict how these compounds might bind to the protein and to generate structural models for performing binding affinity calculation to aid future optimization of these series of compounds.     

HIV-1核衣壳蛋白NCp7抑制剂体外筛选方法的建立

目的表达HIV-1核衣壳蛋白(nucleocapside proteinp7,NCp7),并建立抑制剂筛选方法。方法从pBRU2/ADP202质粒经PCR得到HIV-1NCp7编码序列,克隆到pet28a质粒中构建HIV-1NCp7表达载体。阳性克隆转染E.coliBL21DE3,以IPTG诱导,细胞裂解液经Q SepharoseH.P和SP Sepharose H.P纯化后纯度达到90%以上。将具有锌离子逐出活性的H2O2和2,2′-联硫基二吡啶(2,2′-di-thiodipyridine,AT-2)与NCp7作用,用锌离子特异的荧光染料检测。用该方法检测KIZ-CM系列化合物。结果可以检测H2O2和AT-2的锌离子逐出活性,经该方法筛选,KIZ-CM10,18,19等化合物具有一定的锌离子逐出活性。结论在国内首次建立了HIV-1NCp7锌离子逐出方法,该方法可以用于NCp7抑制剂的筛选。     

RNA as a target for drug design,the example of Tat-TAR interaction

One of the new targets in the battle against HIV-1 infection is the interaction between the viral transactivator and the transactivation response (TAR) element, which is necessary for HIV-1 replication. After an overview of the most recent structural studies of the Tat-TAR system, new TAR-targeted inhibitors are presented in several classes: antisense oligonucleotides, cationic peptides, intercalators and a large class of small RNA binding molecules. The method of library screening of RNA binding ligands in the search for new inhibitors is explained in detail. Inhibition of Tat-TAR interaction is considered as a realistic approach to develop new anti-HIV compounds. The RNA binding molecules in this review also demonstrate that the development of drugs that target RNA will become a feasible goal and that such compounds will be added in the future to the therapeutic arsenal to combat several diseases.     

Discovery of Protein–Protein Interaction Inhibitors of Replication Protein A

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Histaminergic pharmacology of homo-oligomeric β3 γ-aminobutyric acid type A receptors characterized by surface plasmon resonance biosensor technology

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Anti-HIV inhibitors based on nucleic acids: emergence of aptamers as potent antivirals

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Structure-based identification of small molecule compounds targeting cell cyclophilin A with anti-HIV-1 activity

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