Discovery of Surfactins as Inhibitors of MicroRNA Processing Using Cat-ELCCA

Abstract

MicroRNAs (miRNAs) are a family of small noncoding RNAs that regulate gene expression. Due to their important activity in the fine-tuning of protein translation, abnormal expression of miRNAs has been linked to many human diseases, making the targeting of miRNAs attractive as a novel therapeutic strategy. Accordingly, researchers have been heavily engaged in the discovery of small molecule modulators of miRNAs. With an interest in the identification of new chemical space for targeting miRNAs, we developed a high-throughput screening (HTS) technology, catalytic enzyme-linked click chemistry assay (cat-ELCCA), aimed at the discovery of small molecule ligands for pre-miR-21, a miRNA that is frequently overexpressed in human cancers. From our HTS campaign, we found that natural products, a source of many impactful human medicines, may be a promising source of potential pre-miR-21-selective maturation inhibitors. Herein we describe our first efforts in natural product inhibitor discovery leading to the identification of a depsipeptide class of natural products as RNA-binding inhibitors of Dicer-mediated miRNA processing.

Anti-Mycoplasma Activity of Bacilotetrins C–E, Cyclic Lipodepsipeptides from the Marine-Derived Bacillus subtilis and Structure Revision of Bacilotetrins A and B

“…The HMBC signals from the α -proton and amide proton of each amino acid to the carbonyl carbon of the adjacent amino acid or β -OH acid and the NOESY correlations between the α -proton and amide proton of amino acids established the sequence of 1 as (cyclo-( β -OH acid-Glu-Leu-1-Leu-2-Leu-3)) ( Figure 2 ). The β -OH acid chain was estimated to be a linear type due to the remaining one methyl signal ( δ C 14.5 and δ H 0.89), which matched well with recently reported chemical shifts for the terminal methyl signal ( δ C 14.4 and δ H 0.90) of a linear β -OH acid [ 19 ].…”

“…However, by the detailed analysis of 2D NMR data, we found that the HDTA unit in 5 is a mixture of a 3-hydroxy-12-methyltetradecanoic acid and a 3-hydroxy-13-methyltetradecanoic acid, which have the same molecular weight and formula to HDTA, as shown in Figure 5 . This fact was also supported by the chemical shifts of the methyl signals ( δ C 19.8/ δ H 0.86, δ C 11.9/ δ H 0.87, and δ C 23.1/ δ H 0.87) of the β -OH acid in 5 , which were well matched with the literature values for the anteiso- and iso-type β -OH acids [ 19 ]. Therefore, the planar structures of 4 and 5 should be revised to have the same planar core structure as baciloterins C–E ( 1 – 3 ).…”

“…In addition, the methine signals ( δ C 30.6 and δ H 1.50) for the anteiso-type β -OH acid in the original NMR data of 4 were not true signals. The methyl signals ( δ C 14.6 and δ H 0.89) of the β -OH acid in 4 were in good agreement with those ( δ C 14.5 and δ H 0.89) of 1 and the literature values for the linear-type β -OH acid [ 19 ]. Thus, we revise the planar structure of 4 to have a linear-type β -OH acid instead of the anteiso-type β -OH acid, and to be cyclo-( R - β -OH acid-L-Glu-L-Leu-L-Leu-L-Leu) instead of cyclo-( R - β -OH acid-L-Leu-L-Leu-L-Leu-L-Glu) ( Figure 5 ).…”

“…Bacilotetrin E ( 3 ) also displayed HMBC signals from H-14 and H-15 ( δ H 0.87) of the β -OH acid to C-13 ( δ C 29.2) of β -OH acid and from H-12 ( δ H 1.16) to C-14 ( δ C 23.1) and C-15 ( δ C 23.1) of the β -OH acid, suggesting the presence of an iso-methyl branched fatty acid. In addition, anteiso- and iso-methyl signals of 2 and 3 were in good agreement with reference values (anteiso: δ C 19.6/ δ H 0.86 and δ C 11.8/ δ H 0.88; iso: δ C 23.1/ δ H 0.88) [ 19 ]. Thus, the sequences of 1 – 3 were identified as cyclo-( R - β -OH acid-L-Glu-L-Leu-D-Leu-L-Leu).…”

Identification of a New Antimicrobial, Desertomycin H, Utilizing a Modified Crowded Plate Technique

“…Using our developed technique, we isolated over 1400 culturable antibiotic-producing isolates from soil, aquatic, and marine environments as part of the Tiny Earth TM Program [ 31 ]. More importantly, we coupled our culture technique with a data-based chemical analysis [ 32 , 33 ], leading to the identification of a new macrocyclic polyketide class of antibiotic, desertomycin H ( 2 ), together with the known congener desertomycin A ( 1 ). Structure elucidation of the metabolites was performed based on detailed spectroscopic analysis.…”