ABSTRACT
Previous studies identified a MarR (multiple antibiotic resistance regulator) family transcription factor OtrR in the oxytetracycline biosynthetic gene cluster, which regulated the expression of an efflux pump OtrB. The genes otrB and otrR were divergent arranged and the inter-ORF (open reading frame) region between the two genes contained the promoter otrBp. In this study, we demonstrated that the reverse complementary sequence of otrBp contained the promoter of otrR, and its activity was also repressed by OtrR by sharing the same operator otrO within otrBp, and allosteric regulated by oxytetracycline. Our findings offered a solid base for the synthetic biological application of the bi-direction promoter in controlling two elements at the same time using only one signal molecule.
Subject(s)
Anti-Bacterial Agents/biosynthesis , Gene Expression Regulation, Bacterial , Oxytetracycline/biosynthesis , Promoter Regions, Genetic , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Base Sequence , Multigene Family , Open Reading Frames , Streptomyces/genetics , Streptomyces/metabolismABSTRACT
Aurora kinases have emerged as promising targets for cancer therapy because of their critical role in mitosis. These kinases are well-conserved in all eukaryotes, and IPL1 gene encodes the single Aurora kinase in budding yeast. In a virtual screening attempt, 22 compounds were identified from nearly 15,000 microbial natural products as potential small-molecular inhibitors of human Aurora-B kinase. One compound, Jadomycin B, inhibits the growth of ipl1-321 temperature-sensitive mutant more dramatically than wild-type yeast cells, raising the possibility that this compound is an Aurora kinase inhibitor. Further in vitro biochemical assay using purified recombinant human Aurora-B kinase shows that Jadomycin B inhibits Aurora-B activity in a dose-dependent manner. Our results also indicate that Jadomycin B competes with ATP for the kinase domain, which is consistent with our docking prediction. Like other Aurora kinase inhibitors, Jadomycin B blocks the phosphorylation of histone H3 on Ser10 in vivo. We also present evidence suggesting that Jadomycin B induces apoptosis in tumor cells without obvious effects on cell cycle. All the results indicate that Jadomycin B is a new Aurora-B kinase inhibitor worthy of further investigation.
Subject(s)
Protein Kinase Inhibitors/pharmacology , Protein Serine-Threonine Kinases/antagonists & inhibitors , Aurora Kinase B , Aurora Kinases , Blotting, Western , Cell Line , Cell Proliferation/drug effects , Drug Evaluation, Preclinical , Flow Cytometry , Histones/antagonists & inhibitors , Histones/metabolism , Humans , Isoquinolines/chemistry , Isoquinolines/pharmacology , Molecular Structure , Phosphorylation , Protein Kinase Inhibitors/chemistry , Recombinant Proteins/antagonists & inhibitorsABSTRACT
The high mortality rate of immunocompromised patients with fungal infections and the limited availability of highly efficacious and safe agents demand the development of new antifungal therapeutics. To rapidly discover such agents, we developed a high-throughput synergy screening (HTSS) strategy for novel microbial natural products. Specifically, a microbial natural product library was screened for hits that synergize the effect of a low dosage of ketoconazole (KTC) that alone shows little detectable fungicidal activity. Through screening of approximately 20,000 microbial extracts, 12 hits were identified with broad-spectrum antifungal activity. Seven of them showed little cytotoxicity against human hepatoma cells. Fractionation of the active extracts revealed beauvericin (BEA) as the most potent component, because it dramatically synergized KTC activity against diverse fungal pathogens by a checkerboard assay. Significantly, in our immunocompromised mouse model, combinations of BEA (0.5 mg/kg) and KTC (0.5 mg/kg) prolonged survival of the host infected with Candida parapsilosis and reduced fungal colony counts in animal organs including kidneys, lungs, and brains. Such an effect was not achieved even with the high dose of 50 mg/kg KTC. These data support synergism between BEA and KTC and thereby a prospective strategy for antifungal therapy.
Subject(s)
Antifungal Agents/pharmacology , Depsipeptides/administration & dosage , Drug Combinations , Drug Evaluation, Preclinical/methods , Ketoconazole/administration & dosage , Mycoses/drug therapy , Algorithms , Animals , Cell Line , Disease Models, Animal , Drug Resistance, Fungal/genetics , Humans , Immunocompromised Host , Mice , Microbial Sensitivity TestsABSTRACT
Tetracycline repressor gene (tetR) from E. coli transposon Tn10 was fused in frame with green fluorescent protein gene (gfp) from jellyfish Aequorea Victoria on an E. coli expression vector and the fusion protein (TR::GFP) was purified. The binding of TR::GFP with tetracycline (tc) was demonstrated by nitrocellulose filter binding assay. TR::GFP also maintained the fluorescence property of GFP. Most significantly, fluorescence emission intensity of TR::GFP increased by 2-fold in the presence of tc, from 1.132 to 2.214, while those of GFP and TetR showed little change under similar conditions. The results indicated TR::GFP possesses characteristics of a tetracycline biosensor.