Blasticidin A

Blasticidin A (1) and aflastatin A (2), Streptomyces metabolites with similar structures, are specific inhibitors of aflatoxin production by Aspergillus parasiticus. The stereochemistry of the polyol fragment of 1 (3a) containing ten chiral centers was elucidated by applying acetonide and MTPA methods to a variety of acetonide derivatives of 3a, which determined the absolute configuration of 3a. By using the similar methods, the absolute configuration of the polyol fragment of 2 (4a) was determined, which was the same as that elucidated by J-based and other chemical methods previously.

Influenza A virus (IAV) poses significant threats to public health because of the recent emergence of highly pathogenic strains and wide-spread resistance to available anti-influenza drugs. Therefore, new antiviral targets and new drugs to fight influenza virus infections are needed. Although IAV RNA transcription/replication represents a promising target for antiviral drug development, no assay ideal for high-throughput screening (HTS) application is currently available to identify inhibitors targeting these processes. In this work, we developed a novel HTS assay to analyze the transcription and replication of IAV RNA using an A549 cell line stably expressing IAV RNA-dependent RNA polymerase (RdRp) complex, NP and a viral mini-genomic RNA. Both secreted Gaussia luciferase (Gluc) and blasticidin resistance gene (Bsd) were encoded in the viral minigenome and expressed under the control of IAV RdRp. Gluc serves as a reporter to monitor the activity of IAV RdRp, and Bsd is used to maintain the expression of all foreign genes. Biochemical studies and the statistical analysis presented herein demonstrate the high specificity, sensitivity and reproducibility of the assay. This work provides an ideal HTS assay for the identification of inhibitors targeting the function of IAV RdRp and a convenient reporting system for mechanism study of IAV RNA transcription / replication.

Blasticidin A (BcA), an antibiotic produced by Streptomyces, inhibits aflatoxin production without strong growth inhibition toward aflatoxin-producing fungi. During the course of our study on the mode of action of BcA by two-dimensional differential gel electrophoresis (2D-DIGE), we found a decrease in the abundances of ribosomal proteins in Saccharomyces cerevisiae after exposure to BcA. This phenomenon was also observed by treatment with blasticidin S (BcS) or cycloheximide. BcA inhibited protein synthesis in a galactose-induced expression system in S. cerevisiae similar to BcS and cycloheximide. BcS, but not cycloheximide, inhibited aflatoxin production in Aspergillus parasiticus without inhibition of fungal growth, similar to BcA. A decrease in the abundances of aflatoxin biosynthetic enzymes was observed in 2D-DIGE experiments with Aspergillus flavus after exposure to BcA or BcS. These results suggested that protein synthesis inhibitors are useful to control aflatoxin production.