Abstract
BACKGROUND: Microbial secondary metabolism is regulated by a complex and mostly-unknown network of global and pathway-specific regulators. A dozen biosynthetic gene clusters for secondary metabolites have been reported in myxobacteria, but a few regulation factors have been identified. RESULTS: We identified a transcription regulator Esi for the biosynthesis of epothilones. Inactivation of esi promoted the epothilone production, while overexpression of the gene suppressed the production. The regulation was determined to be resulted from the transcriptional changes of epothilone genes. Esi was able to bind, probably via the N-terminus of the protein, to an inverted repeat sequence in the promoter of the epothilone biosynthetic gene cluster. The Esi-homologous sequences retrieved from the RefSeq database are all of the Proteobacteria. However, the Esi regulation is not universal in myxobacteria, because the esi gene exists only in a few myxobacterial genomes. CONCLUSIONS: Esi binds to the epothilone promoter and down-regulates the transcriptional level of the whole gene cluster to affect the biosynthesis of epothilone. This is the first transcription regulator identified for epothilone biosynthesis.