Selective Overproduction of the Proteasome Inhibitor Salinosporamide A via Precursor Pathway Regulation

SummaryThe chlorinated natural product salinosporamide A is a potent 20S proteasome inhibitor currently in clinical trials as an anticancer agent. To deepen our understanding of salinosporamide biosynthesis, we investigated the function of a LuxR-type pathway-specific regulatory gene, salR2, and observed a selective effect on the production of salinosporamide A over its less active aliphatic analogs. SalR2 specifically activates genes involved in the biosynthesis of the halogenated precursor chloroethylmalonyl-CoA, which is a dedicated precursor of salinosporamide A. Specifically, SalR2 activates transcription of two divergent operons—one of which contains the unique S-adenosyl-L-methionine-dependent chlorinase encoding gene salL. By applying this knowledge to rational engineering, we were able to selectively double salinosporamide A production. This study exemplifies the specialized regulation of a polyketide precursor pathway and its application to the selective overproduction of a specific natural product congener.

► Gene deletion mutants were constructed to identify SalR2 as a transcriptional activator ► SalR2 acts selectively on the chloroethylmalonyl-CoA pathway ► Overexpression of salR2 results in the selective and increased production of the chlorinated anticancer agent salinosporamide A