Improvement in doxorubicin productivity by overexpression of regulatory genes in Streptomyces peucetius

Biosynthesis of doxorubicin (DXR) is tightly regulated, limiting its production in Streptomyces peucetius cultures. The regulatory genes dnrN, dnrI, afsR, and metK1-sp from S. peucetius ATCC 27952 were cloned into the pIBR25 expression vector under the control of the strong ermE* promoter to enhance DXR production. The constructed expression plasmids, pNI25 (with dnrN-dnrI), pNIS25 (with dnrN-dnrI-metK1-sp), pNIR25 (with dnrN-dnrI-afsR), pRS25 (with afsR-metK1-sp) and pNIRS25 (with dnrN-dnrI-afsR-metK1-sp), were transformed into S. peucetius. The recombinant strains NI, NIS and NIR produced greater amounts of DXR than the parental strain with an increment of 1.2-fold by pNI25, 1.4-fold by pNIS25 and 4.3-fold by pNIR25, whereas pRS25 and pNIRS25 had no significant effect on DXR production. We also studied the transcriptional level of overexpressed regulatory genes and relative production of DXR, daunorubicin (DNR) and ɛ-rhodomycinone (RHO) in each recombinant strain.