The dnrO gene encodes a DNA-binding protein that regulates daunorubicin production in Streptomyces peucetius by controlling expression of the dnrN pseudo response regulator gene

The dnrO gene is located adjacent to and divergently transcribed from the r esponse regulator gene, dnrN, that activates the transcription of the dnrI gene, which in turn activates transcription of the daunorubicin biosynthesi s genes in Streptomyces peucetius, Gene disruption and replacement of dnrO produced the dnrO::aphll mutant strain and resulted in the complete loss of daunorubicin biosynthesis, Suppression of the dnrO::aphll mutation by the introduction of dnrN or dnrI on a plasmid suggested that DnrO is required f or the transcription of dnrN, whose product is known to be required for dnr I expression, These conclusions were supported by the effects of the dnrO m utation on expression of dnrO dnrN and dnrI, as viewed by melC fusions to e ach of these regulatory genes, DnrO was overexpressed in Escherichia coli a nd the cell-free extract was used to conduct mobility shift DNA-binding ass ays. The results showed that DnrO binds specifically to the overlapping dnr N/dnrO(p1) promoter region. Thus, DnrO may regulate the expression of both the dnrN and dnrO genes.