Contribution of UbrA, a ubiquitin ligase essential for Arg/N-degron pathway, to peptidase gene expression in <i>Aspergillus oryzae</i>

Peptidases produced by <i>Aspergillus oryzae</i> are important in the production of Japanese fermented foods and are used as industrial enzymes for various food-processing and pharmaceutical applications. The expression of dipeptide/tripeptide transporter gene in budding yeast is controlled by a positive feedback mechanism through the dipeptide-mediated activation of the E3 ubiquitin ligase, Ubr1, which is essential for the Arg/N-degron pathway, which determines the lifetime of intracellular proteins. In this study, we demonstrated that <i>A. oryzae</i> UbrA (an ortholog of yeast Ubr1) regulates peptidase gene expression in addition to dipeptide/tripeptide transporter genes. Disruption of <i>ubrA</i> decreases the expression of major acidic peptidase genes and increases the expression of alkaline peptidase gene. In addition, the expression levels of dipeptide/tripeptidyl peptidase genes and dipeptide/tripeptide transporter genes were reduced by <i>ubrA</i> disruption. These results suggest that UbrA regulates the expression of various peptidase genes to facilitate positive feedback of dipeptide/tripeptide transporter genes.