Identification of functional cis-elements required for repression of the Taka-amylase A gene under secretion stress in Aspergillus oryzae.

Abstract

The expression of secreted proteins in filamentous fungi is down-regulated by a transcriptional feedback mechanism under endoplasmic reticulum stress, termed repression under secretion stress (RESS). To investigate the RESS mechanism, we analyzed the expression of the Taka-amylase A gene (amyB) in Aspergillus oryzae, which was depressed under secreted protein stress. We conducted a truncation and deletion analysis of the amyB promoter to identify cis-elements required for RESS. A nucleotide sequence (positions -378 to -291) without any binding sites for the transcriptional activator AmyR, which is involved in amylolytic gene expression, was required for RESS. The octamer sequence TCACGGGC (positions -307 to -300) constituted the core sequence of the upstream activating element essential for amyB down-regulation under secretion stress. Both the inactivation of AmyR and RESS contributed to the down-regulation of amyB expression under ER stress.