Inducer-Dependent Nuclear Localization of a Zn(II)₂Cys₆ Transcriptional Activator, AmyR, in Aspergillus nidulans

Abstract

AmyR is a Zn(II)₂Cys₆ transcriptional activator that regulates expression of the amylolytic genes in Aspergillus species. Subcellular localization studies of GFP-fused AmyR in A. nidulans revealed that the fusion protein preferentially localized to the nucleus in response to isomaltose, the physiological inducer of the amylolytic genes. The C-terminal domains of AmyR, designated MH3 (residues 419–496) and MH4 (residues 516–542), were essential for sensing the inducing stimulus and regulating the subcellular localization. The MH2 domain (residues 234–375) located in the middle of AmyR was required for transcriptional activation of the target genes, and the nuclear localization signals were identified within the N-terminal Zn(II)₂Cys₆ DNA binding motif.