Inducer-dependent nuclear localization of a Zn(II)(2)Cys(6) transcriptional activator, AmyR, in Aspergillus nidulans.

AmyR is a Zn(II)(2)Cys(6) 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)(2)Cys(6) DNA binding motif.