Depression of the xylanase-encoding cgxA gene of Chaetomium gracile in Aspergillus nidulans

Regulation of the Chaetomium gracile xylanase A gene (cgxA) was investigate d using Aspergillus nidulans as an intermediate host. Deletion of a 185 bp DNA fragment from its promoter region led to higher levels of the cgxA gene expression, indicating that the 185 bp DNA fragment contains an element in volved in repression of the gene. A nuclear extract was assayed for protein s which bind to the 185 bp DNA fragment. A protein designated AnRP bound se quence specifically to the DNA fragment. The minimum sequence required for AnRP binding, 5'TTGACAAAT-3', was determined by means of gel mobility shift assays with various double-stranded oligonucleotides. Furthermore, this se quence repressed the expression of the cgxA gene when inserted at the 5' en d of the cgxA gene on pXAH, which was deleted for the repressive element fr om the promoter region.