The wide-domain carbon catabolite repressor CreA indirectly controls expression of the Aspergillus nidulans xlnB gene, encoding the acidic endo-beta-(1,4)-xylanase X-24

The Aspergillus nidulans xlnB gene, which encodes the acidic endo-beta-(1,4 )-xylanase X-24, is expressed when xylose is present as the sole carbon sou rce and repressed in the presence of glucose. That the mutation creA(d)30 r esults in considerably elevated levels of xlnB mRNA indicates a role for th e wide-domain repressor CreA in the repression of xlnB promoter (xlnBp) act ivity. Functional analyses of xlnBp::goxC reporter constructs show that non e of the four CreA consensus target sites identified in xlnBp are functiona l in vivo. The CreA repressor is thus likely to exert carbon catabolite rep ression via an indirect mechanism rather than to influence xlnB expression by acting directly on xlnB.