Regulation of cellulolytic genes by McmA, the SRF-MADS box protein in Aspergillus nidulans.

Cellobiose triggers the production of two endoglucanases, EglA and EglB, in Aspergillus nidulans. The cellulose responsive element (CeRE) cis-element that is essential for induction has been identified on the eglA promoter, but transcription factors that bind to CeRE have not yet been identified. CeRE contained a consensus sequence CC(A/T)6GG for binding of the SRF-type MADS box proteins. Introduction of a missense mutation into mcmA, encoding for the sole SRF-MADS protein in A. nidulans, caused a significant reduction in cellulase induction. Real-time RT-PCR analysis revealed that inductive expression of not only eglA but also eglB and cbhA by cellobiose were under control of McmA. The McmA protein expressed in Escherichia coli specifically bound to two regions of the eglA promoter: CeRE and its upstream proximal region. These results, together with our previous study on the eglA promoter structure, imply that McmA regulates eglA expression by binding directly to its promoter. This is the first evidence for participation of an SRF-MADS protein in cellulase regulation.