Abstract
The Aspergillus oryzae Taka-amylase A (TAA) gene has been used as a model gene to characterize the regulatory mechanisms of gene expression in Aspergilli. TAA gene contained a typical eukaryotic promoter with a TATA box and putative regulatory elements such as a CCAAT sequence in its 5′-noncoding region. A nuclear protein designated AnCP bound to the CCAAT sequence. Replacement of the CCAAT sequence with CGTAA was found to abolish the binding of AnCP and to have an inhibitory effect on taa promoter activity. Although AnCP was not purified to homogeneity, AnCP appeared to have an apparent molecular mass of approximately 120 kDa.
In Saccharomyces cerevisiae, the CCAAT-binding HAP complex is a heteromeric protein comprising at least four subunits (yHAP2, yHAP3, yHAP4 and yHAP5) and is involved in the regulation of genes responsible for oxidative phosphorylation. A gene designated hapC with significant homology to yHAP3 has been isolated from A. nidulans by Hynes et al. We expressed hapC gene as a fusion protein with MalE in E. coli, purified HapC protein and prepared anti-HapC antiserum. The MalE-HapC fusion protein was able to substitute for the authentic HapC in AnCP. Furthermore, addition of the anti-HapC antiserum to the DNA binding reaction mixture retarded the mobility of the shifted band. These indicate clearly that HapC protein acts as a subunit of AnCP and that AnCP is a counterpart of the yeast Hap complex.
