A novel nuclear factor, SREB, binds to a cis-acting element, SRE, requiredfor inducible expression of the Aspergillus oryzae Taka-amylase A gene in A-nidulans

The Taka-amylase A gene (taaG2) of Aspergillus oryzae is inducibly expresse d in A. nidulans upon exposure to inducing carbon sources, such as starch a nd maltose. In order to identify nuclear factor(s) possibly involved in the induction of the taaG2 gene, gel mobility shift assays and DNase I footpri nting analyses were carried out. and revealed a novel nuclear factor in A. nidulans extracts, which specifically bound to two sites in the tanG2 promo ter region, -204 to -189 and -182 to -168, which share the common sequence GGAAATT. The nuclear factor was detected in nuclei from both induced and un induced mycelia. Mutational analysis within and around the binding sequence s demonstrated that only the upstream binding sequence. designated SRE (sta rch responsive element), was required for the inducible expression of the t aaG2 gene, and thus we designated the nuclear factor SREB (SRE binding fact or). The downstream binding site contained an inverted SRE (ISRE) and playe d no role in the induction of taaG2 expression. SREB was shown by gel retar dation assays to have higher affinity for SRE than for ISRE.