The Aspergillus nidulans homoaconitase gene lysF is negatively regulated by the multimeric CCAAT-binding complex AnCF and positively regulated by GATA sites

In beta -lactam-antibiotic-producing fungi, such as Aspergillus (Emericella ) nidulans, L-alpha -aminoadipic acid is the branching point of the lysine and penicillin biosynthesis pathways. To obtain a deeper insight into the r egulation of lysine biosynthesis genes, the regulation of the A. nidulans l ysF gene, which encodes homoaconitase, was studied. Band-shift assays indic ated that the A. nidulans multimeric CCAAT-binding complex AnCF binds to tw o of four CCAAT motifs present in the lysF promoter region. AnCF consists a t least of three different subunits, designated HapB, HapC, and HapE. In bo th a Delta hapB and a Delta hapC strain, the expression of a translational lysF-lacZ gene fusion integrated in single copy at the chromosomal argB gen e locus was two to three-fold higher than in a wild-type strain. These data show that AnCF negatively regulates lysF expression. The results of Northe rn blot analysis and lysF-lacZ expression analysis did not indicate a lysin e-dependent repression of lysF expression. Furthermore, mutational analysis of the lysF promoter region revealed that two GATA sites matching the GATA consensus sequence HGATAR positively affected lysF-lacZ expression. Result s of Northern blot analysis also excluded that the global nitrogen regulato r AreA is the responsible trans-acting GATA-binding factor.