The TamA protein fused to a DNA-binding domain can recruit AreA, the majornitrogen regulatory protein, to activate gene expression in Aspergillus nidulans

The areA gene of Aspergillus nidulans encodes a GATA zinc finger transcript ion factor that activates the expression of a large number of genes subject to nitrogen metabolite repression. The amount and activity of the AreA pro tein under different nitrogen conditions is modulated by transcriptional, p osttranscriptional, and post-translational controls. One of these controls of AreA activity has been proposed to involve the NmrA protein interacting with the DNA-binding domain and the extreme C terminus of AreA to inhibit D NA binding under nitrogen sufficient conditions. In contrast, mutational ev idence suggests that the tamA gene has a positive role together with areA i n regulating the expression of genes subject to nitrogen metabolite repress ion. This gene was identified by the selection of mutants resistant to toxi c nitrogen source analogues, and a number of nitrogen metabolic activities have been shown to be reduced in these mutants. To investigate the role of this gene we have used constructs encoding the TamA protein fused to the DN A-binding domain of either the FacB or the AmdR regulatory proteins. These hybrid proteins have been shown to activate expression of the genes of acet ate or GABA utilization, respectively, as well as the amdS gene. Strong act ivation was shown to require the AreA protein but was not dependent on AreA binding to DNA. The homologous areA gene of A. and nit-2 gene of Neurospor a crassa can substitute for A. nidulans areA in this interaction. We have s hown that the same C-terminal region of AreA and NIT-8 that is involved in the interaction with NmrA is required for the TamA-AreA interaction. Ho How ever, it is unlikely that TamA requires the same residues as NmrA within th e GATA DNA-binding domain of AreA.