The GATA factor AreA is essential for chromatin remodelling in a eukaryotic bidirectional promoter

The linked niiA and niaD genes of Aspergillus nidulans are transcribed dive rgently. The expression of these genes is subject to a dual control system, They are induced by nitrate and repressed by ammonium. AreA mediates derep ression in the absence of ammonium and NirA supposedly mediates nitrate ind uction. Out of 10 GATA sites, a central cluster (sites 5-8) is responsible for similar to 80% of the transcriptional activity of the promoter on both genes. We show occupancy in viva of site 5 by the AreA protein, even under conditions of repression. Sites 5-8 are situated in a pre-set nucleosome-fr ee region, Under conditions of expression, a drastic nucleosomal rearrangem ent takes place and the positioning of at least five nucleosomes flanking t he central region is lost. Remodelling is strictly dependent on the presenc e of an active areA gene product, and independent from the NirA-specifie an d essential transcription factor. Thus, nucleosome remodelling is independe nt from the transcriptional activation of the niiA-niaD promoter The result s presented cast doubts on the role of NirA as the unique transducer of the nitrate induction signal. We demonstrate, for the first time in vivo, that a GATA. factor is involved directly in chromatin remodelling.