The GATA factor AreA regulates localization and in vivo binding site occupancy of the nitrate activator NirA: GATA factor regulation of NirA activity

The GATA factor AreA is a wide-domain regulator in Aspergillus nidulans with transcriptional activation and chromatin remodelling functions. AreA interacts with the nitrate-specific Zn2-C6 cluster protein NirA and both proteins cooperate to synergistically activate nitrate-responsive genes. We have previously established that NirA in vivo DNA binding site occupancy is AreA dependent and in this report we provide a mechanistic explanation for our previous findings. We now show that AreA regulates NirA at two levels: (i) through the regulation of nitrate transporters, AreA affects indirectly the subcellular distribution of NirA which rapidly accumulates in the nucleus following induction; (ii) AreA directly stimulates NirA in vivo target DNA occupancy and does not act indirectly by chromatin remodelling. Simultaneous overexpression of NirA and the nitrate transporter CrnA bypasses the AreA requirement for NirA binding, permits utilization of nitrate and nitrite as sole N-sources in an areA null strain and leads to an AreA-independent nucleosome loss of positioning.