In Aspergillus nidulans, the global nitrogen regulatory gene areA, encoding a positively acting GATA transcription factor AreA, is required for activating genes involved in nitrogen metabolism. When a good nitrogen source like ammonium or glutamine is available, areA-dependent genes are expressed at a low level, while the expression of these genes is up regulated when only a poor nitrogen source, like alanine, is present (nitrogen limiting condition). This differential expression is controlled by areA transcript stability and the interaction of AreA with a negative regulator NmrA. A further increase in gene expression, which is not mediated by these two regulatory mechanisms, is observed under nitrogen starvation and correlates with AreA accumulation in the nucleus. Nuclear accumulated AreA is rapidly exported upon addition of a nitrogen source via the CrmA exportin. We therefore sought to investigate the importance of post-translational modifications on nuclear localization and function of AreA. We have shown that AreA is multiply phosphorylated and its phosphorylation status differs under nitrogen sufficient, limiting or starvation conditions. A number of conserved potential phosphorylation sites on AreA have been mutated and assessed for their roles in AreA function. In addition, AreA contains a highly conserved small ubiquitin-like modifier (SUMO) modification site adjacent to a putative CrmA exportin binding motif. We have deleted the gene encoding the SUMO peptide and mutated the putative sumoylation site on AreA to address the involvement of sumoylation in the regulation of AreA.
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)