Nuclear localization of Aspergillus nidulans AreA is regulated by nitrogen and carbon starvation.

Richard B. Todd, James A. Fraser, Michael J. Hynes and Meryl A. Davis.


The global transcriptional regulator AreA activates transcription of many genes required for nitrogen catabolism under nitrogen limitation. AreA levels and activity are regulated autogenously, by differential mRNA turnover and interaction with the NmrA and TamA proteins. We describe an additional level of regulation of AreA activity. We have epitope tagged AreA by gene replacement at the areA locus and used immunofluorescence microscopy to determine the subcellular localization of AreA. Under nitrogen starvation the AreA protein hyperaccumulates in the nucleus. This correlates with a significant elevation of nitrogen catabolic gene expression. Furthermore, hyperaccumulation is NmrA-independent and does not require residues 60-423 or 854-876 of AreA. The AreA protein is not observed to accumulate in the nucleus in the presence of a nitrogen source. Transfer from nitrogen starvation to nitrogen sufficient conditions triggers rapid exit of AreA from the nucleus, consistent with the idea that AreA is transcriptionally inactive during nitrogen sufficiency. The increase in certain nitrogen catabolic enzyme levels in response to nitrogen starvation is prevented by carbon starvation. We show that simultaneous carbon starvation prevents the AreA hyperaccumulation observed under nitrogen starvation. Furthermore, transfer from nitrogen starvation conditions to carbon starvation conditions rapidly reverses AreA hyperaccumulation. These studies demonstrate that AreA activity can be differentially regulated by subcellular localization in response to distinct signals generated under nitrogen and carbon starvation

abstract No: 

Fungal Genet. Newsl. 50 (Supl):abstract

Full conference title: 

22nd Fungal Genetics Conference
    • Fungal Genetics Conference 22nd (2001)