Pka, Ras and RGS Protein Interactions Regulate Sterigmatocystin Biosynthesis inAspergillus nidulans.

Kiminori Shimizu, Julie K. Hicks, Tzu-Pi Huang and Nancy P. Keller.


Sterigmatocystin (ST) is a carcinogenic polyketide produced by several filamentous fungi including Aspergillus nidulans. Expression of ST biosynthetic genes (stc genes) requires activity of a Zn(II)2Cys6 transcription factor, AflR. aflR is transcriptionally and post-transcriptionally regulated by a G-protein/cAMP/protein kinase A (PkaA) signaling pathway involving FlbA, a RGS (Regulator of G-protein Signaling) protein. Prior genetic data showed that FlbA transcriptional regulation of aflR was PkaA dependent. Here we show that mutation of three PkaA phosphorylation sites in AflR allows resumption of stcexpression in an overexpression pkaA background but does not remediate stc expression in a DflbA background. This demonstrates negative regulation of AflR activity by phosphorylation and shows that FlbA post-transcriptional regulation of aflR is PkaA independent. AflR nucleocytoplasmic location further supports PkaA independent regulation of AflR by FlbA. GFP tagged AflR is localized to the cytoplasm when pkaA is overexpressed but nuclearly located in a DflbA background. Genetic interaction between AflR and RasA is also investigated.

abstract No: 

Fungal Genet. Newsl. 50 (Supl):abstract

Full conference title: 

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