Gene expression can be regulated at the transcriptional, translational or post-translational level. While structural genes are predominantly controlled at the transcriptional level, regulators also show a number of post-translational modes of regulation including ligand dependence, nuclear exclusion and interactions with coactivating or antagonistic regulatory proteins. Understanding the mechanisms which control the activity of regulatory factors is important to our understanding of regulatory networks and their action. The facB gene of Aspergillus nidulans encodes a C6Zn(II)Z binuclear cluster DNA binding domain protein and is the major transcriptional activator of genes required for acetate utilisation. FacB positively regulates the expression of the glyoxylate bypass genes acuD and acuE as well as facA and facC. Their products are required for the anaplerotic glyoxylate bypass which converts acetyl-CoA from acetate or fatty acids into TCA cycle intermediates. In addition, FacB activates the expression of the amdS gene. The facB gene and its product are regulated at multiple levels. The gene is controlled transcriptionally by acetate induction, but not by FacB, and carbon catabolite repression by the negatively acting CreA. Full transcriptional activation of FacB also requires acetate. Here we show that the cellular localisation of FacB is regulated. In the absence of acetate, FacB as a LacZ or GFP fusion is cytoplasmically localised. Addition of acetate causes the rapid translocation of FacB to the nucleus. A 142 amino acid region of FacB, spanning the C,Zn(II)z DNA binding motif is sufficient for nuclear localisation. A mutation which destroys DNA binding by FacB does not inhibit nuclear localisation.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)