Open AccessThe Formamidase Gene of Aspergillus nidulans: Regulation by Nitrogen Metabolite Repression and Transcriptional Interference by an Overlapping Upstream Gene
Author(s) -
James A. Fraser,
Meryl A. Davis,
Michael J. Hynes
Publication year - 2001
Publication title -
genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.792
H-Index - 246
eISSN - 1943-2631
pISSN - 0016-6731
DOI - 10.1093/genetics/157.1.119
Subject(s) - biology , aspergillus nidulans , gene , psychological repression , coding region , gene expression , genetics , promoter , gene cluster , regulation of gene expression , microbiology and biotechnology , biochemistry , mutant
The ability to utilize formamide as a sole nitrogen source has been found in numerous fungi. We have cloned the fmdS gene encoding a formamidase from Aspergillus nidulans and found that it belongs to a highly conserved family of proteins separate from the major amidase families. The expression of fmdS is primarily regulated via AreA-mediated nitrogen metabolite repression and does not require the addition of exogenous inducer. Consistent with this, deletion analysis of the 5' region of fmdS has confirmed the presence of multiple AreA-binding sites containing a characteristic core GATA sequence. Under carbon starvation conditions the response to nitrogen starvation is eliminated, indicating that the lack of a carbon source may result in inactivation of AreA. Sequence analysis and isolation of cDNAs show that a gene of unknown function lies directly 5' of fmdS with its transcript overlapping the fmdS coding region. Disruption of the 5' gene and analysis of the effects of overexpression of this gene on fmdS expression has shown that expression of this upstream gene interferes with fmdS transcription, resulting in a strong dependence on AreA activation for expression. Therefore the relative position of these two genes is essential for normal regulation of fmdS.