Operator derepressed mutations in the proline utilisation gene cluster of Aspergillus nidulans

Abstract

The proline utilisation gene cluster of Aspergillus nidulans can be repressed efficiently only when both repressing nitrogen and repressing carbon sources are present. We show that two cis-acting mutations in this cluster permit the efficient transcription of the prnB gene under repressing conditions, resulting in direct or indirect derepression of two other transcripts of the pathway. These mutations are transitions that define a 5'GAGACCCC3' sequence. Similar sequences are found upstream of other genes subject to carbon catabolite repression. We propose that this sequence defines the binding site for the negatively-acting CreA protein, which mediates carbon catabolite repression in this fungus.

The Aspergillus nidulans Proline Permease as a Model for Understanding the Factors Determining Substrate Binding and Specificity of Fungal Amino Acid Transporters

“…7 was able to improve the growth on GABA as the sole nitrogen source (data not shown) of a herein constructed (see "Experimental Procedures") strain carrying deletion of the main GABA transporter of A. nidulans, GabA (62). At this point it is worth mentioning that the expression of prnB alleles under these conditions is low but significant, because all are under the control of the native prnB promoter, which is significantly induced only in the presence of proline (7,20). In fact, as observed by epifluorescence microscopy (data not shown) and in-gel fluorescence analysis, the protein levels of intact PrnB-GFP are about 5-fold lower at derepressed than at induced conditions (Fig.…”

“…The prnB gene has been extensively used as a model for transcriptional and post-transcriptional regulation of gene expression (15)(16)(17)(18)(19)(20).…”

Regulation of secreted protein production by filamentous fungi: recent developments and perspectives

“…The zinc finger domain shows high similarity to the DNA-binding region of the yeast MIGl repressor, also involved in carbon catabolite repression, and putative binding sites for CREA have been described in several promoters from A . nidulans (Sophianopoulou et al, 1993;see Table l), N. crassa (I. Connerton, personal communication), T . reesei (Ilmkn et al, 1992) and Trichoderma viride (Goldman et al, 1992).…”

The gene encoding the major proline transporter of Aspergillus nidulans is upregulated during conidiospore germination and in response to proline induction and amino acid starvation

“…The prnA gene codes for a proline-responsive transcriptional activator, prnX is a proline-inducible gene of unknown function, prnD codes for proline oxidase, prnB for the proline transporter and prnC for ⌬ 1 -pyrroline-5-carboxylate dehydrogenase. prnA, prnX and prnD are transcribed divergently from prnB and prnC and thus there is a region between the prnD and prnB genes which may involve cisacting elements affecting the transcription of both genes (Arst and MacDonald, 1975;Arst et al, 1980;Sharma and Arst, 1985;Sophianopoulou and Scazzocchio, 1989;Gavrias et al, 1994;Sophianopoulou et al, 1993;Cubero and Scazzocchio, 1994).…”

“…glucose) and a nitrogen (e.g. ammonium)-repressing source are simultaneously present (Arst and Cove, 1973;Bailey and Arst, 1975;Arst et al, 1980;Sophianopoulou et al, 1993). A mechanism accounting for the repression pattern of these genes has been proposed (Gavrias et al, 1994).…”