title: The sulfur controller-2 negative regulatory gene of Neurospora crassa encodes a protein with beta-transducin repeats.
abstract: The sulfur regulatory system of Neurospora crassa is composed of a set of structural genes involved in sulfur catabolism controlled by a genetically defined set of trans-acting regulatory genes. These sulfur regulatory genes include cys-3+, which encodes a basic region-leucine zipper transcriptional activator, and the negative regulatory gene scon-2+. We report here that the scon-2+ gene encodes a polypeptide of 650 amino acids belonging to the expanding beta-transducin family of eukaryotic regulatory proteins. Specifically, SCON2 protein contains six repeated G beta-homologous domains spanning the C-terminal half of the protein. SCON2 represents the initial filamentous fungal protein identified in the beta-transducin group. Additionally, SCON2 exhibits a specific amino-terminal domain that potentially defines another subfamily of beta-transducin homologs. Expression of the scon-2+ gene has been examined using RNA hybridization and gel mobility-shift analysis. The dependence of scon-2+ expression on CYS3 function and the binding of CYS3 to the scon-2+ promoter indicate the presence of an important control loop within the N. crassa sulfur regulatory circuit involving CYS3 activation of scon-2+ expression. On the basis of the presence of beta-transducin repeats, the crucial role of SCON2 in the signal-response pathway triggered by sulfur limitation may be mediated by protein-protein interactions.
authors.affiliation: Department of Biochemistry and Molecular Biology, Wright State University, Dayton, OH 45435, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kumar
authors.forename: J V
authors.initials: JV
authors.lastname: Paietta
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics*; D005800:Genes, Fungal / Q000235:genetics*; D005809:Genes, Regulator / Q000235:genetics*; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000378:metabolism; D015293:Transducin / Q000235:genetics*
chemical_list: D005656:Fungal Proteins; D012333:RNA, Messenger; C093148:SCON-2 protein, Neurospora crassa; D013455:Sulfur; D015293:Transducin