title: Characterization of pco-1, a newly identified gene which regulates purine catabolism in Neurospora.
abstract: A new gene of Neurospora crassa, designated pco-1, was characterized and shown to regulate the expression of several genes which encode enzymes required for the catabolism of purines. Unlike the wild type, a pco-1 mutant created by repeat-induced point mutation cannot utilize purines as a nitrogen source. The PCO1 protein contains a Zn(II)2Cys6 binuclear cluster motif near its N-terminus, followed by a putative coiled-coil motif. A chemical crosslinking experiment demonstrated that PCO1 forms homodimers. PCO1 binds to CGG-N6-CCG elements located in the upstream promoter region of four genes encoding purine catabolic enzymes. Northern blot analysis demonstrated that a functional PCO1 protein is required for induction of xdh, which encodes xanthine dehydrogenase. Moreover, PCO1 was required for induction of three different purine catabolic enzymes. Two glutamine-rich domains occur in the C-terminal region of PCO1 and at least one of the glutamine-rich regions is required for PCO1 function, suggesting that they might play a role in transcriptional activation. The PCO1 protein does not interact with the global-acting NIT2 protein or the negative-acting NMR protein that functions in nitrogen catabolite repression. Induction of the xdh gene and synthesis of xanthine dehydrogenase is completely dependent upon PCO1, but does not require the global-acting NIT2 protein, suggesting that it is controlled by a novel regulatory mechanism.
authors.affiliation: Department of Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: T D
authors.initials: TD
authors.lastname: Liu
authors.forename: G A
authors.initials: GA
authors.lastname: Marzluf
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D018076:DNA, Complementary; D024202:Electrophoretic Mobility Shift Assay; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000235:genetics* / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D005656:Fungal Proteins; D011687:Purines