title: Gln3-Gcn4 hybrid transcriptional activator determines catabolic and biosynthetic gene expression in the yeast Saccharomyces cerevisiae.
abstract: The yeast Saccharomyces cerevisiae is able to sense the availability and quality of nitrogen sources and the intrinsic variation of amino acid disponibility for protein synthesis. When this yeast is provided with secondary nitrogen sources, transcription of genes encoding enzymes involved in their catabolism is elicited through the action of Gln3, which constitutes the main activator of the Nitrogen Catabolite Repression network (NCR). Activation of genes encoding enzymes involved in the amino acid biosynthetic pathways is achieved through the action of the GCN4-encoded transcriptional modulator whose transcriptional activation is induced at the translational level by limitation for any amino acid. Thus the role of each one of these activators had been secluded to either catabolic or biosynthetic pathways. However, some observations have suggested that under peculiar physiological conditions, Gln3 and Gcn4 could act simultaneously in order to contemporaneously increase expression of both sets of genes. This paper addresses the question of whether Gln3 and Gcn4 cooperatively determine expression of their target genes. Results presented herein show that induced expression of catabolic and biosynthetic genes when cells are grown under nitrogen derepressive conditions and amino acid deprivation is dependent on the concurrent action of Gln3 and Gcn4, which form part of a unique transcriptional complex. We propose that the combination of Gln3 and Gcn4 results in the constitution of a hybrid modulator which elicits a novel transcriptional response, not evoked when these modulators act in a non-combinatorial fashion.
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-242, 04510 Mexico City, Mexico.
authors.forename: Hugo
authors.initials: H
authors.lastname: Hernández
authors.forename: Cristina
authors.initials: C
authors.lastname: Aranda
authors.forename: Lina
authors.initials: L
authors.lastname: Riego
authors.forename: Alicia
authors.initials: A
authors.lastname: González
mesh_terms: D000581:Amidohydrolases / Q000235:genetics; D000596:Amino Acids / Q000172:deficiency; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D026901:Membrane Transport Proteins / Q000235:genetics; D009584:Nitrogen / Q000172:deficiency; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D050976:Basic-Leucine Zipper Transcription Factors; C503299:DAL5 protein, S cerevisiae; C501391:GCN4 protein, S cerevisiae; C071664:GLN3 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000581:Amidohydrolases; C492138:DAL1 protein, S cerevisiae; D009584:Nitrogen