title: Ras-pathway has a dual role in yeast galactose metabolism.
abstract: In the yeast Saccharomyces cerevisiae the genes involved in galactose metabolism (GAL1,7,10) are transcriptionally activated more than a 1000-fold in the presence of galactose as the sole carbon source in the culture media. In the present work, we monitored the activity of the GAL10 gene promoter in different Ras-cAMP genetic backgrounds. We demonstrate that overexpression of C-terminus of the nucleotide exchange factor Cdc25p stimulates GAL10 transcription in yeast strains carrying the contemporary deletion of both RAS genes. Moreover, the deletion of the chromosomal CDC25 gene provokes impaired growth on galactose based media in yeast strain lacking both RAS genes and adenylate cyclase (whose viability is assured by the presence of the Bcy1-11 allele). Surprisingly, reconstitution of the Ras-pathway inhibits GAL10-promoter activation. Activation of GAL10 gene promoter is indeed possible in the presence of Ras protein but only in strains with chromosomal deletion of adenylate cyclase. These results indicate a dual role of Ras-pathway on galactose metabolism and suggest that Cdc25p has a Ras-independent role in cellular metabolism.
authors.affiliation: Dipartimento di Biopatologia e Metodologie Biomediche, Via Divisi, 83, Università degli studi di Palermo, 90133 Palermo, Italy. mirisola@unipa.it
authors.forename: Mario G
authors.initials: MG
authors.lastname: Mirisola
authors.forename: Alessia
authors.initials: A
authors.lastname: Gallo
authors.forename: Giacomo
authors.initials: G
authors.lastname: De Leo
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000483:Alleles; D005690:Galactose / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D010641:Phenotype; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D020666:ras-GRF1; D018631:ras Proteins; D000262:Adenylyl Cyclases; D005690:Galactose