DIFFERENTIAL REGULATION OF YEAST PKA SUBUNIT PROMOTERS IN FERMENTATIVE AND OXIDATIVE GROWTH

GALELLO, FIORELLA; RECA, SOL; PAUTASSO, CONSTANZA; ROSSI, SILVIA

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2014

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Glucose is the preferred energy source of Saccharomyces cerevisiae. Three signaling pathways are required to correctly respond to glucose availability: the Rgt2/Snf3, the Snf1/Mig1 and the cAMP/PKA pathways. When glucose is limited, Snf1 kinase induces genes involved in the metabolism of alternative carbon sources. In S.cerevisiae three genes encode the PKA catalytic subunit, TPK1, TPK2, TPK3; while one gene, BCY1, encodes the regulatory subunit. Employing reporter gene methodology we studied the activity regulation of PKA subunits promoters in fermentative(glucose) or non fermentative (glycerol) growth. We found that the activity of all promoters is stronger in glycerol than in glucose medium. In glucose, TPK1 and TPK2 promoters are inhibited by Mig1. TPK2 promoter was inhibited by Mig1 and also Mig2 transcription factors. The four promoter activities are regulated by Snf1 kinase; and the Snf1 downstream effectors Cat8 and Sip4 regulate TPK2, TPK3 and BCY1 promoter activities. In cells grown in glycerol, the four promoters are upregulated by Snf1/Cat8. TPK1 promoter activity is downregulated by Mig1, and BCY1 byMig2 and Mig3; while TPK2 and TPK3 promoters are upregulated by Mig1, Mig2 and Mig3. Results of ChIP assays show the presence of Cat8 in the TPK1 promoter transcriptionally active. These results were confirmed by mRNAs quantification by qRT-PCR.