Yeast PKA subunit promoters are differentially regulated in fermentative and oxidative growth

GALELLO, F; PAUTASSO, C; RECA, S; ROSSI, S

Mar del Plata

Congreso; LI Reunion SAIB; 2015

SAIB

In Saccharomyces cerevisiae three signaling pathways are required to correctly respond to glucose availability: the Rgt2/Snf3, the Snf1/Mig1 and the cAMP/PKA pathways. In glucose depletion conditions, genes involved in the metabolism of alternative carbon sources are induced by Snf1. Three genes encode the PKA catalytic subunit, TPK1, TPK2, TPK3; while the regulatory subunit is encoded by one gene, BCY1. Employing reporter gene methodology we studied the activity regulation of PKA subunits promoters in fermentative (glucose) or non fermentative (glycerol) growth. Our results indicate that the activity of all promoters is stronger in glycerol than in glucose medium and that the kinase activity of PKA inhibits its own promoters, in glycerol growing cells. Mig1-Hxk2 regulatory complex inhibits TPK1 promoter while Snf1 kinase activates TPKs and BCY1 promoters, possibly acting through Cat8 transcription factor. In addition, Mig3 transcription factor differentially modulates TPK3 and BCY1 promoters, and Mig2 only activates TPK2 promoter. The results were further confirmed by mRNAs quantification by qRT-PCR, and measurements of Tpk1 and Bcy1 proteins levels by Western blot. Results of ChIP assays show the presence of Cat8 and Mig1 in the TPK1 promoter transcriptionally active.