EXPRESSION REGULATION OF CATALYTIC SUBUNITS OF PKA FROM Saccharomyces cerevisiae

PAUTASSO, CONSTANZA; PORTELA, PAULA; ROSSI, SILVIA

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Yeast cells respond to environmental changes by signal transduction cascades which are modulated according to the type of response. This modulation may involve gene activation or inactivation. We studied the expression regulation of two catalytic isoforms of PKA, Tpk1 and Tpk3, using reporter gene. We found that in wt strains, the transcriptional activity of Tpk1 promoter was increased during stationary phase. ß-galactosidase assays in wt strains grown to exponential phase in glucose or glycerol revealed that the expression was 10-fold increased using glycerol as a carbon source. Influence of PKA activity on these promoters was assessed. Strains with low PKA activity (Tpk1w) showed a 4-5 fold increase of Tpk1 and Tpk3 promoters activity, while strains with high PKA activity (Δ Bcy1) had a decreased activity for both promoters. We also studied the role of Msn2/4 on Tpk1 and Tpk3 expression. In strains lacking these stress responding factors, we found that Tpk1 promoter activity decreased and Tpk3 promoter activity remained invariable. In heat shock and osmotic stress conditions Tpk1 expression increased, while Tpk3 expression was not affected. The endogenous mRNAs levels from Tpks were also measured showing the same regulation. These results suggest differential regulation of Tpk1 and Tpk3 promoters depending on the carbon source, the stress condition and on the own cAMP-PKA pathway.