EXPRESSION REGULATION OF C SUBUNITS OF PROTEIN KINASE A FROM Saccharomyces cerevisiae

PAUTASSO, CONSTANZA; PORTELA, PAULA; ROSSI, SILVIA

Los Cocos, Córdoba

Congreso; The First South American Spring Symposium in Signal Transduction and Molecular Medicine; 2010

SISTAM

One mechanism that yeast cells use to protect the internal system from the effects of environmental variation is to initiate a common gene expression program to protect the cell and many of these genes can be related to specific signaling pathways. The aim of this work is to study the expression regulation of two catalytic isoforms of protein kinase A, Tpk1 and Tpk3, in S.cerevisiae, under different conditions of stress and carbon source availability. The activity of TPK1 promoter is high in the diauxic-shift, while TPK3 promoter activity remains constant. In the presence of glycerol, both promoters activities are higher than in glucose presence. We demonstrated that TPK1 and TPK3 promoters activities are inhibited by PKA and this regulation is isoform-specific. Under heat shock and osmotic stress conditions, TPK1 promoter activity increases while TPK3 promoter activity remains constant. By in silico analysis and using different mutants we demonstrated that Msn2/4, stress transcription factors, regulate positively TPK1 but not TPK3 promoter activity. ChIP assays showed a decreased Msn2 occupancy of TPK1 promoter, during heat shock, but an increase of Pol II occupancy indicating that the promoter was transcriptionally active. These results are in agreement with "black widow" model.