Comparison Of The Activity Of The PKA Catalytic Subunits In S.cerevisiae

In Sacchramysis cerevisiae, the Ras-cAMP signaling pathway plays an important role to regulate metabolism, proliferation, differentiation, stress resistance and pseudohyphal differentiation. PKA is an important target of the Ras-cAMP pathway. The catalytic subunits of the PKA are encoded by TPK1, TPK2 and TPK3, and the dimeric regulatory subunit is encoded by BCY1. cAMP combines the regulatory subunit , releases the catalytic subunits and activates the PKA. PKA down-regulates the Zn-finger transcriptional factor Msn2/4 and protein kinase Rim15 to control the response reaction of the cells to heat-shock. The cells of high PKA activity are sensitive to heat stress, and the cells of low PKA activity are resistant to heat stress. Yak1, down-regulated by PKA and down-stream of the PKA, represses the growth of the cells. The deletion of the gene YAK1 can elevate the PKA activity. Three TPK genes have specific targets respectively, but the difference between them in PKA activity is unknown.In this study, the strains were constructed by deletion one TPK gene or two TPK genes, and compare their heat resistance. It's revealed that the cooperation of different TPK products produces different PKA activity. In the background of the deletion of the YAK1, the PKA activity of TPK2 product is highest and the TPK3 product is lowest; but in the background of deletion of BCY1 gene, the hierarchy is reverse. At the same time, it's also presumed that the product of YAK1 gene is necessary to the stess resistance system and the product of TPK3 up-regulates the stess resistance system.