PKA affects protein abundance of Rpg1 and eIF4G1 translation factors in Saccharomyces cerevisiae

ADRIANA C. CAMARANO; CARLA E. BARRAZA; CLARA A. SOLARI; PAULA PORTELA

Rosario

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

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

In Saccharomyces cerevisiae protein translation is decreased during stationary phase being initiation the most regulated step of this process. Previously, we described that PKA has a role in the translation inhibition that occurs during entry into stationary phase. Here we show that in exponentially growing cells, the limiting translation factors eIF4G1 and Rpg1 are highly expressed. In contrast, their protein abundance is severely reduced during stationary phase. We analyse the role of PKA activity on eIF4G1 and Rpg1 protein abundance. In strains with reduced PKA activity, eIF4G1 and Rpg1 are not expressed neither in exponential nor in stationary phase cells. However, high PKA activity promotes high expression of eIF4G1 and Rpg1 proteins even during stationary phase of growth. We also determine that the half-life of these factors is lengthened in a strain harbouring high PKA activity versus exponentially growing wild type cells. Moreover, eIF4G1 and Rpg1 mRNA levels were constant in both exponential and stationary phase of growth in cells with high or reduced PKA activity. Studies of the protein abundance of eIF4G1 and Rpg1 in strains with impaired proteasome activity showed that the degradation of these factors during stationary phase is proteasome-mediated. Taken together, we demonstrate that PKA increases the eIF4G1 and Rpg1 proteins abundance through a post-transcriptional mechanism.