Effects of stress activated protein kinases on the expression of EST3 gene that encodes telomerase subunit in Saccharomyces cerevisiae

Abstract

The EST3 gene of Saccharomyces cerevisiae encodes one of the essential subunits of telomerase enzyme. Expression of the EST3 gene is regulated at the translation level by +1 programmed ribosomal frameshift (PRF). It is known that physiological stress affects telomere length. In this study, we have investigated the effects of different types of stresses and stress activated protein kinases on the frameshift rate in EST3 gene. PRF rate of EST3 gene was measured as 13% in the normal growth conditions in the wild type cells. But, the PRF rate of EST3 in the wild type strain grown in glucose limited conditions decreased more than 6-fold. Contrary to glucose limitation, osmotic stress increased frameshift rate from 13% to 25%. Amino acid starvation and boron stress also activate PRF rate by 2-fold in EST3 in a Gcn2 dependent manner. When the PRF rate was analysed in gcn2 and snf1 mutants, frame shift rate of EST3 was approximately 6% in normal growth conditions. It seems that the basal level expression of EST3 is highly dependent on the Gcn2 kinase complex, indicating that Gcn2 might have a significant function in connecting the stress signals to biosynthesis of the full-length Est3 peptide. This regulation might connect the biosynthesis of functional telomerase and telomere replications to cell physiology through stress activated protein kinases.