Apoptosis Signaling Pathway Regulates the Gene Expression in the Yeast Retrotransposons Ty1 and Ty2
Ceyda Çolakoğlu, Sezai TürkelObjective: Ty elements are retroviral–like entities present in the yeast Saccharomyces cerevisiae. Apoptosis is a programmed cell death mechanism, conserved in all eukaryotes. In this study, we aimed to analyze how apoptotic signals affect the transcriptions of Ty1 and Ty2 elements in S. cerevisiae. Materials and Methods: To analyze the effects of apoptotic signals on the transcription of Ty element, Ty1-LacZ, and Ty2-LacZ gene fusions were used as reporter genes. These gene fusions were transformed into the wild type and certain yeast mutants that are defective in various signaling pathways. Acetic acid was added to the growth medium of logarithmically growing yeast transformants to induce apoptosis. Transcription levels of the Ty-lacZ gene fusions were analyzed by ß-Galactosidase assays. Results: The results of this study show that transcription of Ty1 and Ty2 decreases approximately 3-fold in response to apoptosis in S. cerevisiae. It appears that apoptosis acts through the transcription factors Tec1p and Sgc1p that associate with the regulatory region of Ty1 and Ty2. Moreover, AMP-activated protein kinase Snf1p, and to a lesser extent Tor1p, seem to be required for the transcriptional repression of Ty1 and Ty2 in apoptosis-induced yeast cells. Conclusion: Ty1 and Ty2 transcription is regulated in response to apoptosis signaling in a differential manner. It seems that protein kinases Tor1p and Snf1p and transcription factors Tec1p and Sgc1p are involved in the apoptosis dependent regulation of Ty transcription.