Apoptosis Signaling Pathway Regulates the Gene Expression in the Yeast Retrotransposons Ty1 and Ty2

Abstract

Objective: Ty elements are retroviral–like entities present in the yeast Saccharomyces cerevisiae. Apoptosis is a programmedcell death mechanism, conserved in all eukaryotes. In this study, we aimed to analyze how apoptotic signals affect thetranscriptions 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-LacZgene fusions were used as reporter genes. These gene fusions were transformed into the wild type and certain yeast mutantsthat are defective in various signaling pathways. Acetic acid was added to the growth medium of logarithmically growingyeast transformants to induce apoptosis. Transcription levels of the Ty-lacZ gene fusions were analyzed by ß-Galactosidaseassays.Results: The results of this study show that transcription of Ty1 and Ty2 decreases approximately 3-fold in response toapoptosis in S. cerevisiae. It appears that apoptosis acts through the transcription factors Tec1p and Sgc1p that associate withthe regulatory region of Ty1 and Ty2. Moreover, AMP-activated protein kinase Snf1p, and to a lesser extent Tor1p, seem to berequired 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 seemsthat protein kinases Tor1p and Snf1p and transcription factors Tec1p and Sgc1p are involved in the apoptosis dependentregulation of Ty transcription.