Investigation of the Effects of Autophagy Signaling on the Transcription of Yeast Retrotransposon Ty2-917

Abstract

Objective: Ty2-917 is a low copy retrotransposon found in the Saccharomyces cerevisiae genome. It has structural similarities to metazoan retroviruses in terms of genome organization and propagation mechanisms in the host cells. The objective of this study is to analyze the effects of autophagy signaling on the transcriptional regulation of Ty2 in yeast cells. Materials and Methods: Ty2-LacZ gene fusions on the YEp vectors have been used as reporter genes to analyze the effects of amino acid starvation, nitrogen source, and autophagy signals on the transcription of Ty2. These reporter gene fusions have been transformed into the wild type and also isogenic mutant yeast strains that are defective for one of the regulatory factors involved in nutrient sensing and signaling. To activate autophagy signaling, yeast transformants were treated with caffeine or 3-amino 1-2-3 triazole. Transcription levels of Ty2-LacZ gene fusions in treated and untreated yeast cells were analyzed by β-galactosidase assays. Results: Results of this study show that transcription of Ty2 decreases up to eightfold in response to amino acid starvation. Caffeine treatment of the yeast cells also represses Ty2 transcription, independent of the TOR1 pathway. In addition, our results suggest that Ty2 transcription is also regulated in a nitrogen source-dependent manner through the GATA factors. Conclusions: Our results suggest that activation of autophagy signal results in significant level repression of Ty2 transcription. We have found that the GATA class of transcription factors is involved in the regulation of Ty2 transcription in response to autophagy signaling.