Regulation of yeast RPS3 transcription by two yeast major transcription factors, Gcn4p and Rap1p

다국어 초록 (Multilingual Abstract)

RPS3 is an essential gene in yeast Saccharomyces cerevisiae. RPS3 protein (Rps3p) is a component of the ribosomal small subunit, and it also has an extra-ribosomal function, an AP endonuclease activity. Generally, there are upstream activating sequences in ribosomal protein genes, i.e. UASrpg, which are essential for the transcription of most ribosomal protein genes. One of these is the binding site of Rap1p, yeast transcription factor which activates transcription of ribosomal protein genes. In the promoter region of RPS3, five putative UASrpgs were found and serial upstream deletion mutants of promoter region were constructed. By using β-galactosidase reporter system and EMSA, the UASrpg of RPS3 was identified. This is necessary both for basal level transcription and down-regulation under stress condition. Interestingly, RPS3 promoter region has two putative Gcn4p-responsive elements (UASGCRE), which are not usually found in the ribosomal protein promoters. Gcn4p acts as a master regulator of transcription in stress conditions, such as an amino acid starvation condition, UV stress, and purine depletion. This study revealed that Gcn4p and Rap1p bind to the promoter of RPS3 in vitro. In addition, the physical interactions between Gcn4p and Rap1p in vitro and in vivo were confirmed. Gcn4p and Rap1p appear to regulate the gene in a negatively and a positively way, respectively. When an amino acid starvation condition was induced by 3-amino triazole, i.e. 3-AT, or a rapamycin treatment or post-confluent culture condition, the transcriptional level of RPS3 appears to be controlled by Gcn4p.