Analysis of the effects of non-histone proteins and transcriptional mediators on the regulation of HXT genes transcription

Thesis Type: Postgraduate

Institution Of The Thesis: Bursa Uludağ University, Fen Bilimleri Enstitüsü, Biyoloji , Turkey

Approval Date: 2005

Thesis Language: Turkish


Supervisor: Sezai Türkel


In the yeast Saccharomyces cerevisiae, HXT2 and HXT4 genes encodes two different glucose transporters which are required for the glucose uptake. In this research, the effects of chromatin modifying factors on the HXT2 and HXT4 genes transcriptions were investigated by using mutant yeast strains. It was found that transcriptional activation of HXT2 and HXT4 are completely depends on the non-histone proteins Nhp6A/B. Approximately 5-10 fold decrease was determined in the transcription of HXT2 and HXT4 genes in ∆nhp6A/B mutant yeast cells. In addition to this results, 2 fold decrease in the transcription of HXT2 in ∆nhp10 mutation indicated that Nhp10 may be required for the activation of HXT2 genes. The effects of SAGA complex on the HXT2 and HXT4 transcriptions were investigated using ∆spt7 mutant yeast strain. It was found that the transcription of HXT4 decreased approximately 20-fold in ∆spt7 mutant yeast strain. Unlike HXT4 transcription, HXT2 transcription decreases 2-fold in ∆spt7 mutants. The effects of yeast mediator complex on the transcription of HXT2 and HXT4 were also analysed. It is found that both basal and activated transcription of HXT4 decrease 15 fold in the ∆med2 mutant yeast strain. But, transcription of HXT2 decreased only 2-fold in ∆med2 mutant strain. It was also found that, Srb10p, which is another mediator protein, doesn’t have any significant effect on HXT2 and HXT4 genes transcription. These results indicated that the transcription of HXT2 and HXT4 genes are regulated by SAGA complex, Nhp6A/B and Med2p, in addition to previously identified regulatory transcription factors.