Investigation of the effects of nitrogen signaling pathway on the programmed ribosomal frameshift rate in EST3 gene

Thesis Type: Postgraduate

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

Approval Date: 2016

Thesis Language: Turkish

Student: Mahmoud Arafat

Supervisor: SEZAİ TÜRKEL


Telomeres are the special structures located on the ends of the chromosomes. Replication of telomeres is carried out by speciel enzyme, telomerase complex, not by DNA polymerase. Complete and the full length replication of telomere ends are the crucial factors for genome stability in eukaryotes. EST3 is one of the regulatory subunits of telomerase enzyme. The expression of EST3 is regulated by the programmed ribosomal frameshift (PRF) during translation elongation stage. It is known that telomere lenghts are regulated by stress factors and the growth conditions. In this research, the effect of nitrogen sources, stress factors and the growth conditions on the PRF rate was investigated. It was found that the PRF rate decreases 50% in the stationary stage. Moreover, PRF rate decreased at least 4-fold in in the pseudohypeal growth conditions. While the PRF rate is 14.78% in normal conditions, it decreased to 4.39% in pseudohypeal growth. Growth on different nitrogen sources had low level effects on the PRF rate, depending on the nitrogen sources. While the PRF rate is 14.78% in ammonia containing medium, it decreases to 11.82% in urea medium. PRF rate decreased to 10.78% in ethanol stress applied cells. Furthermore, caffeine had a significant effect on the PRF rate and PRF rate decreased to 8.9% in caffein applied cultures. When ethanol is present as the sole carbon and energy source PRF rate decreased to 1%. Overall, this result indicated that PRF rate of EST3 can be controlled depending on the growth conditions.