Molecular Biology and Genetics / Moleküler Biyoloji ve Genetik

Permanent URI for this collectionhttps://hdl.handle.net/11147/9

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  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Trna Wobble Base Modifications and Boric Acid Resistance in Yeast: Boron-Resistant Deletion Mutants Induce the General Amino Acid Control Mechanism and Activate Boron Efflux
    (Pleiades Publishing, 2020) Uluisik, I.; Karakaya, H.C.; Koc, A.
    Abstract: Boric acid is essential for plants and has many vital roles in animals and microorganisms. However, its high doses are toxic to all organisms. We previously screened yeast deletion collections to identify boric acid-resistant and susceptible mutants to identify genes that play a role in boron tolerance. Here, we analyzed boron resistant mutants (elp1∆, elp3∆, elp6∆, ncs2∆, ncs6∆ and kti12∆) for their abilities to modulate the general amino acid control system (GAAC) and to induce boron efflux pump ATR1. The mutants analyzed in this study lack the genes that play roles in tRNA Wobble base modifications. We found that all of the boron resistant mutants activated Gcn4-dependent reporter gene activity and increased the transcript level of the ATR1 gene. Additionally, boron resistant cells accumulated less boric acid in their cytoplasm compared to the wild type cells upon boron exposure. Thus, our findings suggested that loss of wobble base modifications in tRNA leads to GAAC activation and ATR1 induction, which in turn reduced intracellular boron levels and caused boron resistance. © 2020, Pleiades Publishing, Inc.
  • Article
    Evidence for the Presence of a Second Electron Donor for the Cytoplasmic Thioredoxins in the Yeast Saccharomyces Cerevisiae
    (TUBITAK, 2006) Koç, Ahmet; Karakaya, Hüseyin Çağlar; Ünlü, Ercan Selçuk
    In yeast, the cytoplasmic thioredoxin system is composed of NADPH, thioredoxin reductase-1 (TRR1) and 2 thioredoxin genes (TRX1, TRX2). In this study, using yeast knockout mutants for TRR1, TRX1 and TRX2 genes, the role of the thioredoxin system in methionine sulfoxide reduction was investigated. Cells lacking both TRX1 and TRX2 genes simultaneously were not able to reduce methionine sulfoxides to methionine; however, mutants missing the TRR1 gene were able to reduce methionine sulfoxides to methionine, which showed that electrons could be transferred from NADPH to thioredoxins in the absence of TRR1. Similar results were observed for 3-phosphoadenosine 5-phosphosulfate reduction in the inorganic sulfate assimilation pathway. Results from both assays suggested that yeast cells have additional cytoplasmic thioredoxin reductase activity that could compensate for methionine sulfoxide reduction and sulfate assimilation in the absence of TRR1. This report also constitutes the first evidence that thioredoxins are the in vivo electron donors for methionine sulfoxide reductases in yeast.