Browsing by Author "Gevrekci, Aslihan Ors"

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Fission Yeast srm1 is Involved in Stress Response and Cell Cycle
(2017) Gevrekci, Aslihan Ors; 28345120
Polyamines are well-conserved, multifunctional polycations that contribute to a number of processes in the cells such as cell cycle, apoptosis, stress response, and gene expression. Therefore, polyamine levels should be kept under strict regulation by specific polyamine transporters and polyamine synthases. In this study, the aim is to experimentally characterize a predicted spermidine synthase gene srm1, which was identified upon sequence similarity, in fission yeast Schizosaccharomyces pombe. In an attempt to understand the role of this gene in cell cycle and stress response, deletion mutant of srm1 was generated and analyzed in terms of cell cycle regulation and environmental stress response. The results showed that srm1 Delta cells had elongated cell size and were sensitive to osmotic stress, while they showed no sensitivity to DNA-damaging agents. To the best of our knowledge, this is the first experimental characterization of srm1 gene and its role in cell cycle progression and stress response.
The role of predicted spermidine family transporters in stress response and cell cycle in Schizosaccharomyces pombe
(2017) Gevrekci, Aslihan Ors
Fission yeast Schizosaccharomyces pombe has a variety of stress-signaling proteins that protect cells against environmental or intracellular stress. These proteins help the cells to respond to stress conditions and regulate intracellular functions such as cell division or gene expression. Polyamines (spermidine, spermine, and putrescine) are known to be important in the regulation of stress response and cell division. In this study, we tried to experimentally characterize novel S. pombe genes that are involved in the polyamine pathway and understand their potential roles. Sequence analysis revealed four genes that code for (predicted) spermidine family transporters in S. pombe. In an attempt to characterize these (predicted) spermidine family transmembrane transporters and their possible roles, deletion mutants of these candidate genes were created. These mutants were exposed to different stress conditions, such as DNA-damaging agents and osmotic stress, to understand their significance in the stress response. Next, the mutants were analyzed in terms of cell size, growth rate, and spore formation to understand their contribution to cell cycle control. The results revealed that individual deletion of two of these genes, SPBC36.01c and SPBC36.02c, resulted in sensitivity to DNA-damaging agents, indicating their role in DNA damage response.
The Roles of Polyamines in Microorganisms
(2017) Gevrekci, Aslihan Ors; 29080149
Polyamines are small polycations that are well conserved in all the living organisms except Archae, Methanobacteriales and Halobacteriales. The most common polyamines are putrescine, spermidine and spermine, which exist in varying concentrations in different organisms. They are involved in a variety of cellular processes such as gene expression, cell growth, survival, stress response and proliferation. Therefore, diverse regulatory pathways are evolved to ensure strict regulation of polyamine concentration in the cells. Polyamine levels are kept under strict control by bio-synthetic pathways as well as cellular uptake driven by specific transporters. Reverse genetic studies in microorganisms showed that deletion of the genes in polyamine metabolic pathways or depletion of polyamines have negative effects on cell survival and proliferation. The protein products of these genes are also used as drug targets against pathogenic protozoa. These altogether confirm the significant roles of polyamines in the cells. This mini-review focuses on the differential concentrations of polyamines and their cellular functions in different microorganisms. This will provide an insight about the diverse evolution of polyamine metabolism and function based on the physiology and the ecological context of the microorganisms.