Assesment of chronological life span dependent molecular damages of S.cerevisiae deficient in mitochondrial antioxidant genes

Thesis (Master)--Izmir Institute of Technology, Molecular Biology and Genetics, Izmir, 2009Includes bibliographical references (leaves: 38-40)Text in English; Abstract: Turkish and Englishx, 40 leavesAging is referred as the time-dependent accumulation of biological and physiological changes in an organism. This complex process is the major factor that is associated with many diseases such as cancer, diabetes and neurodegenerative disorders.The free radical theory of aging, which states that the molecular damages formed upon free radicals lead to the aging process, is the most widely accepted aging theory. The free radicals that are primarily produced in the mitochondria upon aerobic metabolism, are known to damage the biomolecules such as DNA, proteins and lipids. However, cells have evolved different defense systems for the elimination of these molecular damages. Antioxidant defense mechanism is one these systems that play role in the repair of the molecular damages. Since mitochondria are the main sites for the free radical production, the antioxidant genes that function in mitochondria gained an importance for their roles in preventing the molecular damages in a cell. In this study, the differences in the life spans and levels of molecular damages among different mitochondrial antioxidant gene mutants of Saccharomyces cerevisiae were tried to be identified throughout the chronological aging process, which is the model that mimics post-mitotic cell aging in higher eukaryotes. It was shown that deletion of some mitochondrial antioxidant genes resulted in different levels of biomolecular damages as well as different sensitivities against reactive species, which may be a critical outcome for the prevention of the detrimental effects of free radicals on biomolecules formed during chronological aging

Assesment of chronological life span dependent molecular damages of S.cerevisiae deficient in mitochondrial antioxidant genes

Thesis (Master)--Izmir Institute of Technology, Molecular Biology and Genetics, Izmir, 2009Includes bibliographical references (leaves: 38-40)Text in English; Abstract: Turkish and Englishx, 40 leavesAging is referred as the time-dependent accumulation of biological and physiological changes in an organism. This complex process is the major factor that is associated with many diseases such as cancer, diabetes and neurodegenerative disorders.The free radical theory of aging, which states that the molecular damages formed upon free radicals lead to the aging process, is the most widely accepted aging theory. The free radicals that are primarily produced in the mitochondria upon aerobic metabolism, are known to damage the biomolecules such as DNA, proteins and lipids. However, cells have evolved different defense systems for the elimination of these molecular damages. Antioxidant defense mechanism is one these systems that play role in the repair of the molecular damages. Since mitochondria are the main sites for the free radical production, the antioxidant genes that function in mitochondria gained an importance for their roles in preventing the molecular damages in a cell. In this study, the differences in the life spans and levels of molecular damages among different mitochondrial antioxidant gene mutants of Saccharomyces cerevisiae were tried to be identified throughout the chronological aging process, which is the model that mimics post-mitotic cell aging in higher eukaryotes. It was shown that deletion of some mitochondrial antioxidant genes resulted in different levels of biomolecular damages as well as different sensitivities against reactive species, which may be a critical outcome for the prevention of the detrimental effects of free radicals on biomolecules formed during chronological aging

Assessment of chronological lifespan dependent molecular damages in yeast lacking mitochondrial antioxidant genes

The free radical theory of aging states that oxidative damage to biomolecules causes aging and that antioxidants neutralize free radicals and thus decelerate aging. Mitochondria produce most of the reactive oxygen species, but at the same time have many antioxidant enzymes providing protection from these oxidants. Expecting that cells without mitochondrial antioxidant genes would accumulate higher levels of oxidative damage and, therefore, will have a shorter lifespan, we analyzed oxidative damages to biomolecules in young and chronologically aged mutants lacking the mitochondrial antioxidant genes: G. RX2, CCP1, SOD1, GLO4, TRR2, TRX3, CCS1, SOD2, GRX5, and PRX1. Among these mutants, ccp1Δ, trx3Δ, grx5Δ, prx1Δ, mutants were sensitive to diamide, and ccs1Δ and sod2Δ were sensitive to both diamide and menadione. Most of the mutants were less viable in stationary phase. Chronologically aged cells produced higher amount of superoxide radical and accumulated higher levels of oxidative damages. Even though our results support the findings that old cells harbor higher amount of molecular damages, no significant difference was observed between wild type and mutant cells in terms of their damage content. © 2010 Elsevier Inc.Turkish Academy of Science GEBIP and the DPT 2003K12069

Identification of respiratory chain gene mutations that shorten replicative life span in yeast

Aging is the progressive accumulation of alterations in cells that elevates the risk of death. The mitochondrial theory of aging postulates that free radicals produced by the mitochondrial respiratory system contribute to the aging process. However, the roles of individual electron transfer chain (ETC) components in cellular aging have not been elucidated. In this study, we analyzed the replicative life span of 73 yeast deletion mutants lacking the genes of the mitochondrial electron transfer chain system, and found that nine of these mutants (δ nde1, δ tcm62, δ rip1, δ cyt1, δ qrc8, δ pet117, δ cox11, δ atp11, δ fmc1) had significantly shorter life spans. These mutants had lower rates of respiration and were slightly sensitive to exogenous administration of hydrogen peroxide. However, only two of them, δ nde1 and δ fmc1, produced higher amounts of intrinsic superoxide radicals in the presence of glucose compared to that of wild type cells. Interestingly, there were no significant alterations in the mitochondrial membrane potentials of these mutants. We speculate that the shorter life spans of ETC mutants result from multiple mechanisms including the low respiration rate and low energy production rather than just a ROS-dependent path. © 2011 Elsevier Inc