Cell Cycle Sensing of Oxidative Stress in Saccharomyces cerevisiae by Oxidation of a Specific Cysteine Residue in the Transcription Factor Swi6p

Abstract

Yeast cells begin to bud and enter the S phase when growth conditions are favorable during the G 1 phase. When subjected to some oxidative stresses, cells delay entry at G 1 , allowing repair of cellular damage. Hence, oxidative stress sensing is coordinated with the regulation of cell cycle. We identified a novel function of the cell cycle regulator of Saccharomyces cerevisiae, Swi6p, as a redox sensor through its cysteine residue at position 404. When alanine was substituted at this position, the resultant mutant, C404A, was sensitive to several reactive oxygen species and oxidants including linoleic acid hydroperoxide, the superoxide anion, and diamide. This mutant lost the ability to arrest in G 1 phase upon treatment with lipid hydroperoxide. The Cys-404 residue of Swi6p in wild-type cells was oxidized to a sulfenic acid when cells were subjected to linoleic acid hydroperoxide. Mutation of Cys-404 to Ala abolished the down-regulation of expression of the G 1 cyclin genes CLN1, CLN2, PCL1, and PCL2 that occurred when cells of the wild type were exposed to the lipid hydroperoxide. In conclusion, oxidative stress signaling for cell cycle regulation occurs through oxidation of the G 1 /S-speicific transcription factor Swi6p and consequently leads to suppression of the expression of G 1 cyclins and a delay in cells entering the cell cycle.The cell cycle consists of a series of coordinated events that ensure duplication of genetic material, chromosome segregation, cell growth, and cytokinesis, producing two daughter cells. In eukaryotes, cell cycle events are governed by phasespecific cyclins that complex and activate cyclin-dependent kinase (CDK) 2 for activation of phase-specific events. Cell division is regulated in part by the periodic expression of genes specific to each of the four phases (G 1 , S, G 2 , and M) (1, 2). In Saccharomyces cerevisiae, the single CDK, Cdc28, can complex with nine cyclins that are transcribed distinctly in the four stages of the cell cycle. Cells enter the cell cycle to undergo division when both intrinsic and extrinsic requirements are met. In S. cerevisiae, when cells attain a critical size in the presence of sufficient nutrients in the late G 1 phase, they reach an interval called "Start," at which the bud begins to emerge, DNA replication is initiated, and cells duplicate their spindle pole body preparing for mitosis and cytokinesis (3).Cell cycle initiation and progression are tightly regulated to ensure that cell division does not take place under unfavorable conditions (4, 5). In proliferating cells, oxidative stress can arise from reactive oxygen species that are generated from incomplete reduction of oxygen from the electron transport chain. Environmental factors, including heat and other stresses, ionizing radiation, metal ions, herbicides such as paraquat, and the vitamin K precursor menadione, can also induce reactive oxygen species production in cells (6). Reactive oxygen species are highly toxic because of their ability to directly damage nucleic acids, proteins, an...

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The Response to Heat Shock and Oxidative Stress inSaccharomyces cerevisiae

“…Similarly, LoaOOH exposure causes a G1 cell cycle delay, which is mediated by the Swi6 transcription factor (Alic et al 2001;Fong et al 2008). Swi6 is thought to act as a redox sensor that suppresses the expression of G1 cyclins in response to oxidation of a specific cysteine residue in Swi6 (Chiu et al 2011). Swi6 therefore provides an example of an oxidant-specific mechanism for controlling the cell cycle.…”

Defects in a New Class of Sulfate/Anion Transporter Link Sulfur Acclimation Responses to Intracellular Glutathione Levels and Cell Cycle Control

“…Moreover, alterations in redox homeostasis can cause defects in cell cycle progression (Esposito et al, 1997;Reichheld et al, 1999;Alic et al, 2001;Menon et al, 2003;Markovic et al, 2009;Tsukagoshi et al, 2010). Glutathione is a thiol-containing tripeptide whose function is not only important to maintain redox homeostasis when coping with biotic and abiotic stresses (Cobbett et al, 1998;Ball et al, 2004;Rouhier et al, 2008;Foyer and Noctor, 2009;Mhamdi et al, 2010;Dubreuil-Maurizi and Poinssot, 2012;Shanmugam et al, 2012) but also acts as a redox signal or sensor for cell cycle control (Chiu et al, 2011;Chiu and Dawes, 2012). Therefore, defects in glutathionemediated redox balance can lead to aberrant cell cycle progression and, subsequently, defects in growth and development (Vernoux et al, 2000;Cairns et al, 2006;Jiao et al, 2013).…”