Oxidant-induced cell-cycle delay in Saccharomyces cerevisiae: the involvement of the SWI6 transcription factor

Abstract

Cells treated with low doses of linoleic acid hydroperoxide (LoaOOH) exhibit a cell-cycle delay that may provide a mechanism to overcome oxidative stress. Strains sensitive to LoaOOH from the genome-wide deletion collection were screened to identify deletants in which the cell-cycle delay phenotype was reduced. Forty-seven deletants were identified that were unable to mount the normal delay response, implicating the product of the deleted gene in the oxidant-mediated cell-cycle delay of the wild-type. Of these genes, SWI6 was of particular interest due to its role in cell-cycle progression through Start. The swi6 deletant strain was delayed on entry into the cell cycle in the absence of an oxidant, and oxidant addition caused no further delay. Transforming the swi6 deletant with SWI6 on a plasmid restored the G1 arrest in response to LoaOOH, indicating that Swi6p is involved in oxidant sensing leading to cell division delay. Micro-array studies identified genes whose expression in response to LoaOOH depended on SWI6. The screening identified 77 genes that were upregulated in the wild-type strain and concurrently downregulated in the swi6 deletant treated with LoaOOH. These data show that functions such as heat shock response, and glucose transport are involved in the response.

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

“…All of the strains are isogenic with the haploid BY4741 background and were cultured in synthetic complete medium (SC) with the omission of leucine where necessary for plasmid maintenance. SWI6 coding sequence and its flanking sequences (1 kb upstream and 0.5 kb downstream) were cloned into the centromeric plasmid pRS415, and the resultant plasmid pSWI6 was transformed into the swi6⌬ mutant (16). This complemented wild-type strain was designated SWI6 to differentiate it from the wildtype strain BY4741 carrying the empty vector pRS415.…”

“…From a genome-wide screen of S. cerevisiae deletion mutants to identify genes needed to maintain resistance to a range of different oxidative stresses, 259 deletants were found to be sensitive to the lipid hydroperoxide, linoleic acid hydroperoxide (LoaOOH) (15). Because LoaOOH induces G 1 arrest in yeast, the LoaOOH-sensitive mutants were subjected to a second screen to identify genetic factors that may be involved in signaling and regulation of G 1 arrest in response to LoaOOH (16). Deletion of SWI6, which encodes the G 1 /S phase-specific transcription factor, resulted in the loss of the G 1 delay phenotype in response to LoaOOH (16).…”

“…Because LoaOOH induces G 1 arrest in yeast, the LoaOOH-sensitive mutants were subjected to a second screen to identify genetic factors that may be involved in signaling and regulation of G 1 arrest in response to LoaOOH (16). Deletion of SWI6, which encodes the G 1 /S phase-specific transcription factor, resulted in the loss of the G 1 delay phenotype in response to LoaOOH (16).…”

The Response to Heat Shock and Oxidative Stress inSaccharomyces cerevisiae

“…The superoxideinduced G1 arrest appears to be mediated via an inhibition of transcription of the CLN1 and CLN2 G1 cyclins (Lee et al 1996). 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).…”

Type 2C Protein Phosphatases in Fungi

“…A ptc1 mutant is also slightly sensitive to linoleic acid hydroperoxide, an oxidizing compound produced by lipid peroxidation that causes a delay in the G 1 phase of the cell cycle. It has been speculated that the mechanism by which PTC1 may be involved in the tolerance to this agent would involve Mms22, a protein required for resistance to ionizing radiation, although a possible role for the HOG pathway has not been discarded (19). Furthermore, the toxicity of oxalate increases in cells lacking PTC1.…”