Transcription of Schizosaccharomyces pombe Thioltransferase-1 in Response to Stress Conditions

The gene encoding gamma-glutamyl transpeptidase II in the fission yeast is regulated by oxidative and metabolic stress

gamma-Glutamyl transpeptidase (GGT, EC 2.3.2.2.) catalyzes the transfer of the gamma-glutamyl moiety from gamma-glutamylcontaining compounds, notably glutathione (GSH), to acceptor amino acids and peptides. A second gene (GGTII) encoding GGT was previously isolated and characterized from the fission yeast Schizosaccharomyces pombe. In the present work, the GGTII-lacZ fusion gene was constructed and used to study the transcriptional regulation of the S. pombe GGTII gene. The synthesis of beta-galactosidase from the GGTII-lacZ fusion gene was significantly enhanced by NO-generating SNP and hydrogen peroxide in the wildtype yeast cells. The GGTII mRNA level was increased in the wild-type S. pombe cells treated with SNP. However, the induction by SNP was abolished in the Pap1-negative S. pombe cells, implying that the induction by SNP of GGTII is mediated by Pap1. Fermentable carbon sources, such as glucose (at low concentrations), lactose and sucrose, as a sole carbon source, enhanced the synthesis of beta-galactosidase from the GGTII-lacZ fusion gene in wildtype KP1 cells but not in Pap1-negative cells. Glycerol, a non-fermentable carbon source, was also able to induce the synthesis of beta-galactosidase from the fusion gene, but other non-fermentable carbon sources such as acetate and ethanol were not. Transcriptional induction of the GGTII gene by fermentable carbon sources was also confirmed by increased GGTII mRNA levels in the yeast cells grown with them. Nitrogen starvation was also able to induce the synthesis of beta-galactosidase from the GGTII-lacZ fusiongene in a Pap1-dependent manner. On the basis of the results, it is concluded that the S. pombe GGTII gene is regulated by oxidative and metabolic stress.

Methods for monitoring oxidative stress response in yeasts

Changes in the chemical or physical conditions of the cell that impose a negative effect on growth demand rapid cellular responses, which are essential for survival. Molecular mechanisms induced upon exposure of cells to such adverse conditions are commonly designated as stress responses. Herein, different methods which can be used to monitor oxidative stress response in yeasts are presented including monitoring of oxygen partial pressure during yeast cultivation, cell viability determination, measuring activity of enzymatic and level of nonenzymatic primary antioxidant defense systems, and examination of transcriptome and proteome changes. Additionally, some studies are given as examples of particular method's application for studying oxidative stress response in yeasts.

Carbon source-dependent regulation of a second gene encoding glutaredoxin from the fission yeast Schizosaccharomyces pombe

Glutaredoxin (Grx), also known as thioltransferase (TTase), is an enzyme that catalyzes the reduction of a variety of disulfide compounds, including protein disulfides, in the presence of reduced glutathione. A second gene encoding Grx (Grx2) was cloned from the chromosomal DNA of the fission yeast Schizosaccharomyces pombe. The determined DNA sequence contains 1645 bp which is able to encode a polypeptide of 110 amino acids with a molecular mass of 12.2 kDa. The genomic DNA consists of 4 exons and 3 introns. The isolated gene was found to produce functional glutaredoxin that could accelerate the growth of the fission yeast, and is highly expressed at the mid- and late exponential phases. Aluminum, cadmium and hydrogen peroxide marginally enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene. Shifts to lower concentrations (0.2, 0.4 or 0.8%) of D-glucose significantly enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene. And shifts to sucrose (0.2, 0.4, 0.8 or 1.6%) as a sole carbon source markedly enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene, the degree of which was inversely dependent on concentration. However, nonfermentable carbon sources reduced the expression of the Grx2 gene due to their growth arrest. The transcription factor Pap1 is not involved in the basal expression and induction of the Grx2 gene. The Grx2 protein was subcellularly localized in the nucleus of the yeast cells. Our results indicate that the Grx2 protein, located in the nucleus, is linked with the yeast growth, and that the gene is regulated by carbon sources.

Characterization of a Salicylic Acid- and Pathogen-induced Lipase-like Gene in Chinese Cabbage

A cDNA clone for a salicylic acid-induced gene in Chinese cabbage (Brassica rapa subsp. pekinensis) was isolated and characterized. The cabbage gene, designated Br-sil1 (for Brassica rapa salicylate-induced lipase-like 1 gene), encodes a putative lipase that has the family II lipase motif GDSxxDxG around the active site serine. A database search showed that plant genomes have a large number of genes that contain the family II lipase motif. The lipase-like proteins include a myrosinase-associated protein, an anther-specific proline-rich protein APG, a pollen coat protein EXL, and an early nodule-specific protein. The Br-sil1 gene is strongly induced by salicylic acid and a nonhost pathogen, Pseudomonas syringae pv. tomato, that elicits a hypersensitive response in Chinese cabbage. Treatment of the cabbage leaves with BTH, methyl jasmonate, or ethephon showed that the Br-sil1 gene expression is induced by BTH, but not by methyl jasmonate or ethylene. This indicates that the cabbage gene is activated via a salicylic acid-dependent signaling pathway. An examination of the tissue-specific expression revealed that the induction of the Br-sil1 gene expression by BTH occurs in leaves and stems, but not in roots and flowers. Without the BTH treatment, however, the Br-sil1 gene is not expressed in any of the tissues that were examined.