The characterization and purification of a human transcription factor modulating the glutathione peroxidase gene in response to oxygen tension

Cellular and exosomal GPx1 are essential for controlling hydrogen peroxide balance and alleviating oxidative stress in hypoxic glioblastoma

Tumor hypoxia promotes malignant progression and therapeutic resistance in glioblastoma partly by increasing the production of hydrogen peroxide (H2O2), a type of reactive oxygen species critical for cell metabolic responses due to its additional role as a second messenger. However, the catabolic pathways that prevent H2O2 overload and subsequent tumor cell damage in hypoxic glioblastoma remain unclear. Herein, we present a hypoxia-coordinated H2O2 regulatory mechanism whereby excess H2O2 in glioblastoma induced by hypoxia is diminished by glutathione peroxidase 1 (GPx1), an antioxidant enzyme detoxifying H2O2, via the binding of hypoxia-inducible factor-1α (HIF-1α) to GPx1 promoter. Depletion of GPx1 results in H2O2 overload and apoptosis in glioblastoma cells, as well as growth inhibition in glioblastoma xenografts. Moreover, tumor hypoxia increases exosomal GPx1 expression, which assists glioblastoma and endothelial cells in countering H2O2 or radiation-induced apoptosis in vitro and in vivo. Clinical data explorations further demonstrate that GPx1 expression was positively correlated with tumor grade and expression of HIF-1α, HIF-1α target genes, and exosomal marker genes; by contrast, it was inversely correlated with the overall survival outcome in human glioblastoma specimens. Our analyses validate that the redox balance of H2O2 within hypoxic glioblastoma is clinically relevant and could be maintained by HIF-1α-promoted or exosome-related GPx1.

Raspberry and blackberry act in a synergistic manner to improve cardiac redox proteins and reduce NF-κB and SAPK/JNK in mice fed a high-fat, high-sucrose diet

BACKGROUND AND AIMS

Increased cardiac inflammation and oxidative stress are common features in obesity, and toll-like receptor (TLR)4 signaling is a key inflammatory pathway in this deleterious process. This study aimed to investigate whether berries could attenuate the detrimental effects of a high-fat, high-sucrose (HFHS) diet on the myocardium at the molecular level.

METHODS AND RESULTS

Eight-week-old male C57BL/6 mice consumed a low-fat, low-sucrose (LFLS) diet alone or supplemented with 10% blackberry (BL), 10% raspberry (RB) or 10% blackberry + raspberry (BL + RB) for four weeks. Animals were then switched to a HFHS diet for 24 weeks with or without berry supplementation or maintained on a LFLS control diet without berry supplementation. Left ventricles of the heart were isolated for protein and mRNA analysis. Berry consumption, particularly BL + RB reduced NADPH-oxidase (NOX)1 and NOX2 and increased catalase (CAT) and superoxide dismutase (SOD)2, expression while BL and RB supplementation alone was less efficacious. Downstream TLR4 signaling was attenuated mostly by both RB and BL + RB supplementation, while NF-κB pathway was attenuated by BL + RB supplementation. Stress-activated protein kinase (SAPK)/Jun amino-terminal kinase (JNK) was also attenuated by BL + RB supplementation, and reduced TNF-α transcription and protein expression was observed only with BL + RB supplementation.

CONCLUSION

The synergistic effects of BL + RB may reduce obesity-induced cardiac inflammation and oxidative stress to a greater extent than BL or RB alone.

Extracellular Glutathione Peroxidase GPx3 and Its Role in Cancer

Mammalian cells possess a multifaceted antioxidant enzyme system, which includes superoxide dismutases, catalase, the peroxiredoxin/thioredoxin and the glutathione peroxidase systems. The dichotomous role of reactive oxygen species and antioxidant enzymes in tumorigenesis and cancer progression complicates the use of small molecule antioxidants, pro-oxidants, and targeting of antioxidant enzymes as therapeutic approaches for cancer treatment. It also highlights the need for additional studies to investigate the role and regulation of these antioxidant enzymes in cancer. The focus of this review is on glutathione peroxidase 3 (GPx3), a selenoprotein, and the only extracellular GPx of a family of oxidoreductases that catalyze the detoxification of hydro- and soluble lipid hydroperoxides by reduced glutathione. In addition to summarizing the biochemical function, regulation, and disease associations of GPx3, we specifically discuss the role and regulation of systemic and tumor cell expressed GPx3 in cancer. From this it is evident that GPx3 has a dichotomous role in different tumor types, acting as both a tumor suppressor and pro-survival protein. Further studies are needed to examine how loss or gain of GPx3 specifically affects oxidant scavenging and redox signaling in the extracellular tumor microenvironment, and how GPx3 might be targeted for therapeutic intervention.

Low oxygen concentrations improve yak oocyte maturation and enhance the developmental competence of preimplantation embryos

Mammalian oocyte maturation and early embryo development are highly sensitive to the in vitro culture environment, and oxygen concentration is one of the important factors. In the present study, we aimed to explore the effects of different oxygen concentrations (20%, 10%, 5% or 1% O₂) on yak oocyte maturation, in vitro fertilization (IVF), and embryo development competence, as well as its effects on the oxidative response, metabolism, and apoptosis in cumulus-oocyte complexes (COCs) and the embryo. The results revealed that the maturation rate of oocytes, blastocysts rate and hatched blastocysts rate in the group with 5% oxygen concentration were significantly higher (P < 0.05) than other groups, but the cleavage rate with 5% oxygen concentration was significantly lower (P < 0.05) than the 20% and 10% oxygen concentrations. The maturation rate of oocytes, the cleavage rate, blastocysts rate and hatched blastocysts rate with the 1% oxygen concentration were the lowest. The blastocyst cultured with 5% oxygen concentration had significantly greater (P < 0.05) numbers of total cells, inner cell mass (ICM) cells and trophectoderm (TE) cells compared to the other groups. Analysis of the apoptosis index of oocytes and blastocyst cells by transferase dUTP nick end labeling (TUNEL) showed that the number of apoptotic cells significantly reduced (P < 0.05) with 5% oxygen concentration, but increased significantly (P < 0.05) in the 1% oxygen concentration group. Also, the qRT-PCR and western immunoblotting analysis confirmed that the transcription levels of the metabolism genes, antioxidant response genes, apoptosis genes, oocyte competence genes and embryonic developmental markers showed significant differences (P < 0.05) in the COCs or blastocysts matured in 5% oxygen concentration group compared to the other groups. In summary, our findings demonstrate that 5% oxygen concentration improves oocyte maturation and blastocyst development in the yak, increases blastocyst cell numbers, reduces apoptosis rate in the oocyte and blastocyst as well as reduces embryo cleavage rate.

An Improved Method for Identifying Specific DNA-Protein-Binding Sites In Vitro

Binding of proteins to specific DNA sequences is essential for a variety of cellular processes such as DNA replication, transcription and responses to external stimuli. Chromatin immunoprecipitation is widely used for determining intracellular DNA fragments bound by a specific protein. However, the subsequent specific or accurate DNA-protein-binding sequence is usually determined by DNA footprinting. Here, we report an alternative method for identifying specific sites of DNA-protein-binding (designated SSDP) in vitro. This technique is mainly dependent on antibody-antigen immunity, simple and convenient, while radioactive isotope labeling and optimization of partial degradation by deoxyribonuclease (DNase) are avoided. As an example, the specific binding sequence of a target promoter by DdrO (a DNA damage response protein from Deinococcus radiodurans) in vitro was determined by the developed method. The central sequence of the binding site could be easily located using this technique.

Glutathione peroxidase 8 is transcriptionally regulated by HIFα and modulates growth factor signaling in HeLa cells

GPx8 is a mammalian Cys-glutathione peroxidase of the endoplasmic reticulum membrane, involved in protein folding. Its regulation is mostly unknown. We addressed both the functionality of two hypoxia-response elements (HREs) within the promoter, GPx8 HRE1 and GPx8 HRE2, and the GPx8 physiological role. In HeLa cells, treatment with HIFα stabilizers, such as diethyl succinate (DES) or 2-2'-bipyridyl (BP), induces GPx8 expression at both mRNA and protein level. Luciferase activity of pGL3(GPx8wt), containing a fragment of the GPx8 promoter including the two HREs, is also induced by DES/BP or by overexpressing either individual HIFα subunit. Mutating GPx8 HRE1 within pGL3(GPx8wt) resulted in a significantly higher inhibition of luciferase activity than mutating GPx8 HRE2. Electrophoretic mobility-shift assay showed that both HREs exhibit enhanced binding to a nuclear extract from DES/BP-treated cells, with stronger binding by GPx8 HRE1. In DES-treated cells transfected with pGL3(GPx8wt) or mutants thereof, silencing of HIF2α, but not HIF1α, abolishes luciferase activity. Thus GPx8 is a novel HIF target preferentially responding to HIF2α binding at its two novel functional GPx8 HREs, with GPx8 HRE1 playing the major role. Fibroblast growth factor (FGF) treatment increases GPx8 mRNA expression, and reporter gene experiments indicate that induction occurs via HIF. Comparing the effects of depleting GPx8 on the downstream effectors of FGF or insulin signaling revealed that absence of GPx8 results in a 16- or 12-fold increase in phosphorylated ERK1/2 by FGF or insulin treatment, respectively. Furthermore, in GPx8-depleted cells, phosphorylation of AKT by insulin treatment increases 2.5-fold. We suggest that induction of GPx8 expression by HIF slows down proliferative signaling during hypoxia and/or growth stimulation through receptor tyrosine kinases.

Glutathione peroxidase-1 in health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species, such as superoxide and hydrogen peroxide, are generated in all cells by mitochondrial and enzymatic sources. Left unchecked, these reactive species can cause oxidative damage to DNA, proteins, and membrane lipids. Glutathione peroxidase-1 (GPx-1) is an intracellular antioxidant enzyme that enzymatically reduces hydrogen peroxide to water to limit its harmful effects. Certain reactive oxygen species, such as hydrogen peroxide, are also essential for growth factor-mediated signal transduction, mitochondrial function, and maintenance of normal thiol redox-balance. Thus, by limiting hydrogen peroxide accumulation, GPx-1 also modulates these processes. This review explores the molecular mechanisms involved in regulating the expression and function of GPx-1, with an emphasis on the role of GPx-1 in modulating cellular oxidant stress and redox-mediated responses. As a selenocysteine-containing enzyme, GPx-1 expression is subject to unique forms of regulation involving the trace mineral selenium and selenocysteine incorporation during translation. In addition, GPx-1 has been implicated in the development and prevention of many common and complex diseases, including cancer and cardiovascular disease. This review discusses the role of GPx-1 in these diseases and speculates on potential future therapies to harness the beneficial effects of this ubiquitous antioxidant enzyme.

Knockout of SOD1 promotes conversion of selenocysteine to dehydroalanine in murine hepatic GPX1 protein

Se-dependent glutathione peroxidase-1 (GPX1) and Cu,Zn-superoxide dismutase (SOD1) are two major intracellular antioxidant enzymes. The purpose of this study was to elucidate the biochemical mechanisms for the 40% loss of hepatic GPX1 activity in SOD1(-/-) mice. Compared with the wild type (WT), the SOD1(-/-) mice showed no change in the total amount of GPX1 protein. However, their total enzyme protein exhibited 31 and 38% decreases (P<0.05) in the apparent k(cat) for hydrogen peroxide and tert-butylperoxide (at 2mM GSH), respectively. Most striking, mass spectrometry revealed two chemical forms of the 47th residue of GPX1: the projected native selenocysteine (Sec) and the Se-lacking dehydroalanine (DHA). The hepatic GPX1 protein of the SOD1(-/-) mice contained 38% less Sec and 77% more DHA than that of WT and showed aggravated dissociation of the tetramer structure. In conclusion, knockout of SOD1 elevated the conversion of Sec to DHA in the active site of hepatic GPX1, leading to proportional decreases in the apparent k(cat) and activity of the enzyme protein as a whole. Our data reveal a structural and kinetic mechanism for the in vivo functional dependence of GPX1 on SOD1 in mammals and provide a novel mass spectrometric method for the assay of oxidative modification of the GPX1 protein.

Upregulation of glutathione peroxidase offsets stretch-induced proatherogenic gene expression in human endothelial cells

OBJECTIVE

Localization of atherosclerotic plaques typically correlates with areas of biomechanical strain where shear stress is decreased while stretch, thought to promote atherogenesis through enhanced oxidative stress, is increased.

METHODS AND RESULTS

In human cultured endothelial cells, nitric oxide synthase expression was exclusively shear stress-dependent whereas expression of glutathione peroxidase-1 (GPx-1), but not that of Cu(2+)/Zn(2+)-superoxide dismutase or Mn(2+)-superoxide dismutase, was upregulated solely in response to cyclic stretch. GPx-1 expression was also enhanced in isolated mouse arteries perfused at high pressure. Combined pharmacological and decoy oligodeoxynucleotide blockade revealed that activation of p38 MAP kinase followed by nuclear translocation of CCAAT/enhancer binding protein plays a pivotal role in stretch-induced GPx-1 expression in human endothelial cells. Antisense oligodeoxynucleotide knockdown of GPx-1 reinforced both their capacity to generate hydrogen peroxide and the transient stretch-induced expression of CD40, monocyte chemoatractant protein-1, and vascular cell adhesion molecule-1. Consequently, THP-1 monocyte adhesion to the GPx-1-depleted cells was augmented.

CONCLUSIONS

Stretch-induced proatherosclerotic gene expression in human endothelial cells seems to be hydrogen peroxide-mediated. The concomitant rise in GPx-1 expression, but not that of other antioxidant enzymes, may comprise an adaptive mechanism through which the cells maintain their antiatherosclerotic properties in spite of a decreased bioavailability of nitric oxide.

Transcriptional regulation of mammalian selenoprotein expression

BACKGROUND

Selenoproteins contain the twenty-first amino acid, selenocysteine, and are involved in cellular defenses against oxidative damage, important metabolic and developmental pathways, and responses to environmental challenges. Elucidating the mechanisms regulating selenoprotein expression at the transcriptional level is a key to understanding how these mechanisms are called into play to respond to the changing environment.

METHODS

This review summarizes published studies on transcriptional regulation of selenoprotein genes, focused primarily on genes whose encoded protein functions are at least partially understood. This is followed by in silico analysis of predicted regulatory elements in selenoprotein genes, including those in the aforementioned category as well as the genes whose functions are not known.

RESULTS

Our findings reveal regulatory pathways common to many selenoprotein genes, including several involved in stress-responses. In addition, tissue-specific regulatory factors are implicated in regulating many selenoprotein genes.

CONCLUSIONS

These studies provide new insights into how selenoprotein genes respond to environmental and other challenges, and the roles these proteins play in allowing cells to adapt to these changes.

GENERAL SIGNIFICANCE

Elucidating the regulatory mechanisms affecting selenoprotein expression is essential for understanding their roles in human diseases, and for developing diagnostic and potential therapeutic approaches to address dysregulation of members of this gene family.

Does yellow fever 17D vaccine protect against melanoma?

BCG vaccine, vaccinia vaccine and certain pathogens that were shown in previous studies to protect against melanoma have antigenic determinants homologous in their amino acids sequence with the melanoma antigen HERV-K-MEL, encoded by a human endogenous retrovirus K (HERV-K), which is expressed in about 95% of malignant melanocytes. Yellow fever vaccine (YFV) likewise contains an antigenic determinant with a close homology to HERV-K-MEL and might therefore also confer protection against melanoma. To investigate this possibility we carried out a cohort study (28,306 subjects) and a nested case-control study (37 melamona cases and 151 tumors not expressing HERV-K-MEL) in Veneto region (North-Eastern Italy). The standardized incidence ratio was 1.33 (95% confidence interval, 0.84-2.11), 1.59 (0.97-2.59) and 0.59 (0.19-1.84), while the age- gender-adjusted odds ratios were 1.00, 0.96 (0.43-2.14) and 0.26 (0.07-0.96), at 0-4, 5-9, and > or =10 years elapsed from YFV administration, respectively. The risk of melanoma may therefore be lowered 10 years after vaccination with yellow fever vaccine.

Tertiary-butyl hydroperoxide induced oxidative stress and male reproductive activity in mice: role of transcription factor NF-kappaB and testicular antioxidant enzymes

Reactive oxygen species (ROS) have been proposed as a major factor affecting male reproductive capacity. The present study has evaluated the possible role of oxidative stress during testicular pathogenesis in male mice exposed to tertiary-butyl hydroperoxide (TBHP). TBHP was administered by daily intraperitoneal injection for 2 weeks. Treatment greatly increased lipid peroxidation in the testis and led to a significant decrease in sperm concentration and motility and a reduction in litter size relative to controls. An increase in testicular mRNA abundance of redox-regulated p50 and p65 subunits of NF-kappaB was observed after TBHP treatment. Evaluation of NF-kappaB regulated antioxidant enzymes in the testis revealed an increase in superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione-S-transferase (GST) activities and corresponding mRNA abundance. These results suggest a potential role of NF-kappaB in oxidative stress mediated changes in the physiology of male reproductive system.

Homocysteine Down-regulates Cellular Glutathione Peroxidase (GPx1) by Decreasing Translation

Hyperhomocysteinemia contributes to vascular dysfunction and an increase in the risk of cardiovascular disease. An elevated level of homocysteine in vivo and in cell culture systems results in a decrease in the activity of cellular glutathione peroxidase (GPx1), an intracellular antioxidant enzyme that reduces hydrogen peroxide and lipid peroxides. In this study, we show that homocysteine interferes with GPx1 protein expression without affecting transcript levels. Expression of the selenocysteine (SEC)-containing GPx1 protein requires special translational cofactors to "read-through" a UGA-stop codon that specifies SEC incorporation at the active site of the enzyme. These factors include a selenocysteine incorporation sequence (SECIS) in the 3'-untranslated region of the GPx1 mRNA and cofactors involved in the biosynthesis and translational insertion of SEC. To monitor SEC incorporation, we used a reporter gene system that has a UGA codon within the protein-coding region of the luciferase mRNA. Addition of either the GPx1 or GPx3 SECIS element in the 3'-untranslated region of the luciferase gene stimulated read-through by 6-11-fold in selenium-replete cells; absence of selenium prevented translation. To alter cellular homocysteine production, we used methionine in the presence of aminopterin, a folate antagonist, co-administered with hypoxanthine and thymidine (HAT/Met). This treatment increased homocysteine levels in the media by 30% (p < 0.01) and decreased GPx1 enzyme activity by 45% (p = 0.0028). HAT/Met treatment decreased selenium-mediated read-through significantly (p < 0.001) in luciferase constructs containing the GPx1 or GPx3 SECIS element; most importantly, the suppression of selenium-dependent read-through was similar whether an SV40 promoter or the GPx1 promoter was used to drive transcription of the SECIS-containing constructs. Furthermore, HAT/Met had no effect on steady-state GPx1 mRNA levels but decreased GPx1 protein levels, suggesting that this effect is not transcriptionally mediated. These data support the conclusion that homocysteine decreases GPx1 activity by altering the translational mechanism essential for the synthesis of this selenocysteine-containing protein.

Protection against melanoma by vaccination with Bacille Calmette-Guerin (BCG) and/or vaccinia: an epidemiology-based hypothesis on the nature of a melanoma risk factor and its immunological control

A multicentre case-control study conducted by the FEBrile Infections and Melanoma (FEBIM) group has demonstrated a reduced risk of melanoma associated with Bacille Calmette-Guerin (BCG) and/or vaccinia vaccination in early childhood and/or with infectious diseases later in life. This has led to the recognition of a new risk indicator of melanoma; namely 'not being vaccinated with either with BCG or vaccinia'. On the basis of these findings, we propose a hypothesis of immune surveillance for melanoma induced or enhanced by prior contacts with pathogens unexpectedly cross-reactive to a cellular 'marker of melanoma risk'. The reduced risk of melanoma due to BCG and vaccinia, as well as certain common causes of infectious disease, is shown to be associated with antigenic determinants exhibiting sequence homologies with the HERV-K-MEL-antigen. The latter is a product of a pseudo-gene that is closely associated with the env-gene of the endogenous human retrovirus K (HERV-K). A suppressive immune reaction appears to inhibit the expression of endogenous retroviral genes, such as the HERV-K env-gene, that could otherwise result in malignant transformation years or even decades later. The HERV-K env-protein has homologous amino acid sequences with the human nuclear factor Oxygen Responsive Element Binding Protein (OREBP) that controls the expression of glutathione peroxidase. The formation of this and other redox-enzymes, needed to maintain appropriate levels of the normal intracellular redox potential, seems to be suppressed by the OREBP-homologous protein. The present hypothesis is in accordance with the concept that immune dysregulation due to adverse environmental impacts is a risk factor not only for some autoimmune disorders, as previously described, but also for certain malignancies such as melanoma.

The Ku protein complex interacts with YY1, is up-regulated in human heart failure, and represses alpha myosin heavy-chain gene expression

Human heart failure is accompanied by repression of genes such as alpha myosin heavy chain (alphaMyHC) and SERCA2A and the induction of fetal genes such as betaMyHC and atrial natriuretic factor. It seems likely that changes in MyHC isoforms contribute to the poor contractility seen in heart failure, because small changes in isoform composition can have a major effect on the contractility of cardiac myocytes and the heart. Our laboratory has recently shown that YY1 protein levels are increased in human heart failure and that YY1 represses the activity of the human alphaMyHC promoter. We have now identified a region of the alphaMyHC promoter that binds a factor whose expression is increased sixfold in failing human hearts. Through peptide mass spectrometry, we identified this binding activity to be a heterodimer of Ku70 and Ku80. Expression of Ku represses the human alphaMyHC promoter in neonatal rat ventricular myocytes. Moreover, overexpression of Ku70/80 decreases alphaMyHC mRNA expression and increases skeletal alpha-actin. Interestingly, YY1 interacts with Ku70 and Ku80 in HeLa cells. Together, YY1, Ku70, and Ku80 repress the alphaMyHC promoter to an extent that is greater than that with YY1 or Ku70/80 alone. Our results suggest that Ku is an important factor in the repression of the human alphaMyHC promoter during heart failure.

Determinants of Human Plasma Glutathione Peroxidase (GPx-3) Expression

Plasma glutathione peroxidase (GPx-3) is a selenocysteine-containing protein with antioxidant properties. GPx-3 deficiency has been associated with cardiovascular disease and stroke. The regulation of GPx-3 expression remains largely uncharacterized, however, and we studied its transcriptional and translational determinants in a cultured cell system. In transient transfections of a renal cell line (Caki-2), the published sequence cloned upstream of a luciferase reporter gene produced minimal activity (relative luminescence (RL) = 0.6 +/- 0.4). Rapid amplification of cDNA ends was used to identify a novel transcription start site that is located 233 bp downstream (3') of the published site and that produced a >25-fold increase in transcriptional activity (RL = 16.8 +/- 1.9; p < 0.0001). Analysis of the novel GPx-3 promoter identified Sp-1- and hypoxia-inducible factor-1-binding sites, as well as the redox-sensitive metal response element and antioxidant response element. Hypoxia was identified as a strong transcriptional regulator of GPx-3 expression, in part through the presence of the hypoxia-inducible factor-1-binding site, leading to an almost 3-fold increase in expression levels after 24 h compared with normoxic conditions (normalized RL = 3.5 +/- 0.3 versus 1.2 +/- 0.1; p < 0.001). We also investigated the role of the translational cofactors tRNA(Sec), SECIS-binding protein-2, and SelD (selenophosphate synthetase D) in GPx-3 protein expression. tRNA(Sec) and SelD significantly enhanced GPx-3 expression, whereas SECIS-binding protein-2 showed a trend toward increased expression. These results demonstrate the presence of a novel functional transcription start site for the human GPx-3 gene with a promoter regulated by hypoxia, and identify unique translational determinants of GPx-3 expression.

A DNA replication-related element downstream from the initiation site of Drosophila selenophosphate synthetase 2 gene is essential for its transcription

Selenophosphate synthetase catalyzes the synthesis of selenophosphate which is a selenium donor for Sec biosynthesis. In Drosophila melanogaster, there are two types of selenophosphate synthetases designated dSPS1 and dSPS2, where dSPS2 is a selenoprotein. The mechanism of gene expression of dSPS2 as well as other selenoproteins in Drosophila has not been elucidated. Herein, we report an essential regulator system that regulates the transcription of the dSPS2 gene (dsps2). Through deletion/substitution mutagenesis, the downstream DNA replication-related element (DRE) located at +71 has been identified as an essential element for dsps2 promoter activity. Furthermore, double-stranded RNA interference (dsRNAi) experiments were performed to ablate transcription factors such as TBP, TRF1, TRF2 and DREF in Schneider cells. The dsRNAi experiments showed that dsps2 promoter activities in DREF- and TRF2-depleted cells were significantly decreased by 90% and 50%, respectively. However, the depletion of TBP or TRF1 did not affect the expression level of dsps2 even though there is a putative TATA box at -20. These results strongly suggest that the DRE/DREF system controls the basal level of transcription of dsps2 by interacting with TRF2.