Sp1: regulation of gene expression by phosphorylation

Harnessing peroxisome proliferator-activated receptor γ agonists to induce Heme Oxygenase-1: a promising approach for pulmonary inflammatory disorders

The activation of peroxisome proliferator-activated receptor (PPAR)-γ has been extensively shown to attenuate inflammatory responses in conditions such as asthma, acute lung injury, and acute respiratory distress syndrome, as demonstrated in animal studies. However, the precise molecular mechanisms underlying these inhibitory effects remain largely unknown. The upregulation of heme oxygenase-1 (HO-1) has been shown to confer protective effects, including antioxidant, antiapoptotic, and immunomodulatory effects in vitro and in vivo. PPARγ is highly expressed not only in adipose tissues but also in various other tissues, including the pulmonary system. Thiazolidinediones (TZDs) are highly selective agonists for PPARγ and are used as antihyperglycemic medications. These observations suggest that PPARγ agonists could modulate metabolism and inflammation. Several studies have indicated that PPARγ agonists may serve as potential therapeutic candidates in inflammation-related diseases by upregulating HO-1, which in turn modulates inflammatory responses. In the respiratory system, exposure to external insults triggers the expression of inflammatory molecules, such as cytokines, chemokines, adhesion molecules, matrix metalloproteinases, and reactive oxygen species, leading to the development of pulmonary inflammatory diseases. Previous studies have demonstrated that the upregulation of HO-1 protects tissues and cells from external insults, indicating that the induction of HO-1 by PPARγ agonists could exert protective effects by inhibiting inflammatory signaling pathways and attenuating the development of pulmonary inflammatory diseases. However, the mechanisms underlying TZD-induced HO-1 expression are not well understood. This review aimed to elucidate the molecular mechanisms through which PPARγ agonists induce the expression of HO-1 and explore how they protect against inflammatory and oxidative responses.

PGF2alpha Inhibits 20alpha-HSD Expression by Suppressing CK1alpha-induced ERK and SP1 Activation in the Corpus Luteum of Pregnant Mice

Prostaglandin F2α (PGF2α) is a luteolytic hormone that promotes parturition in mammals at the end of pregnancy by reducing progesterone secretion from the corpus luteum (CL). In rodents and primates, PGF2α rapidly converts progesterone to 20α-hydroxyprogesterone (20α-OHP) by promoting 20α-hydroxysteroid dehydrogenase (20α-HSD) expression. However, the specific mechanism of 20α-HSD regulation by PGF2α remains unclear. Casein Kinase 1α (CK1α) is a CK1 family member that regulates a variety of physiological functions, including reproductive development. Here, we investigated the effects of CK1α on pregnancy in female mice. Our experiments showed that CK1α is expressed in mouse CL, and its inhibition enhanced progesterone metabolism, decreased progesterone levels, and affected mouse embryo implantation. Further, CK1α mediated the effect of PGF2α on 20α-HSD in mouse luteal cells in vitro. Our results are the first to show that CK1α affects the 20α-HSD mRNA level by affecting the ERK signalling pathway to regulate the expression of the transcription factor SP1. These findings improve our understanding of PGF2α regulation of 20α-HSD.

Peripheral Neuroinflammation and Pain: How Acute Pain Becomes Chronic

The number of individuals suffering from severe chronic pain and its social and financial impact is staggering. Without significant advances in our understanding of how acute pain becomes chronic, effective treatments will remain out of reach. This mini review will briefly summarize how critical signaling pathways initiated during the early phases of peripheral nervous system inflammation/ neuroinflammation establish long-term modifications of sensory neuronal function. Together with the recruitment of non-neuronal cellular elements, nociceptive transduction is transformed into a pathophysiologic state sustaining chronic peripheral sensitization and pain. Inflammatory mediators, such as nerve growth factor (NGF), can lower activation thresholds of sensory neurons through posttranslational modification of the pain-transducing ion channels transient-receptor potential TRPV1 and TRPA1. Performing a dual role, NGF also drives increased expression of TRPV1 in sensory neurons through the recruitment of transcription factor Sp4. More broadly, Sp4 appears to modulate a nociceptive transcriptome including TRPA1 and other genes encoding components of pain transduction. Together, these findings suggest a model where acute pain evoked by peripheral injury-induced inflammation becomes persistent through repeated cycles of TRP channel modification, Sp4-dependent overexpression of TRP channels and ongoing production of inflammatory mediators.

MiR-135a-5p/SP1 Axis Regulates Spinal Astrocyte Proliferation and Migration

Following spinal cord injury (SCI), astrocyte activation and proliferation result in the development of glial scars, which impede axonal growth and neurological recovery. Dysregulation of microRNAs (miRNAs) during SCI results in altered expression of downstream genes. Our previous study has revealed that miR-135a-5p regulates neuronal apoptosis and axonal growth by targeting specificity protein 1 (SP1). This study attempted to investigate whether the miR-135a-5p/SP1 axis has regulatory effect on astrocytes. Herein, lipopolysaccharide (LPS) reduced miR-135a-5p expression in astrocytes. miR-135a-5p overexpression in astrocytes resulted in a decrease in CyclinD1, MMP9, GFAP, and vimentin proteins, and thus attenuated LPS-induced proliferation and migration of astrocytes. Moreover, miR-135a-5p overexpression decreased astrocyte size and the total quantity of cell protrusions, suggesting a role for miR-135a-5p in regulating astrocyte morphology. SP1 silencing also decreased astrocyte proliferation and migration by LPS. SP1 silencing could significantly reverse the promoting effect of miR-135a-5p inhibition on astrocyte proliferation and migration. In summary, the miR-135a-5p/SP1 axis regulates astrocyte proliferation and migration after SCI. This finding benefits for the development of novel ways in treating SCI effectively.

Regulation of USP25 by SP1 Associates with Amyloidogenesis

BACKGROUND

Trisomy 21, an extra copy of human chromosome 21 (HSA21), causes most Down's syndrome (DS) cases. Individuals with DS inevitably develop Alzheimer's disease (AD) neuropathological phenotypes after middle age including amyloid plaques and tau neurofibrillary tangles. Ubiquitin Specific Peptidase 25 (USP25), encoding by USP25 gene located on HSA21, is a deubiquitinating enzyme, which plays an important role in both DS and AD pathogenesis. However, the regulation of USP25 remains unclear.

OBJECTIVE

We aimed to determine the regulation of USP25 by specificity protein 1 (SP1) in neuronal cells and its potential role in amyloidogenesis.

METHODS

The transcription start site and promoter activity was identified by SMART-RACE and Dual-luciferase assay. Functional SP1-responsive elements were examined by EMSA. USP25 expression was examined by RT-PCR and immunoblotting. Student's t-test or one-way ANOVA were applied or statistical analysis.

RESULTS

The transcription start site of human USP25 gene was identified. Three functional SP1 responsive elements in human USP25 gene were revealed. SP1 promotes USP25 transcription and subsequent USP25 protein expression, while SP1 inhibition significantly reduces USP25 expression in both non-neuronal and neuronal cells. Moreover, SP1 inhibition dramatically reduces amyloidogenesis.

CONCLUSION

We demonstrates that transcription factor SP1 regulates USP25 gene expression, which associates with amyloidogenesis. It suggests that SP1 signaling may play an important role in USP25 regulation and contribute to USP25-mediated DS and AD pathogenesis.

Esculetin has therapeutic potential via the proapoptotic signaling pathway in A253 human submandibular salivary gland tumor cells

Esculetin is a natural lactone that is commonly derived from coumarins. According to previous experiments using human cancer cells, esculetin has potent antitumor activity; it also inhibits proliferation and induces the apoptosis of cancer cells. In the present study, the anti-proliferative effect of esculetin on the submandibular salivary gland tumor cell line, A253, was evaluated via in vitro and in vivo analyses. Furthermore, the anti-cancer effects of esculetin in A253 cells and a xenograft model of salivary gland tumors were determined using 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide and TUNEL assay, apoptosis protein array, quantitative polymerase chain reaction and western blot analysis. Esculetin (50-150 µM) was demonstrated to have an anti-proliferative effect in the A253 cell line in vitro; this observed effect was dependent on the dose and duration of treatment. Esculetin also increased the levels of Bax, cleaved caspase-3, cleaved-9 and cleaved poly (ADP-ribose) polymerase apoptosis-related proteins, and decreased the expression levels of the Bcl-2 anti-apoptotic protein. With respect to apoptosis regulation, esculetin significantly decreased the proliferation of tumor cells in a xenograft model (100 mg/kg/day) for 18 days. Overall, esculetin could be a potential oral anticancer drug against salivary gland cancer.

Expression and Impact of C1GalT1 in Cancer Development and Progression

Simple Summary

C1GalT1 is one of the enzymes that catalyze the addition of sugar residues to proteins (protein glycosylation). It specifically controls the synthesis and formation of a special disaccharide structure Galβ1,3GalNAcα-, which occurs predominately in cancer but rarely in normal cells. Recent studies have shown that C1GalT1 is overexpressed in many common cancers including colon, breast, gastric, lung, head and neck, pancreatic, esophageal, prostate, and hepatocellular cancer. C1GalT1 overexpression is also often associated with poorer prognosis and poorer patient survival. This review summarizes our current understanding of the expression of C1GalT1 in various cancers and discusses the impact of C1GalT change on cancer cell activities in cancer development and progression.

Abstract

C1GalT1 (T-synthase) is one of the key glycosyltransferases in the biosynthesis of O-linked mucin-type glycans of glycoproteins. It controls the formation of Core-1 disaccharide Galβ1,3GalNAcα- (Thomsen–Friedenreich oncofetal antigen, T or TF antigen) and Core-1-associated carbohydrate structures. Recent studies have shown that C1GalT1 is overexpressed in many cancers of epithelial origin including colon, breast, gastric, head and neck, pancreatic, esophageal, prostate, and hepatocellular cancer. Overexpression of C1GalT1 is often seen to also be associated with poorer prognosis and poorer patient survival. Change of C1GalT1 expression causes glycosylation changes of many cell membrane glycoproteins including mucin proteins, growth factor receptors, adhesion molecules, and death receptors. This leads to alteration of the interactions of these cell surface molecules with their binding ligands, resulting in changes of cancer cell activity and behaviors. This review summarizes our current understanding of the expression of C1GalT1 in various cancers and discusses the impact of C1GalT change on cancer cell activities in cancer development and progression.

New Insights Into the Role of Mitochondria Quality Control in Ischemic Heart Disease

IHD is a significant cause of mortality and morbidity worldwide. In the acute phase, it's demonstrated as myocardial infarction and ischemia-reperfusion injury, while in the chronic stage, the ischemic heart is mainly characterised by adverse myocardial remodelling. Although interventions such as thrombolysis and percutaneous coronary intervention could reduce the death risk of these patients, the underlying cellular and molecular mechanisms need more exploration. Mitochondria are crucial to maintain the physiological function of the heart. During IHD, mitochondrial dysfunction results in the pathogenesis of ischemic heart disease. Ischemia drives mitochondrial damage not only due to energy deprivation, but also to other aspects such as mitochondrial dynamics, mitochondria-related inflammation, etc. Given the critical roles of mitochondrial quality control in the pathological process of ischemic heart disease, in this review, we will summarise the efforts in targeting mitochondria (such as mitophagy, mtROS, and mitochondria-related inflammation) on IHD. In addition, we will briefly revisit the emerging therapeutic targets in this field.

The Role of Astrocytes in the Neurorepair Process

Astrocytes are highly specialized glial cells responsible for trophic and metabolic support of neurons. They are associated to ionic homeostasis, the regulation of cerebral blood flow and metabolism, the modulation of synaptic activity by capturing and recycle of neurotransmitters and maintenance of the blood-brain barrier. During injuries and infections, astrocytes act in cerebral defense through heterogeneous and progressive changes in their gene expression, morphology, proliferative capacity, and function, which is known as reactive astrocytes. Thus, reactive astrocytes release several signaling molecules that modulates and contributes to the defense against injuries and infection in the central nervous system. Therefore, deciphering the complex signaling pathways of reactive astrocytes after brain damage can contribute to the neuroinflammation control and reveal new molecular targets to stimulate neurorepair process. In this review, we present the current knowledge about the role of astrocytes in brain damage and repair, highlighting the cellular and molecular bases involved in synaptogenesis and neurogenesis. In addition, we present new approaches to modulate the astrocytic activity and potentiates the neurorepair process after brain damage.

Synergistic activation of mutant TERT promoter by Sp1 and GABPA in BRAFV600E-driven human cancers

The activating TERT promoter mutations and BRAF^V600E mutation are well-established oncogenic alterations in human cancers. Coexistence of BRAF^V600E and TERT promoter mutations is frequently found in multiple cancer types, and is strongly associated with poor patient prognosis. Although the BRAF^V600E-elicited activation of ERK has been demonstrated to contribute to TERT reactivation by maintaining an active chromatin state, it still remains to be addressed how activated ERK is selectively recruited to mutant TERT promoter. Here, we report that transcription factor GABPA mediates the regulation of BRAF^V600E/MAPK signaling on TERT reactivation by selectively recruiting activated ERK to mutant TERT promoter, where activated ERK can phosphorylate Sp1, thereby resulting in HDAC1 dissociation and an active chromatin state. Meanwhile, phosphorylated Sp1 further enhances the binding of GABPA to mutant TERT promoter. Taken together, our data indicate that GABPA and Sp1 synergistically activate mutant TERT promoter, contributing to tumorigenesis and cancer progression, particularly in the BRAF^V600E-driven human cancers. Thus, our findings identify a direct mechanism that bridges two frequent oncogenic alterations together in TERT reactivation.

O-GlcNAc Modification During Pregnancy: Focus on Placental Environment

Successful placentation is a key event for fetal development, which commences following embryo implantation into the uterine wall, eliciting decidualization, placentation, and remodeling of blood vessels to provide physiological exchange between embryo-fetus and mother. Several signaling pathways are recruited to modulate such important processes and specific proteins that regulate placental function are a target for the glycosylation with O-linked β-N-acetylglucosamine (O-GlcNAc), or O-GlcNAcylation. This is a reversible post-translational modification on nuclear and cytoplasmic proteins, mainly controlled by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). O-GlcNAcylation has been implicated as a modulator of proteins, both in physiological and pathological conditions and, more recently, O-GlcNAc has also been shown to be an important modulator in placental tissue. In this mini-review, the interplay between O-GlcNAcylation of proteins and placental function will be addressed, discussing the possible implications of this post-translational modification through placental development and pregnancy.

Heregulin-induced cell migration is promoted by aryl hydrocarbon receptor in HER2-overexpressing breast cancer cells

HER2 overexpression accounts for approximately 15-20% of all breast cancers. We have shown that HER2 overexpression leads to elevated expression of the aryl hydrocarbon receptor (AhR) in breast cancer cells. In this study, firstly, we showed that AhR expression was up-regulated by treatment with the HER3 ligand heregulin (HRG) in HER2-overexpressing breast cancer cell lines. Induction of AhR was mediated by transcriptional activation of the region of AhR promoter corresponding to - 190 to - 100 bp. In addition, HRG treatment elicited nuclear translocation of AhR. To investigate the role of AhR in HRG-HER2/HER3 signaling in HER2-overexpressing cells, we established AhR knockout (KO) HER2-overexpressing cells to perform wound-healing assays. HRG-induced cell migration was markedly attenuated by AhR KO. HRG-induced cell migration was associated with increased expression of the inflammatory cytokines interleukin (IL)-6 and IL-8 in wild type cells, but not in AhR KO cells. These results elucidate that AhR is an important factor for the malignancy in HER2 overexpressing breast cancers.

Cytochrome P450 1B1 promotes cancer cell survival via specificity protein 1 (Sp1)-mediated suppression of death receptor 4

Cytochrome P450 1B1 (CYP1B1), a well-known oncogene, has garnered wide attention because of its tumor-specific expression pattern and actions as a carcinogenic factor. Although CYP1B1 might play a crucial role in carcinogenesis, the detailed molecular mechanisms underlying oncogenic involvement in cancer development remain unclear. The present study investigated the manner in which CYP1B1 promotes survival of various cancer cells. Treatment with 2,2',4,6'-tetramethoxystilbene (TMS), a specific CYP1B1 inhibitor, significantly inhibited cell viability in human breast cancer and leukemia cell lines, including MCF-7, MDA-MB-231, HL-60, and U937 cells. In order to characterize the cellular functions of CYP1B1 associated with cancer cell survival, the relationship between this oncogene and death receptor 4 (DR4) was determined. Following induction or inhibition of CYP1B1, mRNA and protein expression levels of DR4 were measured, and this oncogene was found to significantly repress DR4 mRNA and protein expression. Further, the suppression of DR4 by CYP1B1 was restored with 5-aza-2'-deoxycytidine (5-aza-dC), a DNA methyltransferase inhibitor, indicating that DNA methylation may be involved in CYP1B1-mediated DR4 inhibition. Methylation-specific polymerase chain reaction (PCR) in CYP1B1-overexpressed HL-60 cells revealed that this oncogene induced hypermethylation on DR4 promoter. Interestingly, data showed that DR4 suppression of CYP1B1 is mediated by the DNA-binding ability of specificity protein 1 (Sp1). These findings suggest that CYP1B1 promotes cancer cell survival through involvement of DNA methylation-mediated DR4 inhibition and that Sp1 may act as key mediator required for oncogenic action.

Simultaneous high expression of PLD1 and Sp1 predicts a poor prognosis for pancreatic ductal adenocarcinoma patients

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with few therapeutic options. Recently, insight into cancer biology suggested abnormal lipid metabolism to be a risk factor for human malignancies. As a key enzyme implicated in lipid metabolism, PLD1 was elevated in various human cancer associating with malignant phenotypes. However, little was known about its expression and function in PDAC. We showed that PLD1 was elevated in both the cell lines and clinical samples of PDAC, and it positively correlated with vascular invasion (p = 0.041) and responsible for a poor prognosis (p = 0.009). Meanwhile, we also found Sp1 to be elevated in the disease, correlating with vascular invasion (p = 0.007). Moreover, the correlation assay suggested that PLD1 positively correlated with Sp1 in the clinical sample (r = 0.390; p < 0.001) and the cell lines. Finally, we showed that co-high expression of both the factors confers the poorest prognosis for the patients, and that their simultaneous high expression might be an independent prognostic factor (p = 0.001; HR = 3.427; 95% CI 1.629-7.211).

Transcriptional Regulation of Frizzled-1 in Human Osteoblasts by Sp1

The wingless pathway has a powerful influence on bone metabolism and is a therapeutic target in skeletal disorders. Wingless signaling is mediated in part through the Frizzled (FZD) receptor family. FZD transcriptional regulation is poorly understood. Herein we tested the hypothesis that Sp1 plays an important role in the transcriptional regulation of FZD1 expression in osteoblasts and osteoblast mineralization. To test this hypothesis, we conducted FZD1 promoter assays in Saos2 cells with and without Sp1 overexpression. We found that Sp1 significantly up-regulates FZD1 promoter activity in Saos2 cells. Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift (EMSA) assays identified a novel and functional Sp1 binding site at -44 to -40 from the translation start site in the FZD1 promoter. The Sp1-dependent activation of the FZD1 promoter was abolished by mithramycin A (MMA), an antibiotic affecting both Sp1 binding and Sp1 protein levels in Saos2 cells. Similarly, down-regulation of Sp1 in hFOB cells resulted in less FZD1 expression and lower alkaline phosphatase activity. Moreover, over-expression of Sp1 increased FZD1 expression and Saos2 cell mineralization while MMA decreased Sp1 and FZD1 expression and Saos2 cell mineralization. Knockdown of FZD1 prior to Sp1 overexpression partially abolished Sp1 stimulation of osteoblast differentiation markers. Taken together, our results suggest that Sp1 plays a role in human osteoblast differentiation and mineralization, which is at least partially mediated by Sp1-dependent transactivation of FZD1.

Hepatocellular carcinoma redirects to ketolysis for progression under nutrition deprivation stress

Cancer cells are known for their capacity to rewire metabolic pathways to support survival and proliferation under various stress conditions. Ketone bodies, though produced in the liver, are not consumed in normal adult liver cells. We find here that ketone catabolism or ketolysis is re-activated in hepatocellular carcinoma (HCC) cells under nutrition deprivation conditions. Mechanistically, 3-oxoacid CoA-transferase 1 (OXCT1), a rate-limiting ketolytic enzyme whose expression is suppressed in normal adult liver tissues, is re-induced by serum starvation-triggered mTORC2-AKT-SP1 signaling in HCC cells. Moreover, we observe that enhanced ketolysis in HCC is critical for repression of AMPK activation and protects HCC cells from excessive autophagy, thereby enhancing tumor growth. Importantly, analysis of clinical HCC samples reveals that increased OXCT1 expression predicts higher patient mortality. Taken together, we uncover here a novel metabolic adaptation by which nutrition-deprived HCC cells employ ketone bodies for energy supply and cancer progression.

PP2A inhibitors arrest G2/M transition through JNK/Sp1- dependent down-regulation of CDK1 and autophagy-dependent up-regulation of p21

Protein phosphatase 2A (PP2A) plays an important role in the control of the cell cycle. We previously reported that the PP2A inhibitors, cantharidin and okadaic acid (OA), efficiently repressed the growth of cancer cells. In the present study, we found that PP2A inhibitors arrested the cell cycle at the G2 phase through a mechanism that was dependent on the JNK pathway. Microarrays further showed that PP2A inhibitors induced expression changes in multiple genes that participate in cell cycle transition. To verify whether these expression changes were executed in a PP2A-dependent manner, we targeted the PP2A catalytic subunit (PP2Ac) using siRNA and evaluated gene expression with a microarray. After the cross comparison of these microarray data, we identified that CDK1 was potentially the same target when treated with either PP2A inhibitors or PP2Ac siRNA. In addition, we found that the down-regulation of CDK1 occurred in a JNK-dependent manner. Luciferase reporter gene assays demonstrated that repression of the transcription of CDK1 was executed through the JNK-dependent activation of the Sp1 transcription factor. By constructing deletion mutants of the CDK1 promoter and by using ChIP assays, we identified an element in the CDK1 promoter that responded to the JNK/Sp1 pathway after stimulation with PP2A inhibitors. Cantharidin and OA also up-regulated the expression of p21, an inhibitor of CDK1, via autophagy rather than PP2A/JNK pathway. Thus, this present study found that the PP2A/JNK/Sp1/CDK1 pathway and the autophagy/p21 pathway participated in G2/M cell cycle arrest triggered by PP2A inhibitors.

Impact of Different Promoters on Episomal Vectors Harbouring Characteristic Motifs of Matrix Attachment Regions

We previously demonstrated that the characteristic sequence of matrix attachment regions (MARs) allows transgenes to be maintained episomally in CHO cells. In the present study, six commonly used promoters from human cytomegalovirus major immediate-early (CMV), simian vacuolating virus 40 (SV40), Rous sarcoma virus, Homo sapiens ubiquitin C, phosphoglycerate kinase, and β-globin, respectively, were evaluated to determine their effects on transgene expression and stability in CHO cells stably transfected via the episomal vector harbouring characteristic MAR motifs. The CHO cells were transfected with vectors and then screened using G418, after which the stably transfected cells were split into two and further cultured either in the presence or absence of G418. Of the six promoters, the CMV promoter yielded the highest transgene expression levels and the highest transfection efficiency, whereas the SV40 promoter maintained transgene expression more stably during long-term culture than the other promoters did. The CMV and SV40 promoter-containing vectors were furthermore episomally maintained and conferred sustained eGFP expression in the cells even under nonselective conditions. On the basis of these findings, we conclude that the CMV promoter performs best in terms of yielding both high expression levels and high levels of stability using this episomal vector system.

Post-Translational Modifications of Cardiac Mitochondrial Proteins in Cardiovascular Disease: Not Lost in Translation

Protein post-translational modifications (PTMs) are crucial in regulating cellular biology by playing key roles in processes such as the rapid on and off switching of signaling network and the regulation of enzymatic activities without affecting gene expressions. PTMs lead to conformational changes in the tertiary structure of protein and resultant regulation of protein function such as activation, inhibition, or signaling roles. PTMs such as phosphorylation, acetylation, and S-nitrosylation of specific sites in proteins have key roles in regulation of mitochondrial functions, thereby contributing to the progression to heart failure. Despite the extensive study of PTMs in mitochondrial proteins much remains unclear. Further research is yet to be undertaken to elucidate how changes in the proteins may lead to cardiovascular and metabolic disease progression in particular. We aimed to summarize the various types of PTMs that occur in mitochondrial proteins, which might be associated with heart failure. This study will increase the understanding of cardiovascular diseases through PTM.

Lead neurotoxicity: exploring the potential impact of lead substitution in zinc-finger proteins on mental health

This critical review focuses on one possible link between the cellular biology of lead and its neurotoxic effects: the link between Pb²⁺substitution for Zn²⁺in zinc-finger proteins and mental illness in adulthood.

Association between Polymorphisms of the AKT1 Gene Promoter and Risk of the Alzheimer's Disease in a Chinese Han Population with Type 2 Diabetes

AIMS

Alzheimer's disease (AD) is a multifactor disease that has been reported to have a close association with type 2 diabetes (T2D) where the v-akt murine thymoma viral oncogene homolog 1 (AKT1) plays an important role in the protein synthesis pathways and cell apoptosis processes. Evidence has been shown that AKT1 protein may be related to AD risk among patients with T2D. The aim of this study was to analyze the potential association between single nucleotide polymorphisms of AKT1 promoter and the risk of AD among patients with T2D.

METHODS

The association between AKT1 polymorphisms and AD risk in patients with T2D was assessed among 574 consecutive unrelated subjects including 112 AD patients with T2D, 231 patients with AD, and 231 healthy controls in a case-control study. The cognitive function of all subjects was assessed using MMSE. Six single nucleotide polymorphisms with minor allele frequency >0.2 (rs2498786, rs74090038, rs2494750, rs2494751, rs5811155, and rs2494752) in AKT1 promoter were analyzed by polymerase chain reaction (PCR), and the concentration of AKT1 protein in serum was tested using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Overall, there was statistically significant difference in AKT1 rs2498786 polymorphism. The CC frequency of AKT1 rs2498786 polymorphism in AD with T2D group and AD control group was significantly higher than that in healthy control group (PAD+T2D vs. health < 0.0001, PAD vs. health < 0.0001). However, the difference was not found between AD with T2D group and AD control group. Compared with healthy control group, the plasma levels of AKT1 protein in AD with T2D group (PAD+T2D vs. health < 0.0001) and AD control group (PAD vs. health = 0.0003) decreased significantly. Among genotypes of AKT1 rs2498786 polymorphism, the AKT1 protein level in GG genotype was significantly higher than that in GC genotype (PGG vs. GC < 0.0001) and CC genotype (PGG vs. CC < 0.0001).

CONCLUSION

The study suggests that AKT1 rs2498786 polymorphism in insulin signaling pathway may be associated with AD risk and different genotypes may affects levels of protein expression. However, the polymorphism is not shown to be exclusive in AD patients with T2D.

Measles Virus Infection Inactivates Cellular Protein Phosphatase 5 with Consequent Suppression of Sp1 and c-Myc Activities

Measles virus (MeV) causes several unique syndromes, including transient immunosuppression. To clarify the cellular responses to MeV infection, we previously analyzed a MeV-infected epithelial cell line and a lymphoid cell line by microarray and showed that the expression of numerous genes was up- or downregulated in the epithelial cells. In particular, there was a characteristic comprehensive downregulation of housekeeping genes during late stage infection. To identify the mechanism underlying this phenomenon, we examined the phosphorylation status of transcription factors and kinase/phosphatase activities in epithelial cells after infection. MeV infection inactivated cellular protein phosphatase 5 (PP5) that consequently inactivated DNA-dependent protein kinase, which reduced Sp1 phosphorylation levels, and c-Myc degradation, both of which downregulated the expression of many housekeeping genes. In addition, intracellular accumulation of viral nucleocapsid inactivated PP5 and subsequent downstream responses. These findings demonstrate a novel strategy of MeV during infection, which causes the collapse of host cellular functions.

IMPORTANCE

Measles virus (MeV) is one of the most important pathogens in humans. We previously showed that MeV infection induces the comprehensive downregulation of housekeeping genes in epithelial cells. By examining this phenomenon, we clarified the molecular mechanism underlying the constitutive expression of housekeeping genes in cells, which is maintained by cellular protein phosphatase 5 (PP5) and DNA-dependent protein kinase. We also demonstrated that MeV targets PP5 for downregulation in epithelial cells. This is the first report to show how MeV infection triggers a reduction in overall cellular functions of infected host cells. Our findings will help uncover unique pathogenicities caused by MeV.

Apoptotic effects of 7,8-dihydroxyflavone in human oral squamous cancer cells through suppression of Sp1

7,8-Dihydroxyflavone (7,8-DHF) is a member of the flavonoid family and has recently been identified as a brain-derived neurotrophic factor mimetic that selectively activates tropomyosin-receptor kinase B with high affinity. The antioxidant and anticancer effects of 7,8-DHF have been reported. However, the pharmacological mechanisms of 7,8-DHF in oral cancer are unclear. Thus, we investigated the mechanisms of the antiproliferative action of 7,8-DHF on HN22 and HSC4 oral squamous cell carcinoma cell lines. We demonstrated that 7,8-DHF decreased cell growth and induced apoptosis in the HN22 and HSC4 cells through regulation of specificity protein 1 (Sp1) using the MTS assay, DAPI staining, Annexin V, propidium iodide staining, reverse transcription-polymerase chain reaction, immunocytochemistry, pull-down assay and western blot analysis. The results showed that the Sp1 protein bound with 7,8-DHF in the HN22 and HSC4 cells. Taken together, the results suggest that 7,8-DHF could modulate Sp1 transactivation and induce apoptotic cell death by regulating the cell cycle and suppressing antiapoptotic proteins. Furthermore, 7,8-DHF may be valuable for cancer prevention and better clinical outcomes.

Quercetin Induces Antiproliferative Activity Against Human Hepatocellular Carcinoma (HepG2) Cells by Suppressing Specificity Protein 1 (Sp1)

Preclinical Research Quercetin, found in red onions and red apple skin can induce apoptosis insome malignant cells. However, the apoptotic effect of quercetin in hepatocellular carcinoma HepG2 cells via regulation of specificity protein 1 (Sp1) has not been studied. Here, we demonstrated that quercetin decreased cell growth and induce apoptosis in HepG2 cells via suppression of Sp1 using 3-(4,5-dimethyl-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, 4',6-diamidino-2-phenylindole (DAPI) staining, Annexin V, and Western blot analysis, an effect that was dose- and time-dependent manner. Treatment of HepG2 cells with quercetin reduced cell growth and induced apoptosis, followed by regulation of Sp1 and Sp1 regulatory protein. Taken together, the results suggest that quercetin can induce apoptotic cell death by regulating cell cycle and suppressing antiapoptotic proteins. Therefore, quercetin may be useful for cancer prevention. Drug Dev Res 76 : 9-16, 2015.

Specificity protein 1 regulates gene expression related to fatty acid metabolism in goat mammary epithelial cells

Specificity protein 1 (SP1) is a ubiquitous transcription factor that plays an important role in controlling gene expression. Although important in mediating the function of various hormones, the role of SP1 in regulating milk fat formation remains unknown. To investigate the sequence and expression information, as well as its role in modulating lipid metabolism, we cloned SP1 gene from mammary gland of Xinong Saanen dairy goat. The full-length cDNA of the SP1 gene is 4376 bp including 103 bp of 5'UTR, 2358 bp of ORF (HM_236311) and 1915 bp of 3'UTR, which is predicted to encode a 786 amino acids polypeptide. Phylogenetic tree analysis showed that goat SP1 has the closest relationship with sheep, followed by bovines (bos taurus, odobenus and ceratotherium), pig, primates (pongo, gorilla, macaca and papio) and murine (rattus and mus), while the furthest relationship was with canis and otolemur. Expression was predominant in the lungs, small intestine, muscle, spleen, mammary gland and subcutaneous fat. There were no significant expression level differences between the mammary gland tissues collected at lactation and dry-off period. Overexpression of SP1 in goat mammary epithelial cells (GMECs) led to higher mRNA expression level of peroxisome proliferator-activated receptor-γ (PPARγ) and lower liver X receptor α (LXRα) mRNA level, both of which were crucial in regulating fatty acid metabolism, and correspondingly altered the expression of their downstream genes in GMECs. These results were further enhanced by the silencing of SP1. These findings suggest that SP1 may play an important role in fatty acid metabolism.

Sp1 regulates Raf/MEK/ERK-induced p21(CIP1) transcription in TP53-mutated cancer cells

We previously reported that the upregulation of mortalin, an Hsp70 family chaperone, is important for B-Raf(V600E) tumor cells to bypass p21(CIP1) expression, which is activated as a tumor-suppressive mechanism in response to aberrant MEK/ERK activation (Wu et al., 2013). Interestingly, mortalin depletion induced p21(CIP1) transcription not only in wild-type TP53 but also in TP53-mutated B-Raf(V600E) cancer cells, suggesting the presence of an additional mechanism for p21(CIP1) regulation. In the present study, using luciferase reporter truncation analysis in a TP53-mutated B-Raf(V600E) cancer cell line, SK-MEL28, we identified a proximal p21(CIP1) promoter region responsive to mortalin depletion. Interestingly, when Sp1-like cis-elements in this promoter region were mutagenized, the p21(CIP1) promoter luciferase reporter was no longer responsive to mortalin depletion. Consistent with this, our ChIP analysis revealed that mortalin knockdown could induce Sp1 binding to p21(CIP1) promoter in a MEK/ERK-dependent manner. Moreover, RNA interference of Sp1 substantially attenuated p21(CIP1) expression induced by mortalin depletion in SK-MEL28 cells. Consistent with this observation in SK-MEL28 cells, Sp1 was necessary for the tamoxifen-regulated ∆Raf-1:ER to induce p21(CIP1) transcription in U251 cells, in which TP53 is mutated. However, in contrast, Sp1 was not necessary for ∆Raf-1:ER to induce p21(CIP1) transcription in LNCaP cells, in which TP53 is wild type. These data suggest that Sp1 may address TP53-independent p21(CIP1) transcription in Raf/MEK/ERK-activated cancer cells and that its requirement in Raf/MEK/ERK-induced p21(CIP1) transcription is subject to TP53 status.

Beta-Lapachone Suppresses Non-small Cell Lung Cancer Proliferation through the Regulation of Specificity Protein 1

Lung cancer is the leading cause of cancer-related death worldwide, and non-small cell lung cancer (NSCLC) is the most common pathological type with a reported frequency of about 85% of all cases. Despite recent advances in therapeutic agents and targeted therapies, the prognosis for NSCLC remains poor, and therefore it is important to identify the biological targets of this complex disease since a blockade of such targets would affect multiple downstream signaling cascades. β-Lapachone (β-Lap) is an antiproliferative agent that selectively induces apoptosis-related cell death in a variety of human cancer cells. However, the mechanisms of its action require further investigation. In this study, we show that treatment with β-lap triggers apoptosis and cell-cycle arrest in two NSCLC cell lines: H1299 and NCI-H358. The transcription factor specificity protein 1 (Sp1) was markedly inhibited by β-lap in a dose- and time-dependent manner. Furthermore, β-lap modulated the protein expression levels of the Sp1 regulatory genes, including cell-cycle regulatory proteins and antiapoptotic proteins, resulting in apoptosis. Taken together, our results indicate that β-lap may be a potential antiproliferative agent candidate by inducing apoptotic cell death in NSCLC tissue through downregulation of Sp1.

Pin1-mediated Sp1 phosphorylation by CDK1 increases Sp1 stability and decreases its DNA-binding activity during mitosis

We have shown that Sp1 phosphorylation at Thr739 decreases its DNA-binding activity. In this study, we found that phosphorylation of Sp1 at Thr739 alone is necessary, but not sufficient for the inhibition of its DNA-binding activity during mitosis. We demonstrated that Pin1 could be recruited to the Thr739(p)-Pro motif of Sp1 to modulate the interaction between phospho-Sp1 and CDK1, thereby facilitating CDK1-mediated phosphorylation of Sp1 at Ser720, Thr723 and Thr737 during mitosis. Loss of the C-terminal end of Sp1 (amino acids 741-785) significantly increased Sp1 phosphorylation, implying that the C-terminus inhibits CDK1-mediated Sp1 phosphorylation. Binding analysis of Sp1 peptides to Pin1 by isothermal titration calorimetry indicated that Pin1 interacts with Thr739(p)-Sp1 peptide but not with Thr739-Sp1 peptide. X-ray crystallography data showed that the Thr739(p)-Sp1 peptide occupies the active site of Pin1. Increased Sp1 phosphorylation by CDK1 during mitosis not only stabilized Sp1 levels by decreasing interaction with ubiquitin E3-ligase RNF4 but also caused Sp1 to move out of the chromosomes completely by decreasing its DNA-binding activity, thereby facilitating cell cycle progression. Thus, Pin1-mediated conformational changes in the C-terminal region of Sp1 are critical for increased CDK1-mediated Sp1 phosphorylation to facilitate cell cycle progression during mitosis.

Anti-proliferative properties of kahweol in oral squamous cancer through the regulation specificity protein 1

Kahweol, the coffee-specific deterpene, has been shown to have potential anti-cancer effects against several cancers. However, the molecular mechanisms underlying the anti-cancer activity of kahweol have not yet established. In this study, we investigated whether kahweol could show anti-cancer effects on oral squamous cell lines (OSCCs), HN22 and HSC4. We conducted an 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, 4'-6-diamidino2-phenylindole (DAPI) staining, propidium iodide staining, immunocytochemistry, and Western blot analysis for the characterization of kahweol and the underlying signaling pathway. We determined that kahweol-treated cells showed significantly decreased cell viability and increased nuclear condensation and an increased sub-G1 population in OSCCs. Interestingly, suppression of the transcription factor specificity protein 1 (Sp1) was followed by induced apoptosis by kahweol in a dose-dependent manner. In addition, kahweol modulated the protein expression level of the Sp1 regulatory genes including cell cycle regulatory proteins and anti-apoptotic proteins, resulting in apoptosis. Taken together, results from these findings suggest that kahweol may be a potential anti-cancer drug candidate to induce apoptotic cell death through downregulation of Sp1 in OSCCs.

Flavonoid ingredients of Ginkgo biloba leaf extract regulate lipid metabolism through Sp1-mediated carnitine palmitoyltranferase 1A up-regulation

BACKGROUND

Lipid accumulation is the primary evidence of non-alcoholic fatty liver disease (NAFLD). Ginkgo biloba extract (GBE) and its flavonoid ingredients (quercetin, kaempferol, and isorhamnetin) could lessen the lipid accumulation associated with up-regulation of the rate-limiting enzyme, carnitine palmitoyltransferase 1A (CPT1A), in the β-oxidation of long-chain fatty acids. In this study, we investigated the mechanisms by which GBE and its flavonoids induced expression of CPT1A.

RESULTS

CPT1A inhibition with RNAi resulted in triglyceride accumulation in HepG2 cells. Through deletion and mutation analysis of CPT1A's promoter combined with electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) experiments, the CPT1A promoter region (-50 to -5 nt) was determined to contain two putative Sp1 binding sites, namely Sp1a and Sp1b, which might act as the GBE regulation response DNA element. Sp1 might be induced to transfer from cytoplasma to nucleus to bind the promoter region of -50 to -5 nt by GBE. The regulatory effects of GBE on CPT1A were also verified on the flavonoid ingredients quercetin, kaempferol, and isorhamnetin.

CONCLUSION

Sp1 was crucial in regulating CPT1A expression with GBE and its flavonoid ingredients, and the -50 to -5 nt region of CPT1A promoter played important roles in Sp1 binding.

Licochalcone A, a natural chalconoid isolated from Glycyrrhiza inflata root, induces apoptosis via Sp1 and Sp1 regulatory proteins in oral squamous cell carcinoma

Licochalcone A (LCA), a chalconoid derived from root of Glycyrrhiza inflata, has been known to possess a wide range of biological functions such as antitumor, anti-angiogenesis, antiparasitic, anti-oxidant, antibacterial and anti-inflammatory effects. However, the anticancer effects of LCA on oral squamous cell carcinoma (OSCC) have not been reported. Our data showed that LCA inhibited OSCC cell (HN22 and HSC4) growth in a concentration- and time-dependent manner. Mechanistically, it was mediated via downregulation of specificity protein 1 (Sp1) expression and subsequent regulation of Sp1 downstream proteins such as p27, p21, cyclin D1, Mcl-1 and survivin. Here, we found that LCA caused apoptotic cell death in HSC4 and HN22 cells, as characterized by sub-G1 population, nuclear condensation, Annexin V staining, and multi-caspase activity and apoptotic regulatory proteins such as Bax, Bid, Bcl(-xl), caspase-3 and PARP. Consequently, this study strongly suggests that LCA induces apoptotic cell death of OSCC cells via downregulation of Sp1 expression, prompting its potential use for the treatment of human OSCC.

The tetraspanin CD81 protein increases melanoma cell motility by up-regulating metalloproteinase MT1-MMP expression through the pro-oncogenic Akt-dependent Sp1 activation signaling pathways

Despite the importance of multiple tetraspanin proteins in cancer invasion and metastasis, little is known about the role and significance of tetraspanin CD81 in these processes. In the present study, we examined CD81 effects on melanoma cell invasiveness and metastasis. Transfection of CD81 into melanoma cells lacking endogenous CD81 expression significantly enhanced the migrating, invasive, and metastatic abilities of melanoma cells. Interestingly, membrane type 1 matrix metalloproteinase (MT1-MMP) expression was found in CD81-expressing melanoma cells but not in CD81-deficient cells. siRNA knockdown of CD81 in melanoma cells with endogenous CD81 demonstrated decreased MT1-MMP levels and cell motility. Notably, CD81-induced cell migration was abrogated by antibody blocking and siRNA knockdown of MT1-MMP, indicating that MT1-MMP is responsible for CD81-stimulated melanoma cell migration. Promoter analysis revealed an essential role of the Sp1 transcription factor in CD81-induced MT1-MMP transcription. We also demonstrate that the Sp1-activating Akt pathway is involved in adhesion-dependent CD81 signaling to induce MT1-MMP expression and cell motility. Importantly, human skin cancer tissue specimens displayed a positive correlation of CD81 with MT1-MMP expression levels and a close association of CD81 with malignant melanomas. Taken together, these results strongly suggest that CD81 stimulates melanoma cell motility by inducing MT1-MMP expression through the Akt-dependent Sp1 activation signaling pathway, leading to increased melanoma invasion and metastasis.

Hydrogen peroxide sensing, signaling and regulation of transcription factors

The regulatory mechanisms by which hydrogen peroxide (H₂O₂) modulates the activity of transcription factors in bacteria (OxyR and PerR), lower eukaryotes (Yap1, Maf1, Hsf1 and Msn2/4) and mammalian cells (AP-1, NRF2, CREB, HSF1, HIF-1, TP53, NF-κB, NOTCH, SP1 and SCREB-1) are reviewed. The complexity of regulatory networks increases throughout the phylogenetic tree, reaching a high level of complexity in mammalians. Multiple H₂O₂ sensors and pathways are triggered converging in the regulation of transcription factors at several levels: (1) synthesis of the transcription factor by upregulating transcription or increasing both mRNA stability and translation; (ii) stability of the transcription factor by decreasing its association with the ubiquitin E3 ligase complex or by inhibiting this complex; (iii) cytoplasm–nuclear traffic by exposing/masking nuclear localization signals, or by releasing the transcription factor from partners or from membrane anchors; and (iv) DNA binding and nuclear transactivation by modulating transcription factor affinity towards DNA, co-activators or repressors, and by targeting specific regions of chromatin to activate individual genes. We also discuss how H₂O₂ biological specificity results from diverse thiol protein sensors, with different reactivity of their sulfhydryl groups towards H₂O₂, being activated by different concentrations and times of exposure to H₂O₂. The specific regulation of local H₂O₂ concentrations is also crucial and results from H₂O₂ localized production and removal controlled by signals. Finally, we formulate equations to extract from typical experiments quantitative data concerning H₂O₂ reactivity with sensor molecules. Rate constants of 140 M⁻¹ s⁻¹ and ≥1.3 × 10³ M⁻¹ s⁻¹ were estimated, respectively, for the reaction of H₂O₂ with KEAP1 and with an unknown target that mediates NRF2 protein synthesis. In conclusion, the multitude of H₂O₂ targets and mechanisms provides an opportunity for highly specific effects on gene regulation that depend on the cell type and on signals received from the cellular microenvironment.

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Complexity of redox regulation increases along the phylogenetic tree.

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Complex regulatory networks allow for a high degree of H₂O₂ biological plasticity.

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H₂O₂ modulates gene expression at all steps from transcription to protein synthesis.

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Fast response (s) is mediated by sensors with high H₂O₂ reactivity.

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Low reactivity H₂O₂ sensors may mediate slow (h) or localized H₂O₂ responses.

Transcriptional profiles of Rel/NF-κB, inhibitor of NF-κB (IκB), and lipopolysaccharide-induced TNF-α factor (LITAF) in the lipopolysaccharide (LPS) and two Vibrio sp.-exposed intertidal copepod, Tigriopus japonicus

The immune system and the role of immunity-related genes have rarely been studied in copepods, even though copepods have a primitive immune response system and also have a potential in pathogen transport higher trophic levels. In this study, we firstly cloned and characterized three core immune genes such as nuclear factor κB (NF-κB), inhibitor of NF-κB (IκB), and lipopolysaccharide-induced TNF-α factor (LITAF) genes in the intertidal copepod Tigriopus japonicus. Several in silico analyses based on conserved domains, motifs, and phylogenetic relationships were supporting their annotations. To investigate the immune-related role of three genes, we exposed lipopolysaccharide (LPS) and two Vibrio sp. to T. japonicus. After exposure of different concentrations of LPS and two Vibrio sp., transcripts of TJ-IκB and TJ-LITAF genes were significantly elevated during the time course in a dose-dependent manner, while TJ-NF-κB transcripts were not significantly changed during exposure. These findings demonstrated that the copepod T. japonicus has a conserved immunity against infection.

Specificity protein 1 is a novel target of 2,4-bis (p-hydroxyphenyl)-2-butenal for the suppression of human oral squamous cell carcinoma cell growth

Background

The Maillard reaction is a chemical reaction occurring between a reducing sugar and an amino acid, generally requiring thermal processing. Maillard reaction products (MRPs) have antioxidant, antimutagenic, and antibacterial effects though 2,4-bis (p-hydroxyphenyl)-2-butenal (HPB242), a fructose-tyrosine MRP, appears to inhibit proliferation of cancer cells, its mechanism of action has not been studied in detail. The purpose of this study was to investigate the anti-proliferative effects of 2,4-bis (p-hydroxyphenyl)-2-butenal (HPB242) on two oral squamous cell carcinoma (OSCC) cell lines, HN22 and HSC4, through regulation of specificity protein 1 (Sp1).

Results

HPB242 treatment dramatically reduced the cell growth rate and apoptotic cell morphologies. Sp1 was significantly inhibited by HPB242 in a dose-dependent manner. Furthermore, cell cycle regulating proteins and anti-apoptotic proteins, which are known as Sp1 target genes, were altered at the molecular levels. The key important regulators in the cell cycle such as p27 were increased, whereas cell proliferation- and survival-related proteins such as cyclin D1, myeloid leukemia sequence 1 (Mcl-1) and survivin were significantly decreased by HPB242 or suppressed Sp1 levels, however pro-apoptotic proteins caspase3 and PARP were cleaved in HN22 and HSC4.

Conclusions

HPB242 may be useful as a chemotherapeutic agent for OSCC for the purpose of treatment and prevention of oral cancer and for the improvement of clinical outcomes.

Involvement of CRH and hCG in the induction of aromatase by cortisol in human placental syncytiotrophoblasts

INTRODUCTION

Increased estrogen production in placenta towards the end of gestation plays a pivotal role in the onset of human labor. Estrogen transforms myometrium from a quiescent to a contractile status. Glucocorticoids have been shown to induce estrogen production through the transcription factor specificity protein 1 (Sp1)-mediated induction of aromatase transcription upon elevation of cyclic adenosine mono-phosphate (cAMP) level in human placental syncytiotrophoblasts. However, it is unclear how glucocorticoids activate cAMP pathway thereby inducing aromatase expression in human placental syncytiotrophoblasts.

MATERIAL AND METHODS

We investigated this issue in cultured primary human placental syncytiotrophoblasts prepared from placentas collected at term without labor.

RESULTS

We demonstrated that cortisol (0.01-1 μM) dose-dependently increased corticotropin-releasing hormone (CRH) and human chorionic gonadotropin (hCG) α/β subunit expression and their production in the syncytiotrophoblasts. The induction of intracellular cAMP level, Sp1 expression, Sp1 enrichment at the aromatase promoter as well as aromatase expression by cortisol could be partially attenuated by either hCG antibody (1:100) or CRH receptor antagonist α-helical-CRH (1 μM), and further attenuated by combination of hCG antibody and α-helical-CRH.

CONCLUSIONS

Cortisol increases aromatase expression via induction of CRH and hCG production and subsequent elevation of cAMP level and enrichment of Sp1 at the aromatase promoter in human placental syncytiotrophoblasts. These findings may account for the parallel increases of cortisol and estrogen production prior to the onset of parturition.

ZASC1 stimulates HIV-1 transcription elongation by recruiting P-TEFb and TAT to the LTR promoter

Transcription from the HIV-1 LTR promoter efficiently initiates but rapidly terminates because of a non-processive form of RNA polymerase II. This premature termination is overcome by assembly of an HIV-1 TAT/P-TEFb complex at the transactivation response region (TAR), a structured RNA element encoded by the first 59 nt of HIV-1 mRNA. Here we have identified a conserved DNA-binding element for the cellular transcription factor, ZASC1, in the HIV-1 core promoter immediately upstream of TAR. We show that ZASC1 interacts with TAT and P-TEFb, co-operating with TAT to regulate HIV-1 gene expression, and promoting HIV-1 transcriptional elongation. The importance of ZASC1 to HIV-1 transcription elongation was confirmed through mutagenesis of the ZASC1 binding sites in the LTR promoter, shRNAs targeting ZASC1 and expression of dominant negative ZASC1. Chromatin immunoprecipitation analysis revealed that ZASC1 recruits Tat and P-TEFb to the HIV-1 core promoter in a TAR-independent manner. Thus, we have identified ZASC1 as novel regulator of HIV-1 gene expression that functions through the DNA-dependent, RNA-independent recruitment of TAT/P-TEFb to the HIV-1 promoter.

Adaptive regulation of human intestinal thiamine uptake by extracellular substrate level: a role for THTR-2 transcriptional regulation

The intestinal thiamine uptake process is adaptively regulated by the level of vitamin in the diet, but the molecular mechanism involved is not fully understood. Here we used the human intestinal epithelial Caco-2 cells exposed to different levels of extracellular thiamine to delineate the molecular mechanism involved. Our results showed that maintaining Caco-2 cells in a thiamine-deficient medium resulted in a specific and significant increase of [3H]thiamine uptake compared with cell exposure to a high level of thiamine (1 mM). This adaptive regulation was also associated with a higher level of mRNA expression of thiamine transporter-2 (THTR-2), but not thiamine transporter-1 (THTR-1), in the deficient condition and a higher level of promoter activity of gene encoding THTR-2 (SLC19A3). Using 5'-truncated promoter-luciferase constructs, we identified the thiamine level-responsive region in the SLC19A3 promoter to be between -77 and -29 (using transcriptional start site as +1). By means of mutational analysis, a key role for a stimulating protein-1 (SP1)/guanosine cytidine box in mediating the effect of extracellular thiamine level on SLC19A3 promoter was established. Furthermore, extracellular level of thiamine was found to affect SP1 protein expression and binding pattern to the thiamine level-responsive region of SLC19A3 promoter in Caco-2 cells as shown by Western blotting and electrophoretic mobility shift assay analysis, respectively. These studies demonstrate that the human intestinal thiamine uptake is adaptively regulated by the extracellular substrate level via transcriptional regulation of the THTR-2 system, and report that SP1 transcriptional factor is involved in this regulation.

Apoptotic effect of methanol extract of Picrasma quassioides by regulating specificity protein 1 in human cervical cancer cells

In the present study, we examined the effects of methanol extracts of Picrasma quassioides (MEPQ) on apoptosis in human cervical cancer cells. The results showed that MEPQ decreased the viability and induced caspase-dependent apoptosis in HEp-2 cells. MEPQ decreased specificity protein 1 (Sp1) in HEp-2 cells, whereas Sp1 mRNA was not changed. We found that MEPQ reduced Sp1 protein through proteasome-dependent protein degradation, but not the inhibition of protein synthesis. Also, MEPQ increased the expressions of Bad and truncated Bid (t-Bid) but did not alter other Bcl-2 family members. The knock-down of Sp1 by both Sp1 interfering RNA and Mithramycin A, Sp1 specific inhibitor clearly increased Bad and t-Bid expression to decrease cell viability and induce apoptosis. In addition, MEPQ inhibited cell viability and induced apoptotic cell death through the modulation of Sp1 in KB cells. These results suggest that MEPQ may be a potential anticancer agent for human cervical cancer.

Ethanol induces cell cycle arrest and triggers apoptosis via Sp1-dependent p75NTR expression in human neuroblastoma cells

Ethanol exposure has deleterious effects on the central nervous system. Although several mechanisms for ethanol-induced damage have been suggested, the precise mechanism underlying ethanol-induced neuronal cell death remains unclear. Recent studies indicate that the p75 neurotrophin receptor (p75NTR) has a critical role in the regulation of neuronal survival. This study was designed to examine the role of p75NTR in ethanol-induced apoptotic signaling in neuroblastoma cells. Ethanol caused highly increased level of p75NTR expression. The use of small interfering RNA to inhibit p75NTR expression markedly attenuated ethanol-induced cell cycle arrest and apoptosis. DNA binding activity of Sp1 was increased by ethanol, whereas inhibition of Sp1 activity by mithramycin, a Sp1 inhibitor, or short hairpin RNA suppressed ethanol-induced p75NTR expression. In addition, inhibitors of casein kinase 2 (CK2) and extracellular signal-regulated kinase (ERK) augmented ethanol-induced p75NTR expression. Our results also demonstrate that inhibition of ERK and CK2 caused a further increase in the activation of the p75NTR proximal promoter induced by ethanol. This increased activation was partially suppressed by the deletion of the Sp1 binding sites. These results suggest that Sp1-mediated p75NTR expression is regulated at least in part by ERK and CK2 pathways. The present study also showed that treatment with ethanol resulted in significant increases in the expression of p21, but not the levels of p53 and p53 target genes such as Bax, Puma, and Bcl-2. Furthermore, the inhibition of p75NTR expression or Sp1 activity suppressed ethanol-induced p21 expression, cell cycle arrest, and apoptosis. These data suggest that ethanol increases p75NTR expression, and CK2 and ERK signaling inversely regulate Sp1-mediated p75NTR expression in ethanol-treated neuroblastoma cells. Thus, our study provides more insight into the mechanisms underlying ethanol actions.

Antifibrotic effect of synthetic Smad/Sp1 chimeric decoy oligodeoxynucleotide through the regulation of epithelial mesenchymal transition in unilateral ureteral obstruction model of mice

Renal tubulointerstitial fibrosis is considered to be a common final pathway related to the progressive loss of renal function in chronic kidney disease. It is characterized by the excessive accumulation of extracellular matrix through the pivotal role of epithelial-mesenchymal transition. Transforming growth factor-β1 is postulated to play a central role in renal fibrosis via a downstream pathway such as Smad. Specificity protein 1 (Sp1), which is another transcription factor, is also involved in the basal expression of extracellular matrix. In this study, we investigate the effect of Smad decoy oligodeoxynucleotides (ODN) and Sp1 decoy ODN in unilateral ureteral obstruction induced renal fibrosis in mice. Furthermore, the effectiveness of the newly designed chimeric decoy ODN, which contains both Smad and Sp1 binding sequences in one decoy molecule (Smad/Sp1 chi decoy ODN), was demonstrated. The expression of fibrosis and inflammatory related cytokines and products of fibrosis were ameliorated in the Smad, Sp1 and chimeric decoy ODN treated groups compared with the scrambled decoy ODN treated group. Epithelial-mesenchymal transition was suppressed by the Smad, Sp1 and Smad/Sp1 chi decoy ODN. Immunohistochemistry and Western-blot analysis revealed that Smad/Sp1 chi decoy ODN showed a more significant inhibitory effect on fibrosis and EMT compared with Smad and Sp1 decoy ODNs. These results support the efficacy of Smad/Sp1 chi decoy compared with a single Smad or Sp1 decoy ODNs in preventing renal fibrosis induced by unilateral ureteral obstruction.

A248, a novel synthetic HDAC inhibitor, induces apoptosis through the inhibition of specificity protein 1 and its downstream proteins in human prostate cancer cells

Histone deacetylase (HDAC) inhibitors are emerging as potent anticancer agents due to their ability to induce apoptosis in various cancer cells, including prostate cancer cells. In the present study, we synthesized a novel HDAC inhibitor, A248, and investigated its apoptotic activity and molecular target in the DU145 and PC3 human prostate cancer cell lines. A248 inhibited the growth of DU145 and PC3 cells and induced apoptosis, as demonstrated by nuclear fragmentation and the accumulation of cells at subG1 phase of cell cycle. The treatment of DU145 and PC3 prostate cancer cells with A248 resulted in the downregulation of specificity protein 1 (Sp1) expression. Since the expression levels of survivin and Mcl-1 depend on Sp1, we also investigated the effects of A248 on survivin and Mcl-1 expression using western blot analysis and immunocytochemistry. The results showed that A248 markedly decreased the expression of survivin and Mcl-1. These data suggest that A248 has apoptotic activity in human prostate cancer cells and that Sp1 may be the molecular target of A248 treatment for inducing apoptosis in prostate cancer cells.

Novel insights into the synergistic interaction of a thioredoxin reductase inhibitor and TRAIL: the activation of the ASK1-ERK-Sp1 pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death in various types of cancer cells but has little or no effects on normal cells. Unfortunately, not all cancer cells respond to TRAIL; therefore, TRAIL sensitizing agents are currently being explored. Here, we reported that 6-(4-N,N-dimethylaminophenyltelluro)-6-deoxy-β-cyclodextrin (DTCD), a cyclodextrin-derived diorganyl telluride which has been identified as an excellent inhibitor of thioredoxin reductase (TrxR), could sensitize TRAIL resistant human ovarian cancer cells to undergo apoptosis. In vitro, DTCD enhanced TRAIL-induced cytotoxicity in human ovarian cancer cells through up-regulation of DR5. Luciferase analysis and CHIP assays showed that DTCD increased DR5 promoter activity via Sp1 activation. Additionally, DTCD stimulated extracellular signal-regulated kinase (ERK) activation, while the ERK inhibitor PD98059 blocked DTCD-induced DR5 expression and suppressed binding of Sp1 to the DR5 promoter. We further demonstrated that DTCD could induce the release of ASK1 from its complex with Trx-1, and recovered its kinase activity. Meanwhile, suppression of ASK1 by RNA interference led to decreased ERK phosphorylation induced by DTCD. The underlying mechanisms reveal that Trx-1 is heavily oxidized in response to DTCD treatment, in accordance with the fact that DTCD could inhibit the activity of TrxR that reduces oxidized Trx-1. Moreover, using an A2780 xenograft model, DTCD plus TRAIL significantly inhibited the growth of tumor in vivo. Our results suggest that Trx/TrxR system inhibition may play a critical role in apoptosis by combined treatment with DTCD and TRAIL, and raise the possibility that their combination may be a promising strategy for ovarian carcinoma treatment.

ORF50-dependent and ORF50-independent activation of the ORF45 gene of Kaposi's sarcoma-associated herpesvirus

The ORF45 gene of Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a multifunctional tegument protein. Here, we characterize the transcriptional control of the ORF45 gene and show that its promoter can be activated by ORF50 protein, a latent-lytic switch transactivator. The ORF45 promoter can also be induced by sodium butyrate (SB), a histone deacetylase inhibitor, in the absence of ORF50 protein. Although SB induces the ORF45 gene independently of ORF50, its full activation may require the presence of ORF50. Deletion and point mutation analyses revealed that two RBP-Jκ-binding sites in the ORF45 promoter confer the ORF50 responsiveness, whereas NF-Y and Sp1-binding sites mediate the response to SB. Direct binding of NF-Y, Sp1, or RBP-Jκ protein to the ORF45 promoter is required for the promoter activation induced by SB or by ORF50. In conclusion, our study demonstrates both ORF50-dependent and ORF50-independent transcriptional mechanisms operated on the activation of the ORF45 gene.

Downregulation of Sp1 is involved in honokiol-induced cell cycle arrest and apoptosis in human malignant pleural mesothelioma cells

Malignant pleural mesothelioma (MPM) is an extremely aggressive type of cancer and is associated with a poor patient prognosis due to its rapid progression. Novel therapeutic agents such as honokiol (HNK) improve the clinical outcomes of cancer therapy, yet the mechanisms involved have not been fully elucidated. The present study examined the regulatory effects of HNK on the growth and apoptosis of MSTO-211H mesothelioma cells and investigated its anticancer mechanism. The results revealed that HNK significantly reduced the cell viability and increased the sub-G1 population in MSTO-211H cells and suppressed the expression of the specificity protein 1 protein (Sp1). HNK reduced the transcriptional activity of Sp1 regulatory proteins, including cyclin D1, Mcl-1 and survivin, and, thus, induced apoptosis signaling pathways by increasing Bax, reducing Bid and Bcl-xl and activating caspase-3 and PARP in mesothelioma cells. The results suggest that Sp1, a novel molecular target of HNK, may be related to cell cycle arrest and apoptosis induction through the modulation of signal transduction pathways in MPM.

CRABP2 promotes myoblast differentiation and is modulated by the transcription factors MyoD and Sp1 in C2C12 cells

Cellular retinoic acid binding protein 2 (CRABP2), a member of a family of specific carrier proteins for Vitamin A, belongs to a family of small cytosolic lipid binding proteins. Our previous study suggested that CRABP2 was involved in skeletal muscle development; however, the molecular function and regulatory mechanism of CRABP2 in myogenesis remained unclear. In this study, we found that the expression of the CRABP2 gene was upregulated during C2C12 differentiation. An over-expression assay revealed that CRABP2 promotes myogenic transformation by regulating the cell cycle during C2C12 differentiation. The region from -459 to -4 bp was identified as the core promoter and contains a TATA box, a GC box and binding sites for the transcription factors MyoD and Sp1. Over-expression, site-directed mutagenesis and EMSA assays indicated that the transcription factors MyoD and Sp1 regulate CRABP2 expression and promote myoblast differentiation in C2C12 cells.