AMPK-SP1-Guided Dynein Expression Represents a New Energy-Responsive Mechanism and Therapeutic Target for Diabetic Nephropathy

Key Points

AMP kinase senses diabetic stresses in podocytes, subsequently upregulates specificity protein 1–mediated dynein expression and promotes podocyte injury. Pharmaceutical restoration of dynein expression by targeting specificity protein 1 represents an innovative therapeutic strategy for diabetic nephropathy.

Background

Diabetic nephropathy (DN) is a major complication of diabetes. Injury to podocytes, epithelial cells that form the molecular sieve of a kidney, is a preclinical feature of DN. Protein trafficking mediated by dynein, a motor protein complex, is a newly recognized pathophysiology of diabetic podocytopathy and is believed to be derived from the hyperglycemia-induced expression of subunits crucial for the transportation activity of the dynein complex. However, the mechanism underlying this transcriptional signature remains unknown.

Methods

Through promoter analysis, we identified binding sites for transcription factor specificity protein 1 (SP1) as the most shared motif among hyperglycemia-responsive dynein genes. We demonstrated the essential role of AMP-activated protein kinase (AMPK)–regulated SP1 in the transcription of dynein subunits and dynein-mediated trafficking in diabetic podocytopathy using chromatin immunoprecipitation quantitative PCR and live cell imaging. SP1-dependent dynein-driven pathogenesis of diabetic podocytopathy was demonstrated by pharmaceutical intervention with SP1 in a mouse model of streptozotocin-induced diabetes.

Results

Hyperglycemic conditions enhance SP1 binding to dynein promoters, promoted dynein expression, and enhanced dynein-mediated mistrafficking in cultured podocytes. These changes can be rescued by chemical inhibition or genetic silencing of SP1. The direct repression of AMPK, an energy sensor, replicates hyperglycemia-induced dynein expression by activating SP1. Mithramycin inhibition of SP1-directed dynein expression in streptozotocin-induced diabetic mice protected them from developing podocytopathy and prevented DN progression.

Conclusions

Our work implicates AMPK-SP1–regulated dynein expression as an early mechanism that translates energy disturbances in diabetes into podocyte dysfunction. Pharmaceutical restoration of dynein expression by targeting SP1 offers a new therapeutic strategy to prevent DN.

Identification of TMZ resistance-associated histone post-translational modifications in glioblastoma using multi-omics data

BACKGROUD

Glioblastoma multiforme (GBM) is among the most aggressive cancers, with current treatments limited in efficacy. A significant hurdle in the treatment of GBM is the resistance to the chemotherapeutic agent temozolomide (TMZ). The methylation status of the MGMT promoter has been implicated as a critical biomarker of response to TMZ.

METHODS

To explore the mechanisms underlying resistance, we developed two TMZ-resistant GBM cell lines through a gradual increase in TMZ exposure. Transcriptome sequencing of TMZ-resistant cell lines revealed that alterations in histone post-translational modifications might be instrumental in conferring TMZ resistance. Subsequently, multi-omics analysis suggests a strong association between histone H3 lysine 9 acetylation (H3K9ac) levels and TMZ resistance.

RESULTS

We observed a significant correlation between the expression of H3K9ac and MGMT, particularly in the unmethylated MGMT promoter samples. More importantly, our findings suggest that H3K9ac may enhance MGMT transcription by facilitating the recruitment of the SP1 transcription factor to the MGMT transcription factor binding site. Additionally, by analyzing single-cell transcriptomics data from matched primary and recurrent GBM tumors treated with TMZ, we modeled the molecular shifts occurring upon tumor recurrence. We also noted a reduction in tumor stem cell characteristics, accompanied by an increase in H3K9ac, SP1, and MGMT levels, underscoring the potential role of H3K9ac in tumor relapse following TMZ therapy.

CONCLUSIONS

The increase in H3K9ac appears to enhance the recruitment of the transcription factor SP1 to its binding sites within the MGMT locus, consequently upregulating MGMT expression and driving TMZ resistance in GBM.

SP1-stimulated miR-208a-5p aggravates sepsis-induced myocardial injury via targeting XIAP

The development of sepsis can lead to many organ dysfunction and even death. Myocardial injury is one of the serious complications of sepsis leading to death. New evidence suggests that microRNAs (miRNAs) play a critical role in infection myocardial injury. However, the mechanism which miR-208a-5p regulates sepsis-induced myocardial injury remains unclear. To mimic sepsis-induced myocardial injury in vitro, rat primary cardiomyocytes were treated with LPS. Cell viability and apoptosis were tested by CCK-8 and flow cytometry, respectively. The secretion of inflammatory factors was analyzed by ELISA. mRNA and protein levels were detected by RT-qPCR and Western blotting. The interaction among SP1, XIAP and miR-208a-5p was detected using dual luciferase report assay. Ultrasonic analysis and HE staining was performed to observe the effect of miR-208a-5p in sepsis-induced rats. Our findings indicated that miR-208a-5p expression in primary rat cardiomyocytes was increased by LPS. MiR-208a-5p inhibitor reversed LPS-induced cardiomyocytes injury through inhibiting the apoptosis. Furthermore, the inflammatory injury in cardiomyocytes was induced by LPS, which was rescued by miR-208a-5p inhibitor. In addition, downregulation of miR-208a-5p improved LPS-induced sepsis myocardial injury in vivo. Mechanistically, XIAP might be a target gene of miR-208a-5p. SP1 promoted transcription of miR-208a by binding to the miR-208a promoter region. Moreover, silencing of XIAP reversed the regulatory of miR-208a-5p inhibitor on cardiomyocytes injury. To sum up, those findings revealed silencing of miR-208a-5p could alleviate sepsis-induced myocardial injury, which would grant a new process for the treatment of sepsis.

P300/SP1 complex mediating elevated METTL1 regulates CDK14 mRNA stability via internal m7G modification in CRPC

BACKGROUND

N7-methylguanosine (m7G) modification is, a more common epigenetic modification in addition to m6A modification, mainly found in mRNA capsids, mRNA interiors, transfer RNA (tRNA), pri-miRNA, and ribosomal RNA (rRNA). It has been found that m7G modifications play an important role in mRNA transcription, tRNA stability, rRNA processing maturation, and miRNA biosynthesis. However, the role of m7G modifications within mRNA and its "writer" methyltransferase 1(METTL1) in tumors, particularly prostate cancer (PCa), has not been revealed.

METHODS

The differential expression level of METTL1 between hormone-sensitive prostate cancer (HSPC) and castrate-resistant prostate cancer (CRPC) was evaluated via RNA-seq and in vitro experiments. The effects of METTL1 on CRPC progression were investigated through in vitro and in vivo assays. The upstream molecular mechanism of METTL1 expression upregulation and the downstream mechanism of its action were explored via Chromatin Immunoprecipitation quantitative reverse transcription polymerase chain reaction (CHIP-qPCR), Co-immunoprecipitation (Co-IP), luciferase reporter assay, transcriptome-sequencing, m7G AlkAniline-Seq, and mRNA degradation experiments, etc. RESULTS AND CONCLUSION: Here, we found that METTL1 was elevated in CRPC and that patients with METTL1 elevation tended to have a poor prognosis. Functionally, the knockdown of METTL1 in CRPC cells significantly limited cell proliferation and invasive capacity. Mechanistically, we unveiled that P300 can form a complex with SP1 and bind to the promoter region of the METTL1 gene via SP1, thereby mediating METTL1 transcriptional upregulation in CRPC. Subsequently, our findings indicated that METTL1 leads to enhanced mRNA stability of CDK14 by adding m7G modifications inside its mRNA, ultimately promoting CRPC progression.

A novel EHD1/CD44/Hippo/SP1 positive feedback loop potentiates stemness and metastasis in lung adenocarcinoma

BACKGROUND

There is growing evidence that endocytosis plays a pivotal role in cancer metastasis. In this study, we first identified endocytic and metastasis-associated genes (EMGs) and then investigated the biological functions and mechanisms of EMGs.

METHODS

Cancer stem cells (CSCs)-like characteristics were evaluated by tumour limiting dilution assays, three-dimensional (3D) spheroid cancer models. Microarray analysis was used to identify the pathways significantly regulated by mammalian Eps15 homology domain protein 1 (EHD1) knockdown. Mass spectrometry (MS) was performed to identify EHD1-interacting proteins. The function of EHD1 as a regulator of cluster of differentiation 44 (CD44) endocytic recycling and lysosomal degradation was determined by CD44 biotinylation and recycling assays.

RESULTS

EHD1 was identified as a significant EMG. Knockdown of EHD1 suppressed CSCs-like characteristics, epithelial-mesenchymal transition (EMT), migration and invasion of lung adenocarcinoma (LUAD) cells by increasing Hippo kinase cascade activation. Conversely, EHD1 overexpression inhibited the Hippo pathway to promote cancer stemness and metastasis. Notably, utilising MS analysis, the CD44 protein was identified as a potential binding partner of EHD1. Furthermore, EHD1 enhanced CD44 recycling and stability. Indeed, silencing of CD44 or disruption of the EHD1/CD44 interaction enhanced Hippo pathway activity and reduced CSCs-like traits, EMT and metastasis. Interestingly, specificity protein 1 (SP1), a known downstream target gene of the Hippo-TEA-domain family members 1 (TEAD1) pathway, was found to directly bind to the EHD1 promoter region and induce its expression. Among clinical specimens, the EHD1 expression level in LUAD tissues of metastatic patients was higher than that of non-metastatic patients.

CONCLUSIONS

Our findings emphasise that EHD1 might be a potent anti-metastatic target and present a novel regulatory mechanism by which the EHD1/CD44/Hippo/SP1 positive feedback circuit plays pivotal roles in coupling modules of CSCs-like properties and EMT in LUAD. Targeting this loop may serve as a remedy for patients with advanced metastatic LUAD.

[Analysis of clinical indications of acupoint Yinbai (SP1) and its compatible regularities based on data mining technology]

OBJECTIVE

To explore the dominant indications and laws of acupoint compatibility of Yinbai (SP1) by using modern statistics and data mining techniques.

METHODS

Literature about indications and acupoint prescriptions of SP1 published before October of 1949 were retrieved from books Chinese Medical Dictionary (5th edition) and Collection of Modern Medical Journals of Traditional Chinese Medicine, and those published from October 1st of 1949 to January of 2021 retrieved from databa-ses of CNKI, Wanfang, VIP, CBM, Web of Science and Pubmed by using key words of Yinbai (SP1),"Guilei"(),"Guiyan"() and Jing (Well)-point of Spleen Meridian, followed by screening the data and establishing a SQL Server database after standardized processing. Then, the descriptive analysis, clustering analysis and association rule analysis were conducted by using Gephi visualization software, SPSS Statistics 25.0 and SPSS Modeler, separately.

RESULTS

Before October of 1949, the single SP1 acupoint was usually used to treat 12 types of diseases (mainly the internal diseases as asthma, abdominal distension, vomiting, etc.), and the compound prescriptions of SP1 were usually used to treat 20 types of diseases (mainly the internal diseases as insomnia and dreamful sleep, blood syndrome, etc.), and its adjunct acupoints belong to the first three meridians: the Foot Yangming Stomach Meridian, Foot Taiyang Bladder Meridian and Foot Taiyin Spleen Meridian. After October of 1949, the single SP1 was used to dominantly treat 2 types of diseases (mainly the gynecological diseases as metrorrhagia and metrostaxis, and hypermenorrhea, etc.), and the compound prescriptions of SP1 were frequently used to treat 10 diseases (metrorrhagia and metrostaxis, sequela of apoplexy, mental disorders, insomnia and dreamful sleep, etc.), and the adjunct acupoints of compound prescriptions belong to the first three meridians, namely the Foot Taiyin Spleen Meridian, Concept Vessel and Foot Yangming Stomach Meridian. Before and after October of 1949, the adjunct acupoints with the highest degree of correlation were Lidui (ST45), Shaoshang(LU11), Zusanli(ST36), Sanyinjiao (SP9), and Guanyuan (CV4). Cluster analysis showed that 9 effective clusters obtained may be used as potential prescriptions of SP1, and association rule analysis displayed that the first three strongly connected acupoint matching groups were: SP1-ST45, SP1-LU11, and SP1-ST36 frequently used before October of 1949, and SP1-SP9, SP1-ST36 and SP1-CV4 employed after October of 1949.

CONCLUSION

Data mining technology reveals that acupoint SP1 alone is mainly used to treat internal diseases before 1949, and gynecological diseases after 1949; and compound acupoint recipes of SP1 are mainly to treat the internal diseases before 1949, and the gynecological diseases and mental disorders after 1949 in China. The frequently employed adjunct acupoints of SP1 are ST45, LU11, ST36, SP9 and CV4 both before and after 1949.

Inhibitory effect of strawberry geranium (Saxifraga stolonifera) on Toll-like receptor 2-mediated inflammatory response in human skin keratinocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Strawberry geranium (Saxifraga stolonifera [L.] Meeb) has traditionally been used as a drug to treat skin disorders in Japan. However, little is known about its physiological effects on skin keratinocytes.

AIM OF THE STUDY

We investigated the anti-inflammatory effects of a strawberry geranium extract (SGE) on human skin keratinocytes.

MATERIALS AND METHODS

The human keratinocyte cell line, HaCaT, was treated with SGE, and then stimulated with tumor necrosis factor (TNF)-α. The expression of 207 genes related to the innate immune system was analyzed using DNA microarrays. The effect of SGE on the target proteins in primary human epidermal keratinocytes was confirmed by quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. The mechanisms of action and active components involved in the suppressive effect of SGE were evaluated by fractionation and a transcription assay.

RESULTS

The microarray analysis revealed that SGE primarily suppressed Toll-like receptor (TLR)2 expression through procyanidin B2 3,3'-di-O-gallate, without TLR2 downregulation, in TNF-α-stimulated HaCaT cells. SGE suppressed TLR2 expression and interleukin (IL)-8 production induced by TLR2 ligands in primary human epidermal keratinocytes and HaCaT cells. Multiple components downregulating TLR2 expression suppressed the Sp1 activity.

CONCLUSIONS

We identified a novel physiological function of SGE, which suppresses TLR2 expression and TLR2-mediated inflammation in human skin keratinocytes. This study provides significant insights into the anti-inflammatory effect of SGE in human skin.

The function of BAP18 on modulation of androgen receptor action in luteinized granulosa cells from normal weight women with and without PCOS

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in reproductive-age women. In this study, BPTF associated protein of 18 kDa (BAP18) is decreased in luteinized granulosa cells (GCs) from PCOS women. BAP18 depletion significantly decreases CYP19A1 expression levels, leading to an abrogation in transfer capacity of androgen to estrogen in GCs. Also, BAP18 knockdown delays cell cycle G1 to S phase transition and induces cell apoptosis to decrease GCs proliferation. We also provide evidence showing BAP18 interacts with androgen receptor (AR) and enhances AR-mediated transactivation in GCs. Results indicate that AR or BAP18 recruits to androgen response elements (AREs) of CYP19A1 and FSHR, which are putative AR-induced genes in GCs. BAP18 interacts with Sp1 transcription factor and co-recruits to the promoter region of AR gene, resulting in AR transactivation in GCs. Taken together, these data provide new insights on the pathophysiology of PCOS.

Natural killer cells contributed to recurrent miscarriage by SP1-CASP3-PARP1

Recurrent miscarriage (RM) is an early pregnancy complication. Natural Killer cells are an important part of the innate immune system of endometrial. In this study, weighted gene correlation network analysis was used to study the expression profile data of the endometrial tissue of patients with recurrent miscarriage and selected brown module as key module positively related to the numbers of miscarriages. With metascape tool, natural killer cells mediated cytotoxicity related genes, such as CASP3, were selected. DisNor database showed that CASP3 down-regulates PARP1. According to TRRUST database, CASP3 was regulated by SP1. Through comprehensive analysis of uNK cell related genes, we proposed that natural killer cells contribute to recurrent miscarriage by SP1-CASP3-PARP1.

Abnormal nitration and S-sulfhydration modification of Sp1-CSE-H2S pathway trap the progress of hyperhomocysteinemia into a vicious cycle

Sp1-CSE-H2S pathway plays an important role in homocysteine-metabolism, whose disorder can result in hyperhomocysteinemia. H2S deficiency in hyperhomocysteinemia has been reported, while the underlying mechanism and whether it in turn affects the progress of hyperhomocysteinemia are unclear. This study focused on the post-translational modification of Sp1/CSE and revealed four major findings: (1) Homocysteine-accumulation augmented CSE's nitration, inhibited its bio-activity, thus caused H2S deficiency. (2) H2S deficiency inhibited the S-sulfhydration of Sp1, down-regulated CSE and decreased H2S further, which in turn weakened CSE's own S-sulfhydration. (3) CSE was S-sulfhydrated at Cys84, Cys109, Cys172, Cys229, Cys252, Cys307 and Cys310, among which the S-sulfhydration of Cys172 and Cys310 didn't affect its enzymatic activity, while the S-sulfhydration of Cys84, Cys109, Cys229, Cys252 and Cys307 was necessary for its bio-activity. (4) H2S deficiency trapped homocysteine-metabolism into a vicious cycle, which could be broken by either blocking nitration or restoring S-sulfhydration. This study detected a new mechanism that caused severe hyperhomocysteinemia, thereby provided new therapeutic strategies for hyperhomocysteinemia.

Matrix stiffness induces a tumorigenic phenotype in mammary epithelium through changes in chromatin accessibility

In breast cancer, the increased stiffness of the extracellular matrix is a key driver of malignancy. Yet little is known about the epigenomic changes that underlie the tumorigenic impact of extracellular matrix mechanics. Here, we show in a three-dimensional culture model of breast cancer that stiff extracellular matrix induces a tumorigenic phenotype through changes in chromatin state. We found that increased stiffness yielded cells with more wrinkled nuclei and with increased lamina-associated chromatin, that cells cultured in stiff matrices displayed more accessible chromatin sites, which exhibited footprints of Sp1 binding, and that this transcription factor acts along with the histone deacetylases 3 and 8 to regulate the induction of stiffness-mediated tumorigenicity. Just as cell culture on soft environments or in them rather than on tissue-culture plastic better recapitulates the acinar morphology observed in mammary epithelium in vivo, mammary epithelial cells cultured on soft microenvironments or in them also more closely replicate the in vivo chromatin state. Our results emphasize the importance of culture conditions for epigenomic studies, and reveal that chromatin state is a critical mediator of mechanotransduction.

[Activity and transcriptional regulatory elements of the promoter in Arctic fox (Vulpes lagopus) β-defensin103 gene]

The aim of this study was to screen the active regions and transcription factor binding sites in the promoter of the CBD103 gene related to Arctic fox coat color, and to provide a basis for revealing the molecular genetic mechanism of CBD103 gene regulating the coat color formation. The 5'-flanking region fragment 2 123 bp of Arctic fox CBD103 gene was cloned, and 4 truncated promoter reporter vectors of different lengths were constructed. The promoter activity was detected by the dual-luciferase reporter assay system. Point mutations were performed on the 3 predicted specificity protein 1 (Sp1) transcription factor binding sites in the highest promoter active region, and 3 mutant vectors were constructed. The activity was then detected by the dual-luciferase reporter assay system. The results showed that the region 1 656 (-1 604/+51) had the highest activity in the 4 truncated promoters of different lengths, and the promoter activity of the three mutant vectors constructed in this region were significantly lower than that of the wild type (fragment 1 656). The region of -1 604 /+51 was the core promoter region of CBD103 gene in Arctic fox and -1 552/-1 564, -1 439/-1 454 and -329/-339 regions were positive regulatory regions. This study successfully obtained the core promoter region and positive regulation regions of the Arctic fox CBD103 gene, which laid a foundation for further study on the molecular genetic mechanism of this gene regulating Arctic fox coat color.

SP1-induced lncRNA TINCR overexpression contributes to colorectal cancer progression by sponging miR-7-5p

Mounting evidences have indicated that long noncoding RNAs (lncRNAs) play pivotal roles in human diseases, especially in cancers. Recently, TINCR was proposed to be involved in tumor progression. However, its role in colorectal cancer (CRC) remains elusive. In our study, we found that SP1-induced TINCR was significantly upregulated in CRC tissues and cell lines. Moreover, cox multivariate survival analysis revealed that high TINCR was an independent predictor of poor overall survival (OS). Functionally, knockdown of TINCR obviously suppressed CRC cells proliferation, migration and invasion in vitro, and inhibited CRC cells growth and metastasis in vivo. Mechanistically, we identified TINCR could act as a miR-7-5p sponge using RNA pull down, luciferase reporter and RIP assays. Furthermore, we showed that TINCR might promote CRC progression via miR-7-5p-mediated PI3K/Akt/mTOR signaling pathway. Lastly, we revealed that plasma TINCR expression was upregulated in CRC when compared to healthy controls and could be a promising diagnostic biomarker for CRC. Based on above results, our data indicated that TINCR might serve as a potential diagnostic and prognostic biomarker for CRC.

miR29b regulates aberrant methylation in In-Vitro diabetic nephropathy model of renal proximal tubular cells

The role of DNA methylation has not been enough explored in pathophysiology of diabetic nephropathy (DN). However, according to recent reports it has been inferred that hypermethylation could be one of the principle cause associated with the enhancement of DN. An interrelationship between miR29b and DNA methylation has been studied via in-silico analysis. We have validated that miR29b prominently targets DNA methyl transferase (DNMT), specifically DNMT1, DNMT3A and DNMT3B. We have developed in vitro DN model using renal proximal tubule epithelial cells (RPTECs), contributed to a significant alleviation in RNA and protein expression levels of DNMT3A, DNMT3B and DNMT1. The developed model has also demonstrated downregulation in expression of miR29b. Our studies have also suggested that miR29b targets DNMT1 via targeting its transcription factor SP1. In addition to this, downregulation of a specific biomarker for kidney injury, tubular kidney injury molecule-1 (KIM-1) and fibrosis causing glycoprotein i.e. fibronectin, was also demonstrated. Hence, the developed model revealed that hypermethylation is a key factor incorporated in DN, and miR29b could effectively ameliorate defensive actions in DN pathogenesis.

Specificity protein 1: Its role in colorectal cancer progression and metastasis

Specificity protein 1 (Sp1) is a widely expressed transcription factor that plays an important role in the promotion of oncogenes required for tumor survival, progression and metastasis. Sp1 is highly expressed in several cancers including colorectal cancer (CRC) and is related to poor prognosis. Therefore, targeting Sp1 is a rational for CRC therapy. In this review, we will recapitulate the current understanding of Sp1 signaling, its molecular mechanisms, and its potential involvement in CRC growth, progression and metastasis. We will also discuss the current therapeutic drugs for CRC and their mechanism of action via Sp1.

[Effects of Sp1 on the basic transcriptional activity of intestinal trefoil factor promoter]

OBJECTIVE

To explore response element that maintains basic transcriptional activity of intestinal trefoil factor (ITF) promoter.

METHODS

Truncated and mutant 5' flanking sequences of ITF gene were cloned from ITF promoter sequences by PCR, and then they were inserted into the pGL3-basic vector to construct truncated and mutant luciferase vectors to conduct the following experiments. (1) Human embryonic kidney 293 (HEK293) cells were divided into pGL3-basic group, pGL3-300 group, pGL3-280 group, pGL3-260 group, pGL3-240 group, pGL3-220 group, and pGL3-200 group according to the random number table (the same grouping method below), with 3 wells in each group, and they were respectively transfected with 500 ng corresponding plasmids and 15 ng renilla luciferase reporter plasmids pRL-TK. After being cultured for 48 hours, the relative luciferase activity of cells was measured by single tube detection system. (2) Another batch of HEK293 cells were divided into pGL3-basic group, pGL3-300 group, mutant 1, 2, 3, and 4 groups, with 3 wells in each group, and they were respectively transfected with 500 ng pGL3-basic, pGL3-300, mutant 1, 2, 3, and 4 plasmids and 15 ng pRL-TK plasmids. After being cultured for 48 hours, the relative luciferase activity of cells was measured as in (1). (3) Another batch of HEK293 cells were divided into blank control group and 10, 50 μmol/L mithramycin groups, with 3 wells in each group. After being transfected with 500 ng pGL3-300 plasmids and 15 ng pRL-TK plasmids, cells in blank control group were not transfected with mithramycin, while cells in the latter two groups were respectively transfected with 10 and 50 μmol/L mithramycin. After being cultured for 24 hours, the relative luciferase activity of cells was measured as in (1). (4) Another batch of HEK293 cells were divided into blank control group and 0.1, 0.2, and 0.3 μg pcDNA3.1-Sp1 groups, with 3 wells in each group. After being transfected with 500 ng pGL3-300 plasmids and 15 ng pRL-TK plasmids, cells in blank control group were not transfected with pcDNA3.1-Sp1 plasmids, while cells in the latter three groups were respectively transfected with 0.1, 0.2, and 0.3 μg pcDNA3.1-Sp1 plasmids. After being cultured for 48 hours, the relative luciferase activity of cells was measured as in (1). Data were processed with one-way analysis of variance and LSD test.

RESULTS

(1) The relative luciferase activity of cells in pGL3-basic group, pGL3-300 group, pGL3-280 group, pGL3-260 group, pGL3-240 group, pGL3-220 group, and pGL3-200 group was 1.00, 7.99±0.51, 2.03±0.55, 2.50±0.40, 2.50±0.15, 1.72±0.19 and 2.10±0.21, respectively. The relative luciferase activity of cells in pGL3-280 group, pGL3-260 group, pGL3-240 group, pGL3-220 group, and pGL3-200 group was significantly lower than that in pGL3-300 group (with P values below 0.01). (2) The relative luciferase activity of cells in pGL3-basic group, pGL3-300 group, mutant 1, 2, 3, and 4 groups was 1.00, 7.99±0.51, 2.10±0.56, 7.03±1.05, 5.09±1.40 and 8.15±1.48, respectively. The relative luciferase activity of cells in mutant 1 group was significantly lower than that in pGL3-300 group (P<0.01). The relative luciferase activity of cells in pGL3-300 group, mutant 2, 3, and 4 groups was similar (with P values above 0.05). (3) The relative luciferase activity of cells in 10 and 50 μmol/L mithramycin groups was respectively 3.07±0.60 and 2.93±0.55, which was significantly lower than that in blank control group (8.05±0.83, with P values below 0.01). (4) The relative luciferase activity of cells in 0.1, 0.2, and 0.3 μg pcDNA3.1-Sp1 groups was respectively 12.74±1.12, 14.52±1.25, and 15.66±1.82, which was significantly higher than that in blank control group (8.13±0.71, with P values below 0.05).

CONCLUSIONS

One Sp1 binding site, locating in the region from -301 to -293 bp of ITF promoter, is the core element for regulating the basic transcriptional activity of ITF.

Analysis of Response Elements Involved in the Regulation of the Human Neonatal Fc Receptor Gene (FCGRT)

Human epithelial, endothelial and PMA-differentiated THP-1 cell lines were used as model systems to study the transcriptional regulation of the human FCGRT gene encoding the alpha chain of hFcRn. The data obtained from site-directed mutagenesis in transient transfection experiments indicate that the Sp1 sites at positions -641, -635, and -313, CF1/YY1 elements at positions -586 and -357, and the AP-1 motif at -276 within the-660/-233 fragment of the human FCGRT promoter (hFCGRT) participate in the regulation of human FCGRT in all selected cell lines. However, their individual contribution to promoter activity is not equivalent. The Sp1 binding site at -313 and the AP-1 site at -276 are critical for the activity of the hFCGRT promoter in epithelial and endothelial cells. Moreover, the CF1/YY1 site at -586 in differentiated THP-1 cells, plays an essential role in the transcriptional activity of the promoter. In addition, the C/EBPbeta binding site at -497 of the hFCGRT promoter in epithelial and endothelial cells, and the C/EBPbeta motif located at -497 and -233 within the hFCGRT promoter in differentiated THP-1 cells may function as positive regulatory sequences in response to LPS or PMA stimulation. EMSA and supershift analyses showed that the functionally identified binding motifs in the hFCGRT promoter were able to specifically interact with their corresponding (Sp1, Sp2, Sp3, c-Fos, c-Jun, YY1, and C/EBPbeta or C/EBPdelta) transcription factors (TFs), suggesting their possible involvement in the regulation of the human FCGRT gene expression.

HDAC1 inactivation induces mitotic defect and caspase-independent autophagic cell death in liver cancer

Histone deacetylases (HDACs) are known to play a central role in the regulation of several cellular properties interlinked with the development and progression of cancer. Recently, HDAC1 has been reported to be overexpressed in hepatocellular carcinoma (HCC), but its biological roles in hepatocarcinogenesis remain to be elucidated. In this study, we demonstrated overexpression of HDAC1 in a subset of human HCCs and liver cancer cell lines. HDAC1 inactivation resulted in regression of tumor cell growth and activation of caspase-independent autophagic cell death, via LC3B-II activation pathway in Hep3B cells. In cell cycle regulation, HDAC1 inactivation selectively induced both p21^WAF1/Cip1 and p27^Kip1 expressions, and simultaneously suppressed the expression of cyclin D1 and CDK2. Consequently, HDAC1 inactivation led to the hypophosphorylation of pRb in G1/S transition, and thereby inactivated E2F/DP1 transcription activity. In addition, we demonstrated that HDAC1 suppresses p21^WAF1/Cip1 transcriptional activity through Sp1-binding sites in the p21^WAF1/Cip1 promoter. Furthermore, sustained suppression of HDAC1 attenuated in vitro colony formation and in vivo tumor growth in a mouse xenograft model. Taken together, we suggest the aberrant regulation of HDAC1 in HCC and its epigenetic regulation of gene transcription of autophagy and cell cycle components. Overexpression of HDAC1 may play a pivotal role through the systemic regulation of mitotic effectors in the development of HCC, providing a particularly relevant potential target in cancer therapy.

Expression of Sp1 and KLF6 in the developing human cornea

PURPOSE

To examine the temporal and spatial expression of Sp1 and Krüppel-like factor 6 (KLF6) in the cornea in fetal and adult human eyes.

METHODS

Eyes from human fetus (F) of 7, 9, 10, 11, 13, and 27 weeks (w) of gestation, as well as corneas from 11 and 56-day (d)-old children and donors 2, 6, 16, 25, 40, 51, 69, and 83 years (y) of age were obtained. All specimens were fixed in 10% buffered formalin, processed for paraffin sections, and examined for Sp1 and KLF6 expression immunohistochemically.

RESULTS

Staining for Sp1 was evident at the earliest F7w time point in the cornea. From F7w to F27w, the moderate to strong Sp1 immunostaining was seen in the nuclei of epithelial and endothelial cells. Staining in keratocytes was also observed. The intensity of Sp1 staining in all layers of the cornea was substantially decreased 11d after birth and remained low thereafter. Positive KLF6 staining was also noted at F7w in all corneal layers. In the epithelium and endothelium, the staining was mostly cytoplasmic throughout the fetal stages. After birth, the KLF6 staining appeared in the nuclei of corneal epithelial cells along with that in the cytoplasm. The intensity of KLF6 staining in the epithelium and endothelium remained relatively constant from E47d to the 83y-old donor cornea. The KLF6 staining in the stroma however was reduced after F27w.

CONCLUSIONS

The present study indicates that the expression of Sp1 and KLF6 is developmentally regulated, providing a basis for further investigations on the regulation of the Sp1 and KLF6 gene during the course of corneal development and in corneal diseases such as keratoconus.

Human Krüppel-like factor 11 inhibits human proinsulin promoter activity in pancreatic beta cells

AIMS/HYPOTHESIS

The Krüppel-like factor 11 (KLF11; TIEG2), a pancreas-enriched Sp1-like transcription factor, is a known negative regulator of pancreatic exocrine cell growth. A recent study indicated KLF11-induced activation of the human proinsulin promoter (hInsP).

MATERIALS AND METHODS

We investigated the functional role of KLF11 in pancreatic beta cells.

RESULTS

Endogenous KLF11 mRNA expression was found in whole rat pancreas, human pancreatic islets and INS-1E beta cells and was profoundly reduced by high glucose in INS-1E. Cotransfections of INS-1E and beta-TC3 beta cells with a human (h)KLF11 expression plasmid and an hInsP-driven reporter plasmid resulted in a substantial dose-dependent and glucose-independent inhibition of proinsulin promoter activity. 5'-deletion of hInsP demonstrated that hKLF11 acts via DNA sequences upstream of -173 and requires the beta cell-specific transcription machinery, since hKLF11-mediated inhibition of promoter activity was abolished in HEK293 cells. Besides a previously described GC box, we further identified a CACCC box within the hInsP, both putative KLF11-binding motifs. Electrophoretic mobility shift analysis (EMSA) verified binding of in vitro translated hKLF11 to the GC box, but neither hKLF11-induced inhibition nor basal hInsP activity was altered by mutation or 5'-deletion of the GC box. In contrast, CACCC box mutation substantially reduced basal promoter activity and partially diminished hKLF11 inhibition, although binding of in vitro translated hKLF11 to the CACCC box could not be verified by EMSA.

CONCLUSIONS/INTERPRETATION

In rodent beta cell lines, we demonstrate hKLF11overexpression-mediated inhibition [corrected] of human proinsulin gene expression and characterise a prominent role for the CACCC box in maintaining basal proinsulin promoter activity.

Activation of vascular endothelial growth factor (VEGF) by the ER-alpha variant, ERDelta3

Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis in estrogen responsive tissues. Estrogen receptors alpha and beta regulate production of VEGF in both breast and endometrial cancer cells. Alternative splicing of ER-alpha mRNA generates a mixture of transcripts with various exon deletions in normal breast and breast cancer cells and some of these variants are overexpressed in breast cancer. We analyzed the role of exon-deleted variants of ER-alpha in regulation of VEGF production by simultaneous transient transfection of CHO and MDA-MB-231 cells with a VEGF promoter luciferase construct. Estrogen (10 nM) treatment resulted in a 6-fold increase in luciferase activity in cells transfected with the exon 3 deleted variant (ERDelta3) compared to a 2-fold activity induction in cells transfected with wild type ER-alpha. Exon 5 and exon 7 deleted variants were unable to induce activation of the VEGF promoter. Using specific deletion constructs of the VEGF promoter linked to luciferase, we showed that the majority of activation by ERDelta3 was restricted to the -70 to -88 bp fragment that contains two Sp1 sites. Site-directed mutagenesis of both Sp1 sites indicated that ERDelta3 activates the VEGF promoter through interaction with Sp1 proteins. ERDelta3, a variant frequently overexpressed in breast cancer, may significantly contribute to the production of VEGF thus resulting in enhanced tumor growth in vivo.

Identification of a ubiquitously active promoter of the murine activation-induced cytidine deaminase (AICDA) gene

Somatic hypermutation and class switch recombination of immunoglobulin genes are dependent on the presence of the activation-induced cytidine deaminase (AICDA) enzyme. AICDA expression is restricted to activated B-lymphocytes in the germinal centers. It has been suggested that inappropriate expression of AICDA may lead to genome instability and aberrant affinity maturation of putative autoreactive antibodies. To better understand the molecular control of its tightly regulated expression we have identified the transcription initiation site and an upstream, conserved promoter region of the murine AICDA gene. The promoter lacks a consensus TATA box but contains an initiator (Inr) element and is active in several murine and human cell lines irrespective of endogenous AICDA expression. Mutagenesis analysis identified a functionally important Sp-binding site which binds both Sp1 and Sp3 in vitro in all cell types. Contrary to a recent report, no evidence was found for direct Pax5-binding at this DNA site. We discuss the role of ubiquitous and lymphoid-specific factors in the control of AICDA gene transcription.

Mapping of the methylation pattern of the MUC2 promoter in pancreatic cancer cell lines, using bisulfite genomic sequencing

Expression of the MUC2 gene is controlled by the methylation of CpG sites in the promoter region, but the detailed methylation status of this region has yet to be reported. We have mapped the complete methylation status of the MUC2 promoter from position -1989 to position +288 upstream, a region that contains 59 CpG sites, using bisulfite genomic sequencing in two pancreatic cancer cell lines (PANC1, BxPC3) and in isolated normal colon crypts as a control. The MUC2 promoter in PANC1, a cell line that does not express MUC2, was highly methylated (average 87%, complete methylation at 28 of the 59 CpG sites), while the promoter region in the MUC2-expressing BxPC3 cell line (average 43%, complete methylation at 2 of 59 CpG sites) and in MUC2-expressing normal colon crypts (average 33%, no CpG site was completely methylated) were only partially methylated (P<0.0001). 5-Aza-2'-deoxycytidine treatment of PANC1 cells reduced the methylation level (average 36%) and induced MUC2 mRNA expression. However, mRNA expression of AP2, SP1 and CDX2 was not affected by this treatment. Our data provide the first detailed methylation map of the MUC2 promoter region for the first time, using the conversion-specific bisulfite genomic sequencing. Previously unproven methylation sites were detected, and some AP2 and SP1 binding sites showed different methylation levels among PANC1, BxPC3 and colonic crypt cells. Our mapping data provide an essential basis for further studies of methylation-regulated MUC2 inactivation.

Impaired induction of IL-10 expression in the lung following hemorrhagic shock

The balance between pro- and anti-inflammatory cytokines is considered to be an important determinant of the magnitude of inflammation in a number of disease states. We previously showed that resuscitated hemorrhagic shock augmented LPS-induced release of proinflammatory molecules by alveolar macrophages (AM). In the present studies, we evaluated the expression and regulation of the counter inflammatory cytokine IL-10 in the lung using this model. We hypothesized that impaired up-regulation of IL-10 in shock/resuscitated animals might serve as a mechanism contributing to accentuated lung inflammation. In a rodent model, animals exposed to LPS alone exhibited enhanced IL-10 mRNA levels in lung tissue as well as in AM, but antecedent shock/resuscitation delayed and attenuated the LPS-induced IL-10 mRNA levels. The ability of shock to attenuate LPS-stimulated IL-10 was also seen in the protein levels. This effect correlated with an augmented expression of cytokine-induced neutrophil chemoattractant (CINC) mRNA. Shock/resuscitated animals given exogenous IL-10 had reduced proinflammatory response, as shown by decreased expression of CINC mRNA and decreased neutrophil sequestration in the lung. Shock/resuscitation plus LPS markedly reduced the transcription rate of IL-10 mRNA compared to LPS alone but did not affect IL-10 mRNA stability. Reduced IL-10 transcription was not caused solely by impaired nuclear translocation of STAT3 and Sp1/Sp3 transcription factors because LPS-induced nuclear translocation of these factors was augmented by antecedent shock. Considered together, these findings show that shock/resuscitation suppresses LPS-induced IL-10 expression by AM in the lung by inhibiting IL-10 gene transcription. Failed up-regulation of counter inflammatory cytokines may contribute to augmented organ dysfunction in trauma patients.

Effect of pitavastatin on transactivation of human serum paraoxonase 1 gene

Hepatic hydroxymethyl glutary coenzyme A HMG-CoA reductase inhibitors (statins) have various anti atherosclerosis pleiotropic effects that are independent of cholesterol reduction. Human serum paraoxonase 1 (PON1) is associated with high-density lipoprotein (HDL) and inhibits the oxidative modification of low-density lipoprotein (LDL). We investigated the effects of statins on PON1 gene transcription using a reporter gene assay. Promoter activity of the PON1 gene was estimated by measuring luciferase activity of plasmids with a PON1 promoter region transfected into human hepatoma HepG2 cells and human embryonic kidney (HEK) 293 cells. Pitavastatin, simvastatin, and atorvastatin each significantly increased PON1 promoter activity, and the transactivation by pitavastatin was abrogated by mevalonic acid and farnesyl pyrophosphate (FPP), however, not by geranylgeranyl pyrophosphate. Further, PON1 promoter activity was enhanced by farnesyl transferase inhibitor (FTI), but not by geranylgeranyl transferase inhibitor (GGTI). PON1 gene transcription has been reported to be dependent on Sp1 and the transactivation by pitavastatin was completely abrogated by mithramycin, an inhibitor of Sp1. Our results suggest that pitavastatin activates transcription of the PON1 gene through the FPP pathway, which may play an important role in the anti atherosclerotic effects of statins.

RTEF-1, a Novel Transcriptional Stimulator of Vascular Endothelial Growth Factor in Hypoxic Endothelial Cells

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor known to be up-regulated in ischemic heart and hypoxic endothelial cells. However, the transcriptional regulation of VEGF in hypoxia-induced angiogenesis is not fully understood. Transcriptional enhancer factor-1 (TEF-1) is a transcriptional factor family that can regulate many genes expressed in cardiac and skeletal muscle cells by binding to myocyte-specific chloramphenicol acetyltransferase heptamer elements in the promoters of these genes. In this study, we demonstrated that related TEF-1 (RTEF-1), a member of the TEF-1 family, is up-regulated in hypoxic endothelial cells. Overexpression of RTEF-1 increases VEGF promoter activity and VEGF expression. Sequential deletion and site-directed mutation analyses of the VEGF promoter demonstrated that a GC-rich region containing four Sp1 response elements, located between -114 and -50, was essential for RTEF-1 function. This region is beyond the hypoxia-inducible factor-1alpha binding site and does not consist of M-CAT-related elements. By electrophoretic mobility shift assay, RTEF-1 was found to interact with the first Sp1 residue (-97 to -87) of the four consecutive Sp1 elements. Binding activity of RTEF-1 to VEGF promoter is also confirmed by chromatin immunoprecipitation. In addition, induction of VEGF promoter activity by RTEF-1 results in an increase of angiogenic processes including endothelial cells proliferation and vascular structure formation. These results indicate that RTEF-1 acts as a transcriptional stimulator of VEGF by regulating VEGF promoter activity through binding to Sp1 site. In addition, RTEF-1-induced VEGF promoter activity was enhanced in a hypoxic condition, indicating that RTEF-1 may play an important role in the regulation of VEGF under hypoxia.

Down-regulation of telomerase activity in malignant glioma cells by p27KIP1

The cyclin-dependent kinase inhibitor p27KIP1 is considered not only a prognostic factor in cancer, but also a promising anti-cancer agent. However, the relationship between p27KIP1 and telomerase, that has potential as tumor-marker, remains to be elucidated. In this study, using the recombinant adenoviral vector expressing p27KIP1 (Adp27KIP1), we investigated whether p27KIP1 affects telomerase activity in malignant glioma U373-MG cells. Overexpression of p27KIP1 suppressed telomerase activity in tumor cells. The down-regulation of telomerase was due to inhibition of the human telomerase reverse transcriptase (hTERT) gene expression at the transcriptional level. This inhibitory effect was partially induced by interfering with binding sites of the hTERT core promoter for transcription factors Myc and Sp1. These findings identify a novel role for p27KIP1 in down-regulation of telomerase activity.

Regulation of the HIV1 long terminal repeat by mutant heat shock factor

Heat shock is a known transcriptional activator of human immunodeficiency virus type 1 (HIV1) long terminal repeat (LTR). However, HIV1 LTR suppression can occur under hyperthermic conditions. To investigate this phenomenon, a series of HIV1 LTR deletion luciferase constructs were generated and tested in cell culture in combination with a mutant heat shock factor 1 (HSF1+), which is transcriptionally active in the absence of heat stress. HSF1+ suppressed the activity of a minimal HIV1 LTR promoter, which contained NF-kappaB, Sp1, and tat consensus sequences. Electromobility shift assays showed nuclear protein-DNA complex formation with a Sp1 consensus sequence. Immunoprecipitation of nuclear extracts with Sp1 antibody did not affect nuclear protein-Sp1 oligonucleotide complex formation. In contrast, no complexes were formed with the Sp1 consensus sequence when the HSF protein was immunoprecipitated. These experiments indicate that modified heat shock factor can suppress HIV1 promoter activity by a mechanism involving interaction with Sp1 elements in the HIV1 promoter. The ability of HSF1+ to suppress HIV1 promoter activity suggests that HSF1+ could serve as a tool for the treatment of AIDS.

Silencing of mouse Aprt is a gradual process in differentiated cells

Mouse Aprt constructs that are highly susceptible to DNA methylation-associated inactivation in embryonal carcinoma cells were transfected into differentiated cells, where they were expressed. Construct silencing was induced by either whole-cell fusion of the expressing differentiated cells with embryonal carcinoma cells or by treatment of the differentiated cells with the DNA demethylating agent 5-aza-2'-deoxycytidine. Induction of silencing was enhanced significantly by the presence of a methylation center fragment positioned upstream of a truncated promoter comprised of two functional Sp1 binding sites. Initial silencing of the Aprt constructs was unstable, as evidenced by high spontaneous reversion frequencies ( approximately 10(-2)). Stably silenced subclones with spontaneous reversion frequencies of <10(-5) were isolated readily from the unstably silenced clones. These reversion frequencies were enhanced significantly by treatment of the cells with 5-aza-2'-deoxycytidine. A bisulfite sequence analysis demonstrated that CpG methylation initiated within the methylation center region on expressing alleles and that the induction of silencing allowed methylation to spread towards and eventually into the promoter region. Combined with the induction of revertants by 5-aza-2'-deoxycytidine, this result suggested that stabilization of silencing was due to an increased density of CpG methylation. All allelic methylation patterns were variegated, which is consistent with a gradual and evolving process. In total, our results demonstrate that silencing of mouse Aprt is a gradual process in the differentiated cells.

Steroid hormones, endometrial gene regulation and the Sp1 family of proteins

Endometrial gene expression can be regulated exquisitely by cyclical changes in ovarian steroid concentration. Although hormonal induction of many of these genes occurs through classical steroid response elements, other endometrial genes respond to steroids at the transcriptional level but do not contain steroid response elements. A family of transcription factors, namely the Sp1 family, has now been implicated as important mediators of steroid hormone action in the endometrium during the periimplantation and postimplantation periods. This review summarizes the current literature regarding the role of the Sp1 protein family in regulating the response to steroid hormones of genes for tissue factor, plasminogen activator inhibitor-1, insulin-like growth factor binding protein-1, uteroglobin, and uteroferrin in the endometrium.

Cholinergic and peptidergic regulation of phenylethanolamine N-methyltransferase gene expression

The splanchnic nerve, innervating the adrenal medulla, releases a variety of neurotransmitters that stimulate genes involved in catecholamine biosynthesis. In particular, cholinergic agonists have been shown to induce phenylethanolamine N-methyltransferase (PNMT) gene expression through activation of both nicotinic and muscarinic receptors in vivo and in vitro. By contrast, the role of peptidergic neurotransmitters in adrenal medullary PNMT gene expression remains unclear. Using transient transfection assays, we demonstrate that rat PNMT promoter-luciferase reporter gene constructs are markedly activated by 10 nM PACAP when expressed in PC12 cells. PACAP appears to mediate its effects primarily through PAC1 receptors and, subsequently, cAMP-protein kinase A (PKA) and extracellular Ca(2+) signaling mechanisms. Activation of these signal transduction pathways markedly increases nuclear levels of the immediately early gene transcription factor Egr-1 and the developmental factor AP2. A slight decrease in Sp1 expression may also occur, whereas MAZ and glucocorticoid receptor expression remains unaltered. Although PACAP stimulates rapid changes in transcription factor expression and PNMT promoter activity, its effects are long lasting. PNMT promoter induction continues to rise and is sustained for > or=48 hours. By contrast, while muscarine, nicotine, or carbachol (100 micro M) also evoke rapid increases in rat PNMT promoter activity, peak activity is observed at 6 hours, followed by a decline and restoration to basal levels by 24 hours. Cholinergic activation of the PNMT promoter also seems to involve the cAMP-PKA signaling mechanism. However, the magnitude of stimulation and antagonist blockade with H-89 or the polypeptide inhibitor PKI suggests that the extent of activation is much less than that with PACAP.

MDM2 induces NF-kappaB/p65 expression transcriptionally through Sp1-binding sites: a novel, p53-independent role of MDM2 in doxorubicin resistance in acute lymphoblastic leukemia

MDM2 protein is thought to exhibit tumorigenic activity by binding to the p53 tumor-suppressor protein and inhibiting its function. Alternatively, MDM2 may have oncogenic roles other than those resulting from p53 interactions. Here we report that MDM2 can induce expression of the p65 subunit of NF-kappaB, which is an anti-apoptotic factor expressed in certain neoplastic cells in response to chemotherapy. Initially, we noted that the overexpression of MDM2 protein in leukemic bone marrow cells of patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), and an ALL cell line (EU-4) transfected with the MDM2 gene was associated with elevated expression of p65 and in vitro resistance to doxorubicin (Adriamycin). By cotransfection of the MDM2 gene and p65-promoter-reporter constructs into EU-4 cells, we found that transient and high-level MDM2 expression induced p65 promoter activity. In the presence of wild-type (wt) p53, MDM2 increased p65 promoter activity by reversing p53-mediated suppression of p65. In the absence of p53, MDM2 directly increased p65 promoter activity. Deletion and mutation analysis of the p65 promoter indicated that the region between nt -575 and -178, which contains the first and second Sp1-binding sites, was required for activation by MDM2. Further studies using chromatin immunoprecipitation (CHIP) and electrophoretic mobility shift assay (EMSA) showed that MDM2 was able to directly bind to the Sp1 site of the p65 promoter. Our findings suggest that by inducing p65 expression, MDM2 has a p53-independent role in tumorigenesis, which may further elucidate the association between MDM2 overexpression and resistant disease in childhood ALL.

Characterization of the human ABO gene promoter in erythroid cell lineage

BACKGROUND

The human ABO blood group system is important in transfusion and organ transplantation. Although the molecular basis of the ABO gene has been established, recent studies have begun to characterize the mechanism of the ABO gene expression.

MATERIALS AND METHODS

Transient transfection assays were carried out in human erythroleukaemia HEL cells and human gastric cancer KATOIII cells. Electrophoretic mobility shift assays were performed using nuclear extracts derived from both cells.

RESULTS

Our characterization of the 5'-upstream sequence of the ABO genes indicated that the region between -117 and +31 is essential to direct expression of a reporter gene in erythroid cells. We show that a sequence located between positions -22 and -14 of the ABO promoter binds a ubiquitous transcription factor Sp1 or Sp1-like protein(s). Mutation of this site abrogates binding of those factors and reduces the ability of the ABO promoter to function in erythroleukaemia cells and gastric cancer cells.

CONCLUSION

The expression of the ABO promoter appears to be influenced by the binding of Sp1 or Sp1-like protein(s) in both erythroid and epithelial cell lineages.

The reciprocal role of Egr-1 and Sp family proteins in regulation of the PTP1B promoter in response to the p210 Bcr-Abl oncoprotein-tyrosine kinase

Protein-tyrosine phosphatase 1B (PTP1B) is an important regulator of protein-tyrosine kinase-dependent signaling pathways. Changes in expression and activity of PTP1B have been associated with various human diseases; however, the mechanisms by which PTP1B expression is regulated have yet to be characterized. Previously, we have shown that the expression of PTP1B is enhanced by p210 Bcr-Abl and that PTP1B is a specific antagonist of transformation induced by this oncoprotein protein-tyrosine kinase. Here we have characterized the PTP1B promoter and demonstrate that a motif with features of a stress-response element acts as a p210 Bcr-Abl-responsive sequence, termed PRS. We have shown that three C(2)H(2) zinc finger proteins, namely Sp1, Sp3, and Egr-1, bind to PRS. Whereas binding of either Sp1 or Sp3 induced promoter function, Egr-1 repressed Sp3-mediated PTP1B promoter activation. The binding of Egr-1 to PRS is suppressed by p210 Bcr-Abl due to the inhibition of Egr-1 expression, resulting in the enhancement of PTP1B promoter activity. Our data indicate that Egr-1 and Sp family proteins play a reciprocal role in the control of expression from the PTP1B promoter.

Ets factors and regulation of the extracellular matrix

Ets factors are critical mediators of extracellular matrix (ECM) remodelling. As the spectrum of Ets-regulated target genes widens, so does their role in various pathological and physiological processes. Regulation of matrix degrading proteases by Ets factors in tumor invasion and metastasis is well established. Emerging evidence suggests that they may also play a role in the pathology of autoimmune diseases. Newly characterized Ets target genes such as tenascin-C and collagen type I suggest their role in diseases characterized by aberrant collagen deposition (fibrosis). Ets function is also critical in bone and cartilage development. There is increasing knowledge of the complex regulatory mechanisms involved in transcription of Ets target genes. Ets factors may function as activators or as repressors via association with specific cofactors depending on the promoter context. Signaling pathways can modulate the activation status of Ets factors and their transcriptional partners. Precise understanding of the role of Ets factors in the complex cellular network governing the expression of ECM proteins and the enzymes that degrade them will be a focus of future studies.

Oncogene-mediated downregulation of RECK, a novel transformation suppressor gene

The RECK gene was initially isolated as a transformation suppressor gene encoding a novel membrane-anchored glycoprotein and later found to suppress tumor invasion and metastasis by regulating matrix metalloproteinase-9. Its expression is ubiquitous in normal tissues, but undetectable in many tumor cell lines and in fibroblastic lines transformed by various oncogenes. The RECK gene promoter has been cloned and characterized. One of the elements responsible for the oncogene-mediated downregulation of mouse RECK gene is the Sp1 site, where the Sp1 and Sp3 factors bind. Sp1 transcription factor family is involved in the basal level of promoter activity of many genes, as well as in dynamic regulation of gene expression; in a majority of cases as a positive regulator, or, as exemplified by the oncogene-mediated suppression of RECK gene expression, as a negative transcription regulator. The molecular mechanisms of the down-regulation of mouse RECK gene and other tumor suppressor genes are just beginning to be uncovered. Understanding the regulation of these genes may help to develop strategies to restore their expression in tumor cells and, hence, suppress the cells' malignant behavior.

Transcriptional regulation by butyrate of mouse galectin-1 gene in embryonal carcinoma cells

Endogenous galactoside-binding lectins (galectins) have been implicated in cell adhesion, growth, differentiation, neoplastic transformation, and metastasis. Galectin-1 (gal-1), one member of this family, has been best characterized. We isolated a DNA clone containing the gal-1 gene from mouse genomic libraries, and the sequence of the 5' upstream region up to -2430 bp was determined. Our previous study showed that sodium butyrate (butyrate) induced expression of gal-1 at both mRNA and protein levels in the murine embryonal carcinoma (EC) cell line PCC4.aza1R and the induction of gal-1 by butyrate in PCC4.aza1R cells is at least partially regulated at transcriptional level. To locate the region which is responsible for the induction of gal-1 by butyrate, transient transfection of PCC4.aza1R cells with a series of gal-1 promoter/CAT chimeric gene, which have different deletions of the 5' region of the gal-1 promoter, showed that this 2430 bp sequence is a butyrate-inducible promoter, and butyrate-inducible ability remained when only a 62 bp sequence ahead of the transcription site (+1) existed. The sequence from -62 to -41 which contains an Sp1 site at -57 was important for the induction of gal-1 expression by butyrate. Gel shift assay indicated that transcription factor SP1 actually bound to that Sp1 site. The changes of two nucleotides within that Sp1 site, from GG to TT, abolished the nuclear proteins binding to that Sp1 site as well as the response to butyrate. These results suggest that the 5' proximal Sp1 site at -57 is crucial for the butyrate-induced expression of the gal-1, and the direct binding of SP1 to this Sp1 site may be involved in this induction.

Functional map of a placenta-specific enhancer of the human leukemia inhibitory factor receptor gene

We recently reported a placenta-specific enhancer in the human leukemia inhibitory factor receptor (LIFR) gene and now show detailed characterization of the 226-base pair enhancer (-4625/-4400 nucleotides). Four of twenty-two mutants in linker analysis showed reduced promoter activities to 45, 30, 10, and 10%, respectively. Specific binding of region A (-4617/-4602) with nuclear extract was competed by a known Oct-1 oligo and supershifted by Oct-1 antibody. Specific binding of region B (-4549/-4535) was competed by a GATA oligo, but could not be supershifted by four GATA antibodies. Nevertheless, mutagenesis showed that critical bases in region B were identical to the GATA core motif, indicating that region B may bind to a novel GATA family transcription factor. The other two adjacent regions designated as region C (-4464/-4445) showed no known consensus binding sites, and their specific placental JEG-3 nuclear extract binding was not evident in nonplacental nuclear extracts and was not competed by a trophoblast specific element (TSE), indicating that region C is a novel placenta-specific element (PSE, CATTTCCTGAACTAGTTTTT). Footprinting localized the binding boundary of PSE-binding protein (PSEB), and three Gs were found to be important for specific PSE binding. UV cross-linking showed that PSEB had a molecular mass of approximately 160 kDa, substituting the PSE with two previously reported placenta elements TSE or chorionic somatomammotropin enhancer factor 1 (CSEF-1) motifs resulted in markedly different promoter activities, indicating that PSEB is indeed different from TSE binding protein or CSEF-1. These results are the first demonstration that a novel PSE is the major element for placenta-specific enhancer activity in human LIFR gene.

Human chorionic somatomammotropin enhancer function is mediated by cooperative binding of TEF-1 and CSEF-1 to multiple, low-affinity binding sites

The human chorionic somatomammotropin gene enhancer (CSEn) is composed of multiple enhansons (Enh) that share sequence similarities with those of the simian virus, SV40 enhancer (SVEn). The sequence homology includes two GT-IIC-like (Enh1 and Enh4) and three SphI/II-like enhansons (Enh2, Enh3, and Enh5). We previously showed that transcription enhancer factor 1 (TEF-1) and a 30-kDa placental-specific factor, chorionic somatomammotropin enhancer factor 1 (CSEF-1), bind to Enh4, which plays an essential role in enhancer function. In this study, we demonstrate that TEF-1 and CSEF-1 bind specifically to all the other GT-IIC- and SphI/II-like elements within CSEn with a broad range of binding affinities that vary between 0.005 and 0.15 that of Enh4. Each individual concatenated enhanson was able to stimulate hCS promoter activity in an orientation-independent manner in choriocarcinoma cells (BeWo) with an observed stimulation that was directly proportional to its relative binding affinity for TEF-1 and CSEF-1. These results indicate that CSEn function results from the cooperative interaction of TEF-1 and/or CSEF-1 binding to multiple, low-affinity GT-IIC- and SphI/II-like enhansons within the enhancer.

Function of the human T-cell leukemia virus type 1 21-base-pair repeats in basal transcription

The human T-cell leukemia virus type 1 (HTLV-1) promoter contains three copies of an imperfect 21-bp repeat called Tax-responsive element (TRE1). To examine the role of individual TRE1 sequences in basal transcription of the HTLV-1 promoter, site-directed mutations were generated in all possible combinations of one, two, or all three TRE1 elements in the viral long terminal repeat (LTR) and tested in vivo for transcriptional activity. Mutation of the middle TRE1 resulted in the greatest reduction in basal activity. Electrophoretic mobility shift analysis demonstrated that the protein complexes bound to each of the three TRE1 sequences were not identical. The complexes formed with the TATA-distal and middle TRE1s were dependent on the core cyclic AMP response element (CRE) found in all three TRE1s, while the cellular transcription factor Sp1 bound the TATA-proximal TRE1 in a CRE-independent manner. Sp1 binding produced a footprint on the viral LTR which covered the 5' region of the proximal TRE1. Mixing experiments demonstrated that the bindings of CREB and Sp1 to the proximal TRE1 were mutually exclusive. Sp1 was able to activate transcription both from the complete LTR and from the proximal TRE1 alone. These studies demonstrate that the TRE1 elements in the HTLV-1 LTR are functionally nonequivalent and suggest that Sp1 can influence HTLV-1 basal transcription.

Novel DNase I hypersensitive sites in the 3'-flanking region of the human c-myc gene

DNase I hypersensitivity regions correlate with genetic regulatory loci and binding sites for sequence-specific DNA-binding proteins. We present data supporting the presence of novel DNase 1 hypersensitive sites (which we have designated sites VI-IX) in both the body of the human c-myc gene downstream from exon 2 and the 3'-flanking region of the c-myc gene in HL-60 cells. All of these novel DH sites are markedly decreased when HL-60 cells are treated with either dimethyl sulfoxide (DMSO) or retinoic acid. Moreover, a similar pattern of DNase I hypersensitive sites in this region of c-myc was present in MCF-7 human breast cancer cells growing in culture. Our results suggest a potential role for these sites in transcriptional regulation of the human c-myc gene.

Molecular and functional analysis of the utrophin promoter

Utrophin is a ubiquitously expressed cytoskeletal protein which is an important structural component of the mammalian neuromuscular junction. It shows extensive sequence similarity to dystrophin leading to postulation that utrophin may be able to compensate for the absence of dystrophin in Duchenne muscular dystrophy (DMD) patients. In order to study the transcriptional control of utrophin expression including its regulation at the neuromuscular junction, and as a first step in the development of a potential DMD therapy, we have cloned the utrophin promoter region from human and mouse. The utrophin promoter is associated with a CpG island at the 5'-end of the gene, and sequence analysis of the 5'-UTR reveals several Sp1 binding sites and the absence of TATA or CAAT motifs. Transcription is initiated at one major and three minor sites. Using deletion constructs, we have defined an active promoter region of 155 bp. The first exon and 900 bp upstream display limited sequence conservation between human and mouse. The core sequence TTCCGG of the N box which regulates synaptic expression of other genes is also present and may be involved in regulating the specific expression of utrophin at the postsynaptic membrane. This study provides the basis for the understanding of the regulatory mechanism that controls utrophin expression and provides the data needed to develop methods for the upregulation of utrophin in DMD patients.

[The transcriptional regulation of the human gastrin gene by EGF]

Epidermal growth factor (EGF) and phorbol esters stimulate the human gastrin promoter through a novel GC-rich DNA element 5'-68GGGGCGGGGTGGGGGG-53 called gERE (gastrin EGF response element). The transcription factor Sp1 and two fast migrating complexes designated gastrin EGF response proteins (gERP1 and gERP2) bind to gERE. Sp1 binds to the 5' half site and gERP bind to the 3' half site. Both the 5' and 3' domains and some overlap between the two domains are required to confer EGF induction. Complex interactions between Sp1 and other factors binding to overlapping gERE half-sites confer EGF responsiveness to the gastrin promoter.

Promoter regulation of a differentially expressed gene in the human colonic epithelial cell lines HT29-18 and HT29-18-C1

Gene A4 is transcriptionally activated upon enterocyte differentiation of the human colonic epithelial cell line HT29-18 and its highly differentiated subclone HT29-18-C1 [Oliva et al., Arch. Biochem. Biophys. 302 (1993) 183-192]. To characterize the mechanisms regulating the differential transcription of A4, we analyzed its immediate 5'-flanking region for regulatory elements. Promoter-linked transfection experiments of progressively deleted A4 5'-flanking sequences fused to the bacterial cat reporter gene suggest the presence of one negative and two positive DNA elements within the first 371 bp of the A4 promoter (pA4). DNase I footprint and electrophoretic mobility shift assays demonstrate that one positive element which contains the core binding sequence for the transcription factor, Sp1, mediates an equal level of transcription in the two cell types. The second positive element, localized between nucleotide positions--169 and -152, contains a sequence previously unrecognized as a transcription factor-binding site. This element mediates a twofold increase in the activity of pA4 in HT29-18-C1, as compared to HT29-18. Furthermore, nuclear extracts obtained from HT29-18-C1 contain a higher binding activity for this element than those from HT29-18. Southwestern blot analysis suggests that the protein interacting with this element has an estimated molecular mass of 50 kDa. We conclude that this protein may be involved in the differential regulation of A4 in these intestinal cell lines.

Protein-induced bending or flexing at the 5'-end of the duck beta A-globin promoter

The 5'-end of the duck beta A-globin promoter contains a protein binding site BS-3/Sp1, the A + T-rich part of which could be involved in DNA bending. Plasmids were constructed using the pBend2 plasmid containing BS-3/Sp1. Circular permutation analysis of the fragments cut out from the plasmids using various restriction endonucleases, in the presence of a partially purified protein extract from embryonic duck erythrocytes, was performed. The results indicate that a rather complicated change in the fragment shape takes place upon protein binding, which is best explained as an induction of two points of bending or flexure within the fragment. Analogical points of flexure may exist at the protein-binding sites of the duck and chicken beta A-globin promoters in spite of differing DNA sequences.

Identification and characterization of a human herpesvirus 6 gene segment capable of transactivating the human immunodeficiency virus type 1 long terminal repeat in an Sp1 binding site-dependent manner

The human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) is transactivated by various extracellular signals and viral cofactors that include human herpesviruses. These transactivators are capable of transactivating the HIV-1 LTR through the transactivation response element, NF-kappa B, or other regulatory binding elements. Human herpesvirus 6 (HHV-6) is a potential cofactor of HIV-1. Here, we report that an HHV-6 gene segment, ZVH14, which can neoplastically transform NIH 3T3 and human keratinocytes, is capable of transactivating HIV-1 LTR chloramphenicol acetyltransferase constructs in an Sp1 binding site-dependent manner. Transactivation increased synergistically in the presence of multiple Sp1 sites and was dramatically reduced by cotransfection with oligomers designed to form triplex structures with HIV-1 LTR Sp1 binding sites. HIV-1 LTR NF-kappa B sites were not essential for ZVH14-mediated transactivation. A putative open reading frame in ZVH14, B115, which may encode a highly basic peptide consisting of 115 amino acid residues, showed transactivation capacity similar to that of ZVH14. This open reading frame also transactivated the HIV-1 LTR in an Sp1 site-dependent fashion in African green monkey kidney cells and human T cells. These data suggest that HHV-6 may stimulate HIV-1 replication via transactivation of Sp1 binding sites present in the HIV-1 promoter.

Constitutive transcriptional activator of Epidermodysplasia verruciformis-associated human papillomavirus 8

Human papillomavirus (HPV) 8 belongs to the HPV types frequently associated with skin cancers of Epidermodysplasia verruciformis (EV)-patients. There are 33 nucleotides (M33 motif) in the 5'-part of the non-coding regulatory region of HPV8, which appear highly conserved among EV-specific HPVs and are consistently followed by an AP1 binding site. These sequences were shown to constitute an essential activator of transcription driven by the HPV8 late promoter P7535. The M33/AP1 element displayed properties of a constitutive enhancer, being also able to stimulate the activity of the heterologous thymidine kinase promoter in a position-independent manner. No protein binding could be detected within the 5'-part of the M33/AP1 region, which contributed significantly to the overall activity of the HPV8 enhancer. As shown by DNasel-footprinting, the central and the 3'-part of the enhancer region were involved in interactions with nuclear proteins. Three specific complexes could be observed in gel retardation tests with nuclear extracts from epithelial cells. One of these interactions involved the AP1 protein. Analysis of deletion and point mutations revealed binding of the AP1 protein to be essential for transcriptional activation, but DNA-protein interactions within M33 were important for maximal stimulation. The response to the phorbol ester TPA also required a cooperation of M33 and AP1.

Structure and organisation of a murine gene encoding small heat-shock protein Hsp25

The structure and sequence of a gene encoding the mouse small heat-shock protein, Hsp25, is presented and compared to the human hsp27. In contrast to the human hsp27, only two copies of hsp25 could be detected in the mouse genome. The intron-exon structure of the identified hsp25 is similar to the transcribed human hsp27, and the transcription start points of the genes are located at similar sites. The promoter region contains various putative transcription factor-binding elements including two G + C-rich Sp1-binding domains, two heat-shock elements, and an estrogen-responsive element half-site in direct proximity to the TATA box. These elements could explain hsp25 basal expression as well as its induction as a result of heat-shock and estrogen treatment.