Gene Expression In HEK293 Cells Research Articles

3′-tRF-CysGCA overexpression in HEK-293 cells alters the global expression profile and modulates cellular processes and pathways

tRNA fragments (tRFs) are small non-coding RNAs generated through specific cleavage of tRNAs and involved in various biological processes. Among the different types of tRFs, the 3′-tRFs have attracted scientific interest due to their regulatory role in gene expression. In this study, we investigated the role of 3′-tRF-CysGCA, a tRF deriving from cleavage in the T-loop of tRNACysGCA, in the regulation of gene expression in HEK-293 cells. Previous studies have shown that 3′-tRF-CysGCA is incorporated into the RISC complex and interacts with Argonaute proteins, suggesting its involvement in the regulation of gene expression. However, the general role and effect of the deregulation of 3′-tRF-CysGCA levels in human cells have not been investigated so far. To fill this gap, we stably overexpressed 3′-tRF-CysGCA in HEK-293 cells and performed transcriptomic and proteomic analyses. Moreover, we validated the interaction of this tRF with putative targets, the levels of which were found to be affected by 3′-tRF-CysGCA overexpression. Lastly, we investigated the implication of 3′-tRF-CysGCA in various pathways using extensive bioinformatics analysis. Our results indicate that 3′-tRF-CysGCA overexpression led to changes in the global gene expression profile of HEK-293 cells and that multiple cellular pathways were affected by the deregulation of the levels of this tRF. Additionally, we demonstrated that 3′-tRF-CysGCA directly interacts with thymopoietin (TMPO) transcript variant 1 (also known as LAP2α), leading to modulation of its levels. In conclusion, our findings suggest that 3′-tRF-CysGCA plays a significant role in gene expression regulation and highlight the importance of this tRF in cellular processes.

Knockout of the lysosomal membrane protein, LAMP2C, improves transient gene expression in HEK293 cells via increased intracellular plasmid availability.

Plasmid-based transfection can be used in many applications such as transient gene expression (TGE)-based therapeutic protein production. These applications preferentially require maximization of intracellular plasmid availability. Here, we applied a lysosome engineering approach to alleviate lysosome-mediated nucleic acid degradation and enhance the TGE in mammalian cells. By knocking out the lysosomal membrane protein LAMP2C, which is known to be the main player in RNautophagy/DNautophagy (RDA), we significantly improved transient fluorescent protein expression in HEK293 cells by improving the retention rate of transfected plasmids; however, this effect was not observed in CHO cells. Additional knockout of a lysosomal membrane transporter and another RDA player, SIDT2, was ineffective, regardless of the presence of LAMP2C. LAMP2C knockout enhanced TGE-based mAb production in HEK293 cells by up to 2.82-fold increase in specific mAb productivity. Taken together, these results demonstrate that HEK293 cells can be engineered to improve the usage of the transfected plasmid via knockout of the lysosomal membrane protein LAMP2C and provide efficient host cells in TGE systems for therapeutic protein production.

Protective effects of anti-alginate monoclonal antibody against Pseudomonas aeruginosa infection of HeLa cells

Pseudomonas aeruginosa is an opportunistic pathogen that is highly resistant to antibiotics, especially when it grows in biofilms. As an alternative to antibiotic intervention, antimicrobial antibody drugs have drawn attention in recent years due to their immunotherapeutic functions. In this study, we designed a monoclonal scFv-Fc-form antibody, MFb, targeting P. aeruginosa antigen alginate and investigated its function against this bacterium in vitro. MFb was generated by transient gene expression in HEK293 cells and purified by one-step protein A affinity chromatography. Experiments showed that MFb could recognize alginate specifically based on enzyme-linked immunosorbent assays. Its KD value of 8.31 nM was determined by surface plasmon resonance, demonstrating its high affinity for alginate. Further detailed studies revealed that the antibody exerted antibacterial effects by three mechanisms: 1) MFb inhibited P. aeruginosa biofilm formation with an IC50 of 0.58 μg/mL; 2) MFb reduced P. aeruginosa adhesion to HeLa cells, and successfully prevented its invasion on epithelial cells; 3) based on an in vitro macrophage phagocytosis assay, MFb could enhance the phagocytotic capacity of macrophages for P. aeruginosa in a concentration-dependent manner. Taken together, our work demonstrated that the antimicrobial monoclonal antibody MFb has a protective effect on HeLa cells, and it may be a promising novel strategy to treat P. aeruginosa infection.

Development of a recombinant human IL-15·sIL-15Rα/Fc superagonist with improved half-life and its antitumor activity alone or in combination with PD-1 blockade in mouse model

Recombinant human interleukin-15 (IL-15) is a potent cancer immunotherapeutic candidate due to its excellent immune stimulating effects. Previous work demonstrated that IL-15 appeared with short half-life in circulation system, while the complex with its receptor can prolong the half-life as well as benefit its activities in vivo. Therefore, IL-15 complex was more favorably considered for clinical development. Herein we developed IL-15·sIL-15Rα/Fc, a complex comprising of IL-15 and the extracellular region of its receptor alpha subunit which fused to Immunoglobulin G (IgG1) Fc to further prolong the half-life in plasma. Through transient gene expression in HEK293 cells, we expressed the superagonist by co-transfection of plasmids encoding IL-15 and sIL-15Rα/Fc respectively, yielding 36 mg/L of product after purification. Pharmacokinetic study demonstrated that the combination profoundly prolonged the half-life of IL-15 to 13.1 h in mice, about 18 folds longer than that of IL-15 monomer which is around 0.7 h. The bioactivity of the superagonist was characterized by CTLL-2 cells proliferation assay in vitro, showing its capability of stimulating the expansion of memory CD8+ T cells (cluster of differentiation) in mouse spleen. Using a HT-29 xenograft NOD-SCID mouse model, we observed tumor growth inhibition in all groups that received the superagonist, indicating its anti-tumor efficacy via stimulating infused human immune cells. In addition, combo cancer treatment by IL-15·sIL-15Rα/Fc and programmed death-1 (PD-1) antibody have shown stronger inhibitory effects as compared with treatment with either single molecule. Therefore, we developed IL-15·sIL-15Rα/Fc to be a long half-life potential cancer immunotherapy candidate that can be applied alone or in synergy with PD-1/PD-L1 blockade.

A Novel CRISPR/Cas9‐Based Cellular Model to Explore Adenylyl Cyclase and Cyclic AMP Signaling

Functional characterization of adenylyl cyclase (AC) isoforms has proven to be challenging in mammalian cell systems due to the endogenous expression of multiple AC isoforms, and the high background cyclic AMP (cAMP) responses mediated by AC activators such Gαs or forskolin. Hence, the objective of this study was to generate an isolated HEK293 cell line with low cAMP levels by knocking out the two abundantly expressed AC isoforms using CRISPR/Cas9 technology. Based on qPCR studies examining AC isoform gene expression in HEK293 cells, we chose single guide RNA (sgRNA) sequences that target AC3 and AC6, and generated stable HEK293 cell lines lacking either AC6 (HEK‐AC6 KO) or both AC3 and AC6 (HEK‐AC3/AC6 KO). Loss of function of AC3 and AC6 was evaluated genetically and by comparing the forskolin‐ and Gαs‐coupled receptor‐stimulated cAMP responses in the knockout cells and the parental HEK293 cell line. AC activity in response to 50 μM forskolin was reduced by more than 80% in the HEK‐AC6 KO cells, and by an additional 10% when AC3 was also knocked out resulting in a total reduction of cAMP levels by 95% in the HEK‐AC3/AC6 KO cells compared to the HEK293 parental cell line. For Gαs‐coupled receptor‐mediated AC activation, cAMP accumulation was evaluated for the endogenous β2‐adrenergic receptors (β2AR) and prostaglandin E2 receptors (PGE2R). HEK‐AC6 KO cells produced 50% less cAMP at maximal β2‐adrenergic receptor stimulation (10 μM isoproterenol), whereas the HEK‐AC3/AC6 KO cells displayed >75% lower cAMP accumulation than the HEK293 parental cell line. The cAMP response induced by the PGE2R agonist, PGE‐2, was >85% lower in the HEK‐AC6 KO than that observed in the parental cell line, but no additional decrease in cAMP accumulation was detected in the HEK‐AC3/AC6 KO cells. We subsequently used the HEK‐AC3/AC6 KO cell line to pharmacologically characterize the individual membrane‐bound AC isoform responses to forskolin, β2AR, and PGE2R by reintroducing each individual isoform by transient transfection. Forskolin‐mediated cAMP accumulation for AC1‐6 and AC8 revealed 2‐ to 50‐fold increases over the cAMP levels of the control/venus‐transfected cells. In contrast, AC7 and AC9 showed little or no forskolin response, respectively. The cAMP responses for the nine AC isoforms following β2AR and PGE2R activation were also significantly higher than that observed for the control‐transfected cells. Isoform specific AC regulation by other regulatory mechanisms such as Gαi‐coupled receptors, protein kinases, and Ca+2/calmodulin was also recapitulated in the HEK‐AC3/AC6 KO cell line. We have used CRISPR/Cas9 to develop a HEK293 cell line deficient of endogenous AC3 and AC6 that exhibits very low basal and drug‐stimulated cAMP background levels. These HEK‐AC3/AC6 KO cells will facilitate the selective characterization of AC isoform activity and regulation in a mammalian cellular background.Support or Funding InformationNIH MH101673, Department of Medicinal Chemistry and Molecular Pharmacology (MCMP), and Purdue UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Production process reproducibility and product quality consistency of transient gene expression in HEK293 cells with anti-PD1 antibody as the model protein.

Demonstration of reproducibility and consistency of process and product quality is one of the most crucial issues in using transient gene expression (TGE) technology for biopharmaceutical development. In this study, we challenged the production consistency of TGE by expressing nine batches of recombinant IgG antibody in human embryonic kidney 293 cells to evaluate reproducibility including viable cell density, viability, apoptotic status, and antibody yield in cell culture supernatant. Product quality including isoelectric point, binding affinity, secondary structure, and thermal stability was assessed as well. In addition, major glycan forms of antibody from different batches of production were compared to demonstrate glycosylation consistency. Glycan compositions of the antibody harvested at different time periods were also measured to illustrate N-glycan distribution over the culture time. From the results, it has been demonstrated that different TGE batches are reproducible from lot to lot in overall cell growth, product yield, and product qualities including isoelectric point, binding affinity, secondary structure, and thermal stability. Furthermore, major N-glycan compositions are consistent among different TGE batches and conserved during cell culture time.

Comparation of the effects of different 5'-untranslated regions (UTRs) on gene expression in HEK293 cells.

To evaluate four 5'-UTRs on GFP expression in HEK293T cells. The recombinant plasmids were constructed by restriction enzyme digestion, digestion and DNA sequencing. Quantitative real-time PCR and western blotting results showed that the transcription and translation level of PPRV-GFP mRNA was significantly lower than that of the other reporters. The transcription and translation level of ChEF1-GFP was the highest in HEK293T cells. Different UTRs can significantly affect protein expression. Additionally, the findings also will be useful in biological applications that require tuning of gene expression and system optimization.

Double-stranded RNA transcribed from vector-based oligodeoxynucleotide acts as transcription factor decoy

In this study, we designed a short hairpin RNA vector-based oligodeoxynucleotide (VB-ODN) carrying transcription factor (TF) consensus sequence which could function as a decoy to block TF activity. Specifically, VB-ODN for Nuclear factor-κB (NF-κB) could inhibit cell viability and decrease downstream gene expression in HEK293 cells without affecting expression of NF-κB itself. The specific binding between VB-ODN produced double-stranded RNA and NF-κB was evidenced by electrophoretic mobility shift assay. Moreover, similar VB-ODNs designed for three other TFs also inhibit their downstream gene expression but not that of themselves. Our study provides a new design of decoy for blocking TF activity.

A semi-synthetic derivative of artemisinin, artesunate inhibits prostaglandin E2 production in LPS/IFNγ-activated BV2 microglia

Artesunate is a semi-synthetic derivative of artemisinin used to treat malaria, and has been shown to possess anti-inflammatory activity. In this study, we have investigated the effect of artesunate on PGE2 production/COX-2 protein expression in LPS+IFNγ-activated BV2 microglia. To further understand the mechanism of action of this compound, we investigated its interference with NF-κB and p38 MAPK signalling pathways. PGE2 production was determined using EIA, while protein expressions of inflammatory targets like COX-2, mPGES-1, IκB, p38 and MAPKAPK2 were evaluated using western blot. An NF-κB-bearing luciferase reporter gene assay was used to test the effect of artesunate on NF-κB-mediated pro-inflammatory gene expression in HEK293 cells stimulated with TNFα (1ng/ml). Artesunate (2 and 4μM), significantly (p <0.01) suppressed PGE2 production in LPS+IFNγ-activated BV2 microglia. This effect was found to be mediated via reduction in COX-2 and mPGES-1 proteins. Artesunate also produced significant inhibition of TNFα and IL-6 production in activated BV2 microglia. Further investigations showed that artesunate (0.5–4μM) significantly (p <0.001) reduced NF-κB-driven luciferase expression, and inhibited IκB phosphorylation and degradation, through inhibition of IKK. Artesunate inhibited phosphorylation of p38 MAPK and its substrate MAPKAPK2 following stimulation of microglia with LPS+IFNγ. Taken together, we have shown that artesunate prevents neuroinflammation in BV2 microglia by interfering with NF-κB and p38 MAPK signalling.

Enhanced Production of Chikungunya Virus-Like Particles Using a High-pH Adapted Spodoptera frugiperda Insect Cell Line

Chikungunya virus-like particles (VLPs) have potential to be used as a prophylactic vaccine based on testing in multiple animal models and are currently being evaluated for human use in a Phase I clinical trial. The current method for producing these enveloped alphavirus VLPs by transient gene expression in mammalian cells presents challenges for scalable and robust industrial manufacturing, so the insect cell baculovirus expression vector system was evaluated as an alternative expression technology. Subsequent to recombinant baculovirus infection of Sf21 cells in standard culture media (pH 6.2–6.4), properly processed Chikungunya structural proteins were detected and assembled capsids were observed. However, an increase in culture pH to 6.6–6.8 was necessary to produce detectable concentrations of assembled VLPs. Since this elevated production pH exceeds the optimum for growth medium stability and Sf21 culture, medium modifications were made and a novel insect cell variant (SfBasic) was derived by exposure of Sf21 to elevated culture pH for a prolonged period of time. The high-pH adapted SfBasic insect cell line described herein is capable of maintaining normal cell growth into the typical mammalian cell culture pH range of 7.0–7.2 and produces 11-fold higher Chikungunya VLP yields relative to the parental Sf21 cell line. After scale-up into stirred tank bioreactors, SfBasic derived VLPs were chromatographically purified and shown to be similar in size and structure to a VLP standard derived from transient gene expression in HEK293 cells. Total serum anti-Chikungunya IgG and neutralizing titers from guinea pigs vaccinated with SfBasic derived VLPs or HEK293 derived VLPs were not significantly different with respect to production method, suggesting that this adapted insect cell line and production process could be useful for manufacturing Chikungunya VLPs for use as a vaccine. The adaptation of Sf21 to produce high levels of recombinant protein and VLPs in an elevated pH range may also have applications for other pH-sensitive protein or VLP targets.

Focal adhesion kinase regulates the activity of the osmosensitive transcription factor TonEBP/NFAT5 under hypertonic conditions.

TonEBP/NFAT5 is a major regulator of the urinary concentrating process and is essential for the osmoadaptation of renal medullary cells. Focal adhesion kinase (FAK) is a mechanosensitive non-receptor protein tyrosine kinase expressed abundantly in the renal medulla. Since osmotic stress causes cell shrinkage, the present study investigated the contribution of FAK on TonEBP/NFAT5 activation. Osmotic stress induced time-dependent activation of FAK as evidenced by phosphorylation at Tyr-397, and furosemide reduces FAK Tyr-397 phosphorylation in the rat renal medulla. Both pharmacological inhibition of FAK and siRNA-mediated knockdown of FAK drastically reduced TonEBP/NFAT5 transcriptional activity and target gene expression in HEK293 cells. This effect was not mediated by impaired nuclear translocation or by reduced transactivating activity of TonEBP/NFAT5. However, TonEBP/NFAT5 abundance under hypertonic conditions was diminished by 50% by FAK inhibition or siRNA knockdown of FAK. FAK inhibition only marginally reduced transcription of the TonEBP/NFAT5 gene. Rather, TonEBP/NFAT5 mRNA stability was diminished significantly by FAK inhibition, which correlated with reduced reporter activity of the TonEBP/NFAT5 mRNA 3′ untranslated region (3′-UTR). In conclusion, FAK is a major regulator of TonEBP/NFAT5 activity by increasing its abundance via stabilization of the mRNA. This in turn, depends on the presence of the TonEBP/NFAT5 3′-UTR.

Rec. ST6Gal-I variants to control enzymatic activity in processes of in vitro glycoengineering

Background Glycosylation is an important posttranslational modification of proteins influencing protein folding, stability and regulation of the biological activity. The sialyl mojety (sialic acid, 5-N-acetylneuramic acid) is usually exposed at the terminal position of N-glycosylation and therefore, a major contributor to biological recognition and ligand function, e.g. IgG featuring terminal sialic acids were shown to induce less inflammatory response and increased serum half-life. The biosynthesis of sialyl conjugates is controlled by a set of sugar-active enzymes including sialyltransferases which are classified as ST3, ST6 and ST8 based on the hydroxyl position of the glycosyl acceptor the Neu5Ac is transferred to [1]. The ST6 family consists of 2 subfamilies, ST6Gal and ST6GalNAc. ST6Gal catalyzes the transfer of Neu5Ac residues to the hydroxyl group in C6 of a terminal galactose residue of type 2 disaccharide (Galb1-4GlcNAc). To our knowledge, the access to recombinant ST6GalI for therapeutic applications is still limited due to low expression and/or poor activity in various hosts (Pichia pastoris, Spodoptera frugiperda and E. coli). The present study describes the high-yield expression of two variants of human beta-galactoside alpha-2,6 sialyltransferase 1 (ST6Gal-I, EC 2.4.99.1; data base entry P15907) by transient gene expression in HEK293 cells with yields >100 mg/L featuring distinct mono(G2 +1SA) as well as bi(G2+2SA) sialylation activity. Materials and methods Two N-terminally truncated fragments of human ST6Gal-I (delta89, residues 89-406, and delta108, residues 109-406) were designed for transient gene expression (TGE): Instead of the natural leader sequence and N-terminal residues, both ST6Gal-I coding regions harbor the Erythropoietin (EPO) signal sequence in order to ensure correct processing of the polypeptides by the secretion machinery. Following cloning into pM1MT, expression of the ST6Gal-I coding sequences is under control of a hCMV promoter followed by an intron A. Sialyltransferase assays: 1. Asialofetuin was used as acceptor and CMP-9F-NANA as donor substrate. Enzymatic activity was determined by measuring the transfer of 9F-NANA to asialofetuin. 2. Recombinant humanized IgG1 and IgG4 monoclonal antibodies (mabs), characterized as G2+0SA, as well as desialylated EPO were used as targets in sialylation experiments (30 μg enzyme/300 μg target protein). Both enzyme variants of ST6Gal-I (delta89 and delta108) were used under identical reaction conditions and the sialylation status was analyzed by mass spectrometry.

Enhancement of plasmid-mediated stable gene expression by woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) in human embryonic kidney (HEK293) cells

Influence of random integration site on the expression of transgene in mammalian cells makes it a major challenge to achieve high productivity of recombinant proteins. Optimization of expression vector is one of the most popular strategies to resolve this problem. Among this, woodchuck hepatitis virus  post-transcriptional regulatory element (WPRE) is a possible enhancer of gene expression in mammalian  cells that promotes efficient export of unspliced (RNA) into the cytoplasm, as has been proved in  transient transfection. In this study, WPRE was evaluated for enhancing stable gene expression levels in two industrial cell lines, human embryonic kidney (HEK293) and CHO-S, using the enhanced green fluorescent protein (EGFP), prourokinase (pro-UK) and protein C (PC) as the reporter gene. Based on the mean fluorescence intensity (MFI), WPRE exerted a clear positive effect on gene expression in HEK293 cells with an increase of EGFP expression level by approximately 2.5- to 3-fold independent of the  promoter used in plasmid vector. In contrast, in Chinese hamster ovary (CHO)-S cells, only a marginal effect on plasmid-mediated EGFP expression by WPRE was observed. The measurable increase of EGFP expression at the protein level was paralleled by an increase of EGFP RNA. Further test of the effect of WPRE on plasmid-mediated gene expression with two therapeutic proteins showed substantial increase of stable pro-UK and PC expression only in HEK293 by about 2.2-fold and 6.1-fold, respectively. The data of PC expression levels obtained from the random HEK293 cell clones transfected with WPRE-containing or lacking vector further demonstrated the enhancement of stable plasmid-mediated gene expression by WPRE in HEK293 cells. These results in stable transfectants show the positive effect of WPRE on transgene expression is cell-type dependent and promoter-independent, and provide valuable information to improve vectors for efficient and stable gene expression in HEK293 cells. Key words : Mammalian cells, plasmid vector, stable gene expression, protein therapeutics, woodchuck hepatitis virus post-transcriptional regulatory element (WPRE).

Construction of recombinant plasmid pEGFP-C2-L539fs/47 and its expression in HEK293 cells

ObjectiveTo reconstruct pEGFP-C2-L539fs/47, a HERG nonsense mutant in eukaryotic expression plasmid, and observe the fusion protein expressed in HEK293 cells (human embryo kidney cells). MethodsAfter double digestion of pcDNA3-L539fs/47 and pEGFP-C2-HERG with sbf I and Eco91 I, the small product fragment, from pcDNA3-L539fs/47, was subcloned into the big fragment of pEGFP-C2-HERG under T4 ligase. pEGFP-C2-L539fs/47 was identified by agarose gel electrophoresis and sequencing. pcDNA3-L539fs/47 and pEGFP-C2-L539fs/47 were transiently transfected into HEK293 cells by Lipofect, respectively. The expression of fusion protein in HEK293 cells was detected through immunofluorescence, laser confocal imaging scanning in vivo, Western blot and PCR. ResultsMutation region cDNA fragment (about 1 kb) and target vector fragment (about 7.2 kb) were ligated after purification and gel recovery. Agarose gel electrophoresis and sequencing successfully demonstrated eukaryotic expression plasmid pEGFP-C2-L539fs/47, constructed approximately 8.2 kb, sequencing consistent with template gene. The transfection efficiency of recombinant plasmid by fluorescence microscopy was more than 60%. Western blot analysis detected pcDNA3-L539fs/47 expression of the protein size 60 KD, the expression of pEGFP-C2 fusion protein size of approximately 90 KD. The L539fs/47 gene expression in HEK293 cells was significant by PCR analysis. Confocal laser imaging showed that pEGFP-C2-L539fs/47 protein was successfully expressed in cytoplasm and cytomembrane of HEK293 cells. ConclusionspEGFP-C2-L539fs/47 containing the HERG gene mutant was successfully constructed by double digestion method and expressed fusion protein in HEK293 cells, which laid a foundation for the further study on L539fs/47.

Chlorophyll Revisited: Anti-inflammatory Activities of Chlorophyll a and Inhibition of Expression of TNF-α Gene by the Same

In view of the folklore use of green leaves to treat inflammation, the anti-inflammatory property of chlorophylls and their degradation products were studied. Chlorophyll a and pheophytin a (magnesium-free chlorophyll a) from fresh leaves showed potent anti-inflammatory activity against carrageenan-induced paw edema in mice and formalin-induced paw edema in rats. Chlorophyll a inhibited bacterial lipopolysaccharide-induced TNF-α (a pro-inflammatory cytokine) gene expression in HEK293 cells, but it did not influence the expression of inducible nitric acid synthase and cyclooxygenase-2 genes. Chlorophyll b only marginally inhibited both inflammation and TNF-α gene expression. But both chlorophyll a and chlorophyll b showed the same level of marginal inhibition on 12-O-tetradecanoyl-phorbol-13-acetate-induced NF-κB activation. Chlorophylls and pheophytins showed in vitro anti-oxidant activity. The study shows that chlorophyll a and its degradation products are valuable and abundantly available anti-inflammatory agents and promising for the development of phytomedicine or conventional medicine to treat inflammation and related diseases.

High‐performance affinity purification for identification of 15‐deoxy‐Δ12,14‐PGJ2 interacting factors using magnetic nanobeads

Prostaglandin J₂ (PGJ₂) family have been reported to show various kinds of biological activities. Considerable progress has been made toward understanding the mechanism of adipogenesis, however, the mechanisms of other actions of PGJ₂ family remain controversial. The 15-deoxy-Δ(12,14) -PGJ₂ (15d-PGJ₂) is one of the members of PGJ₂ family, and is known as a ligand for peroxisome proliferator-activated receptor γ (PPARγ), which promotes the expression of the crucial genes for adipogenesis. In this study, we found that 15d-PGJ₂ did not stimulate PPARγ-mediated gene expression in HEK293 cells whereas 15d-PGJ₂ transactivated PPARγ-dependent transcription in other cell lines. Moreover, we confirmed that 15d-PGJ₂ suppressed the growth of HEK293 cells. These observations suggest that 15d-PGJ₂ shows another biological activity e.g. growth inhibition in HEK293 cells via unknown receptor for 15d-PGJ₂. The aim of this study is to develop and validate effective purification system for PGJ₂ interacting factors (PGJIFs). We have recently developed high performance magnetic nanobeads. In this study, we have newly developed 15d-PGJ₂-immobilized beads by conjugating 15d-PGJ₂ to the surface of these nanobeads. Firstly, we showed that PPARγ specifically bound to 15d-PGJ₂-immobilized beads. Secondly, we newly identified voltage dependent anionic channel 1 (VDAC1) as new PGJIF from crude extracts of HEK293 cells using this affinity purification system. These data presented here demonstrate that 15d-PGJ₂-immobilized beads are effective tool for purification of PGJIFs directly from crude cell extracts.

Effects of intra- and extracellular factors on anti-aging klotho gene expression

Inactivation of the klotho gene in mice causes serious systemic disorders, resembling human aging. However, at the molecular level, its action mechanisms are not well understood. The stimulatory or inhibitory effects of cis- and trans-regulatory factors on the klotho gene expression are also still unclear. We studied the effects of intra- and extracellular factors on human klotho gene expression. For this purpose, pHKP-Luc and pHKP-GFP reporter vectors were constructed with the 2.1-kbp upstream region of human klotho, covering its promoter region, using luciferase and GFP genes as the reporter. A series of vectors that have deletions in the upstream region of the klotho gene were constructed to assay cis-acting factors. Deletion of some parts of the klotho gene upstream region significantly affected reporter gene expression in HEK293 cells. p16 and p53 proteins inhibited reporter luciferase expression under the control of human klotho promoter in a dose-dependent manner. Calcium and phosphate ions stimulated klotho expression. p21, PTH, IGF-1, and angiotensin-II had no significant effect on klotho expression in HEK293 cells.

Identification of the transcriptional promoters in the proximal regions of human microRNA genes

To identify the transcriptional promoters in the proximal regions of human microRNA (miRNA) genes, we analyzed the 5' flanking regions of intergenic miRNAs and intronic miRNAs. With the TSSG program prediction, we found that the ratio of intronic-s miRNA genes with a least one promoter was significantly lower than those of intergenic miRNA genes and intronic-a miRNA genes. More than half of the miRNA genes have only one promoter and less than 20% of the miRNA genes have more than three promoters in the 5-kb upstream regions. All potential promoters are randomly distributed within these regions. Approximately 60% of the miRNA promoters have a TATA-like box, being significantly higher than that of all human promoters. Luciferase reporter assays showed that 22 of the 30 promoters drove gene expression in HEK-293 cells, indicating a high accuracy of the promoter prediction. This study lays a foundation for future investigation into the transcriptional regulatory mechanisms of human miRNA genes.

Induction of Heparanase-1 Expression by Mutant B-Raf Kinase: Role of GA Binding Protein in Heparanase-1 Promoter Activation

Heparanase-1 (HPR1), an endoglycosidase that specifically degrades heparan sulfate (HS) proteoglycans, is overexpressed in a variety of malignancies. Our present study sought to determine whether oncogene BRAF and RAS mutations lead to increased HPR1 expression. Reverse transcription-polymerase chain reaction analysis revealed that HPR1 gene expression was increased in HEK293 cells transiently transfected with a mutant BRAF or RAS gene. Flow cytometric analysis revealed that B-Raf activation led to loss of the cell surface HS, which could be blocked by two HPR1 inhibitors: heparin and PI-88. Cotransfection of a BRAF or RAS mutant gene with HPR1 promoter-driven luciferase reporters increased luciferase reporter gene expression in HEK293 cells. Knockdown of BRAF expression in a BRAF-mutated KAT-10 tumor cell line led to the suppression of HPR1 gene expression, subsequently leading to increased cell surface HS levels. Truncational and mutational analyses of the HPR1 promoter revealed that the Ets-relevant elements in the HPR1 promoter were critical for BRAF activation-induced HPR1 expression. Luciferase reporter gene expression driven by a four-copy GA binding protein (GABP) binding site was significantly lower in BRAF siRNA-transfected KAT-10 cells than in the control siRNA-transfected cells. We further showed that BRAF knockdown led to suppression of the expression of the GABPβ, an Ets family transcription factor involved in regulating HPR1 promoter activity. Taken together, our study suggests that B-Raf kinase activation plays an important role in regulating HPR1 expression. Increased HPR1 expression may contribute to the aggressive behavior of BRAF-mutated cancer.

Experimental identification of microRNA targets on the 3′ untranslated region of human FMR1 gene

FMR1 gene plays an important role in the development of central nervous system. Down-regulation of the FMR1 expression leads to fragile X syndrome. MicroRNAs (miRNAs) can repress gene expression by base pairing with their mRNA targets. By computer programs analysis, five miRNAs: miR-19a, miR-19b, miR-142, miR-302b* and miR-323-3p potentially target to different sites on the FMR1 3′ untranslated region (3′ UTR), except that miR-19a and miR-19b share the same targeting site. To test whether these miRNAs repress reporter gene expression by interacting with the miRNA targets on the FMR1 3′ UTR, we developed two chimeric constructs: one construct expressing a firefly luciferase with the FMR1 3′ UTR or its miRNA target mutations and the other construct expressing a pre-miRNA fusing with GFP. Luciferase assay co-transfecting with the two constructs showed that the miRNAs, miR-19b, miR-302b* and miR-323-3p could repress gene expression in HEK-293 cells, suggesting a role of these miRNAs in the regulation of the FMR1 expression. The constructs used in this study can be widely used to identify the miRNA targets in any interested genes, which will greatly promote the current progress in understanding the biological function of miRNAs.