SV40 Enhancer Research Articles

Optimization of mammalian expression vector by cis-regulatory element combinations.

The regulation of gene expression in mammalian cells by combining various cis-regulatory features has rarely been discussed. In this study, we constructed expression vectors containing various combinations of regulatory elements to examine the regulation of gene expression by different combinations of cis-regulatory elements. The effects of four promoters (CMV promoter, PGK promoter, Polr2a promoter, and EF-1α core promoter), two enhancers (CMV enhancer and SV40 enhancer), two introns (EF-1α intron A and hybrid intron), two terminators (CYC1 terminator and TEF terminator), and their different combinations on downstream gene expression were compared in various mammalian cells using fluorescence microscopy to observe fluorescence, quantitative real-time PCR (qRT-PCR), and western blot. The receptor binding domain (RBD) sequence from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spike protein was used to replace the eGFP sequence in the expression vector and the RBD expression was detected by qRT-PCR and western blot. The results showed that protein expression can be regulated by optimizing the combination of cis-acting elements. The vector with the CMV enhancer, EF-1α core promoter, and TEF terminator was found to express approximately threefold higher eGFP than the unmodified vector in different animal cells, as well as 2.63-fold higher recombinant RBD protein than the original vector in HEK-293T cells. Moreover, we suggest that combinations of multiple regulatory elements capable of regulating gene expression do not necessarily exhibit synergistic effects to enhance expression further. Overall, our findings provide insights into biological applications that require the regulation of gene expression and will help to optimize expression vectors for biosynthesis and other fields. Additionally, we provide valuable insights into the production of RBD proteins, which may aid in developing reagents for diagnosis and treatment during the COVID-19 pandemic.

Formulation and efficacy of ECO/pRHO-ABCA4-SV40 nanoparticles for nonviral gene therapy of Stargardt disease in a mouse model

It is still a challenge to develop gene replacement therapy for retinal disorders caused by mutations in large genes, such as Stargardt disease (STGD). STGD is caused by mutations in ABCA4 gene. Previously, we have developed an effective non-viral gene therapy using self-assembled nanoparticles of a multifunctional pH-sensitive amino lipid ECO and a therapeutic ABCA4 plasmid containing rhodopsin promoter (pRHO-ABCA4). In this study, we modified the ABCA4 plasmid with simian virus 40 enhancer (SV40, pRHO-ABCA4-SV40) for enhanced gene expression. We also prepared and assessed the formulations of ECO/pDNA nanoparticles using sucrose or sorbitol as a stablilizer to develop consistent and stable formulations. Results demonstrated that ECO formed stable nanoparticles with pRHO-ABCA4-SV40 in the presence of sucrose, but not with sorbitol. The transfection efficiency in vitro increased significantly after introduction of SV40 enhancer for plasmid pCMV-ABCA4-SV40 with a CMV promoter. Sucrose didn't affect the transfection efficiency, while sorbitol resulted in a fluctuation of the in vitro transfection efficiency. Subretinal gene therapy in Abca4−/− mice using ECO/pRHO-ABCA4 and ECO/pRHO-ABCA4-SV40 nanoparticles induced 36% and 29% reduction in A2E accumulation respectively. Therefore, the ECO/pABCA4 based nanoparticles are promising for non-viral gene therapy for Stargardt disease and can be expended for applications in a variety of visual dystrophies with mutated large genes.

Advanced Design of Minimalistic Dumbbell-shaped Gene Expression Vectors.

Minimal DNA vectors exclusively comprising therapeutically relevant sequences hold great promise for the development of novel therapeutic regimen. Dumbbell-shaped vectors represent non-viral non-integrating DNA minimal vectors which have entered an advanced stage of clinical development ( Hardee et al., 2017 ). Spliceable introns and DNA nuclear import signals such as SV40 enhancer sequences are molecular features that have found multiple applications in plasmid vectors to improve transgene expression. In dumbbells however, effects triggered by introns were not investigated and DNA-based nuclear import sequences have not found applications yet, presumably because dumbbell vectors have continuously been minimized with regard to size. We investigated the effects of an intron and/or SV40 enhancer derived sequences on dumbbell vector driven reporter gene expression. The implementation of a spliceable intron was found to enhance gene expression unconditionally in all investigated cell lines. Conversely, the use of the SV40 enhancer improved gene expression in a cell type-dependent manner. Though both features significantly enlarge dumbbell vector size, neither the intron nor the enhancer or a combination of both revealed a negative effect on gene expression. On the contrary, both features together improved dumbbell-driven gene expression up to 160- or 56-fold compared with plasmids or control dumbbells. Thus, it is highly recommended to consider an intron and the SV40 enhancer for dumbbell vector design. Such an advanced design can facilitate pre-clinical and clinical applications of dumbbell-shaped DNA vectors.

Immunogenicity and Protective Efficiency in Mice of a Smallpox DNA Vaccine Candidate

The adverse reactions of the current live smallpox vaccine, and potential use of smallpox as a bioterrorism weapon, have highlighted the need to develop a new effective vaccine for this infectious disease. In the present study, a DNA vaccine vector was produced, which was optimized for expression of the vaccinia virus L1 antigen in a mouse model. Plasmid-encoded IgM-tL1R, which contains a truncated L1R gene fused to an IgM signal sequence, was constructed and expressed under the regulation of an SV40 enhancer. The expressed recombinant tL1 proteins were successfully secreted into the culture media. The DNA vaccine was administered to mice by electroporation, and animals were subsequently challenged with the lethal dose of vaccinia virus. We observed that immunization with IgM-tL1R induced robust neutralizing antibody responses and provided complete protection against a vaccinia virus infection. Isotyping studies revealed a lower IgG1/IgG2a ratio following vaccination with IgM-tL1R, suggesting the stimulation of Th1 immune responses. Our results propose that an optimized DNA vaccine, IgM-tL1R, can be effective in eliciting an anti-vaccinia virus immune response and provide protection against lethal orthopoxvirus challenge.

Advanced Design of Dumbbell-shaped Genetic Minimal Vectors Improves Non-coding and Coding RNA Expression

Dumbbell-shaped DNA minimal vectors lacking nontherapeutic genes and bacterial sequences are considered a stable, safe alternative to viral, nonviral, and naked plasmid-based gene-transfer systems. We investigated novel molecular features of dumbbell vectors aiming to reduce vector size and to improve the expression of noncoding or coding RNA. We minimized small hairpin RNA (shRNA) or microRNA (miRNA) expressing dumbbell vectors in size down to 130 bp generating the smallest genetic expression vectors reported. This was achieved by using a minimal H1 promoter with integrated transcriptional terminator transcribing the RNA hairpin structure around the dumbbell loop. Such vectors were generated with high conversion yields using a novel protocol. Minimized shRNA-expressing dumbbells showed accelerated kinetics of delivery and transcription leading to enhanced gene silencing in human tissue culture cells. In primary human T cells, minimized miRNA-expressing dumbbells revealed higher stability and triggered stronger target gene suppression as compared with plasmids and miRNA mimics. Dumbbell-driven gene expression was enhanced up to 56- or 160-fold by implementation of an intron and the SV40 enhancer compared with control dumbbells or plasmids. Advanced dumbbell vectors may represent one option to close the gap between durable expression that is achievable with integrating viral vectors and short-term effects triggered by naked RNA.

Enhanced Immune Response to DNA Vaccine Encoding Bacillus anthracis PA-D4 Protects Mice against Anthrax Spore Challenge.

Anthrax has long been considered the most probable bioweapon-induced disease. The protective antigen (PA) of Bacillus anthracis plays a crucial role in the pathogenesis of anthrax. In the current study, we evaluated the efficiency of a genetic vaccination with the fourth domain (D4) of PA, which is responsible for initial binding of the anthrax toxin to the cellular receptor. The eukaryotic expression vector was designed with the immunoglobulin M (IgM) signal sequence encoding for PA-D4, which contains codon-optimized genes. The expression and secretion of recombinant protein was confirmed in vitro in 293T cells transfected with plasmid and detected by western blotting, confocal microscopy, and enzyme-linked immunosorbent assay (ELISA). The results revealed that PA-D4 protein can be efficiently expressed and secreted at high levels into the culture medium. When plasmid DNA was given intramuscularly to mice, a significant PA-D4-specific antibody response was induced. Importantly, high titers of antibodies were maintained for nearly 1 year. Furthermore, incorporation of the SV40 enhancer in the plasmid DNA resulted in approximately a 15-fold increase in serum antibody levels in comparison with the plasmid without enhancer. The antibodies produced were predominantly the immunoglobulin G2 (IgG2) type, indicating the predominance of the Th1 response. In addition, splenocytes collected from immunized mice produced PA-D4-specific interferon gamma (IFN-γ). The biodistribution study showed that plasmid DNA was detected in most organs and it rapidly cleared from the injection site. Finally, DNA vaccination with electroporation induced a significant increase in immunogenicity and successfully protected the mice against anthrax spore challenge. Our approach to enhancing the immune response contributes to the development of DNA vaccines against anthrax and other biothreats.

Design of a highly effective therapeutic HPV16 E6/E7-specific DNA vaccine: optimization by different ways of sequence rearrangements (shuffling).

Persistent infection with the high-risk Human Papillomavirus type 16 (HPV 16) is the causative event for the development of cervical cancer and other malignant tumors of the anogenital tract and of the head and neck. Despite many attempts to develop therapeutic vaccines no candidate has entered late clinical trials. An interesting approach is a DNA based vaccine encompassing the nucleotide sequence of the E6 and E7 viral oncoproteins. Because both proteins are consistently expressed in HPV infected cells they represent excellent targets for immune therapy. Here we report the development of 8 DNA vaccine candidates consisting of differently rearranged HPV-16 E6 and E7 sequences within one molecule providing all naturally occurring epitopes but supposedly lacking transforming activity. The HPV sequences were fused to the J-domain and the SV40 enhancer in order to increase immune responses. We demonstrate that one out of the 8 vaccine candidates induces very strong cellular E6- and E7- specific cellular immune responses in mice and, as shown in regression experiments, efficiently controls growth of HPV 16 positive syngeneic tumors. This data demonstrates the potential of this vaccine candidate to control persistent HPV 16 infection that may lead to malignant disease. It also suggests that different sequence rearrangements influence the immunogenecity by an as yet unknown mechanism.

Pluronic L64-mediated stable HIF-1α expression in muscle for therapeutic angiogenesis in mouse hindlimb ischemia.

Intramuscular injection of plasmid DNA (pDNA) to express a therapeutic protein is a promising method for the treatment of many diseases. However, the therapeutic applications are usually hindered by gene delivery efficiency and expression level. In this study, critical factors in a pDNA-based gene therapy system, such as gene delivery materials, a therapeutic gene, and its regulatory elements, were optimized to establish an integrated system for the treatment of mouse hindlimb ischemia. The results showed that Pluronic® L64 (L64) was an efficient and safe material for gene delivery into mouse skeletal muscle. It also showed intrinsic ability to promote in vivo angiogenesis in a concentration-dependent manner, which might be through the activation of nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB)-regulated angiogenic factors. The combination of 0.1% L64 with a hybrid gene promoter (pSC) increased the gene expression level, elongated the gene expression duration, and enhanced the number of transfected muscle fibers. In mice ischemic limbs, a gene medicine (pSC-HIF1αtri/L64) composed of L64 and pSC-based expression plasmid encoding hypoxia-inducible factor 1-alpha triple mutant (HIF-1αtri), improved the expression of stable HIF-1α, and in turn, the expression of multiple angiogenic factors. As a result, the ischemic limbs showed accelerated function recovery, reduced foot necrosis, faster blood reperfusion, and higher capillary density. These results indicated that the pSC-HIF1αtri/L64 combination presented a potential and convenient venue for the treatment of peripheral vascular diseases, especially critical limb ischemia.

An enhancer-blocking element regulates the cell-specific expression of alcohol dehydrogenase 7.

The class IV alcohol dehydrogenase gene ADH7 encodes an enzyme that is involved in ethanol and retinol metabolism. ADH7 is expressed mainly in the upper gastrointestinal tract and not in the liver, the major site of expression of the other closely related ADHs. We identified an intergenic sequence (iA1C), located between ADH7 and ADH1C, that has enhancer-blocking activity in liver-derived HepG2 cells that do not express their endogenous ADH7. This enhancer blocking function was cell- and position-dependent, with no activity seen in CP-A esophageal cells that express ADH7 endogenously. iA1C function was not specific to the ADH enhancers; it had a similar cell-specific effect on the SV40 enhancer. The CCCTC-binding factor (CTCF), an insulator binding protein, bound iA1C in HepG2 cells but not in CP-A cells. Our results suggest that in liver-derived cells, iA1C blocks the effects of ADH enhancers and thereby contributes to the cell specificity of ADH7 expression.

Novel Therapeutic Approaches for Various Cancer Types Using a Modified Sleeping Beauty-Based Gene Delivery System

Successful gene therapy largely depends on the selective introduction of therapeutic genes into the appropriate target cancer cells. One of the most effective and promising approaches for targeting tumor tissue during gene delivery is the use of viral vectors, which allow for high efficiency gene delivery. However, the use of viral vectors is not without risks and safety concerns, such as toxicities, a host immune response towards the viral antigens or potential viral recombination into the host's chromosome; these risks limit the clinical application of viral vectors. The Sleeping Beauty (SB) transposon-based system is an attractive, non-viral alternative to viral delivery systems. SB may be less immunogenic than the viral vector system due to its lack of viral sequences. The SB-based gene delivery system can stably integrate into the host cell genome to produce the therapeutic gene product over the lifetime of a cell. However, when compared to viral vectors, the non-viral SB-based gene delivery system still has limited therapeutic efficacy due to the lack of long-lasting gene expression potential and tumor cell specific gene transfer ability. These limitations could be overcome by modifying the SB system through the introduction of the hTERT promoter and the SV40 enhancer. In this study, a modified SB delivery system, under control of the hTERT promoter in conjunction with the SV40 enhancer, was able to successfully transfer the suicide gene (HSV-TK) into multiple types of cancer cells. The modified SB transfected cancer cells exhibited a significantly increased cancer cell specific death rate. These data suggest that our modified SB-based gene delivery system can be used as a safe and efficient tool for cancer cell specific therapeutic gene transfer and stable long-term expression.

Cell type and context-specific function of PLAG1 for IGF2 P3 promoter activity

The fetal transcription factor PLAG1 is found to be overexpressed in cancers, and has been suggested to bind the insulin like growth factor 2 (IGF2) P3 promoter, and to activate the IGF2 gene. The expression of IGF2 has partly been linked to loss of CTCF-dependent chromatin insulator function at the H19 imprinting control region (ICR). We investigated the role of PLAG1 for IGF2 regulation in Hep3B and JEG-3 cell lines. Chromatin immunoprecipitation revealed cell type-specific binding of PLAG1 to the IGF2 P3 promoter, which was substantially insensitive to recombinant PLAG1 overexpression in the endogenous context. We hypothesized that the H19 chromatin insulator may be involved in the cell type-specific PLAG1 response. By using a GFP reporter gene/insulator assay plasmid construct with and without the H19 ICR and/or an SV40 enhancer, we confirm that the effect of the insulator is specifically associated with the activity of the IGF2 P3 promoter in the GFP reporter system, and furthermore, that the reporter insulator is functional in JEG-3 but not in Hep3B cells. FACS analysis was used to assess the function of PLAG1 in low endogenously expressing, but Zn-inducible stable PLAG1 expressing JEG-3 cell clones. Considerable increase in IGF2 expression upon PLAG1 induction with a partial insulator overriding activity was found using the reporter constructs. This is in contrast to the effect of the endogenous IGF2 gene which was insensitive to PLAG1 expression in JEG-3, while modestly induced the already highly expressed IGF2 gene in Hep3B cells. We suggest that the PLAG1 binding to the IGF2 P3 promoter and IGF2 expression is cell type-specific, and that the PLAG1 transcription factor acts as a transcriptional facilitator that partially overrides the insulation by the H19 ICR.

An Artificial PAP Gene Breaks Self-tolerance and Promotes Tumor Regression in the TRAMP Model for Prostate Carcinoma

Prostate cancer (PCa) is the most commonly diagnosed type of cancer in men in western industrialized countries. As a public health burden, the need for the invention of new cost-saving PCa immunotherapies is apparent. In this study, we present a DNA vaccine encoding for the prostate-specific antigen prostatic acid phosphatase (PAP) linked to the J-domain and the SV40 enhancer sequence. The PAP DNA vaccine induced a strong PAP-specific cellular immune response after electroporation (EP)-based delivery in C57BL/6 mice. Splenocytes from mice immunized with PAP recognized the naturally processed PAP epitopes, indicating that vaccination with the PAP-J gene broke its self-tolerance against PAP. Remarkably, DNA vaccination with PAP-J inhibited tumor growth in the Transgenic Adenocarcinoma of the Mouse Prostate (TRAMP) mouse model that closely resembled human PCa. Therefore, this study highlights a novel cancer immunotherapy approach with the potential to control PCa in clinical settings.

Co-expression of herpes simplex virus thymidine kinase and Escherichia coli nitroreductase by an hTERT-driven adenovirus vector in breast cancer cells results in additive anti-tumor effects

Breast cancers especially in the late and metastatic stages remain refractory to treatment despite advances in surgical techniques and chemotherapy. Tumor-specific promoter-directed suicide gene therapy and adenoviral technology can be promising strategies for such advanced disease. Previous studies suggested that combining herpes simplex virus thymidine kinase (HSV-TK) and ganciclovir (GCV) with Escherichia coli nitroreductase (Coli.NTR) and 5-(azaridin-1-yl)-2, 4-dinitrobenzamide (CB1954) by a recombinant retrovirus delivery system resulted in a co-operative killing effect in vitro. We constructed a bicistronic adenovirus type 5 (Ad5)-based vector which co-expresses herpes HSV-TK and Coli.NTR under the control of the human telomerase reverse transcriptase (hTERT) promoter and SV40 enhancer. NTR gene expression mediated by an internal ribosome entry site (IRES) was inserted after the hTERT and HSV-TK sequences. Anti-tumor activities of the novel vector, Ad-hT-TK/NTR-enh, combined with prodrugs were evaluated in human breast cancer cells (ZR-75-30, MCF-7) in vitro and invivo. We showed that expression of HSV-TK and NTR genes by Ad-hT-TK/NTR-enh in combination with GCV and CB1954 resulted in specific and significant cytotoxic effects in breast cancer cells in vitro. The anti-tumor activity of this system was more efficient than that from a single suicide gene, and only slightly lower than by HSV-TK and NTR driven from separate hTERT promoters in vitro and in vivo while the total amount of adenovirus of Ad-hT-TK/NTR-enh was half that of Ad-hT-TK-enh+Ad-hT-NTR-enh. These results suggest that suicide genes HSV-TK and NTR mediated by a single adenovirus vector under the control of an enhanced hTERT promoter results in additive anti-tumor effects and may provide a relatively safe strategy for the treatment of breast cancer by tumor-specific targeting.

Construction, modification and evaluation of apolipoprotein A-I promoter-driven shRNA expression vectors against hTERT

Liver-specific gene knockdown cannot be achieved by short hairpin RNA (shRNA) generated by RNA polymerase III promoter. Here we constructed, modified and evaluated apolipoprotein A-I (ApoA-I) promoter-driven shRNA expression vectors against human telomerase reverse transcriptase (hTERT) in SMMC-7721 cells. The roles of the cis-acting hammerhead ribozyme and the specific pausing site MAZ, the liver-specific promoter ApoA-I, as well as SV40 and CMV enhancers were first individually evaluated, and then they were incorporated to construct a liver-specific shRNA expression plasmid against hTERT, and the inhibitory effects on hTERT were examined in SMMC-7721 cells. The results showed that the introduction of the cis-acting hammerhead ribozyme and the specific pausing site MAZ did not change gene knockdown efficiency significantly, but eliminated the off-target effect. Green fluorescent protein (GFP) expressing plasmid under the control of ApoA-I promoter can produce liver-specific GFP expression, but at a much lower level compared to the CMV promoter. The CMV or SV40 enhancer-modified ApoA-I promoter caused a four or two folds increase in mRNA expression of GFP relative to ApoA-I alone, respectively. The liver-specific shRNA expression plasmid against hTERT under the control of CMV enhancer-modified ApoA-I promoter with the sequences of the cis-acting hammerhead ribozyme and MAZ, induced significant inhibitory effect on hTERT at both mRNA and protein levels in SMMC-7721 cells. Therefore, liver-specific gene therapy is made possible by utilizing shRNA expression vector under the control of CMV enhancer-modified ApoA-I promoter.

Alternative Ways to Think about Cellular Internal Ribosome Entry

Internal ribosome entry sites (IRESs) are specialized mRNA elements that allow recruitment of eukaryotic ribosomes to naturally uncapped mRNAs or to capped mRNAs under conditions in which cap-dependent translation is inhibited. Putative cellular IRESs have been proposed to play crucial roles in stress responses, development, apoptosis, cell cycle control, and neuronal function. However, most of the evidence for cellular IRES activity rests on bicistronic reporter assays, the reliability of which has been questioned. Here, the mechanisms underlying cap-independent translation of cellular mRNAs and the contributions of such translation to cellular protein synthesis are discussed. I suggest that the division of cellular mRNAs into mutually exclusive categories of "cap-dependent" and "IRES-dependent" should be reconsidered and that the implications of cellular IRES activity need to be incorporated into our models of cap-dependent initiation.

PU.1 Directly Regulates cdk6 Gene Expression, Linking the Cell Proliferation and Differentiation Programs in Erythroid Cells

Cell proliferation and differentiation are highly coordinated processes during normal development. Most leukemia cells are blocked from undergoing terminal differentiation and also exhibit uncontrolled proliferation. Dysregulated expression of transcription factor PU.1 is strongly associated with Friend virus-induced erythroleukemia. PU.1 inhibits erythroid differentiation by binding to and inhibiting GATA-1. PU.1 also may be involved in controlling proliferation of erythroid cells. We reported previously that the G(1) phase-specific cyclin-dependent kinase 6 (CDK6) also blocks erythroid differentiation. We now report that PU.1 directly stimulates transcription of the cdk6 gene in both normal erythroid progenitors and erythroleukemia cells, as well as in macrophages. We propose that PU.1 coordinates proliferation and differentiation in immature erythroid cells by inhibiting the GATA-1-mediated gene expression program and also by regulating expression of genes that control progression through the G(1) phase of the cell cycle, the period during which the decision to differentiate is made.

Identification and Functional Characterization of Cytoplasmic Determinants of Plasmid DNA Nuclear Import

Import of exogenous plasmid DNA (pDNA) into mammalian cell nuclei represents a key intracellular obstacle to efficient non-viral gene delivery. This includes access of the pDNA to the nuclei of non-dividing cells where the presence of an intact nuclear membrane is limiting for gene transfer. Here we identify, isolate, and characterize, cytoplasmic determinants of pDNA nuclear import into digitonin-permeabilized HeLa cells. Depletion of putative DNA-binding proteins, on the basis of their ability to bind immobilized pDNA, abolished pDNA nuclear import supporting the critical role of cytoplasmic factors in this process. Elution of pDNA-bound proteins, followed by two-dimensional sodium dodecyl polyacrylamide gel electrophoresis identified several candidate DNA shuttle proteins. We show that two of these, NM23-H2, a ubiquitous c-Myc transcription-activating nucleoside diphosphate kinase, and the core histone H2B can both reconstitute pDNA nuclear import. Further, we demonstrate a significant increase in gene transfer in non-dividing HeLa cells transiently transfected with pDNA containing binding sequences from two of the DNA shuttle proteins, NM23-H2 and the homeobox transcription factor Chx10. These data support the hypothesis that exogenous pDNA binds to cytoplasmic shuttle proteins and is then translocated to the nucleus using the minimal import machinery. Importantly, increasing the binding of pDNA to shuttle proteins by re-engineering reporter plasmids with shuttle binding sequences enhances gene transfer. Increasing the potential for exogenously added pDNA to bind intracellular transport cofactors may enhance the potency of non-viral gene transfer.

Sleeping Beauty-Mediated Suicide Gene Therapy of Hepatocellular Carcinoma

The aim of this study was to use gene therapy via the Sleeping Beauty (SB) system to increase telomerase promoter activity to target hepatocellular carcinoma (HCC). In previous studies, we identified selective and increased expression of luciferase and suicide genes controlled by the hTERT (human telomerase reverse transcriptase) promoter and the SV40 enhancer in telomerase-positive cancer cell lines. Because telomerase is activated in about 80% of HCCs, it is likely that increasing the activity of the telomerase promoter with a suicide gene will effectively eradicate HCCs. We found that the telomerase promoter mediated SB system can efficiently insert transgene into HCC genomes. Also, telomerase promoter activity was increased using a SB vector expressing suicide gene HSV-TK (herpes simplex virus thymidine kinase) controlled by the hTERT promoter and a SV40 enhancer for the induction of telomerase-positive cancer-specific cell death. HCC cell lines transfected with pT.hTp.HSV-tk.Con with active helper plasmid and ganciclovir (GCV) significantly inhibited cancer cell growth. These results indicate that Sleeping Beauty transposon mediated suicide gene expression can be used in HCC-targeted cancer gene therapy.

Hzf regulates adipogenesis through translational control of C/EBPα

Adipocyte differentiation requires a well-defined programme of gene expression in which the transcription factor C/EBPalpha (CCAAT/enhancer-binding protein) has a central function. Here, we show that Hzf (haematopoietic zinc-finger), a previously identified p53 transcriptional target, regulates C/EBPalpha expression. Hzf is induced during differentiation of preadipocyte cell lines, and its suppression by short hairpin RNA disrupts adipogenesis. In Hzf's absence, expression of C/EBPalpha is severely impaired because of reduced translation of its mRNA. Hzf physically interacts with the 3' untranslated region of C/EBPalpha mRNA to enhance its translation. Taken together, these findings underscore a critical role of Hzf in the adipogenesis regulatory cascade.

Gene targeting in adult rhesus macaque fibroblasts

BackgroundGene targeting in nonhuman primates has the potential to produce critical animal models for translational studies related to human diseases. Successful gene targeting in fibroblasts followed by somatic cell nuclear transfer (SCNT) has been achieved in several species of large mammals but not yet in primates. Our goal was to establish the protocols necessary to achieve gene targeting in primary culture of adult rhesus macaque fibroblasts as a first step in creating nonhuman primate models of genetic disease using nuclear transfer technology.ResultsA primary culture of adult male fibroblasts was transfected with hTERT to overcome senescence and allow long term in vitro manipulations. Successful gene targeting of the HPRT locus in rhesus macaques was achieved by electroporating S-phase synchronized cells with a construct containing a SV40 enhancer.ConclusionThe cell lines reported here could be used for the production of null mutant rhesus macaque models of human genetic disease using SCNT technology. In addition, given the close evolutionary relationship and biological similarity between rhesus macaques and humans, the protocols described here may prove useful in the genetic engineering of human somatic cells.