The human cytomegalovirus immediate early enhancer-promoter is responsive to activation by the adenovirus-5 13S E1A gene

Stable miRNA overexpression in human CAP cells: Engineering alternative production systems for advanced manufacturing of biologics using miR-136 and miR-3074

Chinese hamster ovary (CHO) cells still represent the major production host for therapeutic proteins. However, multiple limitations have been acknowledged leading to the search for alternative expression systems. CEVEC's amniocyte production (CAP) cells are human production cells demonstrated to enable efficient overexpression of recombinant proteins with human glycosylation pattern. However, CAP cells have not yet undergone any engineering approaches to optimize process parameters for a cheaper and more sustainable production of biopharmaceuticals. Thus, we assessed the possibility to enhance CAP cell production capacity via cell engineering using miRNA technology. Based on a previous high-content miRNA screen in CHO-SEAP cells, selected pro-productive miRNAs including, miR-99b-3p, 30a-5p, 329-3p, 483-3p, 370-3p, 219-1-3p, 3074-5p, 136-3p, 30e-5p, 1a-3p, and 484-5p, were shown to act pro-productive and product independent upon transient transfection in CAP and CHO antibody expressing cell lines. Stable expression of miRNAs established seven CAP cell pools with an overexpression of the pro-productive miRNA strand. Subsequent small-scale screening as well as upscaling batch experiments identified miR-136 and miR-3074 to significantly increase final mAb concentration in CAP-mAb cells. Transcriptomic changes analyzed by microarrays identified several lncRNAs as well as growth and apoptosis-related miRNAs to be differentially regulated in CAP-mAb-miR-136 and -miR-3074. This study presents the first engineering approach to optimize the alternative human expression system of CAP-cells.

Stable enhanced green fluorescent protein expression after differentiation and transplantation of reporter human induced pluripotent stem cells generated by AAVS1 transcription activator-like effector nucleases

Human induced pluripotent stem (hiPS) cell lines with tissue-specific or ubiquitous reporter genes are extremely useful for optimizing in vitro differentiation conditions as well as for monitoring transplanted cells in vivo. The adeno-associated virus integration site 1 (AAVS1) locus has been used as a "safe harbor" locus for inserting transgenes because of its open chromatin structure, which permits transgene expression without insertional mutagenesis. However, it is not clear whether targeted transgene expression at the AAVS1 locus is always protected from silencing when driven by various promoters, especially after differentiation and transplantation from hiPS cells. In this paper, we describe a pair of transcription activator-like effector nucleases (TALENs) that enable more efficient genome editing than the commercially available zinc finger nuclease at the AAVS1 site. Using these TALENs for targeted gene addition, we find that the cytomegalovirus-immediate early enhancer/chicken β-actin/rabbit β-globin (CAG) promoter is better than cytomegalovirus 7 and elongation factor 1α short promoters in driving strong expression of the transgene. The two independent AAVS1, CAG, and enhanced green fluorescent protein (EGFP) hiPS cell reporter lines that we have developed do not show silencing of EGFP either in undifferentiated hiPS cells or in randomly and lineage-specifically differentiated cells or in teratomas. Transplanting cardiomyocytes from an engineered AAVS1-CAG-EGFP hiPS cell line in a myocardial infarcted mouse model showed persistent expression of the transgene for at least 7 weeks in vivo. Our results show that high-efficiency targeting can be obtained with open-source TALENs and that careful optimization of the reporter and transgene constructs results in stable and persistent expression in vitro and in vivo.

2-aminopurine enhances the oncolytic activity of an E1b-deleted adenovirus in hepatocellular carcinoma cells

Adenoviruses with deletions of viral genes have been extensively studied as potential cancer therapeutics. Although a high degree of cancer selectivity has been demonstrated with these conditionally replicating adenoviruses, low levels of virus replication can be detected in normal cells. Furthermore, these mutations were also found to reduce the activity of the replicating viruses in certain cancer cells. Recent studies have shown that co-administration of chemotherapeutic drugs may increase the activity of these viruses without affecting their specificity. We constructed an adenovirus with deletions of both the E1b and the VA-RNA genes and found that replication of this virus was selective for human hepatocellular carcinoma (HCC) cell lines when compared to normal cell lines. Furthermore, we show that 2-aminopurine (2′AP) treatment selectively enhanced virus replication and virus-mediated death of HCC cells. 2′AP did not compensate for the loss of VA-RNA activities, but rather the loss of an E1b-55K activity, such as the DNA damage response, suggesting that co-administration of 2′AP derivatives that block host DNA damage response, may increase the oncolytic activity of AdΔE1bΔVA without reducing its selectivity for HCC cells.

Modulation of luciferase activity using high intensity focused ultrasound in combination with bioluminescence imaging, magnetic resonance imaging and histological analysis in muscle tissue

This study investigates the effect of high intensity focused ultrasound (HIFU) to muscle tissue transfected with a luciferase reporter gene under the control of a CMV-promoter. HIFU was applied to the transfected muscle tissue using a dual HIFU system. In a first group four different intensities (802 W/cm2, 1401 W/cm2, 2117 W/cm2, 3067 W/cm2) of continuous HIFU were applied 20 s every other week for four times. In a second group two different intensities (802 W/cm2, 1401 W/cm2) were applied 20 s every fourth day for 20 times. The luciferase activity was determined by bioluminescence imaging. The effect of HIFU to the muscle tissue was assessed by T1-weighted +/- Gd-DTPA, T2-weighted and a diffusion-weighted STEAM sequence obtained on a 1.5-T GE-MRI scanner. Histology of the treated tissue was done at the end. In the first group the photon emission was at 3067.6 W/cm2 1.28 x 10(7) +/- 3.1 x 10(6) photon/s (5.5 +/- 1.2-fold), of 2157.9 W/cm2 8.1 +/- 2.7 x 10(6) photon/s (3.2 +/- 1.1-fold), of 1401.9 W/cm2 9.3 +/- 1.3 x 10(6) photon/s (4.9 +/- 0.4-fold) and of 802.0 W/cm2 8.6x +/- 1.2 x 10(6) photon/s (4.5 +/- 0.6-fold) compared to baseline. In the second group the photon emission was at 1401.9 W/cm2 and 802.0 W/cm2 14.1 +/- 3.6 x 10(6) photon/s (6.1 +/- 1.5-fold), respectively, 5.1 +/- 4.7 x 10(6) photon/s (6.5 +/- 2.0-fold). HIFU can enhance the luciferase activity controlled by a CMV-promoter.

Efficient and reproducible generation of high-expressing, stable human cell lines without need for antibiotic selection

Background

Human cell lines are the most innovative choice of host cell for production of biopharmaceuticals since they allow for authentic posttranslational modification of therapeutic proteins. We present a new method for generating high and stable protein expressing cell lines based on human amniocytes without the requirement of antibiotic selection.

Results

Primary amniocytes from routine amniocentesis samples can be efficiently transformed with adenoviral functions resulting in stable human cell lines. Cotransfection of the primary human amniocytes with a plasmid expressing adenoviral E1 functions plus a second plasmid containing a gene of interest resulted in permanent cell lines expressing up to 30 pg/cell/day of a fully glycosylated and sialylated protein. Expression of the gene of interest is very stable for more than 90 passages and, importantly, was achieved in the absence of any antibiotic selection.

Conclusion

We describe an improved method for developing high protein expressing stable human cell lines. These cell lines are of non-tumor origin, they are immortalized by a function not oncogenic in human and they are from an ethically accepted and easily accessible cell source. Since the cell can be easily adapted to growth in serum-free and chemically defined medium they fulfill the requirements of biopharmaceutical production processes.

Transcription releases protein VII from adenovirus chromatin

Adenovirus protein VII is the major protein component of the viral nucleoprotein core. It is a nonspecific DNA-binding protein that condenses viral DNA inside the capsid. Protein VII remains associated with viral chromatin throughout early phase, indicating its continuing role during infection. Here we characterize the release of protein VII from infectious genomes during a time period that corresponds to the late phase of infection. Interestingly, the early viral transactivator E1A, but not other early gene products, is responsible for releasing protein VII by a mechanism that requires ongoing transcription but not viral DNA replication. Moreover transcription per se, in the absence of E1A, is also sufficient to trigger release. Accordingly, a recombinant genome containing only non-coding "stuffer" DNA is unable to support release of protein VII. Our data support a model in which early gene transcription results in a change in the structure of the viral chromatin.

Amino acid 1-209 is essential for PDX-1-mediated repression of human CMV IE promoter activity

AIM

To explore the different roles of pancreatic duodenal homeobox factors-1 (PDX-1) domains in PDX-1 mediated repression of human cytomegalovirus immediately early (CMV IE) promoter.

METHODS

A series of truncated PDX-1 mutants were constructed. The binding of PDX-1 and CMV IE promoter was identified by electrophoretic mobility shift assay (EMSA). The dual-reporter assay was applied to examine the repression activities of PDX-1 mutants on CMV IE promoter. In addition, RNAi technology was used to specifically knock down the endogenous PDX-1 expression.

RESULTS

The reporter assay indicated that compared to the mock controls (pEGFP-N2), overexpression of PDX-1 resulted in a 41% decrease of CMV IE promoter activity in the 293 cells (P< 0.05) and 43% decrease in HeLa cells (P< 0.05), and the repression levels of various truncated mutants played on CMV IE promoter were different. Specific knock down of the endogenous PDX-1 expression significantly restored the activity of CMV IE promoter. EMSA demonstrated that domain 3 is necessary for nuclear localization and DNA binding activity of PDX-1. However, binding of PDX-1 alone to CMV IE promoter was not sufficient to inhibit its transcriptional activity, and other domains of PDX-1 presented were also required.

CONCLUSION

Our data suggested that the DNA binding activity of PDX-1 domain 3 and the cooperative binding of PDX-1 domain 1/2 with other proteins were required for PDX-1 mediated repression of CMV IE promoter.

Enhanced expression from the human cytomegalovirus immediate-early promoter in a non-replicating adenovirus encoded reporter gene following cellular exposure to chemical DNA damaging agents

We have examined expression from the human cytomegalovirus (CMV) promoter of a reporter gene encoded in a replication-deficient adenovirus following cellular exposure to heat shock and chemical DNA damaging agents. Expression of the reporter gene was enhanced following prior treatment of cells with cisplatin and N-acetoxy-acetylaminofluorine, but not heat shock. This enhancement was more pronounced and induced by lower chemical concentrations in xeroderma pigmentosum (XP) and Cockayne syndrome fibroblasts that are deficient in the transcription-coupled repair (TCR) pathway of nucleotide excision repair (NER) compared to that in TCR-proficient XP-C and normal strains. This is consistent with an induction of expression from the CMV promoter mediated by persistent (unrepaired) DNA damage in active genes. We show also that expression of the CMV-driven reporter is enhanced following treatment of several human tumour cell lines. This later finding has implications for combined chemotherapy and gene therapy using CMV-driven expression vectors.

A cAMP response element within the latency-associated transcript promoter of HSV-1 facilitates induced ocular reactivation in a mouse hyperthermia model

Herpes simplex virus type 1 (HSV-1) recombinant strain 17CRE contains a site-directed mutation in the 7-bp CRE consensus sequence located 38 nucleotides upstream of the transcription start site. Scarified mouse corneas received inoculations of 17syn+ (parent), 17CRE, and rescue 17CREr. Slit lamp examination of herpetic lesions and tear film swabs containing infectious virus showed that 17CRE had the same acute phenotype as 17syn+ and 17CREr. At 4 weeks, when the corneas had healed and latency was established, mice received hyperthermic shock. Eye swabs taken 24 h after hyperthermia showed that 17CRE reactivated significantly less than 17syn+ and 17CREr, while no significant differences were found in HSV-1 DNA genome copy numbers and latent virus in the trigeminal ganglia. These results are evidence that this CRE site in the LAT promoter facilitates ocular HSV-1 reactivation in mice.

Zinc finger and carboxyl regions of adenovirus E1A 13S CR3 are important for transactivation of the cytomegalovirus major immediate early promoter by adenovirus

Reactivation of latent cytomegalovirus (CMV) is an important cause of disease in susceptible patients. We previously demonstrated that an adenovirus early gene product can transactivate the CMV major immediate early (IE) promoter in inflammatory cells. This effect was due to the conserved region 3 (CR3) of the adenovirus E1A 13S gene product. There are two domains in the CR3 region, a zinc finger (aa 147-177) and a carboxyl (aa 180-188) domain. Both are crucial for transactivation of downstream promoter elements of adenovirus in E1A 13S. We sought to determine if either or both of these specific domains is also necessary for transactivation of the CMV IE promoter by the adenovirus E1A 13S gene product. We cotransfected T-lymphocyte Jurkat cells and monocyte/macrophage-like THP-1 cells with plasmids expressing wild-type (WT) or CR3 mutant E1A 13S and a CMV IE chloramphenicol acetyltransferase (CAT) reporter construct. With extracts of cells coinfected with E1A WT set to 100%, mutation in the zinc finger domain, the carboxyl domain, or both domains decreased CMV IE CAT activity by >/= 96%. In contrast, a mutation in the region between the zinc finger and carboxyl domains reduced CMV IE CAT activity by only 24 to 26%. Mixing studies in Jurkat cells confirmed the importance of these domains. We also evaluated the active site of the CMV IE promoter involved in transactivation in THP-1 cells using CMV IE promoter deletions and single promoter element constructs. These studies showed that progressive deletion of the 19-bp CMV IE repeats containing cyclic AMP response element binding protein/activating transcription factor (CREB/ATF) sites resulted in progressive loss of activity. The importance of this element was confirmed using single promoter elements containing CMV IE 16-, 18-, 19-, and 21-bp repeats. Finally, using a 19-bp single promoter element construct and the CR3 mutants we demonstrated that mutations in the zinc finger (C171S) carboxyl region (S185N) or both regions (C171S/ S185N) resulted in significant (83, 94, and 85%) loss of activity. We conclude that the zinc finger and carboxyl domains of the CR3 region of E1A 13S are necessary for transactivation of the CMV promoter and that this occurs mainly through activation of the 19-bp CREB/ATF site of the promoter.

UV-enhanced expression of a reporter gene is induced at lower UV fluences in transcription-coupled repair deficient compared to normal human fibroblasts, and is absent in SV40-transformed counterparts

UV irradiation enhances transcription of a number of cellular and viral genes. We have compared dose responses for alterations in expression from reporter constructs driven by the human and murine cytomegalovirus (CMV) immediate early (IE) promoters in cells from patients with deficiencies in nucleotide excision repair (complementation groups of xeroderma pigmentosum and Cockayne syndrome) following UV exposure, or infection with UV-damaged recombinant vectors. Results suggest that unrepaired damage in active genes triggers increased reporter activity from constructs driven by the CMV promoters in human fibroblasts. Similar to human fibroblasts, HeLa cells and cells from Li-Fraumeni syndrome patients (characterized by an inherited mutation in the p53 gene) also displayed an increase in reporter activity following UV exposure; however, this response was absent in all simian virus 40 (SV40)-transformed cell lines examined. This suggests that a pathway affected by SV40-transformation (other than p53) plays an essential role in UV-enhanced expression from the CMV IE promoter.

A lentivirus packaging system based on alternative RNA transport mechanisms to express helper and gene transfer vector RNAs and its use to study the requirement of accessory proteins for particle formation and gene delivery

A lentivirus-based packaging system was designed to reduce the chance of recombination between helper and gene transfer vector sequences by using the constitutive transport element (CTE) derived from Mason-Pfizer monkey virus for expression of the viral proteins and the Rev-Rev response element (RRE) combination for expression of the gene transfer vector. Using this approach, we evaluated a series of human immunodeficiency virus type 1 packaging constructs that express one or more accessory proteins (Vif, Vpr, and Vpu), in addition to the Gag and Pol proteins, for particle formation and virus stock production for gene transfer. Constructs that also express Vpr or both Vpr and Vpu produced more particles, as measured by a p24 assay, than did plasmids that did not contain these sequences. Transactivation experiments showed that the packaging plasmids that encode Vpr or both Vpr and Vpu also expressed a functional single-exon Tat protein. For these constructs, high-titer virus stocks could be prepared in the absence of a cotransfected Tat-expressing plasmid. Amphotropic-envelope-pseudotyped virus stocks prepared with all of the packaging constructs, irrespective of whether any of the accessory proteins were coexpressed, were equally efficient in transducing growth-arrested HeLa cells. The combination/mixed packaging system was compared to systems that were based on either the CTE alone or Rev and RRE for expression of both the packaging plasmid as well as the gene transfer vector. The combination/mixed packaging system was comparable to the other systems for production of virus stocks, suggesting that this design may prove to be safer for the eventual deployment of lentivirus vectors for therapeutic purposes.

Rapid generation of stable cell lines expressing corticotropin-releasing hormone receptor for drug discovery

Human HEK293 cells that stably express the Epstein Barr nuclear antigen 1 (EBNA1) support the episomal replication of plasmids containing the Epstein Barr virus origin of replication (EBV oriP). A 293EBNA (293E) cell line expressing the human corticotropin-releasing hormone receptor subtype I (CRHR1) from an episomal plasmid was generated (293CR1s), analyzed, adapted to spinner culture, and scaled-up for production in less than 6 weeks. Forty-seven stable CHO cell lines transfected with CRHR1 were also isolated. Expression of the receptor in the best of these lines (as judged by CRH-induced cAMP production), CHO-R22, was compared to that in 293CR1s cells. Results indicate that the CRHR1 episomal expression vector in 293E cells (1) rapidly generates stable cell lines suitable for scale-up; (2) is stably maintained during 3 months in culture; (3) expresses high levels of CRHR1 mRNA; and (4) expresses significantly more CRHR1 than the CHO-R22 line. Coexpression of additional G protein alpha subunit (G alpha s) with CRHR1 in 293E cells converts a higher percentage of receptor to the agonist high-affinity G-protein-coupled state. Our data support the idea that using the EBV oriP-driven episomal system for gene expression results in greater production of protein in a relatively short period of time.

Improved expression cloning using reporter genes and Epstein-Barr virus ori-containing vectors

Levels of expression of two reporter genes cloned into SV40 or Epstein-Barr virus (EBV) ori-containing plasmids were measured following transient transfection of cell lines constitutively expressing T-antigen or EBV nuclear antigen 1 (EBNA1). The TSA201 and COS7 cell lines stably produce T-antigen and support replication of the SV40 ori-containing constructs while the 293EBNA cell line produces EBNA1 and supports replication of EBV ori-containing plasmids. We found that 293EBNA cells express > 25-fold more beta-galactosidase (beta Gal) per mg protein than COS7 cells and 11-fold more beta Gal than TSA201 cells. We also demonstrate that 293EBNA cells are able to express 70-100-fold more angiotensin II type-1 receptor (AT1) per mg protein than COS7 or TSA201 cells. We examined the suitability of each cell line for use in expression cloning using a NaOH 'scrape' method as an improvement over emulsion autoradiography for detection. Measurable AT1 signals can be detected when reporter plasmids are diluted up to 1000-fold for COS7 and TSA201 cells, and up to 80,000-fold for 293EBNA cells. These data demonstrate that 293EBNA cells offer a significant improvement in expression cloning technology as compared to the conventionally used T-antigen-based cell lines.

Constitutive and enhanced expression from the CMV major IE promoter in a defective adenovirus vector

A defective adenovirus (Ad) type 5 E1- vector has been combined with the powerful constitutive cytomegalovirus (CMV) major immediate early (IE) promoter to produce a novel eukaryotic expression system. The Ad vector can replicate to high titres in 293 cells and then be used to infect a wide variety of non-permissive cell types. The Escherichia coli lacZ and CMV IE1 genes have been cloned to generate the Ad recombinants RAd35 and RAd31 respectively. In human fibroblasts infected with RAd35 beta-galactosidase (beta-gal) expression could be detected in virtually 100% of target cells, there was no detectable transcription from the Ad genome and extremely high levels of expression could be achieved with beta-gal representing the predominant cytoplasmic cellular protein. Additionally, a number of agents, including the CMV IE1 gene product (in RAd31) and forskolin, significantly enhanced expression from RAd35-infected human fibroblasts. Lower levels of constitutive beta-gal expression were obtained in RAd35-infected HeLa cells but again expression could be enhanced (up to 60 fold) by chemical inducing agents. Expression from the IE promoter in the Ad vector could be repressed by coinfection with CMV.