Efficient Foreign Gene Research Articles

High-efficiency nonhomologous insertion of a foreign gene into the herpes simplex virus genome.

Efficient, accurate and convenient foreign-gene insertion strategies are crucial for the high-throughput and rapid construction of large DNA viral vectors, but relatively inefficient and labour-intensive methods have limited the application of recombinant viruses. In this study, we applied the nonhomologous insertion (NHI) strategy, which is based on the nonhomologous end joining (NHEJ) repair pathway. Compared to the currently used homologous recombination (HR) strategy, we obtained a higher efficiency of foreign-gene insertion into the herpes simplex virus (HSV) genome that reached 45 % after optimization. By using NHI, we rapidly constructed recombinant reporter viruses using a small amount of clinical viruses, and the recombinant virus was stable for at least ten consecutive passages. The fidelity of NHI ranged from 70–100% and was related to the sequence background of the insertion site according to the sequencing results. Finally, we depict the dynamic process by which the foreign-gene donor plasmid and viral genome are rapidly cleaved by Cas9, as revealed by quantitative pulse analysis. Furthermore, the NHI strategy exerted selection pressure on the wild-type and reverse-integrated viral genomes to efficiently integrate the foreign gene in a predetermined direction. Our results indicate that the use of a rationally designed NHI strategy can allow rapid and efficient foreign gene knock-in into the HSV genome and provide useful guidance for gene insertion into large DNA viral genomes using NHI.

Efficient foreign gene expression in planta using a plantago asiatica mosaic virus-based vector achieved by the strong RNA-silencing suppressor activity of TGBp1

Plant virus expression vectors provide a powerful tool for basic research as well as for practical applications. Here, we report the construction of an expression vector based on plantago asiatica mosaic virus (PlAMV), a member of the genus Potexvirus. Modification of a vector to enhance the expression of a foreign gene, combined with the use of the foot-and-mouth disease virus 2A peptide, allowed efficient expression of the foreign gene in two model plant species, Arabidopsis thaliana and Nicotiana benthamiana. Comparison with the widely used potato virus X (PVX) vector demonstrated that the PlAMV vector retains an inserted foreign gene for a longer period than PVX. Moreover, our results showed that the GFP expression construct PlAMV-GFP exhibits stronger RNA silencing suppression activity than PVX-GFP, which is likely to contribute to the stability of the PlAMV vector.

PiggyBac Transposon-Mediated Gene Transfer in Cashmere Goat Fetal Fibroblast Cells

PiggyBac (PB) has recently been found to be functional in various organisms. To verify and exploit its application in the cashmere goat, a PB transposon system including donor and helper vector of was developed, in which the EGFP gene in donor of vector was used as reporter. Cashmere goat fetal fibroblasts cells (GFFs) were transfected with the PB transposon system and the efficiency of gene transfer was determined. Compared with random integration, PB-mediated EGFP expression levels increased 7.78-fold in the GFFs, confirming that the PB transposon system constructed successfully mediated efficient foreign gene integration in the GFFs. To further investigate the characteristics of PB-mediated integration instance, PB integration site distribution in the goat genome was examined. The results showed that PB had a preference for AT rich regions of the goat genome. Thus this study confirms the function of PB transposon in GFFs and provides a potential genetic tool for producing transgenic goats.

Cloning of a marine cyanobacterial promoter for foreign gene expression using a promoter probe vector

A marine cyanobacterial promoter was cloned to allow efficient foreign gene expression. This was carried out using chloramphenicol acetyl transferase (CAT) as a marker protein. For rapid and simple measurement of CAT activity, a method based on a fluorescently labeled substrate was improved by utilizing HPLC equipped with a flow-through fluorescent spectrophotometer. This method was used in conjunction with a newly constructed promoter probe vector. Cyanobacterial transformants, harboring plasmid containing a cloned 2-kbp marine cyanobacterial genomic fragment, showed a 10-fold higher CAT activity, compared with that achieved using the kanamycin-resistant gene promoter. From the sequence analysis of the cloned fragment, a putative promoter region was found.

Optimal expression of GUS gene from methyl jasmonate-inducible promoter in high density culture of transformed tobacco cell line BY-2

The optimal expression of the β-glucuronidase (GUS) gene was studied in a tobacco cell line, BY-2, that was transformed with the GUS gene under the control of the cathepsin D inhibitor (CDI) promoter. In batch culture, the optimal induction time was in the late growth phase, and the optimal concentration of methyl jasmonate (MJ) was 0.7 mM. In fed-batch culture, the GUS specific activity when MJ was added several times was about 1.7-fold that when MJ was added only once. However, a significant decrease in the growth rate was observed after MJ addition. During the fed-batch culture, no medium components were depleted, and the presence of inhibitory metabolite(s) was observed. To remove inhibitory metabolite(s) from the medium, filtration culture was carried out, which gave a cell growth rate faster than that of the fed-batch culture. The final cell concentration and total GUS activity reached 480 g-fresh weight/ l and 5.2 μkat/ l, which were 1.3-fold and 1.5-fold the amounts obtained in fed-batch culture. The GUS specific activity using the CDI promoter was about 17-fold that obtained in a rbcS-promoter system studied previously. Efficient foreign gene production from transformed BY-2 cells was thus performed on a fermentor scale.

Efficient Foreign Gene Expression in Epstein-Barr Virus-Transformed Human B-Cells

Epstein-Barr virus (EBV) is a herpesvirus that transforms B-cells (B-LCL) and has undergone intense scrutiny owing to its association with Burkitt's lymphoma, nasopharyngeal carcinoma, and immunoblastic lymphomas. B-LCL have also proven useful in the study of human immunology. We describe a novel system for inducing efficient foreign gene expression in B-LCL using biotinylated adenovirus as an endosome-disrupting agent. Plasmid DNA is coupled to the exterior of viral particles by streptavidin-polylysine chimeric proteins. Up to 67% of B-LCL may be induced to express foreign genes in vitro in transient expression systems, and gene expression lasts for at least 17 days. We have expressed firefly luciferase, β-galactosidase (β-gal), chloramphenicol acetyltransferase, HIV gag, and env genes, as well as infectious HIV, and the EBV-specific BZLF gene in B-LCL with this system. In vivo delivery of a β-gal reporter gene to B-LCL was documented in a SCID mouse model. Potential applications include study of genetic regulation of EBV infection and transformation events, study of potential gene therapies for EBV-related B-cell tumors, and production of antigen-presenting cells for use in immunologic assays. Because of the high percentage of cells transformed and the length of foreign gene expression, the possibility of examining foreign gene expression in transient assays, without selection for clonal populations, exists.

Specific Stages of Oocyte Maturity in Medaka to Obtain Efficient Foreign Gene Transfer by Microinjection.

Microinjection of foreign DNA into oocyte nucleus is a useful method for producing transgenic medaka. To find the most appropriate stage of oocyte maturity to obtain efficient foreign gene transfer, we microinjected the plasmid pHV-GH containing Drosophila Hsp70 promoter and rainbow trout growth hormone cDNA into medaka oocytes collected 20-6h before ovulation at intervals of 2 hours. Injected oocytes were cultured until ovulation, inseminated and incubated for 7 days. Oocytes collected 14-6h before ovulation matured in culture while most of those col-lected 20-16h before ovulation did not. The proportion of oocytes which were successfully fertilized and normally developed to the 7-day-old stage after microinjection were highest for oocytes collected at 8h before ovulation, as 79% were successfully fertilized and 58% developed normally. Embryos developed normally to the 7-day-old stage were assayed for the existence of foreign sequences by slot blotting. The proportion of embryos positive for foreign sequences among those assayed was highest (60%) for oocytes at 8 and 10h before ovulation. Thus, the gene transfer efficiency, ie. the ratio of positive embryos to injected oocytes, was highest (35%) at 8h before ovulation.

Expression of the streptokinase gene from Streptococcus equisimilis in Bacillus subtilis.

The previously cloned and sequenced streptokinase gene (skc) from Streptococcus equisimilis H46A was inserted into plasmid vectors capable of replication in Bacillus subtilis. The skc gene was expressed by use of its own transcription and translation signals which appeared to meet the stringent requirements of B. subtilis for efficient foreign gene expression. The secreted streptokinase activity began to decline toward the end of the exponential growth phase suggesting that B. subtilis exoproteases hydrolyzed and inactivated the foreign protein.