Group Ⅱ introns are self-splicing ribozymes, which insert directly into target sites in DNA with high frequency through "retrohoming". They specifically and efficiently recognize and splice DNA target sites, endowing themselves with great potential in genetic engineering. This paper reviewed the gene targeting principle of group Ⅱ introns and the application in microbial genetic modification, and then analyzed the limitations of them in multi-functional gene editing and eukaryotes based on the "retrohoming" characteristics and the dependence on high Mg²⁺ concentration. Finally, we dissected the potential of group Ⅱ introns in the development of novel gene editing tools based on our previous research outcome and the structural characteristics of the introns, hoping to provide a reference for the application of group Ⅱ introns in biotechnology.
DNA ; Eukaryota ; Gene Targeting ; Introns/genetics* ; RNA, Catalytic/genetics*

The methylcytosine dioxygenases TET proteins (TET1, TET2, and TET3) play important regulatory roles in neural function. In this study, we investigated the role of TET proteins in neuronal differentiation using Neuro2a cells as a model. We observed that knockdown of TET1, TET2 or TET3 promoted neuronal differentiation of Neuro2a cells, and their overexpression inhibited VPA (valproic acid)-induced neuronal differentiation, suggesting all three TET proteins negatively regulate neuronal differentiation of Neuro2a cells. Interestingly, the inducing activity of TET protein is independent of its enzymatic activity. Our previous studies have demonstrated that srGAP3 can negatively regulate neuronal differentiation of Neuro2a cells. Furthermore, we revealed that TET1 could positively regulate srGAP3 expression independent of its catalytic activity, and srGAP3 is required for TET-mediated neuronal differentiation of Neuro2a cells. The results presented here may facilitate better understanding of the role of TET proteins in neuronal differentiation, and provide a possible therapy target for neuroblastoma.
Animals ; Catalytic Domain ; Cell Differentiation ; drug effects ; physiology ; Cell Line, Tumor ; DNA-Binding Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Enzyme Inhibitors ; pharmacology ; GTPase-Activating Proteins ; genetics ; metabolism ; Immunohistochemistry ; Mice ; Microscopy, Fluorescence ; Neuroblastoma ; metabolism ; pathology ; Protein Isoforms ; antagonists & inhibitors ; genetics ; metabolism ; Proto-Oncogene Proteins ; antagonists & inhibitors ; genetics ; metabolism ; RNA Interference ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; metabolism ; Valproic Acid ; pharmacology

Robust and efficient control of therapeutic gene expression is needed for timing and dosing of gene therapy drugs in clinical applications. Ribozyme riboswitch provides a promising building block for ligand-controlled gene-regulatory system, based on its property that exhibits tunable gene regulation, design modularity, and target specificity. Ribozyme riboswitch can be used in various gene delivery vectors. In recent years, there have been breakthroughs in extending ribozyme riboswitch's application from gene-expression control to cellular function and fate control. High throughput screening platforms were established, that allow not only rapid optimization of ribozyme riboswitch in a microbial host, but also straightforward transfer of selected devices exhibiting desired activities to mammalian cell lines in a predictable manner. Mathematical models were employed successfully to explore the performance of ribozyme riboswitch quantitively and its rational design predictably. However, to progress toward gene therapy relevant applications, both precision rational design of regulatory circuits and the biocompatibility of regulatory ligand are still of crucial importance.
Animals ; Cell Line ; Gene Expression ; Gene Expression Regulation ; Genetic Therapy ; Humans ; Ligands ; Models, Theoretical ; RNA, Catalytic ; genetics ; Riboswitch ; genetics

OBJECTIVETo construct a full-genome hepatitis C virus (HCV) replicon that will allow for direct initiation of replication and generation of infectious viral particles in an in vitro and in vivo cell system.

METHODSSelf-cleaving ribozyme sequences were added to each side of the HCV cDNA clone JFH1 and the replication-deficient clone JFH1/GND, then inserted into the pcDNA3.1 vector downstream of the CMV promoter. The resultant recombinant plasmids, pcDNA3.1-RZ-JFH1 and pcDNA3.1-RZ-JFH1/GND, were tested for activity in vitro and in vivo by transiently transfecting into Huh7.5 cells (5 mug/100 mm culture dish) and injecting by high-pressure tail vein injection into Kunming mice (10 - 30 mug/mouse). Quantitative reverse transcription-PCR, immunofluorescence, immunohistochemistry, and serological testing were performed to determine the replication ability and assess the properties of the recombinant plasmids in the two systems.

RESULTSHCV RNA (1 - 3 * 10(6) copies/ml) was detected in the supernatant of transfected Huh7.5 cells up to 16 weeks after transfection. In addition, the viral particles from the supernatant were able to infect nave Huh7.5 cells. However, only transient viremia was achieved upon tail vein injection of the plasmid, and no HCV antigen-positive cells were detected by immunohistochemistry nor HCV-specific antibodies by serological testing.

CONCLUSIONThe constructed HCV replicon was capable of stable expression in cultured cells and of efficiently generating infectious viral particles in the in vitro system over a long period. However, the HCV replicon did not show infective characteristics in an in vivo mouse system. The full-length HCV replicon may represent a useful tool for in vitro study of HCV pathological mechanisms, possibly including anti-HCV drug screening.

Animals ; Base Sequence ; Cell Line ; Genetic Vectors ; Genome, Viral ; Hepacivirus ; genetics ; physiology ; Humans ; Male ; Mice ; Mice, Inbred Strains ; RNA, Catalytic ; genetics ; Recombination, Genetic ; Replicon ; Virus Replication ; genetics

Hepatitis C virus (HCV), one of the major pathogens of viral hepatitis, causes significant hazards in humans. Interferon treatment in combination with ribavirin is used as the first line clinical treatment for HCV infection. However, good response to this treatment has only been observed in few patients and repeated recurrence has also been reported frequently. Therefore, new antiviral agents and therapies are in urgent demand. Here, we report a newly constructed Escherichia coli RNase P based M1GS ribozyme that can specifically and efficiently target the core gene of HCV. The guide sequence (GS) of this M1IGS was designed according to the sequence of the core coding region of HCV genome. The GS was then covalently linked to the 3' terminus of M1 RNA, the catalytic subunit of RNase P from Escherichia coli. The specification of this sequence-specific ribozyme, M1GS, was then examined using an in vitro cleavage assay. The cytotoxicity and its activity in inhibition of HCV gene expression and viral proliferation were further studied in vivo. Our results show that the reconstructed M1GS ribozyme displayed obvious catalytic activity in cleaving target mRNAs fragment in vitro. Notable reduction in the expression of HCV core protein and a 1 000-fold reduction in viral growth were also observed in cultured HCV infected Huh7.5.1 cells expressing the functional M1GS ribozyme. This study demonstrated a direct evidence for the antiviral activity of the customized M1GS-HCV/C141 ribozyme, and thus provided a promising new strategy for clinical treatment of HCV infection.
Antiviral Agents ; pharmacology ; Escherichia coli ; genetics ; Genetic Engineering ; Hepacivirus ; genetics ; physiology ; RNA, Catalytic ; genetics ; pharmacology ; RNA, Guide ; genetics ; Ribonuclease P ; genetics ; Viral Core Proteins ; genetics

Various artificial riboswitches have been constructed by utilization of designed aptamers or by modification of natural riboswitch systems, because they can regulate gene expression in a highly efficient, precise and fast way, and promise to supply simple cis-acting, modular, and non-immunogenic system for use in future gene therapy applications. In this review, we present an overview of currently available technologies to design and select engineered riboswitches, and discuss some possible technologies that would allow them highly responsive to non-natural ligands, and dynamic control of gene expression in mammalian cells. Though how to bring custom-designed riboswitches as a novel and versatile tool box to gene control system is still a great challenge, the combination of structure-activity relationship information, computer based molecular design, in vitro selection, and high-through screening will serve as powerful tools for further development of riboswitch based gene regulatory systems.
Aptamers, Nucleotide ; genetics ; Gene Expression Regulation ; genetics ; Genetic Engineering ; Genetic Therapy ; Humans ; Protein Biosynthesis ; RNA, Catalytic ; chemistry ; genetics ; Ribosomes ; genetics ; Riboswitch ; genetics

OBJECTIVETo investigate the effect of the vector carrying short hairpin RNA targeting epidermal growth factor receptor (shRNA-EGFR) on the radiosensitivity of human nasopharyngeal carcinoma xenografts in nude mice.

METHODSshRNA-EGFR was transfected into human nasopharyngeal carcinoma cell line CNE1 via Lipofectamine 2000. The transfected cells were collected for quantitative RT-PCR detection of the expression level of EGFR mRNA. Western blotting was used to examine the expression of EGFR protein. CNE1 cells were inoculated into nude mice and the tumor volume was measured every 2 days. shRNA-EGFR was intratumorally injected in the mice, and 16 days after radiotherapy, the mice were sacrificed and tumors examined for radiosensitivity.

RESULTSshRNA-EGFR was effectively delivered via Lipofectamine 2000 into CNE cells to result in a significant downregulation of EGFR mRNA and protein expressions (P<0.05). A significant difference was noted in the tumor volume and weight in the tumor-bearing nude mice between shRNA-EGFR plus radiotherapy group and the control, exclusive radiotherapy and shRNA-EGFR groups (P<0.05).

CONCLUSIONshRNA-EGFR combined with radiotherapy can effectively inhibit the growth of nasopharyngeal carcinoma in nude mice. shRNA-EGFR can enhance sensitivity of nasopharyngeal carcinoma to radiotherapy.

Animals ; Gene Expression Regulation, Neoplastic ; Mice ; Mice, Nude ; Nasopharyngeal Neoplasms ; genetics ; radiotherapy ; RNA, Catalytic ; genetics ; RNA, Small Interfering ; genetics ; Radiation Tolerance ; genetics ; Receptor, Epidermal Growth Factor ; genetics ; Transfection ; Xenograft Model Antitumor Assays

OBJECTIVESTo construct a stable HCV-producing cell model for anti-HCV drug research.

METHODSThe HCV-ribozyme recombinant plasmid pJFH1-Rbz was constructed to generate the exact 5' and 3' ends of HCV genomic RNA by placing two self-cleaving ribozymes at both ends of the HCV JFH-1 cDNA. The plasmid was then transfected into HepG2 cells and the resultant clones were screened with G418. Subsequently, immunofluorescence and Western blot were performed to detect the expression of HCV core protein, HCV RNA level was quantitated by TaqMan real-time PCR method and HCV particles was detected by electron microscopy.

RESULTSHCV core protein was detected in the screened cell clone, and the level of HCV RNA was up to 1000,0000 copies/ml in the culture medium. Electron microscopy showed the viral particles in the culture suspension were approximately 55 nm in diameter. IFN-treating experiment demonstrated that the HCV RNA level decreased with the increasing concentration of IFN alpha.

CONCLUSIONWe constructed a stable HCV-producing cell model which can be used for anti-HCV drug research.

DNA, Complementary ; Genome, Viral ; Hep G2 Cells ; Hepacivirus ; genetics ; Humans ; Plasmids ; RNA, Catalytic ; genetics ; Transfection ; Viral Core Proteins ; genetics ; Virion ; Virus Replication

Although human telomerase catalytic subunit (TERT) has several cellular functions including telomere homeostasis, genomic stability, cell proliferation, and tumorigenesis, the molecular mechanism underlying anti-apoptosis regulated by TERT remains to be elucidated. Here, we show that ectopic expression of TERT in spontaneously immortalized human fetal fibroblast (HFFS) cells, which are a telomerase- and p53-positive, leads to increases of cell proliferation and transformation, as well as a resistance to DNA damage response and inactivation of p53 function. We found that TERT and a mutant TERT (no telomerase activity) induce expression of basic fibroblast growth factor (bFGF), and ectopic expression of bFGF also allows cells to be resistant to DNA-damaging response and to suppress activation of p53 function under DNA-damaging induction. Furthermore, loss of TERT or bFGF markedly increases a p53 activity and DNA-damage sensitivity in HFFS, HeLa and U87MG cells. Therefore, our findings indicate that a novel TERT-bFGF axis accelerates the inactivation of p53 and consequent increase of resistance to DNA-damage response.
*Apoptosis ; *Catalytic Domain ; Cell Line, Transformed ; Cell Proliferation ; DNA Damage ; Fetus/cytology ; Fibroblast Growth Factor 2/*genetics/metabolism ; Fibroblasts/cytology/metabolism ; Gene Expression Regulation, Neoplastic ; Hela Cells ; Humans ; RNA, Messenger/genetics/metabolism ; Telomerase/deficiency/*metabolism ; Tumor Suppressor Protein p53/*metabolism

Recent studies have unequivocally established the link between FTO and obesity. FTO was biochemically shown to belong to the AlkB-like family DNA/RNA demethylase. However, FTO differs from other AlkB members in that it has unique substrate specificity and contains an extended C-terminus with unknown functions. Insight into the substrate selection mechanism and a functional clue to the C-terminus of FTO were gained from recent structural and biochemical studies. These data would be valuable to design FTO-specific inhibitors that can be potentially translated into therapeutic agents for treatment of obesity or obesity-related diseases.
AlkB Homolog 1, Histone H2a Dioxygenase ; Alpha-Ketoglutarate-Dependent Dioxygenase FTO ; Amino Acid Motifs ; Animals ; Catalytic Domain ; DNA ; metabolism ; DNA Repair Enzymes ; metabolism ; Humans ; Methylation ; Obesity ; genetics ; Proteins ; chemical synthesis ; classification ; genetics ; RNA ; metabolism ; Substrate Specificity