Jun-He Zhang

A mini review of MAR-binding proteins

Genomic DNA encompasses several levels of organization, the nuclear matrix mediates the formation of DNA loop domains that are anchored to matrix attachment regions (MARs). By means of specific interaction with MAR binding proteins (MARBPs), MAR plays an important regulation role in enhancing transgene expression, decreasing expression variation among individuals of different transformants and serving as the replication origin. Through these years, some MARBPs have been identified and characterized from humans, plants, animals and algae so far and the list is growing. Most of MARBPs exist in a co-repressor/co-activator complex and involve in chromosome folding, regulation of gene expression, influencing cell development and inducing cell apoptosis. This review covers recent advances that have contributed to our understanding of MARBPs.

Simple, Time-Saving Dye Staining of Proteins for Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis Using Coomassie Blue

A fixation-free and fast protein-staining method for sodium dodecyl sulfate–polyacrylamide gel electrophoresis using Coomassie blue is described. The protocol comprises staining and quick washing steps, which can be completed in 0.5 h. It has a sensitivity of 10 ng, comparable with that of conventional Coomassie Brilliant Blue G staining with phosphoric acid in the staining solution. In addition, the dye stain does not contain any amount of acid and methanol, such as phosphoric acid. Considering the speed, simplicity, and low cost, the dye stain may be of more practical value than other dye-based protein stains in routine proteomic research.

Progesterone alleviates hypoxic-ischemic brain injury via the Akt/GSK-3β signaling pathway.

This aim of this study was to investigate whether progesterone (PROG) alleviates the neuronal apoptosis in neonatal rats with hypoxic-ischemic (HI) brain damage through the phosphatidylinositol 3-kinase (PI3K)/Akt/glycogen synthase kinase-3β (GSK-3β) signaling pathway. A total of 96 newborn Wistar rats aged 7 days were randomly divided into four groups: sham surgery, HI, drug prevention (PROG) and Akt inhibitor groups. HI animal models were established by a conventional method. All animals were sacrificed 24 h after hypoxia. Immunohistochemistry was used to detect the distribution and expression of phosphorylated Akt (p-Akt) and the GSK-3β proteins in the brain, and western blot analysis was used to determine the p-Akt and GSK-3β protein contents. An enzyme-linked immunosorbent assay was also used to determine the GSK-3β content of the brain tissue, and flow cytometry was used to evaluate the apoptosis rate of neural cells. The expression of p-Akt protein was reduced in the brain tissues of the HI group, whereas GSK-3β expression was increased. In addition, the GSK-3β content of the brain and the neuronal apoptosis rate were significantly increased. PROG pre-treatment increased p-Akt expression, decreased GSK-3β expression and GSK-3β content, and also reduced neuronal apoptosis. Following administration of the Akt inhibitor wortmannin, p-Akt expression decreased, GSK-3β expression increased, and the GSK-3β content and neuronal apoptosis rate significantly increased (P<0.05). In conclusion, PROG activates the PI3K/Akt/GSK-3β pathway to promote Akt activation, enhance p-Akt expression and inhibit GSK-3β expression, thereby inhibiting neuronal apoptosis, alleviating HI brain injury and inducing a cerebroprotective effect.

Matrix attachment region combinations increase transgene expression in transfected Chinese hamster ovary cells

Matrix attachment regions (MARs) are cis-acting DNA elements that can increase transgene expression levels in a CHO cell expression system. To investigate the effects of MAR combinations on transgene expression and the underlying regulatory mechanisms, we generated constructs in which the enhanced green fluorescent protein (eGFP) gene flanked by different combinations of human β-interferon and β-globin MAR (iMAR and gMAR, respectively), which was driven by the cytomegalovirus (CMV) or simian virus (SV) 40 promoter. These were transfected into CHO-K1 cells, which were screened with geneticin; eGFP expression was detected by flow cytometry. The presence of MAR elements increased transfection efficiency and transient and stably expression of eGFP expression under both promoters; the level was higher when the two MARs differed (i.e., iMAR and gMAR) under the CMV but not the SV40 promoter. For the latter, two gMARs showed the highest activity. We also found that MARs increased the ratio of stably transfected positive colonies. These results indicate that combining the CMV promoter with two different MAR elements or the SV40 promoter with two gMARs is effective for inducing high expression level and stability of transgenes.

Impact of Different Promoters on Episomal Vectors Harbouring Characteristic Motifs of Matrix Attachment Regions.

We previously demonstrated that the characteristic sequence of matrix attachment regions (MARs) allows transgenes to be maintained episomally in CHO cells. In the present study, six commonly used promoters from human cytomegalovirus major immediate-early (CMV), simian vacuolating virus 40 (SV40), Rous sarcoma virus, Homo sapiens ubiquitin C, phosphoglycerate kinase, and β-globin, respectively, were evaluated to determine their effects on transgene expression and stability in CHO cells stably transfected via the episomal vector harbouring characteristic MAR motifs. The CHO cells were transfected with vectors and then screened using G418, after which the stably transfected cells were split into two and further cultured either in the presence or absence of G418. Of the six promoters, the CMV promoter yielded the highest transgene expression levels and the highest transfection efficiency, whereas the SV40 promoter maintained transgene expression more stably during long-term culture than the other promoters did. The CMV and SV40 promoter-containing vectors were furthermore episomally maintained and conferred sustained eGFP expression in the cells even under nonselective conditions. On the basis of these findings, we conclude that the CMV promoter performs best in terms of yielding both high expression levels and high levels of stability using this episomal vector system.

Progesterone inhibits the expression of cycloxygenase-2 and interleukin-1β in neonatal rats with hypoxic ischemic brain damage

Recent studies found that progesterone (PROG) has a noticeable preventive effect on brain injuries. However, the underlying mechanisms of these effects, particularly on hypoxic ischemic brain damage (HIBD), remain unclear. This study observed the influence of PROG on the expression of cycloxygenase-2 (COX-2) and interleukin-1β (IL-1β) in HIBD neonatal rats, and explored the corresponding molecular mechanisms underlying the neuroprotective effect of PROG. Sixty 7-day-old neonatal Wistar rats were divided into sham operation (control), hypoxic ischemia (HI), and drug prophylaxis (PROG) groups, and HIBD animal models were routinely established. The PROG group was intraperitoneally injected with 0.5 g/L PROG at a dosage of 8 mg/kg 30 min before establishment of the model. All the animals were sacrificed 24 h after modeling. Changes in the COX-2 and IL-1β contents in the brain tissues were determined using enzyme-linked immunosorbent assay. Protein expression was observed using immunohistochemistry, and mRNA expression was determined using reverse transcription polymerase chain reaction. The expression and contents of COX-2 and IL-1β in the HI group were significantly higher than those in the control group (P < 0.01). Compared with the HI group, the PROG group showed noticeably lower expression and contents of COX-2 and IL-1β (P < 0.05). In conclusion, PROG can inhibit the expression of COX-2 and IL-1β in brain tissue, further reducing the level of COX-2 and IL-1β, which may be one of the mechanisms for protection from HIBD.

Treating Colon Cancer Cells with FK228 Reveals a Link between Histone Lysine Acetylation and Extensive Changes in the Cellular Proteome

The therapeutic value of FK228 as a cancer treatment option is well known, and various types of cancer have been shown to respond to this drug. However, the complete mechanism of FK228 and the affect it has on histone lysine acetylation and the colon cancer cell proteome are largely unknown. In the present study, we used stable isotope labeling by amino acids in cell culture (SILAC) and affinity enrichment followed by high-resolution liquid chromatograph-mass spectrometer (LC-MS)/MS analysis to quantitate the changes in the lysine acetylome in HCT-8 cells after FK228 treatment. A total of 1,194 lysine acetylation sites in 751 proteins were quantified, with 115 of the sites in 85 proteins being significantly upregulated and 38 of the sites in 32 proteins being significantly downregulated in response to FK228 treatment. Interestingly, 47 histone lysine acetylation sites were identified in the core histone proteins. We also found a novel lysine acetylation site on H2BK121. These significantly altered proteins are involved in multiple biological functions as well as a myriad of metabolic and enzyme-regulated pathways. Taken together, the link between FK228 function and the downstream changes in the HCT-8 cell proteome observed in response to FK228 treatment is established.

Episomal Lentiviral Vector-Mediated miR-145 Overexpression Inhibits Proliferation and Induces Apoptosis of Human Esophageal Carcinomas Cells.

BACKGROUND Gene therapy is a promising approach for the treatment of various cancers. However, most viral vectors used for this purpose carry risks, including potential integration into the host genome. OBJECTIVE We addressed this issue in the present study by constructing an episomal lentiviral vector using the .-interferon matrix attachment region to express the microRNA -145(miR-145), and examining the effect of miR-145 overexpression on human esophageal carcinomas (EC) cells. Some recent relevant patents are also discussed. METHOD Expression levels of miR-145 and the marker protein enhanced green fluorescent protein (EGFP) in infected ECA109 and EC9706 human esophageal carcinoma cells were detected by quantitative PCR and flow cytometry, respectively. Cell proliferation and apoptosis were assessed by Cell Counting Kit-8 and flow cytometry, respectively. Plasmid rescue experiments and fluorescence in situ hybridization were used to determine the episomal status of the transfected vector. RESULTS We found that EGFP and miR-145 were highly expressed in EC cells, and miR-145 overexpression inhibited cell proliferation and induced apoptosis. Moreover, the lentiviral vector did not integrate into the host genome, but was maintained episomally at lower copy numbers. CONCLUSION Taken together, our results demonstrate that miR-145-expressing episomal lentiviral vectors are a promising tool for gene therapy in the treatment of EC.

Cell compatibility of an eposimal vector mediated by the characteristic motifs of matrix attachment regions.

The characteristic sequence of β-interferon matrix attachment regions (MARs) can mediate transgene expression via episomal vectors in Chinese hamster ovary (CHO) cells. However, the host cells were from hamster ovaries, which are not suitable target cells for gene therapy. In this study, we aimed to evaluate the suitability of 12 different human cell lines as target cells for gene therapy. We transfected the cells with episomal vectors and obtained colonies stably expressing the vector products after G418 screening. Therefore the stably transfected cells were split into two and further cultured either in the presence or the absence of G418. Flow cytometry was used to observe the positive rate of cell transfection and level of green fluorescent protein (GFP) expression. Plasmid rescue assays, fluorescence in situ hybridization (FISH), and fluorescence quantitative polymerase chain reaction (PCR) were used to investigate the presence and gene copy numbers of plasmid in mammalian cells. The results showed that transfection efficiency and transgene expression levels in A375, Eca-109, and Changliver cells were high. In contrast, transgene silencing was observed in BJ, HSF, and A431 cells, and low expression of the transgene was observed in the other six cell lines. In addition, the plasmid was present in the episomal state in A375, Eca-109, and Chang-liver cells with relatively low copy numbers even under nonselective conditions. Thus, our results provide the first evidence showing transgene expression of an episomal vector mediated by the characteristic motifs of MARs for maintenance of the longterm stability of episomes in different types of cells.

The EF-1α promoter maintains high-level transgene expression from episomal vectors in transfected CHO-K1 cells

In our previous study, we demonstrated that episomal vectors based on the characteristic sequence of matrix attachment regions (MARs) and containing the cytomegalovirus (CMV) promoter allow transgenes to be maintained episomally in Chinese hamster ovary (CHO) cells. However, the transgene expression was unstable and the number of copies was low. In this study, we focused on enhancers, various promoters and promoter variants that could improve the transgene expression stability, expression magnitude (level) and the copy number of a MAR‐based episomal vector in CHO‐K1 cells. In comparison with the CMV promoter, the eukaryotic translation elongation factor 1 α (EF‐1α, gene symbol EEF1A1) promoter increased the transfection efficiency, the transgene expression, the proportion of expression‐positive clones and the copy number of the episomal vector in long‐term culture. By contrast, no significant positive effects were observed with an enhancer, CMV promoter variants or CAG promoter in the episomal vector in long‐term culture. Moreover, the high‐expression clones harbouring the EF‐1α promoter tended to be more stable in long‐term culture, even in the absence of selection pressure. According to these findings, we concluded that the EF‐1α promoter is a potent regulatory sequence for episomal vectors because it maintains high transgene expression, transgene stability and copy number. These results provide valuable information on improvement of transgene stability and the copy number of episomal vectors.