VP22 fusion protein-based dominant negative mutant can inhibit hepatitis B virus replication

AP4 activates cell migration and EMT mediated by p53 in MDA-MB-231 breast carcinoma cells

Tumor metastasis is the primary cause of mortality in most cancer patients. Before disassociation from the tumors, most of malignant tumor cells undergo the epithelial-mesenchymal transition to break away from the adhesions between the cells and the surrounding extracellular matrix. Recently, activating enhancer-binding protein (AP4) has been shown to be a mediator of EMT in colorectal cancer and high level of AP4 correlates with poor prognosis in cancer patients. It has been found that AP4 upregulates the genes involved in EMT and cell proliferation in colorectal cancer cells and that the aggressive human breast cancer cells MDA-MB-231 are highly metastatic. Therefore, we tested the hypothesis that AP4 may also affect cell migration and EMT in this cell type. Three different assays, including the wound-healing assay, the Boyden chamber assay, and the cell tracking assay, were employed to confirm that AP4 activated both cell migration and invasion. Immunofluorescence staining and Western blot analysis revealed that the cells underwent EMT when AP4 was upregulated. In contrast, overexpression of dominant-negative AP4, lacking the DNA-binding domain, inactivated the DNA-binding ability of endogenous AP4 and led to lower cell motility. Furthermore, we found that AP4 enhanced p53 expression at both transcriptional and translational levels. Knockdown of p53 by siRNA significantly diminished the activation of cell migration by AP4, indicating that AP4 can regulate cell migration via the activity of p53.

Inhibition effect produced by dominant negative mutant fusion protein PreS2-TLM-ScFv-HBcDN on HBV replication in vitro

A mammalian expression vector comprised of the PreS2-TLM (translocation motif), a single-chain variable fragment (ScFv) that binds to hepatitis B surface antigen (HBsAg) and the EGFP gene was constructed. A stably transformed cell line that could express and secrete the fusion protein (PreS2-TLM-ScFv-EGFP) was established. HBsAg-positive HepG2.2.15 cells and HepG2 and HeLa cells were incubated with the supernatant of the transformed cell line cultures for evaluating the cellular permeability of PreS2-TLM-ScFv-EGFP. The location of the fusion protein PreS2-TLM-ScFv-EGFP in HepG2.2.15 cells was observed with immunofluorescence staining. EGFP was next replaced by a dominant negative mutant of the hepatitis B virus core gene (HBcDN) for producing fusion protein PreS2-TLM-ScFv-HBcDN, which was detected by western blot. The supernatant containing fusion protein PreS2-TLM-ScFv-HBcDN was added to the cultures of HepG2.2.15 cells, and the packaged hepatitis B virus (HBV) pregenomic RNA expression levels in the cells were measured using qRT-PCR. The results of the in vitro study indicated that the packaged HBV pregenomic RNA expression levels in HepG2.2.15 cells significantly decreased when these cells were exposed to the supernatant at the dose of 25% for 24, 48 and 72 h, or at the dose of 12.5% for 72 h.