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He C.,University of British Columbia | Genchev G.Z.,University of Illinois at Chicago | Lu H.,University of Illinois at Chicago | Lu H.,Key Laboratory of Medical Embryo Molecular Biology | Li H.,University of British Columbia
Journal of the American Chemical Society | Year: 2012

Protein structure is highly diverse when considering a wide range of protein types, helping to give rise to the multitude of functions that proteins perform. In particular, certain proteins are known to adopt a knotted or slipknotted fold. How such proteins undergo mechanical unfolding was investigated utilizing a combination of single molecule atomic force microscopy (AFM), protein engineering, and steered molecular dynamics (SMD) simulations to show the mechanical unfolding mechanism of the slipknotted protein AFV3-109. Our results reveal that the mechanical unfolding of AFV3-109 can proceed via multiple parallel unfolding pathways that all cause the protein slipknot to untie and the polypeptide chain to completely extend. These distinct unfolding pathways proceed via either a two- or three-state unfolding process involving the formation of a well-defined, stable intermediate state. SMD simulations predict the same contour length increments for different unfolding pathways as single molecule AFM results, thus providing a plausible molecular mechanism for the mechanical unfolding of AFV3-109. These SMD simulations also reveal that two-state unfolding is initiated from both the N- and C-termini, while three-state unfolding is initiated only from the C-terminus. In both pathways, the protein slipknot was untied during unfolding, and no tightened slipknot conformation was observed. Detailed analysis revealed that interactions between key structural elements lock the knotting loop in place, preventing it from shrinking and the formation of a tightened slipknot conformation. Our results demonstrate the bifurcation of the mechanical unfolding pathway of AFV3-109 and point to the generality of a kinetic partitioning mechanism for protein folding/unfolding. © 2012 American Chemical Society. Source


Xie S.-Y.,Beijing Jiaotong University | Li W.,Beijing Jiaotong University | Ren Z.-R.,Beijing Jiaotong University | Ren Z.-R.,Key Laboratory of Medical Embryo Molecular Biology | And 7 more authors.
International Journal of Hematology | Year: 2011

Although the therapeutic efficacy of β654-thalassaemia treatment using a combination of RNAi and antisense RNA to balance the synthesis of α- and β-globin chains has been demonstrated previously, and the safety of lentiviral delivery remains unclear. Herein, we used the same β654-thalassaemia mouse model to develop a therapy involving direct delivery of siRNA and antisense RNA plasmids via intravenous injection to simultaneously knock down α-globin transcript levels and restore correct β-globin splicing. The amount of α-globin mRNAs in siRNA-treated MEL cells decreased significantly, and the properly spliced β-globin mRNA was restored in HeLaβ654 cells transfected with pcDNA-antisense plasmid. Furthermore, treatment of β654-thalassaemic mice with siRNA and antisense RNA plasmids resulted in significant reduction of poikilocytosis and reticulocyte counts in blood samples, decreased nucleated cell populations in bone marrow, and reduced intrasinusoidal extramedullary haematopoiesis loci and iron accumulation in liver. RT-PCR analysis revealed that treatment resulted in down-regulation of α-globin mRNA synthesis by ∼50% along with an increase in the presence of normally spliced β-globin transcripts, indicating that the phenotypic changes observed in β654-thalassaemic mice following treatment resulted from restoration of the balance of α/β-globin biosynthesis. © The Japanese Society of Hematology 2011. Source


Ou H.,Beijing Jiaotong University | Ou H.,Guiyang Medical University | Huang Y.,Beijing Jiaotong University | Huang Y.,Key Laboratory of Medical Embryo Molecular Biology | And 10 more authors.
Journal of Biotechnology | Year: 2013

The introduction of double-strand breaks (DSBs) at target sites could greatly enhance homologous recombination, and engineered nucleases, such as zinc finger and transcription activator-like effector nucleases, have been successfully developed for making such breaks. In this study, we present a highly efficient site-specific integration strategy based on homologous recombination and ΦC31 integrase. An attB sequence was introduced at the homologous arm of an insertion targeting vector. DSBs at the target locus and donor were then simultaneously generated by the ΦC31 integrase when co-transfected with the donor vector, consequently stimulating homologous recombination. The results demonstrated that our strategy is feasible and the efficiency at the BF4 target site, which we previously identified in the bovine genome, was as high as 93%. The frequency at another site (BF10) was almost two-fold greater in comparison to the vector without homologous arms. This technology requires no sophisticated nuclease design efforts, and the off-target effect is reduced by ΦC31 integrase compared to the use of engineered nucleases, thereby offering a simple and safe way to effectively express a donor gene at a desired locus. This development has great potential value, especially in transgenesis or gene therapy applications. © 2013 Elsevier B.V. Source


Ren X.,Shanghai JiaoTong University | Gong X.,Shanghai JiaoTong University | Cai Q.,Shanghai JiaoTong University | Cai Q.,Key Laboratory of Medical Embryo Molecular Biology | And 9 more authors.
Biotechnology Letters | Year: 2015

Objectives: To investigate the reasons for the instability of human coagulation factor FVIII (hFVIII) in milk which is an intractable obstacle during the hFVIII production by a transgenic mammary gland bioreactor. Results: We constructed P1A3-hFVIIIBDD and P1A3-hFVIIIBDD-IRES-vWF co-expression cassettes for generating transgenic mice. P1A3-hFVIII/CMV-vWF double heterozygotes were also prepared by mating P1A3-hFVIIIBDD with CMV-vWF mice. hFVIII bioactivity in milk was determined under different storage conditions. The half-life (in vitro) of hFVIII bioactivity in P1A3-hFVIIIBDD-IRES-vWF mice was significantly longer than P1A3-hFVIIIBDD mice [77 ± 4.9 vs. 44 ± 2.6 h at 4 °C, 32.5 ± 5 vs. 19.7 ± 0.6 h at room temperature and 7.4 ± 1.4 vs. 3.4 ± 0.6 at 37 °C, respectively (P < 0.05)]. The half-life (in vitro) of hFVIII bioactivity in milk of double heterozygotes was similar to P1A3-hFVIIIBDD-IRES-vWF ones, demonstrating that the vWF transgene expression in hFVIII transgenic mice can efficiently improve the stabilization of hFVIII bioactivity in milk. Conclusion: We provide a new approach of P1A3-hFVIIIBDD-IRES-vWF co-expression to generate more stable hFVIII in transgenic milk with rapid and low cost as well as valuable information for producing pharmaceutical proteins by transgenic mammary gland bioreactor. © 2015, Springer Science+Business Media Dordrecht. Source

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