Acta Biochimica et Biophysica Sinica - Advance Access

Modeling of protein refolding from inclusion bodies

Thu, 12 Nov 2009 00:37:13 PST

Overexpression of foreign proteins in Escherichia coli often leads to the formation of inclusion bodies (IBs), which becomes the major bottleneck in the preparation of recombinant proteins and their applications. In the present study, 36 proteins from IBs were refolded using a simple refolding method. Refolding yields of these proteins were defined as the percentage of soluble proteins following dilution refolding in the amount of denatured proteins in the samples before diluting into refolding buffer. Furthermore, a mathematical model was deduced to evaluate the role of biochemical properties in the protein refolding. Our results indicated that under the experimental conditions, isoelectric point of proteins might be mostly contributing to the high efficacy of protein refolding since the increment of one unit resulted in a decrease of 14.83% in the refolding yield. Other important mediators were components of protein secondary structure and the molecular weight (R² = 0.98, P = 0.000, F-test). Six proteins with low efficiency in the protein refolding possessed relatively low isoelectric points. Furthermore, refolding yields of six additional proteins from IBs were predicted and further validated by refolding the proteins under the same conditions. Therefore, the model of protein refolding developed here could be used to predict the refolding yields of proteins from IBs through a simple method. Our study will be suggestive to optimize the methods for protein refolding from IBs according to their intrinsic properties.

B23 interacts with PES1 and is involved in nucleolar localization of PES1

Zhang, J., Yang, Y., Wu, J. — Thu, 12 Nov 2009 00:37:12 PST

PES1, the human homolog of zebrafish pescadillo, is a nucleolar protein that is essential for cell proliferation. We report herein that a nucleolar marker protein B23 physically interacts with PES1 and is involved in the nucleolar localization of PES1. In vivo interaction between B23 and PES1 was verified by co-immunoprecipitation of endogenous B23 and PES1 proteins, and they showed cellular co-localizations under both normal and actinomycin D-induced stress conditions. Furthermore, we mapped their interaction domains via in vitro pull-down assays. When B23 was knocked down by RNA interference, there appeared an increased nucleoplasmic distribution of PES1. Our results support a previous hypothesis that B23 might be a nucleolar hub protein for protein targeting to the nucleolus, and shed light on the nucleolar localization mechanism of PES1. The physical interaction between B23 and PES1 implies that they may participate in ribosome biogenesis in a protein complex.

Recovery of infectious foot-and-mouth disease virus from full-length genomic cDNA clones using an RNA polymerase I system

Chang, Y., Zheng, H., Shang, Y., Jin, Y., Wang, G., Shen, X., Liu, X. — Thu, 12 Nov 2009 00:37:12 PST

The prototypic foot-and-mouth disease virus (FMDV) was shown more than a century ago to be the first filterable agent capable of causing FMD, and it has served as an important model for studying basic principles of Aphthovirus molecular biology. However, the complex structure and antigenic diversity of FMDV have posed a major obstacle to the attempts at manipulating the infectious virus by reverse genetic techniques. Here, we report the recovery of infectious FMDV from cDNAs based on an efficient in vivo RNA polymerase I (polI) transcription system. Intracellular transcription of the full-length viral genome from polI-based vectors resulted in efficient formation of infectious virus displaying a genetic marker. Compared with wild-type virus, an abundance of genomic mRNA and elevated expression levels of viral antigens were indicative of the hyperfunction throughout the life-cycle of this cDNA-derived virus at transcription, replication, and translation levels. The technology described here could be an extremely valuable molecular biology tool for studying FMDV complex infectious characteristics. It is an operating platform for studying FMDV functional genomics, molecular mechanism of pathogenicity and variation, and lays a solid foundation for the development of viral chimeras toward the prospect of a genetically engineered vaccine.

Discovery of YB-1 as a new immunological target in neuroblastoma by vaccination in the context of regulatory T cell blockade

Zheng, J., Jing, W., Orentas, R. J. — Thu, 12 Nov 2009 07:40:43 PST

Neuroblastoma is one of the most common solid tumors in infancy and early childhood. Using the A/J mouse and a syngeneic neuroblastoma cell line AGN2a, we induced a strong anti-neuroblastoma cellular immune response when AGN2a transfected to express costimulatory molecules (CD80/CD86/CD54/CD137L) was used as a vaccine in the context of regulatory T cell blockade. Strong humoral immunity was induced by AGN2a-4p immunization in the context with regulatory T cell blockade. Serum from treated mice was used to screen an AGN2a cDNA expression library that was constructed with ZAP express vector in order to identify tumor-associated antigens by SEREX. Twenty-one clones were identified by sequencing and comparative analysis of gene pools. Most transcripts play some roles in the neuronal differentiation, cell metabolism, or have previously been identified as transcripts that are over-expressed in other malignancies. The most commonly identified tumor-associated antigen, using serum from AGN2a-4p immunization with Treg blockade mice, was YB-1 protein that also induced a T cell response. These results indicated that potential neuroblastoma-associated antigens were found by the sera from mice immunized with tumor cells expressing costimulatory molecules with regulatory T cell function blockade. The identification of YB-1 as tumor-associated antigens capable of eliciting a T cell response validates our experimental approach and argues for the antigens we have identified here to be evaluated as targets of effector immunity and as vaccine candidates.

Proteolytic regulatory mechanism of chemerin bioactivity

Du, X.-Y., Leung, L. L.K. — Thu, 12 Nov 2009 00:37:11 PST

Chemerin is a novel chemoattractant recognized by chemokine-like receptor 1 (CMKLR1), a serpentine receptor expressed primarily by plasmacytoid dendritic cells, natural killer cells, and macrophages. Human prochemerin circulates in plasma as an inactive precursor. Its chemotactic activity is expressed upon cleavage of the C-terminal amino acid residues by proteases of the coagulation, fibrinolytic, and inflammatory system. The C-terminal cleavage site of prochemerin is highly conservative, indicating that the proteolytic regulation of chemerin bioactivity is a common mechanism undertaken by different species. In this review, we summarized chemerin–proteases interactions, chemerin receptors, and their importance in normal and pathologic conditions.

Antioxidant activity of mangostin in cell-free system and its effect on K562 leukemia cell line in photodynamic therapy

Sun, D., Zhang, S., Wei, Y., Yin, L. — Tue, 10 Nov 2009 23:09:01 PST

Mangostin (MAG), a kind of xanthone widely used in diet and medicine, has antioxidant, anti-inflammatory, antimicrobial, and anticancer activities. On account of its antioxidant activity, MAG might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species production was stimulated leading to irreversible tumor cell injury. In this study, the antioxidant activity of MAG was investigated and the influence of MAG on K562 cells in 5-aminolevulinic acid (ALA)-based PDT is demonstrated. The results showed that MAG could scavenge hydroxyl radical, superoxide anion, and hydrogen peroxide and inhibit the formation of malondialdehyde (MDA), but increase the amounts of singlet oxygen in cell-free systems. MAG inhibits cell proliferation and enhances cell apoptosis, lipid peroxidation, and DNA damage in ALA-PDT on K562 cells. NaN₃, a singlet oxygen quencher, suppresses the MAG-induced cell apoptosis, lipid peroxidation, and DNA damage. In conclusion, MAG enhances the PDT-induced cytotoxicity in K562 cells and singlet oxygen was involved in this process. These results implied that the effect of antioxidants on PDT might be determined by its sensitization ability to singlet oxygen.

Genome-wide identification of target genes repressed by the zinc finger transcription factor REST/NRSF in the HEK 293 cell line

Liu, Z., Liu, M., Niu, G., Cheng, Y., Fei, J. — Tue, 10 Nov 2009 23:09:00 PST

Transcriptional repression is as important as transcriptional activation in establishing cell-type specific patterns of gene expression. RE1-silencing transcription factor (REST), also known as neuronal restrictive silencing factor (NRSF), is a transcriptional regulator that represses a battery of neuronal differentiation genes in non-neuronal cells or in neural progenitor cells by binding to a specific DNA sequence (repressor element-1/neuron-restrictive silencer element, RE1/NRSE). REST/NRSF functions in the neuronal development are widely studied, however, little is known about target genes in various non-neuronal lineages that may result in cell differentiation. Here, we use RNA interference (RNAi) technology combined with the microarray strategy to identify potential REST/NRSF targets and RE1/NRSEs in human non-neuronal cell line HEK 293. Expression of 54 genes was up-regulated by inhibition of REST/NRSF in the HEK 293 cells according to the microarray experiment and 13 of those were further confirmed by quantitative RT-PCR. Our results confirmed the good confidence and reliability of current research data based on in silico, chromatin immunoprecipitation in combination with microarrays (ChIP-chip), and high-throughput sequencing (ChIP-seq). However, in view of the fact that thousands of genes have been testified or predicted to be recognized by REST/NRSF, our data show that only a few genes among those are directly up-regulated by the interaction of REST/NRSF with RE1/NRSEs sites in gene sequences.

Potentiation of (-)-epigallocatechin-3-gallate-induced apoptosis by bortezomib in multiple myeloma cells

Wang, Q., Li, J., Gu, J., Huang, B., Zhao, Y., Zheng, D., Ding, Y., Zeng, L. — Tue, 10 Nov 2009 23:08:59 PST

The green tea constituent, (–)-epigallocatechin-3-gallate (EGCG), has chemopreventive and anticancer effects. This is partially because of the selective ability of EGCG to induce apoptosis and death in cancer cells without affecting normal cells. In the present study, the activity of EGCG against the myeloma cell line, KM3, was examined. Our results demonstrated, for the first time, that the treatment of the KM3 cell line with EGCG inhibits cell proliferation and induces apoptosis, and there is a synergistic effect when EGCG and bortezomib are combined. Further experiments showed that this effect involves the NF-B pathway. EGCG inhibits the expression of the P65 mRNA and P65/pP65 protein, meanwhile it downregulates pIB expression and upregulates IB expression. EGCG also activates caspase-3, -8, cleaved caspase-9, and poly-ADP-ribose polymerase (PARP) and subsequent apoptosis. These findings provided experimental evidence for efficacy of EGCG alone or in combination with bortezomib in multiple myeloma therapy.

Hyperhomocysteinemia stimulates hepatic glucose output and PEPCK expression

Yu, X., Huang, Y., Hu, Q., Ma, L. — Mon, 09 Nov 2009 23:52:33 PST

Homocysteine is an intermediate in the sulfur amino acid metabolism. Recent studies suggested that there might be links between hyperhomocysteinemia and insulin resistance. In the present study, we investigated the effect of homocysteine on glucose metabolism. We demonstrated that the levels of insulin were significantly higher in mice with hyperhomocysteinemia than those in the normal mice after administration of glucose. The effect of insulin on glucose output was significantly blocked in the homocysteine-treated hepatocytes. In addition, the expression of phosphoenolpyruvate carboxykinase (PEPCK) gene was elevated in the liver of mice with hyperhomocysteinemia and primary mouse hepatocytes treated with homocysteine. The action of homocysteine was suppressed by H89, a protein kinase A (PKA) inhibitor. Thus, hyperhomocysteinemia may be considered as a risk factor that contributes to the development of insulin resistance with respect to elevated glucose output and upregulation of PEPCK, probably via the PKA pathway. Our study provides a novel mechanistic explanation for the development of insulin resistance in hyperhomocysteinemia.

A non-viral vector for potential DMD gene therapy study by targeting a minidystrophin-GFP fusion gene into the hrDNA locus

Mon, 28 Sep 2009 23:49:02 PDT

Gene therapy has emerged as a promising approach for the lethal disorder of Duchenne muscular dystrophy (DMD). Using a novel non-viral delivery system, the human ribosomal DNA (hrDNA) targeting vector, we targeted a minidystrophin-GFP fusion gene into the hrDNA locus of HT1080 cells with a high site-specific integrated efficiency of 10^–5, in which the transgene could express efficiently and continuously. The minidystrophin-GFP fusion protein was easily found to localize on the plasma membrane of HT1080 cells, indicating its possible physiologic performance. Our findings showed that the hrDNA-targeting vector might be highly useful for DMD gene therapy study.