To provide technical support for spider silk functional modification, we developed a simple and efficient functional platform via intein trans-splicing. Small ubiquitin-related modifier protein (SUMO) was fused to the recombinant spider silk protein (W2CT) by peptide bond via S0 split intein Ssp DnaB trans-splicing, resulting in a protein SUMOW2CT. However, incorporation of exogenous protein led to mechanical property defect and lower fiber yield, and also slowed down the fiber assembly velocity but no obvious differences in supercontraction and chemical resistance when compared with fibers from W2CT (W). SUMO protease digestion showed positive results on the fibers, indicating that the SUMO protein kept its native conformation and bioactive. Above all, this work provides a technical support for spider silk high simply and efficient functionalized modification.
Animals ; Inteins ; Protein Splicing ; Recombinant Proteins ; chemistry ; Silk ; chemistry ; Small Ubiquitin-Related Modifier Proteins ; chemistry ; Spiders ; Trans-Splicing

Recent anti-cancer approaches have been based to target tumor-specifically associated and/or causative molecules such as RNAs or proteins. As this specifically targeted anti-cancer modulator, we have previously described a novel human cancer gene therapeutic agent that is Tetrahymena group I intron-based trans-splicing ribozyme which can reprogram and replace human telomerase reverse transcriptase (hTERT) RNA to selectively induce tumor-specific cytotoxicity in cancer cells expressing the target RNA. Moreover, the specific ribozyme has been shown to efficiently retard tumor tissues in xenograft mice which had been inoculated with hTERT-expressing human cancer cells. In this study, we assessed specificity of trans-splicing reaction in cells to evaluate the therapeutic feasibility of the specific ribozyme. In order to analyze the trans-spliced products by the specific ribozyme in hTERT-positive cells, RT, 5'-end RACE-PCR, and sequencing reactions of the spliced RNAs were employed. Then, whole analyzed products resulted from reactions only with the hTERT RNA. This study suggested that the developed ribozyme perform highly specific RNA replacement of the target RNA in cells, hence trans-splicing ribozyme will be one of specific agents for genetic approach to revert cancer.
Animals ; Genes, Neoplasm ; Heterografts ; Humans ; Introns* ; Mice ; RNA ; Sensitivity and Specificity* ; Telomerase ; Tetrahymena ; Trans-Splicing*

Fusion proteins resulting from chimeric sequences are excellent targets for therapeutic drug development. We developed a database of chimeric sequences by examining the genomic alignment of mRNA and EST sequences in the GenBank. We identified 688 chimeric mRNA and 20,998 chimeric EST sequences. Including EST sequences greatly expands the scope of chimeric sequences even though it inevitably accompanies many artifacts. Chimeric sequences are clustered according to the ECgene ID so that the user can easily find chimeric sequences related to a specific gene. Alignments of chimeric sequences are displayed as custom tracks in the UCSC genome browser. ChimerDB, available at http://genome.ewha.ac.kr/ECgene/ChimerDB/, should be a valuable resource for finding drug targets to treat cancers.
Artifacts ; Databases, Nucleic Acid* ; Genome ; RNA, Messenger ; Trans-Splicing ; Translocation, Genetic

Low levels of coagulation factor VIII (fVIII) protein expression caused by its inefficient secretion and the over-sized fVIII gene affect the transgene-based gene therapy for hemophilia A adversely. Our previous study demonstrated that intein-mediated protein trans-splicing for delivery of the fVIII gene with a dual-vector system could improve secretion of post-translationally spliced fVIII by light chain in cis. In this study, a human/porcine hybrid fVIII (HP-fVIII) containing replaced A1 and A3 domains of porcine fVIII was investigated for secretion and activity of the spliced HP-fVIII after intein-based dual-vector delivery of the HP-fVIII gene. A pair of expression plasmids comprising intein-fused HP-fVIII heavy and light chains were constructed and transiently co-transfected into COS-7 cells. The spliced HP-fVIII and bio-activity in culture media were quantitatively analyzed by ELISA and Coatest method respectively. The intracellular splicing of HP-fVIII was detected by Western blotting. The results showed that in the culture supernatant of cells co-transfected with HP-fVIII, the amount and activity of spliced HP-fVIII were significantly higher than those of spliced hfVIII secreted from the cells co-transfected with human fVIII [(184+/-34 ng/mL) vs (48+/-12) ng/mL, P<0.01; (1.18+/-0.22) IU/mL vs (0.31+/-0.10) IU/mL, P<0.01], demonstrating the dramatically enhancing effect of porcine A1 and A3 domains on the secretion of intein-spliced HP-fVIII. The spliced HP-fVIII protein and its activity were also detected in the supernatant from combined cells separately transfected with intein-fused HP-fVIII heavy and light chain genes, indicating that the intein-mediated HP-fVIII splicing was independent of cellular mechanism and could occur outside the cell after the secretion of precursor proteins. Additionally, an intracellularly spliced HP-fVIII band was found with a molecular weight similar to human fVIII protein, confirming the HP-fVIII splicing. These results provided experimental basis for ongoing study using intein-based dual adeno-associated virus (AAV) vector to transfer HP-fVIII gene in animal models.
Animals ; COS Cells ; Cercopithecus aethiops ; Dependovirus ; genetics ; metabolism ; Factor VIIIa ; biosynthesis ; genetics ; Genetic Vectors ; Humans ; Inteins ; Protein Splicing ; Recombinant Fusion Proteins ; genetics ; Swine ; Trans-Splicing

We recently demonstrated that an intein-mediated protein splicing can be used to transfer B-domain-deleted FVIII (BDD-FVIII) gene by a dual-vector. In this study, we observed the effect of a variant heavy chain with six potential glycosylation sites of B domain and L303E/F309S mutations in its A1 domain, which were proven to be beneficial for FVIII secretion, on secretion of spliced BDD-FVIII. By transient co-transfection of cultured 293 cells with intein-fused variant heavy chain (DMN6HCIntN) and light chain (IntCLC) genes, the culture supernatant was analyzed quantitatively by ELISA for secreted spliced BDD-FVIII antigen and by a chromogenic assay for bioactivity. The data showed that the amount of spliced BDD-FVIII protein and coagulation activity in culture supernatant from DMN6HCIntN plus IntCLC co-transfected cells were up to (149 +/- 23) ng x mL(-1) and (1.12 +/- 0.14) u x mL(-1) respectively greater than that of intein-fused wild type heavy (HCIntN) and light chain (IntCLC) co-transfected cells [(99 +/- 14) ng x mL(-1) and (0.77 +/- 0.13) u x mL(-1)] indicating that the variant heavy chain is able to improve the secretion of spliced BDD-FVIII and activity. A cellular mechanism-independent BDD-FVIII splicing was also observed. It provided evidence for ongoing animal experiment using intein-mediated dual-AAV vector technology for delivery of the BDD-FVIII genes.
Factor VIII ; genetics ; metabolism ; secretion ; Glycosylation ; HEK293 Cells ; Humans ; Inteins ; Mutation ; Peptide Fragments ; genetics ; metabolism ; secretion ; Protein Splicing ; Trans-Splicing ; Transfection

This study is to construct a chimeric human/porcine BDD-FVIII (BDD-hpFVIII) containing the substituted porcine A1 and A3 domains which proved to have a pro-secretory function. By exploring Ssp DnaB intein's protein trans-splicing a dual-vector was adopted to co-transfer the chimeric BDD-hpFVIII gene into cultured COS-7 cell to observe the intracellular BDD-hpFVIII splicing by Western blotting and secretion of spliced chimeric BDD-hp FVIII protein and bio-activity using ELISA and Coatest assay, respectively. The dada showed that an obvious protein band of spliced BDD-hpFVIII can be seen, and the amount of spliced BDD-hpFVIII protein and bio-activity in the supernatant were up to (340 +/- 64) ng x mL(-1) and (2.52 +/- 0.32) u x mL(-1) secreted by co-transfected cells which were significantly higher than that of dual-vector-mediated human BDD-FVIII gene co-transfection cells [(93 +/- 22) ng x mL(-1), (0.72 +/- 0.13) u x mL(-1)]. Furthermore, a spliced BDD-hpFVIII protein and activity can be detected in supernatant from combined cells separately transfected with intein-fused BDD-hpFVIII heavy and light chain genes indicating that intein-mediated BDD-hpFVIII splicing occurs independently of cellular mechanism. It provided evidence for enhancing FVIII secretion in the research of animal models using intein-based dual vector for the delivery of the BDD-hpFVIII gene.
Animals ; COS Cells ; Cercopithecus aethiops ; Factor VIII ; genetics ; metabolism ; secretion ; Genetic Vectors ; Humans ; Inteins ; Peptide Fragments ; genetics ; metabolism ; secretion ; Plasmids ; Protein Splicing ; Swine ; Trans-Splicing ; Transfection

In our recent study by exploring an intein-based dual-vector to deliver a B-domain-deleted FVIII (BDD-FVIII) gene, it showed that covalently ligated intact BDD-FVIII molecules with a specific coagulant activity could be produced from expressed heavy and light chains by protein trans-splicing. Here, we assessed the hypothesis that the efficiency of trans-splicing may be increased by adding to the intein sequences a pair of leucine zippers that are known to bring about specific and strong protein binding. The intein-fused heavy and light chain genes were co-transferred into cultured COS-7 cells using a dual-vector system. After transient expression, the intracellular BDD-FVIII splicing was observed and the spliced BDD-FVIII and bioactivity secreted to culture media were quantitatively analyzed. An enhanced splicing of BDD-FVIII with decreased protein precursors from gene co-transfected cells was observed by Western blotting. The amount of spliced BDD-FVIII and bioactivity secreted to the culture media were 106 +/- 12 ng x mL(-1) and 0.89 +/- 0.11 U x mL(-1) analyzed by ELISA and Coatest method respectively, which was greater than leucine zipper free intein-fused heavy and light chain genes co-transfected cells (72 +/- 10 ng x mL(-1) and 0.62 +/- 0.07 U x mL(-1)). The activity of cellular mechanism-independent protein splicing was also improved, as showed by the increasing of spliced BDD-FVIII and bioactivity in culture media from combined cells separately transfected with heavy and light chain genes which was 36 +/- 11 ng x mL(-1) and 0.28 +/- 0.09 U x mL(-1). It demonstrated that the leucine zippers could be used to increase the efficiency of protein trans-splicing to improve the efficacy of a dual-vector mediated BDD-FVIII gene delivery by strengthening the interaction between the two intein-pieces fused to heavy and light chains. It provided evidence for further study in animal model using a dual-adeno-associated virus vector to deliver FVIII gene in vivo.
Animals ; COS Cells ; Cercopithecus aethiops ; Factor VIII ; chemistry ; genetics ; metabolism ; Genetic Vectors ; Inteins ; Leucine Zippers ; Peptide Fragments ; chemistry ; genetics ; metabolism ; Protein Splicing ; Trans-Splicing ; Transfection

The self-splicing group I intron from Tetrahymena thermophila has been demonstrated to perform splicing reaction with its substrate RNA in the trans configuration. In this study, we explored the potential use of the trans-splicing group I ribozymes to replace a specific RNA with a new RNA that exerts any new function we want to introduce. We have chosen thymidine phosphorylase (TP) RNA as a target RNA that is known as a valid cancer prognostic factor. Cancer-specific expression of TP RNA was first evaluated with RT-PCR analysis of RNA from patients with gastric cancer. We determined next which regions of the TP RNA are accessible to ribozymes by employing an RNA mapping strategy, and found that the leader sequences upstream of the AUG start codon appeared to be particularly accessible. A specific ribozyme recognizing the most accessible sequence in the TP RNA with firefly luciferase transcript as a 3' exon was then developed. The specific trans-splicing ribozyme transferred an intended 3' exon tag sequence onto the targeted TP transcripts, resulting in a more than two fold induction of the reporter activity in the presence of TP RNA in mammalian cells, compared to the absence of the target RNA. These results suggest that the Tetrahymena ribozyme can be a potent anti-cancer agent to modify TP RNAs in tumors with a new RNA harboring anti-cancer activity.
Codon, Initiator ; Exons ; Fireflies ; Humans ; Introns ; Luciferases ; RNA* ; RNA, Catalytic ; Stomach Neoplasms ; Tetrahymena ; Tetrahymena thermophila ; Thymidine Phosphorylase ; Trans-Splicing*

Telomerase reverse transcriptase (TERT) is an enzymatic ribonucleoprotein that prolongs the replicative life span of cells by maintaining protective structures at the ends of eukaryotic chromosomes. Telomerase activity is highly up-regulated in 85-90% of human cancers, and is predominately regulated by hTERT expression. In contrast, most normal somatic tissues in humans express low or undetectable levels of telomerase activity. This expression profile identifies TERT as a potential anticancer target. By using an RNA mapping strategy based on a trans-splicing ribozyme library, we identified the regions of mouse TERT (mTERT) RNA that were accessible to ribozymes. We found that particularly accessible sites were present downstream of the AUG start codon. This mTERTspecific ribozyme will be useful for validation of the RNA replacement as cancer gene therapy approach in mouse model with syngeneic tumors.
Animals ; Catalytic Domain* ; Codon, Initiator ; Genes, Neoplasm ; Genetic Therapy ; Humans ; Mice* ; Ribonucleoproteins ; RNA* ; RNA, Catalytic ; Telomerase* ; Trans-Splicing

As synthesized by vascular endothelial cells and megakaryocytes, the von Willebrand factor (vWF) plays an important hemostatic role in the binding to and stabilizing blood coagulation factor VIII (FVIII) and preventing its enzymatic degradation. Our recent work demonstrated intein can efficiently ligate BDD-FVIII (B-domaim deleted FVIII) posttranslationally by protein trans-splicing after transfer of split BDD-FVIII gene by a dual-vector system. In this study we investigated the effect of vWF on secretion and activity of intein-ligated BDD-FVIII. We observed the levels of full-length BDD-FVIII antigen secreted into culture supernatant by ELISA and their activity by Coatest assay after transfection of cultured 293 cells with intein-fused BDD-FVIII heavy- and light-chain genes simultaneously with the vWF gene co-transfected. The data showed that the amount of full-length BDD-FVIII protein and their bioactivity in vWF gene co-transfected cell supernatant were 235 +/- 21 ng x mL(-1) and 1.98 +/- 0.2 u x mL(-1), respectively, greater than that of non-vWF co-transfected cell (110 +/- 18) ng x mL(-1) and 1.10 +/- 0.15 u x nL(-1)) or just BDD-FVIII gene transfected control cell (131 +/- 25 ng x mL(-1) and 1.22 +/- 0.18 u x mL(-1)) indicating the benefit of vWF gene co-transfection in the secretion and activity of intein-spliced BDD-FVIII protein. It provided evidence that vWF gene co-transfer may be useful to improve efficacy of gene therapy for hemophilia A in protein splicing-based split FVIII gene transfer.
Factor VIII ; genetics ; metabolism ; secretion ; Genetic Therapy ; Genetic Vectors ; HEK293 Cells ; Hemophilia A ; therapy ; Humans ; Inteins ; Peptide Fragments ; genetics ; metabolism ; secretion ; Plasmids ; Protein Splicing ; Trans-Splicing ; Transfection ; von Willebrand Factor ; genetics ; metabolism ; physiology