[ study of the effect of human prothrombin's signal peptide on the secretion efficiency of recombinant human FIX in the HEK293T cell line]

Objective: Eukaryotic proteins generally have signal peptides which are not only crucial for their secretion efficiencies but are important for their expression levels. Coagulation factor IX [FIX] is a glycoprotein that plays a fundamental role in the blood coagulation pathway. Reduced levels or dysfunctional FIX are associated with hemophilia B. This study investigates the function of the human prothrombin signal peptide in an attempt to improve the human FIX [hFIX] secretion efficiency in a heterologous expression system. With this aim, we have used the SignalP and PrediSi programs for in silico evaluation of the signal peptide efficiency prior to conducting this experiment

Methods: We used molecular techniques to amplify and join the coding region of the human prothrombin signal peptide to the cDNA of mature hFIX. The chimeric fragment was examined for transient expression in a mammalian cell line [HEK293T] in comparison with the native hFIX, under a CMVp regulation. Using the neural networkbased prediction programs, we evaluated the scores for cleavage position and secretion efficiency of the human prothrombin and hFIX signal peptides. The expression efficiencies of hFIX expressed by the recombinant cells were analyzed by RT-PCR and ELISA

Results: In silico analysis more efficiently predicted the human prothrombin signal peptide with a high score compared to the native hFIX signal peptide. This data was confirmed by the RT-PCR and ELISA results obtained from expression analyses at the RNA and protein levels, respectively

Conclusion: The present study showed that the signal peptide derived from the human prothrombin has the potential for efficient secretion of hFIX as evidenced by the results taken from a transient expression system. The results were consistent with in silico analysis. This replacement could be evaluated in a stable state condition

Optimization of the electroporation conditions for transfection of human factor IX into the goat fetal fibroblasts

Electroporation is the most common method used for the transfection of DNA. Although this method has been attributed for various cell using different buffer compositions, the effects of DNA concentration on the transfection efficiency has not yet been studied. Here the correlation between the efficiency of electroporation reaction and increments of DNA concentration has been investigated. Following this investigation, a study was set out to produce a transgenic goat which is capable of secreting recombinant human coagulation factor IX in its milk. In this experimental study, a linearized recombinant vector [pBC1] entailing human coagulation factor IX [5.7 kb] cDNA was introduced into goat fetal fibroblast cells [three sub passages] via electroporation in four separate experiments [while other variables were kept constant], beginning with 10 micro g DNA per pulse in the first experiment and increments of 10 micro g/pulse for the next three reactions. Thereafter, polymerase chain reaction [PCR]-positive cell culture plates were diluted by several factors for further analysis of the transfected wells. Subsequently, positive cells were isolated for fluorescence in situ hybridization. Logistic regression model was used for data analyzing. Significance was defined as p< 0.05. The results showed no significant difference among three first concentrations except for group 1 [10 micro g/pulse] and group 3 [30 micro g/pulse], but there was a significant difference between these groups and the fourth group [p<0.05], as this group [40 micro g/pulse] statistically showed the highest rate of transfection. As the fluorescence in situ hybridization [FISH] results indicated the transgene was integrated in a single position in PCR positive cells. Increasing amount of using the vector 40micro g/pulse efficiently increased the number of transfected cells. Besides of voltage and buffer strength which had been previously shown to play a critical role in electroporation efficiency, our results showed an increase in DNA concentration could affect an exponential surge in the electroporation efficiency

Bacterial expression and purification of C1C2 domain of human factor VIII

The cDNA from the mycoparasitic fungus Trichoderma atroviride PTCC5220 encoding a 42 kDa chitinase [Chit42] was isolated. The nucleotide sequence of the cDNA fragment as having a 1263 bp open reading frame that encodes a 421 amino acid polypeptide, and a high homology was found with other reported Chit42 belonging to the Trichoderma sp. The 22 amino acid N-terminal sequence is a putative signal pep-tide for the possible secretion of the protein. The protein has been expressed and secreted as a mature form in Escherichia coll BL21[DE3] using the pelB leader sequence. The E. coll strain expressed Chit42 in an active form and secreted the protein into the medium. This recombinant chitinase has been shown to have inhibitory activity on mycelial growth and also, lytic activity on the cell wall of Rhizoctonia solani [AG2-2], causal agent of root rot in sugar beet in vitro. Expressed chitinase was optimally active at pH 5 and at 40°C. It is thermally stable at 60°C for more than 120 min at pH5