Improved PCR-based gene synthesis method and its application to the Citrobacter freundii phytase gene codon modification

A novel phytase from Citrobactergillenii: characterization and expression in Pichia pastoris (Komagataella pastoris)

The phyCg gene encoding a new phytase from Citrobacter gillenii was optimized, synthesized, cloned and expressed in Pichia pastoris. Analysis of the amino acid sequence of the enzyme showed that it belongs to the histidine acid phosphatase family. The amino acid sequence of the PhyCg phytase has the highest homology (73.49%) with a phytase sequence from Citrobacter braakii. The main characteristics for the purified recombinant phytase were established. The optimum pH and temperature were 4.5 and 50°C, respectively. The specific activity of the enzyme was 1577 U/mg. The Michaelis constant (Km) and the maximum reaction rate (Vmax) for sodium phytate were 0.185 mM and 2185 U/mg, respectively. The enzyme showed the pH and trypsin stability and had a high activity over a wide pH range.

Programmed assembly of long DNA synthons: design, mechanism, and online monitoring

Synthesis of custom de novo DNA sequences is highly demanded by fast-growing field of synthetic biology. Usually DNA sequences with length more than 1 kb are assembled from smaller synthetic DNA fragments (synthons) obtained by PCR assembly. The ability to synthesize longer synthons sufficiently reduces efforts and time for DNA synthesis. We developed a novel rational oligonucleotide design and programmed approach for the assembly of synthetic DNA synthons up to 1550 bp. The developed procedure was thoroughly investigated by synthesis of cholesterol oxidase gene from Streptomyces lavendulae (1544 bp). Our approach is based on combined design, oligonucleotide concentration gradient, and specialized assembly program that directs assembly reaction to full-length gene in a stepwise manner. The process includes conventional thermodynamically balanced assembly, thermodynamically balanced inside-out elongation, and further amplification. The ability of DNA polymerase to perform programmed assembly is highly influenced by the presence of 5' → 3'-exonuclease activity. Oligonucleotide probing of PCR assembly products allowed us to shed light on the nature of high molecular weight spurious by-products and to understand the mechanism of their formation. For the first time, we applied light scattering techniques for tracking of oligonucleotide annealing, analysis of gene assembly products, and even for real-time monitoring of gene assembly process.

Expression of Xylanase Gene from Pyromyces finnis in Pichia pastoris and Characterization of Recombinant Protein

The heterologous expression and characteristics of a new xylanase from Pyromyces finnis have been described. The endo-l,4-β-xylanase XylP (EC 3.2.1.8) consists of 223 amino acids and 19 residues of a putative signal peptide in the N-terminal region. The amino acid sequence of the mature protein has the greatest homology with the sequence of the native catalytic N-terminal domain of Neocallimastix patriciarum endo-l,4-β-xylanase (84%). A synthetic nucleotide sequence encoding a mature XylP protein was expressed in Pichia pastoris. The purified recombinant enzyme showed activity with birch xylan and arabinoxylan. When using birch xylan as a substrate, the optimum pH for the enzyme was 5.0, and the optimum temperature was 50 °C. The specific activity of the xylanase was 4700 U/mg protein, and Km and Vmax were equal to 0.51 mg/mL and 7395.3 umol/(min∙mg), respectively. The recombinant XylP protein showed moderate thermal stability and high pH stability, resistance to digestive enzymes and protein inhibitors of grain xylanases. It was also shown that the Mg2+, Co2+ and Li+ ions have a positive effect on the enzyme activity. xylanase, xylan, feed enzyme, Pichia pastoris, Pyromyces finnis The work was performed with the financial support of the Ministry of Education and Science of Russia (Unique Project Identifier RFMEFI60717X0180) using the Unique Scientific Installation -National Bioresource Center «All-Russian Collection of Industrial Microorganisms», NRC «Kurchatov Institute» - GOSNIIGENETIKA

Increase in the Production of Endo-1,4-β-Xylanase from Paenibacillus brasilensis in Pichia pastoris

A Pichia pastoris yeast strain producing endo-l,4-β-xylanase from Paenibacillus brasilensis with an activity of 54,400 U/mL after 140 h of fermentation in a laboratory fermenter has been obtained. A number of approaches were used to increase the level of the xylanase production in this strain: optimization of the target gene codon composition, multiple integration of the expression cassette into the recipient strain chromosome using the Cre-lox recombination system, and also improving the heterologous protein folding via the overexpression of the HAC1i gene from Pichia pastoris. xylanase, xylan, Cre-lox system, HAC1p transcriptional activator, multicopy strain, Paenibacillus brasilensis, Pichia pastoris The work was performed with the financial support of the Ministry of Education and Science of Russia (Unique Project Identifier RFMEFI60717X0180) using the Multipurpose Scientific Installation of «All-Russian Collection of Industrial Microorganisms» National Bio-Resource Center, NRC «Kurchatov Institute» - GosNIIgenetika.

A Novel Platform for High-Throughput Gene Synthesis to Maximize Recombinant Expression in Escherichia coli

Gene synthesis is becoming an important tool in many fields of recombinant DNA technology, including recombinant protein production. De novo gene synthesis is quickly replacing the classical cloning and mutagenesis procedures and allows generating nucleic acids for which no template is available. Here, we describe a high-throughput platform to design and produce multiple synthetic genes (<500 bp) for recombinant expression in Escherichia coli. This pipeline includes an innovative codon optimization algorithm that designs DNA sequences to maximize heterologous protein production in different hosts. The platform is based on a simple gene synthesis method that uses a PCR-based protocol to assemble synthetic DNA from pools of overlapping oligonucleotides. This technology incorporates an accurate, automated and cost-effective ligase-independent cloning step to directly integrate the synthetic genes into an effective E. coli expression vector. High-throughput production of synthetic genes is of increasing relevance to allow exploring the biological function of the extensive genomic and meta-genomic information currently available from various sources.

Development of a gene synthesis platform for the efficient large scale production of small genes encoding animal toxins

Background

Gene synthesis is becoming an important tool in many fields of recombinant DNA technology, including recombinant protein production. De novo gene synthesis is quickly replacing the classical cloning and mutagenesis procedures and allows generating nucleic acids for which no template is available. In addition, when coupled with efficient gene design algorithms that optimize codon usage, it leads to high levels of recombinant protein expression.

Results

Here, we describe the development of an optimized gene synthesis platform that was applied to the large scale production of small genes encoding venom peptides. This improved gene synthesis method uses a PCR-based protocol to assemble synthetic DNA from pools of overlapping oligonucleotides and was developed to synthesise multiples genes simultaneously. This technology incorporates an accurate, automated and cost effective ligation independent cloning step to directly integrate the synthetic genes into an effective Escherichia coli expression vector. The robustness of this technology to generate large libraries of dozens to thousands of synthetic nucleic acids was demonstrated through the parallel and simultaneous synthesis of 96 genes encoding animal toxins.

Conclusions

An automated platform was developed for the large-scale synthesis of small genes encoding eukaryotic toxins. Large scale recombinant expression of synthetic genes encoding eukaryotic toxins will allow exploring the extraordinary potency and pharmacological diversity of animal venoms, an increasingly valuable but unexplored source of lead molecules for drug discovery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-016-0316-3) contains supplementary material, which is available to authorized users.

Combined Overlap Extension PCR Method for Improved Site Directed Mutagenesis

The combined overlap extension PCR (COE-PCR) method developed in this work combines the strengths of the overlap extension PCR (OE-PCR) method with the speed and ease of the asymmetrical overlap extension (AOE-PCR) method. This combined method allows up to 6 base pairs to be mutated at a time and requires a total of 40–45 PCR cycles. A total of eight mutagenesis experiments were successfully carried out, with each experiment mutating between two to six base pairs. Up to four adjacent codons were changed in a single experiment. This method is especially useful for codon optimization, where doublet or triplet rare codons can be changed using a single mutagenic primer set, in a single experiment.

Design and evaluation of a recombinant multi-epitope antigen for serodiagnosis of Toxoplasma gondii infection in humans

Background

Serological investigation remains the primary approach to achieve satisfactory results in Toxoplasma gondii identification. However, the accuracy of the native antigen used in the current diagnostic kits has proven to be insufficient as well as difficult to standardize, so significant efforts have been made to find alternative reagents as capture antigens. Consequently, multi-epitope peptides are promising diagnostic markers, with the potential for improving the accuracy of diagnostic kits. In this study, we described a simple, inexpensive and improved strategy to acquire such diagnostic markers. The study was aimed at producing novel synthetic protein consisting of multiple immunodominant epitopes of several T. gondii antigens.

Findings

To accomplish our goals, a single synthetic gene of approximately 456 bp, which encodes potential epitopes of T. gondii antigens, was successfully constructed using gene assembly PCR. The constructed gene was cloned into a pET32a expression vector and transformed into BL21 E. coli. The entire protein was successfully expressed and purified. Subsequently, the preliminary diagnostic performance of expressed protein was evaluated by developing IgG enzyme-linked immunosorbent assay (ELISA) and Western blot analysis using human sera. The results showed 100 % sensitivity and specificity.

Conclusion

A purified protein expressing multi-immunodominant epitopes of T. gondii was generated. Further studies are required to evaluate the immunogenicity in animal models and to verify the immuno-reactivity of USM.TOXO1 as a diagnostic antigen.

A solid-phase platform for combinatorial and scarless multipart gene assembly

With the emergence of standardized genetic modules as part of the synthetic biology toolbox, the need for universal and automatable assembly protocols increases. Although several methods and standards have been developed, these all suffer from drawbacks such as the introduction of scar sequences during ligation or the need for specific flanking sequences or a priori knowledge of the final sequence to be obtained. We have developed a method for scarless ligation of multipart gene segments in a truly sequence-independent fashion. The big advantage of this approach is that it is combinatorial, allowing the generation of all combinations of several variants of two or more modules to be ligated in less than a day. This method is based on the ligation of single-stranded or double-stranded oligodeoxynucleotides (ODN) and PCR products immobilized on a solid support. Different settings were tested to optimize the solid-support ligation. Finally, to show proof of concept for this novel multipart gene assembly platform a small library of all possible combinations of 4 BioBrick modules was generated and tested.

Rapid synthesis of defined eukaryotic promoter libraries

Current gene synthesis methods allow the generation of long segments of dsDNA. We show that these techniques can be used to create synthetic regulatory elements and describe a method for the creation of completely defined, synthetic variants of the PHO5 promoter from the budding yeast Saccharomyces cerevisae. Overall, 128 promoters were assembled by high-temperature ligation, cloned into plasmids by isothermal assembly, maintained in E. coli, and consequently transformed into yeast by homologous recombination. Synthesis errors occurred at frequencies comparable to or lower than those achieved with current gene synthesis methods. The promoter synthesis method reported here is robust, fast, and readily accessible. Synthetically engineered promoter libraries will be useful tools for dissecting the intricacies of promoter input-output functions and may serve as tunable components for synthetic genetic networks.

Industrial scale gene synthesis

The most recent developments in the area of deep DNA sequencing and downstream quantitative and functional analysis are rapidly adding a new dimension to understanding biochemical pathways and metabolic interdependencies. These increasing insights pave the way to designing new strategies that address public needs, including environmental applications and therapeutic inventions, or novel cell factories for sustainable and reconcilable energy or chemicals sources. Adding yet another level is building upon nonnaturally occurring networks and pathways. Recent developments in synthetic biology have created economic and reliable options for designing and synthesizing genes, operons, and eventually complete genomes. Meanwhile, high-throughput design and synthesis of extremely comprehensive DNA sequences have evolved into an enabling technology already indispensable in various life science sectors today. Here, we describe the industrial perspective of modern gene synthesis and its relationship with synthetic biology. Gene synthesis contributed significantly to the emergence of synthetic biology by not only providing the genetic material in high quality and quantity but also enabling its assembly, according to engineering design principles, in a standardized format. Synthetic biology on the other hand, added the need for assembling complex circuits and large complexes, thus fostering the development of appropriate methods and expanding the scope of applications. Synthetic biology has also stimulated interdisciplinary collaboration as well as integration of the broader public by addressing socioeconomic, philosophical, ethical, political, and legal opportunities and concerns. The demand-driven technological achievements of gene synthesis and the implemented processes are exemplified by an industrial setting of large-scale gene synthesis, describing production from order to delivery.

Gene synthesis: methods and applications

DNA synthesis techniques and technologies are quickly becoming a cornerstone of modern molecular biology and play a pivotal role in the field of synthetic biology. The ability to synthesize whole genes, novel genetic pathways, and even entire genomes is no longer the dream it was 30 years ago. Using little more than a thermocycler, commercially synthesized oligonucleotides, and DNA polymerases, a standard molecular biology laboratory can synthesize several kilobase pairs of synthetic DNA in a week using existing techniques. Herein, we review the techniques used in the generation of synthetic DNA, from the chemical synthesis of oligonucleotides to their assembly into long, custom sequences. Software and websites to facilitate the execution of these approaches are explored, and applications of DNA synthesis techniques to gene expression and synthetic biology are discussed. Finally, an example of automated gene synthesis from our own laboratory is provided.