Mammalian Cell Expression Vector

Mammalian Cell Expression Vector

Expression vector, or a building is known as an expression, typically a plasmid that a particular gene in a target cell is started. Once inside the cell expression vector, the protein encoded by the gene is produced by the cellular transcription machinery andtranslation. Plasmid often increase regulatory sequences that function as promoter regions and efficient transcription of genes carried on expression vector is engineered to give birth. The goal of a well designed stable expression vector produces large amounts of messenger RNA.
A vector that despite the large amounts of eukaryotic protein classification will produce, and not necessarily a protein from a mammal.
Expression vectors but only the transcription is required for translation of vector insert, thus more than simple transcription factors require only vectors. Require expression vectors that encode for sequences:

* Polyadenylation tails: Written pre-mRNA from the exon mRNA polyadenylation tail at the end of defense makes

* Minimum UTR length: UTRs specific characteristics that transcription or translation, and thus at least UTRs or none at all may be interrupted for optimal expression vectors are encoded in.

* Kozak sequence: Vector mRNA, the translation of mRNA to the ribosome assembles a Kozak sequence should encode.

Example: Baculovirus expression vectors widely cultured mammalian cells is to express heterologous proteins. Recent advances in multi-subunit protein complexes, co-expression of protein modifying enzymes for the production of heterologous protein production improvement and further development of this system include additional applications of baculovirus display technology. Mammalian cells modified baculovirus vectors for gene expression applications continues to expand.

Selectable Markers

A gene whose expression allows one to identify cells that have been transformed or transfected with a vector containing the marker gene.


A selection marker gene introduced into a cell, especially in a culture of cells or bacteria, that artificial selection offers the appropriate specialty. They press laboratory microbiology, molecular biology used in a variety of genes, and a reagent for genetic or other foreign DNA in a cell meant to introduce signs of success are engineering process. Antibiotic selection markers often resistancegenes, bacteria that is subject to a process to introduce foreign DNA are a medium on which an antibiotic, and the bacterial colonies that grow successfully taken up and begin to express the genetic material are.

An alternative to a selectable marker is a screenable marker, which allows the researcher to distinguish between wanted and unwanted cells.

Examples of selectable markers include:
* the Abicr gene
* Neo gene from Tn5, which confers antibiotic resistance to geneticin.

Expression systems

Commonly used protein expression systems include de those derived from bacteria, yeast,baculovirus/insect, and mammalian cells.
There are two types of expression systems:
* Cell-based systems
* Cell free systems.

Cell-based systems
The oldest and most widely used cell based expression system and an expression vector, then cloned DNA, and vector to provide a reference to a host cell to allow foreign gene function, the host of "combination can be defined as that is, a "high level expression of protein production. Often have a very high level and therefore referred to as overexpression.

Many expressions for a cell to introduce foreign DNA methods, and there are many different host cells, which can be used for expression - every expression system has distinct advantages and liabilities. Expression systems commonly host DNA or genetic material delivery system sent by the source is. For example, the normal host (such as E. coli, B. subtilis) bacteria, yeast (such as S.cerevisiae) or eukaryotic cell lines. Common DNA sources and delivery mechanisms (such as baculovirus, retrovirus, adenovirus) as viruses, plasmids, artificial chromosomes and bacteriophage (such as lambda). The best option depends on gene expression systems include, for example, Saccharomyces cerevisiae protein that is often modified significantposttranslational insect or mammalian cell lines used and the mRNA splicing is essential as the human need for love. However, bacterial protein expression is easy, the X-ray crystallography or nuclear magnetic resonance experiments for structure determination is essential to have the advantage of mass production.

Escherichia coli

Fig:E. coli, one of the most popular hosts for artificial gene expression.
Fig:E. coli, one of the most popular hosts for artificial gene expression.

E. coli is one of the most widely used expression hosts, and DNA is normally introduced in a plasmid expression vector. Techniques for overexpression in E. coli are well developed and increase the number of copies of genes or the promoter region trancription support work by increasing the bond strength.
For example, a DNA sequence or a protein of interest can be cloned into a high copy number promoter subcloned million, which is then transformed into bacteriumEscherichia coli containing the plasmid. Addition of IPTG (a lactose analog) million promoter is active and causes the bacteria to express proteins of interest.

Cell-free systems

Cell-free protein expression possible RNA polymerase, ribosomes, tRNA and purified using the ribonucleotides. These reagents to cells or a cell-based expression systems can be produced by extraction. Cell-free system, cell-based system due to low expression levels and higher costs are more widely used.

Two gene expression vectors

Two common vectors are plasmids and viral vectors.

plasmids generally circular double-stranded DNA sequences that automatically copied into the host cells are capable of. Plasmid vectors minimalistically origin of replication of plasmid in the host semi-independent replication and allows you to insert the transgene consisting of. Modern plasmids generally, especially a "multiple cloning site", which include nucleotide overhangs for insertion of an insert and several restriction enzyme sites consensus from both sides, including putting more features, it is. In the case of transcription plasmids used as vectors, plasmids incubating bacteria with hundreds or thousands of copies of the bacteria within hours resulting in the vector, and vectors can be extracted from bacteria, and be cut by restriction enzymes multiple cloning site hundred or thousand amplified products can enter duty. These plasmid vectors transcription feature is the lack of significant sequences that code forpolyadenylation protein expression vectors to make impossible shots translation and transcription termination sequences in mRNAs translation.

Viral vectors
Usually genetically engineered viral vectors modified viral DNA or RNA were rendered noninfectious stomach virus, but still viral promoters and the transgene, thus through viral promoters have to allow for translation of transgene . However, because viral vectors lack sequences are often infectious, they are helpful for large-scale transfection or virus packaging lines is required. Viral vectors often put in the host genome are designed to include a permanent, and thus included after transgene specific genetic marker in the host genome release. For example, a feature Retroviruses retroviral integration pattern that is detectable after the entry indicates that the viral vector and host genome has been involved in the release.


A bioreactor may refer to any device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which is carried out a chemical process which involves organisms or biochemically active substances derived from such organisms. This process can either be aerobic or anaerobic. These bioreactors are commonly cylindrical, ranging in size from liters to cubic meters, and are often made of stainless steel.
A bioreactor may also refer to a device or system meant to grow cells or tissues in the context ofcell culture. These devices are being developed for use in tissue engineering.
On the basis of mode of operation, a bioreactor may be classified as batch, fed batch orcontinuous (e.g. a continuous stirred-tank reactor model). An example of a continuous bioreactor is the chemostat.
Organisms growing in bioreactors may be suspended or immobilized. The simplest, where cells are immobilized, is a Petri dish with agar gel. Large scale immobilized cell bioreactors are:
* moving media
* packed bed
* fibrous bed
* membrane

Bioreactor design

Fig: General structure of batch type bioreactor
Fig: General structure of batch type bioreactor

Bioreactor design is a relatively complex engineering work, which is studied in the discipline of biochemical engineering. Under optimal conditions, microorganisms or cells to 100 percent rate of success that you want to work with are capable of. Bioreactor's environmental conditions like gas (ie, air, oxygen, nitrogen, carbon dioxide) flow rate, temperature, pH and dissolved oxygen levels, and movement / circulation rate being closely monitored and controlled the pace needs.

Most industrial bioreactor manufacturers use vessels, sensors and a control system networked together.

Fouling can harm the overall sterility and efficiency of the bioreactor, especially the heat exchangers. To avoid it, the bioreactor must be easily cleaned and as smooth as possible (therefore the round shape).
A heat exchanger is needed to maintain the bioprocess at a constant temperature. Biological fermentation is a major source of heat, therefore in most cases bioreactors need refrigeration. They can be refrigerated with an external jacket or, for very large vessels, with internal coils.

An aerobic process, optimal oxygen transfer is perhaps the most difficult to meet the oxygen is poorly soluble in water - even less in fermentation broths - and relatively air (20.95%) is less .. Oxygen transfer is usually the movement, which also mix the nutrients needed to help keep the fermentation is homogeneous. There are, however, limits to the speed of movement, both because of the high power consumption (the electric motor is proportional to the cube of speed) due to excessive tip speed for damage to organisms. In practice, bioreactors often, pressure is rising, the water solubility of oxygen.

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