Inducible protein expression system

Mammalian protein expression systems are the best choice for the production of eukaryotic proteins, especially when correct folding and post-translational modification is required. They produce eukaryotic recombinant proteins in the most natural state, with native tertiary structure, physiochemical characteristics and bioactivities. They have been successfully applied in the biopharmaceutical production of cytokines, monoclonal antibodies, growth factors and so on. Email:marketing@medicilon.com.cn web:www.medicilon.com

Inducible gene expression systems and a method thereof. A first inducible gene expression system includes a first vector comprising at least one retroviral promoter and at least one factor to induce the retroviral promoter. At least one gene product is expressed in proportion to retroviral promoter induction. The method includes providing a first vector comprising at least one retroviral promoter and providing at least one factor corresponding to the retroviral promoter. The retroviral promoter is induced with the at least one factor. At least one protein is expressed based on the induction of the retroviral promoter. A second inducing expression system includes a first vector comprising at least one retroviral promoter, an inducer for the retroviral promoter, and at least one protein expressed in proportion to retroviral promoter induction.

The advent of recombinant DNA technology has made it possible to produce foreign proteins in mammalian cells through the introduction of foreign DNA encoding such proteins. Mammalian expression systems are available in which the foreign protein is constitutively expressed from an active promoter. This results in the continual expression of the foreign gene. Viral promoters are commonly used as regulatory elements in gene therapy vectors due to their strong activity in various cell lines in vitro. A widely used promoter in expression systems is the human cytomegalovirus immediate-early gene (CMV) promoter. The CMV promoter induces high-level constitutive expression in a variety of cell lines.

Frequently, the abundant presence of the foreign protein is toxic to the host cell. As a result of constitutive expression, the host cell population may become moribund and perish. Furthermore, the abundant presence of the toxic protein exerts selective pressures on the host cells which can result in the emergence of a cell population containing mutated versions of the foreign DNA, which express grossly modified protein or which have deleted the foreign gene. As a result, commercially useful levels of constitutive expression may never be maintained in the recombinant cell population.

Efforts to combat this shortcoming have resulted in the development of inducible mammalian expression systems that control the expression of the foreign protein. Inducible expression can be achieved by using promoters that are controlled by the presence or absence of a specific regulator. Another means of controlling foreign gene expression involves the use of a promoter that becomes more active in the presence of a specific activator protein. A foreign gene under the control of such a promoter is expressed at high levels only following the induction of synthesis of the activator. However, many of these inducible systems currently available suffer from decreased levels of expression and “leaky” control of expression. A more ideal inducible system would have 1) low basal expression levels; 2) high induced expression; and 3) inducer-specific, modulated expression.

Accordingly, it would be desirable to provide a tightly regulated and highly inducible protein expression system that would overcome the aforementioned and other disadvantages.

A first aspect of the invention provides an inducible gene expression system. The system includes a first inducible gene expression system including a first vector comprising at least one retroviral promoter and at least one factor to induce the retroviral promoter. At least one gene product is expressed in proportion to retroviral promoter induction.

A second aspect of the invention provides a method of gene expression. The method includes providing a first vector comprising at least one retroviral promoter and providing at least one factor corresponding to the retroviral promoter. The retroviral promoter is induced with the at least one factor. At least one protein is expressed based on the induction of the retroviral promoter.

A third aspect of the invention provides an inducible gene expression system. The system includes first vector means comprising at least one retroviral promoter. Means for inducing the retroviral promoter are provided. Further included are means for expressing at least one protein based on the induction of the retroviral promoter.

The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention, rather than limiting the scope of the invention being defined by the appended claims and equivalents thereof.