Introduction to the Q-mate™ Inducible Expression System

System for inducible gene expression in mammalian cells

• Controllable gene expression
• Tight regulation of transgenes
• Possibility to co-express GFP
• No transactivator required
• Rapid response after induction
• No pleiotropic effect on mammalian cells

The ability to regulate both the level and the duration of gene expression permits the study of proteins whose constitutive expression may not be tolerated by the host cell. Most of the available inducible systems involve regulation by heavy metals, steroid hormones, or heat shock. The limitation of such inducible mammalian expression systems is the pleiotropic effects that the inducers may exercise (heat shock, glucocorticoids etc.).

Qbiogene has developed a new system for inducible gene expression in mammalian cells: the Q-mate™ Inducible Expression System. It is based on a prokaryotic regulatory system adapted to construct inducible systems that function in mammalian cells. Since prokaryotic inducer molecules usually do not have any target sites in mammalian cells, the possibility of interference with cellular processes is reduced.

The Q-mate™ CymR System
In the Q-mate™ CymR system, repression of gene expression is mediated by the cumate repressor protein CymR bound to operator sites in the absence of the inducer molecule cumate. With cumate present, CymR binds to cumate and undergoes a
conformational change resulting in its release from the operator sites. This permits transgene expression. The reporter construct consists of three components: a strong promoter, the CymR binding sites (cumate operator sequences, CuO), and a reporter or a transgene (Figure 1).

Background Information
The Q-mate™ CymR system makes use of the cym operon, which in Pseudomonas putida F1 controls the expression of genes intervening in the transformation of p-cymene (found in volatile oils from several plant species) to p-cumate (Figure 2).

The cmt operon, located downstream of the cym operon, controls the further degradation of the cumate molecule. Upstream of the cym operon lies a regulatory gene, cymR, encoding a 28-kDa repressor molecule (CymR), which monitors expression of both the cym and cmt operons and is
induced by p-cumate. CymR is in a DNA-binding configuration only in the absence of cymene and cumate.