Jump-In™ CHO-K1 Kit

We would recommend engineering an expression marker/reporter in the plasmid used to create the platform line, and then screening the platform line for expression of this marker to identify a high-expressing locus. Otherwise, the process can get quite labor-intensive, as multiple lines would have to be screened after retargeting.

The pJTI Phic31 Int vector does not contain an NLS. Adding an NLS could increase the efficiency of site-specific integration at pseudo attP sites, but there are no data to support it. There is one paper describing the use of an NLS on a PhiC31 integrase vector, but the authors didn't measure integration into pseudo attP sites.

The amount of DNA to be used to obtain single copies should be determined by control experiments done in the absence of integrase. The same amount of DNA that yields less than 5 colonies in the absence of integrase should be used in the presence of integrase. Typically, the integrase expression plasmid makes up most of the amount of DNA used for transfection.

Find additional tips, troubleshooting help, and resources within our Protein Expression Support Center.

We recommend using the Jump-In Fast system if you need stable mammalian expression and want to quickly generate well-expressing clones. You can have well-expressing clones with one or more integrations at the PhiC31 pseudo-att P sites. A Southern blot is necessary to confirm the number of integrated events. Use the Jump-InTI system if you need isogenic expression, where every cloned gene would be expressed from the same locus in the same background, with no chromosomal position effects.

The Jump-In system is PhiC31-integrase mediated and is a stable, targeted, and irreversible mammalian expression system. It consists of the Jump-In Fast system that involves a single integration step and the Jump-InTI (targeted integration) system that needs two integration steps, both of which are targeted and irreversible. In contrast, the Flp-In system is a stable, targeted mammalian expression system that is reversible. The first integration is random (integration of pFRT/lacZeo), and the second integration (integration of the Flp-In expression vector) is targeted but reversible.