Placing the RPL32 Promoter Upstream of a Second Promoter Results in a Strongly Increased Number of Stably Transfected Mammalian Cell Lines That Display High Protein Expression Levels

<table>Optimal orientations of the RPL32 promoter in relation to the <i>β</i>-actin promoter. The RPL32 promoter was placed in configurations as shown at the top of the figure. Control constructs contained only the RPL32 promoter, the <i>β</i>-actin promoter without any DNA element, or with flanking STAR 7/67/7 elements. Equal amounts of DNA were transfected to CHO-DG44 and after approximately two weeks colonies were counted. Up to 24 stable colonies were isolated, and d2EGFP expression values were determined. The respective colony numbers are shown above the d2EGFP expression values.</table>

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Figure 4

Figure 4: Placing the RPL32 Promoter Upstream of a Second Promoter Results in a Strongly Increased Number of Stably Transfected Mammalian Cell Lines That Display High Protein Expression Levels 

Figure 4 | Placing the RPL32 Promoter Upstream of a Second Promoter Results in a Strongly Increased Number of Stably Transfected Mammalian Cell Lines That Display High Protein Expression Levels 