Contribution of Regions 3′ and 5′ to the hIL-5 Gene on the Expression of rhIL-5 in CHO-Cells

The effect of the presence of the regions 5′ and 3′ of the hIL-5 gene on the expression of recombinant hIL-5 in CHO-cells was investigated. The 3.2 kb hIL-5 gene-fragment was cloned and four different dexamethasone-inducible rhIL-5 mammalian expression-vectors were constructed, each containing a different part of the gene-fragment. Results indicated that deletion of the region 5′ to the gene increases production three-fold whereas a four-fold decrease in production was observed with deletion of the region 3′ to the gene. Deletion of both regions increased rhIL-5 production by only one and a half-fold. These results indicate that there are elements in a 928 bp region 3′ to the gene, including the 3′-NTR, that have an enhancing or stabilizing effect on expression of hIL-5 in CHO-cells.