Comparison of human lymphotoxin gene expression in CHO cells directed by genomic DNA or cDNA sequences

Four recombinant plasmids coding for human lymphotoxin (LT) were constructed with genomic DNA (gDNA) or cDNA sequences. The simian virus 40 (SV40) early region, which contains the early promoter, an intron of the small-t-antigen-encoding gene, and polyadenylation signal sequences, was used for transcriptional and post-transcriptional regulatory elements in the construction of these plasmids. Two of them contained gDNA and the other two contained cDNA. One of the gDNA plasmids and one of the cDNA plasmids carry the SV40 intron between the structural gene and polyadenylation signal. Transient and stable gene expression levels of these plasmids in Chinese hamster ovary (CHO) cells were measured by assaying the secreted LT. The plasmid carrying gDNA without the SV40 intron was expressed more efficiently than the other three plasmids in both transient and stable gene expression assays.