Woodchuck hepatitis virus post-transcriptional regulation element enhances transgene expression from adenovirus vectors.

In studies of both gene therapy and gene function, transgene expression can be modulated at both the transcriptional and post-transcriptional levels. In a previous study, we optimized the transcriptional regulatory elements for adenovirus (Ad) vectors to mediate efficient transgene expression, including promoter, enhancer, intron, and poly(A) sequence. In the present study, we systematically investigated the ability of the Woodchuck hepatitis virus post-transcriptional regulation element (WPRE) to enhance the expression of the luciferase gene, as a model gene, in the context of Ad vectors. We found that the WPRE in the sense orientation cloned between the luciferase gene and the poly(A) sequence stimulated 2- to 7-fold more luciferase expression in vitro and 2- to 50-fold more in the liver, kidney and lung of mouse than occurred without the use of the WPRE. The most efficient Ad vector in this study, which contained the improved CMV promoter (the conventional CMV promoter with the intron A) and the WPRE, showed more than 700-fold luciferase expression in mouse liver than did the Ad vector containing the conventional CMV promoter but no WPRE. These results indicate that inclusion of the WPRE, combined with the optimization of transcriptional regulatory elements in Ad vectors, will permit a given therapeutic goal to be achieved with substantially fewer viral particles. This information would be helpful for the construction of adenovirus vectors for studies regarding both gene therapy and gene function.