Human thyroxine binding globulin (TBG) promoter directs efficient and sustaining transgene expression in liver-specific pattern

The liver performs a vital role in metabolic process, which makes it an attractive target organ for gene therapy. To improve the effects of gene therapy in disorders caused by metabolic disturbance, we quantitatively evaluated six promoters, CMV, EF1 alpha, PGK, apoE, thyroxine binding globulin (TBG), and cytochrome P450 2E1 (CYP2E1) by measuring the expression of alpha 1-antitrypsin, which is controlled by these promoters and introduced via a lentivirus-mediated delivery system in the liver. The results showed that the TBG promoter presents as highly active though in general it is slightly lower than the ubiquitous CMV and EF1 alpha. The expression of exogenous genes driven by the TBG promoter demonstrates to be much higher than by PGK, apoE, and CYP2E1 promoters, and the fragment of -435 bp to -26 bp from transcription start site (TSS) in the TBG promoter region is identified as the optimum region to direct transgene expression at a higher level. In addition, we further confirmed that the TBG promoter confers transgene persistent and specific expression within the liver up to several months after integration. The data suggests that the TBG promoter is a valuable tool and will greatly facilitate the optimization of vector design in hepatic gene therapy. (C) 2012 Elsevier B.V. All rights reserved.