RNA-polymerase III-driven expression cassettes in human gene therapy.

tRNAs, U6 small nuclear RNA and adenovirus virus associated RNAs are transcribed by RNA polymerase III. These RNAs are expressed in high levels and possess increased stability due to their small, compact size. Promoters expressing these RNAs have therefore been used to express a variety of interfering RNAs, including ribozymes, antisense RNAs and sense or decoy RNAs. Intracellular expression and activity of RNA polymerase III-driven interfering RNAs have been demonstrated in several studies. This review will summarize the design and application of RNA polymerase III-driven expression cassettes in human gene therapy using retroviral vectors as the primary method of gene delivery.