Conditional modification of sirnas expression

摘要

The present invention provides an in vitro and in vivo method for modulating the expression of a target gene in a conditional manner, utilizing small interfering (si) RNA. It also provides non-eukaryotic RNA polymerase expression constructs and siRNA expression constructs suitable for said method, a kit comprising said expression cassettes as well as the use of said expression cassettes for the preparation of medicaments for the treatment of various diseases associated with dysfunctional gene expression. <??>By functionally fusing the nucleotide sequence of a non-eukaryotic-RNA-polymerase (N-EU-Pol) with eukaryotic transcription regulating sequences, an induced cell-type specific or otherwise regulated expression of the foreign RNA polymerase in eukaryots becomes possible. Since the non-eukaryotic-RNA polymerase lacks a nucleic signal peptide, it will remain in the cytoplasm after translation. Thus, it is only able to transcribe target sequences cytoplasmatically, and the nucleus-bound functions such as the addition of a cap-structure or of a polyA-tail will not take place. siRNA coding sequences, which are functionally linked with a recognition sequence for the non-eukaryotic-RNA-polymerase will be transcribed in the cytoplasm by the non-eukaryotic-RNA-polymerase, resulting in non-capped and non- polyadenylated siRNAs. Since the expression of the non-eukaryotic-RNA-polymerase cell-type specific or otherwise regulated, the expression of the siRNA is accordingly also cell-type specific or otherwise regu-Iated. The functional link between coding sequences for siRNA with a recognition sequence for a conditionally regulated and expressed non-eukaryotic foreign-RNA polymerase will finally result in an intracellularly located, conditionally directed synthesis and function of siRNA in eukaryotic cells. <IMAGE>