ShRNAs

Fig. 2 RNAi inducers used in antiviral strategies. In general, RNAi is induced either by transfection of synthetic siRNAs into cells, or by stable or transient intracellular expression of double-stranded siRNA precursors (shRNA, e-shRNA, IhRNA, or pri-miRNAs). After transcription in the nucleus shRNAs, IhRNAs and e-shRNAs are exported to the cytoplasm and subsequently diced into mature siRNAs. Pri-miRNAs modified to encode antiviral siRNAs first undergo cleavage by Drosha before they are exported to the cytoplasm. Here the antiviral pre-miRNAs (also called shRNA-miRs) are processed by Dicer into the mature miRNAs. After loading of the antisense strand of the siRNAs/miRNAs into RISC, the complex will target and cleave viral transcripts bearing the complementary sequences...

Despite the availability of an effective HBV vaccine, the virus is still a major health problem with approximately 350 million persons infected worldwide. Hepatitis an infection of the liver that is caused by a variety of RNA viruses (hepatitis A virus, hepatitis B virus, hepatitis C virus). RNAi has been used to inhibit HBV replication both in vitro and in vivo (Carmona et al. 2006 Ely et al. 2008 Hamasaki et al. 2003 Klein et al. 2003 Konishi et al. 2003 Weinberg et al. 2007 Ying et al. 2003). HBV is a member of the Hepadnaviridae and its genome is a 3.2-kb double-stranded circular DNA. Synthetic siRNAs and shRNA expression constructs showed potent inhibition of HBV replication in mice (Chen et al. 2005, 2007 GUadi et al. 2003 McCaffrey et al. 2003 Morrissey et al. 2005b Shin et al. 2006 Wu et al. 2005b ... 

Li MJ, Kim J, Li S, Zaia J, Yee JK, Anderson J, Akkina R, Rossi JJ (2005b) Long-term inhibition of HlV-1 infection in primary hematopoietic cells by lentiviral vector delivery of a triple combination of anti-HIV shRNA, anti-CCR5 ribozyme, and a nucleolar-localizing TAR decoy. Mol Ther 12 900-909... 

Westerhout EM, Vink M, Haasnoot PC, Das AT, Berkhout B (2006) A conditionally replicating HIV-based vector that stably expresses an antiviral shRNA against HlV-1 replication. Mol Ther 14 268-275... 

The small adeno-associated virus (AAV) vectors can be easily prodnced, have not been found to canse major toxicity, and persist in the transduced hepatocyte typically as an episomal transcriptionally active DNA molecule. Because of the limited packaging capacity for foreign DNA of 4.6 kb, these vectors have been preferentially nsed to express small transgenes and shRNAs directed against HBV or HCV... 

Biological function of targets (pathway dissection, miRNA/siRNA/ shRNA studies, model building in vitro and in vivo)... 

HT-RNAi screens of mammalian cells primarily use either short interfering RNA (siRNA) or small-hairpin RNA (shRNA) libraries. Although there are similarities between the two platforms, screening using siRNA libraries has the advantages of having minimal... 

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