Category: RNAi by shRNA

Featured Paper:  "Expression of small hairpin RNA by lentivirus-based vector confers efficient and stable gene-suppression of HIV-1 on human cells including primary non-dividing cells."

Authors:  Nishitsuji H, Ikeda T, Miyoshi H, Ohashi T, Kannagi M, Masuda T.

Year of Publication: 2004

Journal:  Microbes Infect.  Vol. 6, 76-85.

Online Availability:  Abstract from PubMed.

Significance

One problem faced by RNAi research is that of stable siRNA expression within cells.  After an siRNA molecule base pairs with RISC, it participates in a finite number of cleavages.  The targeted mRNA is continually produced.  Therefore, more siRNA has to be produced to continually silence the gene. 

          This problem has been dealt with by encoding shRNA (short hairpin RNA).  When a short strand of RNA can base pair with itself, producing a "hairpin" of non base paired nucleotides at one end, it is called an shRNA.  An shRNA molecule is shown to the right.

          A vector such as a lentivirus could introduce a plasmid-like construct into a cell.  The construct, when transcribed, will produce a single stranded RNA transcript that can base pair with itself to form a double stranded shRNA.  This shRNA will then be cleaved by DICER to form siRNA.  In this manner, siRNA can be stably expressed in a cell for a long period of time.

          In the featured experiment, constructs encoding shRNAs provided resistance to cells against four sequentially repeated HIV infections.  The resistance lasted for over 35 days.