Polyarginine, typically consisting of nine to eleven arginine residues, has been widely used as a multifunctional fusion tag. Particularly, polyarginine-tags function as cell-penetrating peptides (CPP), and can be used to improve the cellular uptake of various cargoes, including proteins, nucleic acids (oligonucleotides, peptide-nucleic acids, siRNAs), nanoparticles and liposomes in a wide range of cells.1
Although the HIV-1 derived Tat peptide is a classic example of a cell-penetrating peptide, polyarginine CPP has been shown to be 20-fold more efficient than Tat49-57 at cellular uptake.2 This property makes polyarginine peptide a powerful tool for cell biology and clinical translational studies. It was reported that the polyarginine (11R)-fused p53 protein (p53-11R) was delivered effectively into cancer cells and had transcriptional regulatory activity there. Moreover, p53-11R inhibited the proliferation of the cancer cells.3
Recently, the polyarginine-tagged protein transduction technology was successfully used in generation of induced pluripotent stem (iPS) cells. Somatic cells were first reprogrammed to a pluripotent state, known as induced pluripotent stem (iPS) cells, by Drs. Takahashi and Yamanaka using adult human dermal fibroblasts (HDF) from Cell Applications, Inc. To achieve this transformation, the HDF were transfected with four transcription factors: Sox2, Oct-4, c-Myc, and KLF4, under ES cell culture conditions.4
It is well known that the potential of iPS cells is enormous. However, the clinical application of iPS cells faces many obstacles. One of the challenges is that since the cells are artificially created to have pluripotency by inducing genes, they are inclined to form tumors. In order to eliminate any risk of modifying the target cell genome by exogenous genetic sequences, which are associated with all previous iPSC methods, Dr. Sheng Ding’s lab designed and fused a polyarginine (i.e., 11R) tag to the C terminus of the four reprogramming factors (Sox2, Oct-4, c-Myc, and KLF4,), and made recombinant fusion proteins in E. coli. It was shown that the purified 11R-tagged recombinant transcription factors readily entered MEF cells, and that the cells were fully reprogrammed into pluripotent stem cells (iPS) as a result.5 Thus the polyarginine-tagged protein transduction method provides a more efficient way of producing iPS cells without the tendency to form tumors.
Additionally, a polyarginine specific rabbit polyclonal antibody was developed with a proprietary NatureTope™ technology at Cell Applications, Inc. This antibody was used to specifically detect polyarginine-tagged proteins in a variety of assays, including Western blot, immunofluorescent staining, and immunoprecipitation. It should provide a useful tool to facilitate and extend the applications of polyarginine-tags.
References:
1. Tunnemann, G. et al: J. Peptide Sci. 14:469–76, 2008
2. Wender, P.A. et al: Proc. Natl. Acad. Sci. USA 97:13003-8, 2000
3. Takenobu, T. et al: Mol. Cancer Ther. 1:1043-9, 2002
4. Takahashi, K. & Yamanaka, S: Cell 126:663-76, 2006
5. Zhou, H. et al: Cell Stem Cell 4:381-4, 2009
