Screening of DNA aptamer against mouse prion protein by competitive selection.

Prion disease is a neurodegenerative disorder, in which the normal prion protein (PrP) changes structurally into an abnormal form and accumulates in the brain. There is a great demand for the development of a viable approach to diagnosis and therapy. Not only has the ligand against PrP been used for diagnosis, but it has also become a promising tool for therapy, as an antibody. Aptamers are a novel type of ligand composed of nucleic acids. DNA aptamers in particular have many advantages over antibodies. Therefore, we tried to isolate the DNA aptamer for mouse PrP. We developed a competitive selection method and tried to screen the DNA aptamer with it. In the fourth round of selection, several clones of the aptamer with an affinity to PrP were enriched, and clone 4-9 showed the highest affinity of all. The investigation by aptamer blotting and Western blotting showed that clone 4-9 was specifically able to recognize both alpha-PrP and beta-PrP. Moreover, it was indicated that clone 4-9 could recognize the flexible region of the N-terminal domain of PrP. These characteristics suggest that clone 4-9 might be a useful tool in prion-disease diagnosis and research.