In vitro selection procedures for identifying DNA and RNA aptamers targeted to nucleic acids and proteins

In vitro selection or systematic evolution of ligands by exponential enrichment is a combinatorial procedure that allows the identification of oligonucleotides showing properties of interest-so-called aptamers-through iterative selection/amplification rounds. Libraries containing as many as 1014 different sequences can be screened against a wide range of molecules. Ribonucleic acid (RNA), deoxyribonucleic acid (DNA), or chemically modified aptamers generally display high affinity and exquisite specificity of interaction with the target. Aptamers show a promising potential for diagnostic and therapeutic purposes. We describe here methods successfully used in our laboratory for the selection of RNA or DNA aptamers against an RNA structure (the transactivation response element of HIV-1) and a protein (the human ribonuclease H1).