In vitro evolution of functional nucleic acids: high-affinity RNA ligands of HIV-1 proteins.

SELEX (Systematic Evolution of Ligands by EXponential enrichment) is a protocol for isolating, from a pool of variant nucleic acid sequences, high-affinity ligands to a target protein [Tuerk and Gold, Science 249 (1990) 505-510]. This procedure involves cycles of affinity selection by a target molecule from a heterogeneous population of nucleic acids, replication of the bound species (the ligands), and in vitro transcription to generate an enriched pool of RNA. We have used the SELEX procedure to obtain high-affinity RNA ligands against the reverse transcriptase and the Rev and Tat proteins of human immunodeficiency virus 1 (HIV-1). Through sequence comparisons within the collection of ligands isolated for each of these target proteins, we derive consensus descriptions of what secondary structure and primary sequences are required for binding. These descriptions serve as the starting point for the ultimate development of compounds intended to alter the course of HIV-1 infection.