Assays for the Evaluation of HIV-1 Integrase Inhibitors

Integration is an essential step in the replication cycle of a retrovirus, such as the human immunodeficiency virus type 1 (HIV-1) (for a review, see ref. 1). After reverse transcription of the RNA genome, the DNA copy is transported into the nucleus and integrated in the host chromosome. The only viral enzyme required for HIV-1 integration is integrase (IN), a protein of 32 kDa encoded by the 3′-end of the pol gene. The enzyme is produced by protease-mediated cleavage of the gag-pol precursor during virion maturation. Integrase can be considered a site-specific endonuclease; the removal of two nucleotides creates a hydroxyl residue at each 3′-end of the viral DNA that will carry out a nucleophilic attack on the phosphodiester backbone of the host DNA.