Integration requires a specific interaction of the donor DNA terminal 5′-cytosine with glutamine 148 of the HIV-1 integrase flexible loop

Abstract

Integration is essential for retroviral replication and gene therapy using retroviral vectors. Human immunodeficiency virus, type 1 (HIV-1), integrase specifically recognizes the terminal sequences of each long terminal repeat (LTR) and cleaves the 3′-end terminal dinucleotide 5′-GT. The exposed 3′-hydroxyl is then positioned for nucleophilic attack and subsequent strand transfer into another DNAduplex (target or chromosomal DNA).We report that both the terminal cytosine at the protruding 5′-end of the long terminal repeats (5′-C) and the integrase residue Gln-148 are critical for strand transfer. Proximity of the 5′-C and Gln-148 was demonstrated by disulfide cross-linking. Cross-linking is inhibited by the inhibitor 5CITEP 1-(5-chloroindol-3-yl)-3-hydroxy-3-(2H-tetrazol-5-yl)-propenone. We propose that strand transfer requires a conformational change of the integrase-viral (donor)DNAcomplex with formation of an H-bond between the N-3 of the 5′-C and the amine group of Gln-148. These findings have implications for the molecular mechanisms coupling 3′-processing and strand transfer as well as for the molecular pharmacology of integrase inhibitors.