INTERMOLECULAR DISINTEGRATION AND INTRAMOLECULAR STRAND TRANSFER ACTIVITIES OF WILD-TYPE AND MUTANT HIV-1 INTEGRASE

We report the activities of HIV integrase protein on a novel DNA subst rate, consisting of a pair of gapped duplex molecules. Integrase catal yzed an intermolecular disintegration reaction that requires positioni ng of a pair of the gapped duplexes in a configuration that resembles the integration intermediate. However, the major reaction resulted fro m an intramolecular reaction involving a single gapped duplex, giving rise to a hairpin. Surprisingly, a deletion mutant of integrase that l acks both the amino and carboxyl terminal regions still catalyzed the intermolecular disintegration reaction, but supported only a very low level of the intramolecular reaction. The central core region of integ rase is therefore sufficient to both bind the gapped duplex DNA and ju xtapose a pair of such molecules through protein-protein interactions. We suggest that the branched DNA structures of the previously reporte d disintegration substrate, and the intermolecular disintegration subs trate described here, assist in stabilizing protein-protein interactio ns that otherwise require the amino and carboxyl terminal regions of i ntegrase.