COMPLEMENTATION BETWEEN HIV INTEGRASE PROTEINS MUTATED IN DIFFERENT DOMAINS

HIV integrase (IN) cleaves two nucleotides off the 3' end of viral DNA and integrates viral DNA into target DNA. Previously, three functiona l domains in the HIV IN protein have been identified: (i) the central catalytic domain, (ii) the C-terminal DNA binding domain, and (iii) th e N-terminal region, which is also necessary for activity. We have now investigated whether IN proteins mutated in different domains can com plement each other. Mutant D116I does not contain an intact active sit e, but does bind DNA, whereas the C-terminal deletion mutant CDELTA73 does not bind DNA, but does have an intact active site. Neither mutant protein mediates site-specific cleavage or integration. However, a mi xture of both proteins is active, suggesting that IN functions as an o ligomer, and that two subunits can have different functions; one subun it binds the (viral) DNA and another subunit provides the active site. We found three classes of mutants, corresponding to the three domains mentioned above. Mutants from different classes, but not from the sam e class, can complement each other. However, complementation is most e fficient when the N- and C-termini are present on the same molecule.