Structure–Activity of Inhibition of HIV-1 Integrase and Virus Replication by G-quartet Oligonucleotides

As novel anti-HIV agents, the G-tetrad-forming oligonucleotides have been explored for their structure–activity relations with regard to inhibition of integrase (IN) (N. Jing, Expert Opin. Investig. Drugs (2000) 9, 1777–1785). We have now developed two families of G-quartet oligonucleotides: T40217–T40222, with potential formation of a tail-to-tail G-quartet dimer, and T40224–T40227, with phosphorothioate (PT) linkages in the guanine loops. The results obtained from biophysical measurements and the assays of the inhibition of HIV-1 IN and virus replication demonstrated that an increase in the length of the G-quartet structure from a monomer (15Å) to a tail-to-tail dimer (47Å) does not distinctly disrupt the inhibition of HIV-1 IN activity or the inhibition of HIV-1 replication in cell cultures. G-quartet oligonucleotides were observed to induce molecular aggregation of HIV-1 IN and interrupt the binding of viral DNA to HIV-1 IN. Also, PT substitutions did not confer any advantages compared with the regular phosphodiesters for the inhibition of HIV-1 replication by intramolecular G-quartets. The G-quartet motif is the primary requirement for the remarkable nuclease resistance and pronounced biological efficacy of these oligonucleotides.