Inhibition of HIV-1 Tat-TAR interaction by diphenylfuran derivatives: Effects of the terminal basic side chains

A series of four biscationic diphenylfuran derivatives was used to investig ate drug binding to the transactivation response element (TAR) RNA. The dru gs, which are active against the Pneumocystis carinii pathogen (PCP), diffe r by the nature of the terminal basic side chains. Furimidazoline (DB60) is more potent at inhibiting binding of the Tat protein to TAR than furamidin e (DB75) and the amidine-substituted analogues DB244 and DB226. In vivo stu dies using the fusion-induced gene stimulation (FIGS) assay entirely agree with the in vitro gel mobility shift data. The capacity of the drugs to ant agonize Tat binding correlates with their RNA binding properties determined by melting temperature and RNase protection experiments. Footprinting stud ies indicate that the bulge region of TAR provides the identity element for the diphenylfurans. Access of the drugs to the major groove cavity at the pyrimidine bulge depends on the bulk of the alkylamine substituents. Experi ments using TAR mutants show that the bulge of TAR is critical for drug bin ding but also reveal that the fit of the drugs into the major groove cavity of TAR does not involve specific contacts with the highly conserved residu e U23 or the C . G26-39 base pair. The binding essentially involves shape r ecognition. The results are also discussed with respect to the known activi ty of the drug against PCP which is the major cause of mortality in AIDS pa tients. This study provides guidelines for future development of TAR-target ed anti-HIV-l drugs. (C) 1999 Elsevier Science Ltd. All rights reserved.