Selective inhibition of HIV-1 reverse transcriptase-associated ribonuclease H activity by hydroxylated tropolones

• Published in: Nucleic acids research Vol. 33; no. 4; pp. 1249 - 1256
• Main Authors: Budihas, Scott R., Gorshkova, Inna, Gaidamakov, Sergei, Wamiru, Antony, Bona, Marion K., Parniak, Michael A., Crouch, Robert J., McMahon, James B., Beutler, John A., Le Grice, Stuart F. J.
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.01.2005; Oxford Publishing Limited (England)
• Subjects: Anti-HIV Agents - chemistry; Anti-HIV Agents - metabolism; Anti-HIV Agents - pharmacology; Benzocycloheptenes - chemistry; Benzocycloheptenes - pharmacology; Binding Sites; Coumarins - metabolism; Coumarins - pharmacology; HIV-1 - drug effects; HIV-1 - enzymology; Pyranocoumarins; Reverse Transcriptase Inhibitors - chemistry; Reverse Transcriptase Inhibitors - metabolism; Reverse Transcriptase Inhibitors - pharmacology; Ribonuclease H - antagonists & inhibitors; Ribonuclease H - metabolism; Tropolone - analogs & derivatives; Tropolone - chemistry; Tropolone - pharmacology
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gki268

High-throughput screening of a National Cancer Institute library of pure natural products identified the hydroxylated tropolone derivatives β-thujaplicinol (2,7-dihydroxy-4-1(methylethyl)-2,4,6-cycloheptatrien-1-one) and manicol (1,2,3,4-tetrahydro-5-7-dihydroxy-9-methyl-2-(1-methylethenyl)-6H-benzocyclohepten-6-one) as potent and selective inhibitors of the ribonuclease H (RNase H) activity of human immunodeficiency virus-type 1 reverse transcriptase (HIV-1 RT). β-Thujaplicinol inhibited HIV-1 RNase H in vitro with an IC50 of 0.2 μM, while the IC50 for Escherichia coli and human RNases H was 50 μM and 5.7 μM, respectively. In contrast, the related tropolone analog β-thujaplicin (2-hydroxy-4-(methylethyl)-2,4,6-cycloheptatrien-1-one), which lacks the 7-OH group of the heptatriene ring, was inactive, while manicol, which possesses a 7-OH group, inhibited HIV-1 and E.coli RNases H with IC50 = 1.5 μM and 40 μM, respectively. Such a result highlights the importance of the 2,7-dihydroxy function of these tropolone analogs, possibly through a role in metal chelation at the RNase H active site. Inhibition of HIV-2 RT-associated RNase H indirectly indicates that these compounds do not occupy the nonnucleoside inhibitor-binding pocket in the vicinity of the DNA polymerase domain. Both β-thujaplicinol and manicol failed to inhibit DNA-dependent DNA polymerase activity of HIV-1 RT at a concentration of 50 μM, suggesting that they are specific for the C-terminal RNase H domain, while surface plasmon resonance studies indicated that the inhibition was not due to intercalation of the analog into the nucleic acid substrate. Finally, we have demonstrated synergy between β-thujaplicinol and calanolide A, a nonnucleoside inhibitor of HIV-1 RT, raising the possibility that both enzymatic activities of HIV-1 RT can be simultaneously targeted.