Journal Article

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

Scott R. Budihas, Inna Gorshkova, Sergei Gaidamakov, Antony Wamiru, Marion K. Bona, Michael A. Parniak, Robert J. Crouch, James B. McMahon, John A. Beutler and Stuart F. J. Le Grice

in Nucleic Acids Research

Volume 33, issue 4, pages 1249-1256
Published in print February 2005 | ISSN: 0305-1048
Published online February 2005 | e-ISSN: 1362-4962 | DOI: http://dx.doi.org/10.1093/nar/gki268

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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.

Journal Article.  4922 words.  Illustrated.

Subjects: Chemistry ; Biochemistry ; Bioinformatics and Computational Biology ; Genetics and Genomics ; Molecular and Cell Biology

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