title: Selective inhibition of HIV-1 reverse transcriptase-associated ribonuclease H activity by hydroxylated tropolones.
abstract: High-throughput screening of a National Cancer Institute library of pure natural products identified the hydroxylated tropolone derivatives beta-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). beta-Thujaplicinol inhibited HIV-1 RNase H in vitro with an IC50 of 0.2 microM, while the IC50 for Escherichia coli and human RNases H was 50 microM and 5.7 microM, respectively. In contrast, the related tropolone analog beta-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 microM and 40 microM, 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 beta-thujaplicinol and manicol failed to inhibit DNA-dependent DNA polymerase activity of HIV-1 RT at a concentration of 50 microM, 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 beta-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.
authors.affiliation: Resistance Mechanisms Laboratory, HIV Drug Resistance Program, National Cancer Institute at Frederick Frederick, MD 21702, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Budihas
authors.forename: Inna
authors.initials: I
authors.lastname: Gorshkova
authors.forename: Sergei
authors.initials: S
authors.lastname: Gaidamakov
authors.forename: Antony
authors.initials: A
authors.lastname: Wamiru
authors.forename: Marion K
authors.initials: MK
authors.lastname: Bona
authors.forename: Michael A
authors.initials: MA
authors.lastname: Parniak
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Crouch
authors.forename: James B
authors.initials: JB
authors.lastname: McMahon
authors.forename: John A
authors.initials: JA
authors.lastname: Beutler
authors.forename: Stuart F J
authors.initials: SF
authors.lastname: Le Grice
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001567:Benzocycloheptenes / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D003374:Coumarins / Q000378:metabolism / Q000494:pharmacology; D015497:HIV-1 / Q000187:drug effects* / Q000201:enzymology; D039681:Pyranocoumarins; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D016914:Ribonuclease H / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014334:Tropolone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D001567:Benzocycloheptenes; D003374:Coumarins; D039681:Pyranocoumarins; D018894:Reverse Transcriptase Inhibitors; C497842:beta-thujaplicinol; C497843:manicol; D014334:Tropolone; D016914:Ribonuclease H; C075959:calanolide A
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