Illimaquinone, a selective inhibitor of the RNase H activity of human immunodeficiency virus type 1 reverse transcriptase

Abstract

We studied the effect of the natural marine substance mimaquinone on the catalytic activities of reverse transcriptase from human immunodeficiency virus type 1. Illimaquinone inhibited the RNase H activity of the enzyme at concentrations of 5 to 10 ,ug/ml, whereas RNA-dependent DNA polymerase and DNA-dependent DNA polymerase activities were considerably less susceptible to this inhibition. Two synthetic derivatives of illimaquinone, in which the 6'-hydroxyl group at the ortho position to one of the carbonyl groups of the quinone ring was modified, proved ineffective in inhibiting the human immunodeficiency virus type 1 reverse transcriptase RNase H function, suggesting involvement of the 6'-hydroxyl group in blocking the enzymatic activity.Reverse transcriptases (RTs) are key enzymes in the life cycle of retroviruses, since they are responsible for the transcription of the viral RNA into the provirus DNA that is subsequently integrated into the host cell DNA (34). RT is a multifunctional enzyme; the same protein molecules exhibit both RNA-dependent DNA polymerase (RDDP) and DNAdependent DNA polymerase (DDDP) activities as well as an inherent RNase H activity (32). Drugs acting at the reverse transcription level block specifically the replication of human immunodeficiency virus (HIV), the human retrovirus that causes acquired immunodeficiency syndrome, by preventing the unique transcription of genomic viral RNA. Several compounds with diverse molecular structures, including various 2',3'-dideoxynucleosides (14, 21, 22) and 3'-azidothymidine (9, 23, 35) that inhibit the viral RT in the form of 5'-triphosphates, foscarnet (28, 33), suramine (2, 7), rifabutin (1), and HPA 23 (26), have been shown to be active against HIV RT in vitro. In contrast to the relatively large volume of research on the inhibition of the DNA polymerase activities associated with various retroviral RTs, there is a paucity of information on the inhibition of the RT-associated RNase H function. RNase H specifically degrades the RNA in the RNA-DNA heteroduplex after the minus-strand DNA has been synthesized. Removal of the RNA strand enables the synthesis of the plus strand of DNA and the formation of the proviral double-stranded DNA, which is subsequently inserted into the host cellular genome (34). The fact that there is a distinction between the DNA polymerase and RNase H activities of retroviral RTs, including that of HIV (11,25,30,31), could be utilized to develop drugs that will specifically inhibit the RNase H function without appreciably affecting the DNA-polymerizing function. Since the physiological significance of RNase H in mammalian cells is far from clear (6), it is possible that even a partial inhibition of this activity would have minimal effects on the metabolism of normal cells but a substantial inhibitory effect on the virus. The availability of large amounts of nearly authentic (560 amino acids long with an apparent molecular weight of * Corresponding author. 66,000) enzymatically active and soluble recombinant HIV type 1 (HI...

Polycitone A, a novel and potent general inhibitor of retroviral reverse transcriptases and cellular DNA polymerases

“…It is possible that the lipophilic structure of polycitone A interacts with the hydrophobic region of the enzyme, whereas the polar negatively-charged groups may contribute to the formation of the enzyme-inhibitor complex through hydrogen bonding. These results are in line with our previous findings that phenol groups are key elements in anti-HIV-1 RT activity [12,13,15,17,18]. In short, optimal anti-HIV-1 RT inhibitory effects are achieved by an intact molecule containing both the N-acylated tyramine unit and the two types of dibromophenol moieties.…”

Sesquiterpene Aminoquinones, from a Marine Sponge, Induce Erythroid Differentiation in Human Chronic Myelogenous Leukemia, K562 Cells

“…9,11,12) In this study, we clarified that these sesquiterpene aminoquinones exhibit differentiation-inducing activity to K562 cells into erythroblasts. The clinical application of Glivec 13) (a synthetic compound targeting Bcr-Abl (breakpoint cluster region-Abelson leukemia sequence), 14) which has been recognized as the cause of CML) has provided light on a cure for this disease.…”

Reactivity and Biological Activity of the Marine Sesquiterpene Hydroquinone Avarol and Related Compounds from Sponges of the Order Dictyoceratida

“…The compounds inhibit indiscriminately the RNA-dependent and DNA-dependent DNA polymerase as well as the ribonuclease H activity of HIV-1 reverse transcriptase. Ilimaquinone (3) was also active, but it was found to inhibit only the ribonuclease H and not DNA polymerase activities [100]. It should be mentioned that ilimaquinone was found to inhibit the lyase activity of eukariotic DNA polymerase β [101].…”