Inhibitors of HIV-1 Reverse Transcriptase—Associated Ribonuclease H Activity

Abstract

HIV-1 enzyme reverse transcriptase (RT) is a major target for antiviral drug development, with over half of current FDA-approved therapeutics against HIV infection targeting the DNA polymerase activity of this enzyme. HIV-1 RT is a multifunctional enzyme that has RNA and DNA dependent polymerase activity, along with ribonuclease H (RNase H) activity. The latter is responsible for degradation of the viral genomic RNA template during first strand DNA synthesis to allow completion of reverse transcription and the viral dsDNA. While the RNase H activity of RT has been shown to be essential for virus infectivity, all currently used drugs directed at RT inhibit the polymerase activity of the enzyme; none target RNase H. In the last decade, the increasing prevalence of HIV variants resistant to clinically used antiretrovirals has stimulated the search for inhibitors directed at stages of HIV replication different than those targeted by current drugs. HIV RNase H is one such novel target and, over the past few years, significant progress has been made in identifying and characterizing new RNase H inhibitor pharmacophores. In this review we focus mainly on the most potent low micromolar potency compounds, as these provide logical bases for further development. We also discuss why HIV RNase H has been a difficult target for antiretroviral drug development.

Early cytoplasmic uncoating is associated with infectivity of HIV-1

“…The potential role of the interplay of reverse transcription and uncoating has been recently suggested to provide an enclosed environment facilitating firststrand transfer during HIV-1 reverse transcription (29). With the easy adaptability of our live-imaging fluorescence HIV-iGFP system, we tested this possibility in the transient presence of 7390, an RNase H activity inhibitor specific to HIV-1 reverse transcription (47) (Fig. 5B).…”

“…CsA was used at 5 μM; NVP was obtained from the NIH repository of the NIH AIDS Reagent Program, Division of AIDS, National Institute of Allergy and Infectious Diseases, NIH, and used at 10 μM (dissolved in water according to NIH AIDS Reagent Program solubility limit); MG132 was used at 1 μg/mL; Polybrene was used at 10 μg/mL; Oxyfluor/OxyRase was used at a 1:200 dilution; DL-lactate was used at 15 mM; and RnaseH inhibitor 7390 (shown as 8b in ref. 47) was used at 10 μM for live imaging and CsA washout experiments.…”

“…Using an RnaseH inhibitor specific to HIV-1 reverse transcription (7390; shown as 8b in ref. 47), we can block the first-strand transfer of reverse transcription while allowing reverse transcription activity (Fig. S4).…”

Inhibitors of Nucleotidyltransferase Superfamily Enzymes Suppress Herpes Simplex Virus Replication

“…The HIV RNase H and integrase have attracted much attention as potential drug targets, with hundreds of compounds being reported to inhibit these enzymes (43,44). Most of the inhibitors bind at the active site via interactions with the divalent cations (45)(46)(47)(48).…”

3-Hydroxypyrimidine-2,4-Diones as Novel Hepatitis B Virus Antivirals Targeting the Viral Ribonuclease H

“…Such compounds act by chelating the two metal cofactors that are coordinated to the catalytic RNH active site residues (14)(15)(16)(17)(18). The HPDs chosen for this study (see Table S1 in the supplemental material) were previously reported to potently inhibit HIV-1 RNH activity (18) and thus were appealing candidates for HBV RNH screening.…”