Dataset Information

Ribonuclease H: properties, substrate specificity and roles in retroviral reverse transcription.

ABSTRACT: Retroviral reverse transcriptases possess both a DNA polymerase and an RNase H activity. The linkage with the DNA polymerase activity endows the retroviral RNases H with unique properties not found in the cellular counterparts. In addition to the typical endonuclease activity on a DNA/RNA hybrid, cleavage by the retroviral enzymes is also directed by both DNA 3' recessed and RNA 5' recessed ends, and by certain nucleotide sequence preferences in the vicinity of the cleavage site. This spectrum of specificities enables retroviral RNases H to carry out a series of cleavage reactions during reverse transcription that degrade the viral RNA genome after minus-strand synthesis, precisely generate the primer for the initiation of plus strands, facilitate the initiation of plus-strand synthesis and remove both plus- and minus-strand primers after they have been extended.

SUBMITTER: Champoux JJ

PROVIDER: S-EPMC2742777 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Publications

Ribonuclease H: properties, substrate specificity and roles in retroviral reverse transcription.

Champoux James J JJ Schultz Sharon J SJ

The FEBS journal 20090218 6

Retroviral reverse transcriptases possess both a DNA polymerase and an RNase H activity. The linkage with the DNA polymerase activity endows the retroviral RNases H with unique properties not found in the cellular counterparts. In addition to the typical endonuclease activity on a DNA/RNA hybrid, cleavage by the retroviral enzymes is also directed by both DNA 3' recessed and RNA 5' recessed ends, and by certain nucleotide sequence preferences in the vicinity of the cleavage site. This spectrum o ...[more]

PMID: 19228195

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Project description:Human immunodeficiency virus (HIV) reverse transcriptase (RT) contains two distinct functional domains: a DNA polymerase (pol) domain and a ribonuclease H (RNase H) domain, both of which are required for viral genome replication. Over the last 3 decades, RT has been at the forefront of HIV drug discovery efforts with numerous nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) approved by the FDA. However, all these RT inhibitors target only the pol function, and inhibitors of RT-associated RNase H have yet to enter the development pipeline, which in itself manifests both the opportunity and challenges of targeting RNase H: if developed, RT RNase H inhibitors would represent a mechanistically novel class of HIV drugs that can be particularly valuable in treating HIV strains resistant to current drugs. The challenges include (1) the difficulty in selectively targeting RT RNase H over RT pol due to their close interplay both spatially and temporally and over HIV-1 integrase strand transfer (INST) activity because of their active site similarities; (2) to a larger extent, the inability of active site inhibitors to confer significant antiviral effect, presumably due to a steep substrate barrier by which the pre-existing substrate prevents access of small molecules to the active site. As a result, previously reported RT RNase H inhibitors typically lacked target specificity and significant antiviral potency. Achieving meaningful antiviral activity via active site targeting likely entails selective and ultrapotent RNase H inhibition to allow small molecules to cut into the dominance of substrates. Based on a pharmacophore model informed by prior work, we designed and redesigned a few metal-chelating chemotypes, such as 2-hydroxyisoquinolinedione (HID), hydroxypyridonecarboxylic acid (HPCA), 3-hydroxypyrimidine-2,4-dione (HPD), and N-hydroxythienopyrimidine-2,4-dione (HTPD). Analogues of these chemotypes generally exhibited improved potency and selectivity inhibiting RT RNase H over the best previous compounds and further validated the pharmacophore model. Extended structure-activity relationship (SAR) on the HPD inhibitor type by mainly altering the linkage generated a few subtypes showing exceptional potency (single-digit nanomolar) and excellent selectivity over the inhibition of RT pol and INST. In parallel, a structure-based approach also allowed us to design a unique double-winged HPD subtype to potently and selectively inhibit RT RNase H and effectively compete against the RNA/DNA substrate. Significantly, all potent HPD subtypes consistently inhibited HIV-1 in the cell culture, suggesting that carefully designed active site RNase H inhibitors with ultrapotency could partially overcome the barrier to antiviral phenotype. Overall, in addition to identifying our own inhibitor types, our medicinal chemistry efforts demonstrated the value of pharmacophore and structure-based approaches in designing active side-directed RNase H inhibitors and could provide a viable path to validating RNase H as a novel antiviral target.

Dataset Information

Ribonuclease H: properties, substrate specificity and roles in retroviral reverse transcription.

Publications

Ribonuclease H: properties, substrate specificity and roles in retroviral reverse transcription.

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