Hepatitis B Virus Ribonuclease H: Mechanisms of Catalysis and Inhibition
Abstract
Topic Area: This proposal is responsive to the Topic Area “Hepatitis B and Hepatitis C” because it proposes to generate key biochemical data about function and inhibition of the Hepatitis B Virus (HBV) ribonuclease H (RNaseH), a recently validated drug target. It will provide key information needed to develop HBV RNaseH inhibitors as novel drugs for the disease Hepatitis B. Overview of the Research Project: Central problem to be addressed: HBV chronically infects at least 257 million people world-wide and kills more than 887,000 people every year. Current drugs can usually control the virus in the bloodstream, but they only reduce disease and death by about two-fold. Therefore, more effective treatments are badly needed. The HBV RNaseH is an enzyme that binds to its viral RNA:DNA heteroduplex substrate and degrades the RNA strand. This activity is essential for the virus to copy itself. The idea underlying this application is that gaining a detailed biochemical understanding of how the HBV RNaseH works will be essential to support design and development of HBV RNaseH inhibitors as novel drugs to treat chronic HBV infections. Research Description: This project will leverage our position as the only lab in the world that can conduct biochemical analyses of the HBV RNaseH and our leading position in anti-RNaseH drug development. The RNaseH needs to bind to both magnesium ions (Mg++) and the heteroduplex substrate to be active, and the inhibitors we discovered appear to work by binding to the Mg++ ions to block their function. Therefore, in Aim 1 we ask, “How do Mg++ ions and the heteroduplex substrate interact with the RNaseH?” We will conduct basic biochemical binding and enzymatic studies to evaluate how Mg++ binds to the enzyme, how Mg++ affects the ability of the RNaseH to bind to the substrate, whether the RNaseH’s two modes of enzymatic activity (endo- and exo-nucleolytic) have similar Mg++ needs, and mutate the RNaseH to identify amino acids in the enzyme that influence substrate binding and RNaseH activity. In Aim 2, we ask, “How do RNaseH inhibitors interact with the RNaseH?” We will do extensive molecular binding and enzymatic kinetics studies with wild-type and mutant RNaseH enzymes to evaluate how the inhibitors bind to the enzyme and to identify amino acids in the RNaseH that contribute to action of the inhibitors. Similar techniques will be employed to determine the role of the Mg++ ions in the binding, efficacy, and stability of the inhibitors as they interact with the RNaseH. Ultimate Applicability and Impact of the Research: Our current ignorance of how the HBV RNaseH works is significantly impeding antiviral drug discovery against the RNaseH. Therefore, the short-term impact of this work will be to provide key data needed to improve our anti-RNaseH drug discovery assays and guide synthesis of better inhibitors of the RNaseH. The long-term impact will be to accelerate our drive to get anti-RNaseH drugs into clinical testing, and eventually into use for the afflicted HBV patient population. Development of anti-RNaseH drugs will help reduce the disease, suffering, and premature deaths caused by HBV. Military Relevance: There were 21,900 new HBV infections in the United States in 2015, leading the Institute of Medicine, the Department of Health and Human Services, and the Food and Drug Administration to all make developing more effective anti-HBV therapies a high priority. Unfortunately, active HBV infections are over three-fold more common among our Veterans than in the general US population. Furthermore, deployment of US troops in regions with high HBV endemicity in past armed conflicts, including China, Korea, and Vietnam, led to many marriages between US military personnel and their local partners. As the HBV infection rate in Southeast Asia is 5%-8%, a large number of these Veterans’ families, loved ones, and beneficiaries also suffer from chronic HBV infection. Therefore, de
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 29, 2018
- Source ID
- W81XWH1810307
Entities
People
- John E Tavis
Organizations
- Saint Louis University
- United States Army