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Villa JA, Pike DP, Patel KB, Lomonosova E, Lu G, Abdulqader R, Tavis JE. Purification and enzymatic characterization of the hepatitis B virus ribonuclease H, a new target for antiviral inhibitors. Antiviral Res 2016; 132:186-95. [PMID: 27321664 DOI: 10.1016/j.antiviral.2016.06.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 06/10/2016] [Accepted: 06/12/2016] [Indexed: 01/05/2023]
Abstract
Hepatitis B virus (HBV) reverse transcription requires coordinated function of the reverse transcriptase and ribonuclease H (RNaseH) activities of the viral polymerase protein. The reverse transcriptase has been biochemically characterized, but technical difficulties have prevented both assessment of the RNaseH and development of high throughput inhibitor screens against the RNaseH. Expressing the HBV RNaseH domain with both maltose binding protein and hexahistidine tags led to stable, high-level accumulation of the RNaseH in bacteria. Nickel-affinity purification in the presence of Mg(2+) and ATP removed co-purifying bacterial chaperones and yielded nearly pure monomeric recombinant enzyme. The endonucleolytic RNaseH activity required an DNA:RNA duplex ≥14 nt, could not tolerate a stem-loop in either the RNA or DNA strands, and could tolerate a nick in the DNA strand but not a gap. The RNaseH had no obvious sequence specificity or positional dependence within the RNA, and it cut the RNA at multiple positions even within the minimal 14 nt duplex. The RNaseH also possesses a processive 3'-5' exoribonuclease activity that is slower than the endonucleolytic reaction. These results are consistent with the HBV reverse transcription mechanism that features an initial endoribonucleolytic cut, 3'-5' degradation of RNA, and a sequence-independent terminal RNA cleavage. These data provide support for ongoing anti-RNaseH drug discovery efforts.
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Affiliation(s)
- Juan Antonio Villa
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Daniel P Pike
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Kunjan B Patel
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Elena Lomonosova
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Gaofeng Lu
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA; Department of Gastroenterology, The Second Affiliated Hospital, Zhengzhou University, Zhengzhou, Henan, China
| | - Roz Abdulqader
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - John E Tavis
- Department of Molecular Microbiology and Immunology and Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.
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