Hepadnavirus assembly and reverse transcription require a multi-component chaperone complex which is incorporated into nucleocapsids

Hu, Jianming; Toft, David O.; Seeger, Christoph

doi:10.1093/emboj/16.1.59

Cited by 298 publications

(313 citation statements)

References 80 publications

Supporting

Mentioning

299

Contrasting

Unclassified

Order By: Relevance

“…29,30 The formation of this macromolecular structure is mediated by several host factors including the cellular heat shock protein Hsp 90. 31 Hsp 90 is thought to mediate and stabilize the initial complex and is required for proper nucleocapsid formation. 31 Although preliminary data suggest that core protein production is not altered by the treatment with N-nonyl-DGJ, it is possible that these compounds inhibit the proper interaction with specific cellular factors such as Hsp 90 and thereby inhibit nucleocapsid assembly and hence HBV DNA formation.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Hepatitis B Virus Dna Replication by Imino Sugars Without the Inhibition of the Dna Polymerase: Therapeutic Implications

Mehta¹,

Carrouée

Conyers³

et al. 2001

Hepatology

View full text Add to dashboard Cite

Previously we have shown that the imino sugar inhibitor of N-linked glycan processing, N-nonyl-deoxynojirimycin (N-nonyl-DNJ), had antiviral activity in the woodchuck model of chronic hepatitis B virus (HBV) infection. In studying the mechanism of action of this compound, it was discovered that imino sugars could inhibit HBV secretion without inhibiting N-linked glycoprocessing. Although Nnonyl-DNJ is an inhibitor of the endoplasmic reticulum (ER) glucosidase, here it is shown that N-nonyl-DNJ retained antiviral activity at concentrations that had no significant impact on ER glucosidase function. Taken together, these results suggested that N-nonyl-DNJ possessed an antiviral activity attributable to a function other than an impact on glycoprocessing. Hepatitis B virus (HBV) is the prototypic member of the hepadnaviradae family of viruses, which includes duck hepatitis virus, woodchuck hepatitis virus, and ground squirrel hepatitis virus. 1 Worldwide, more than 350 million people are chronically infected with HBV and between 15% and 40% of these individuals will die, if left untreated, from serious liver diseases. 2 The major complication is the development of (primary) hepatocellular carcinoma, which causes an estimated 500,000 deaths annually. 3 Currently there is no definitive cure for chronic HBV infection; however, several FDA (United States Food and Drug Administration) approved clinical approaches have shown promise in some individuals. The first, interferon ␣, is an immunomodulator and has shown to be effective in achieving certain serologic milestones in between 7% and 40% of treated patients. 4 However, the need for parenteral administration, the poor long-term response, and the high frequency of adverse side effects makes interferon not ideal. 4 Also, the actual basis of the activity of interferon ␣ against HBV is unclear. The other FDA-approved HBV medicine is a nucleoside analogue, "3TC-lamivudine," now sold as "lamivudine/Epivir HBV." It is effective against human immunodeficiency virus, as well as HBV, and its mechanism of action is well understood: it is a competitive inhibitor of the viral reverse transcriptase. 5 Unlike interferon, it is orally available and effective in reducing viremia in almost all patients. 6 However, constitutive therapy is necessary and, unfortunately, escape mutants that have gained resistance to 3TC-lamivudine occur in 10% to 20% of those treated per year. Sadly, after 3 years of use, almost 70% of those treated were, again, viremic with HBV. 6 Although the pathogenicity of 3TC-lamivudineresistant escape mutants is uncertain, there clearly remains a need for alternatives and complements to interferon and the nucleoside analogues such as 3TC-lamivudine.N-butyl-deoxynojirimycin (N-butyl-DNJ) and N-nonyldeoxynojirimycin (N-nonyl-DNJ) are glucosidase inhibitors that have been shown to be antiviral against HBV in tissue culture and in the woodchuck model of chronic HBV infection. 7-11 The ␣-glucosidases (I and II) mediate the first steps in the glycan-processing pathway and a...

show abstract

Section: Discussionmentioning

confidence: 99%

Inhibition of Hepatitis B Virus Dna Replication by Imino Sugars Without the Inhibition of the Dna Polymerase: Therapeutic Implications

Mehta¹,

Carrouée

Conyers³

et al. 2001

Hepatology

View full text Add to dashboard Cite

show abstract

“…Virion morphogenesis starts with encapsidation by the capsid, or core, protein of a complex consisting of one of the viral RNAs, the reverse transcriptase, and probably cellular chaperones [5]. After reverse transcription, the DNA-containing nucleocapsid buds into a pre-Golgi compartment, exiting from the cell as enveloped virion [6].…”

Section: Introductionmentioning

confidence: 99%

Packaging of up to 240 subunits of a 17 kDa nuclease into the interior of recombinant hepatitis B virus capsids

2000

View full text Add to dashboard Cite

The icosahedral nucleocapsid of hepatitis B virus (HBV) consists of multiple subunits of a single 183 amino acids (aa) core protein encasing the viral genome. However, recombinant core protein alone also forms capsid-like particles. We have recently shown that a 238 aa protein centrally inserted into the core protein can be displayed on the particle surface. Here we demonstrate that replacement of the C-terminal basic domain by the 17 kDa Staphylococcus aureus nuclease also yields particles but that in these the foreign domains are located in the interior. The packaged nuclease is enzymatically active, and the chimeric protein forms mosaic particles with the wild-type core protein.Hence the HBV capsid is useful as a molecular platform which, dependent on the fusion site, allows foreign protein domains to either be packaged into or be exposed on the exterior of the particle. These results are of relevance for the use of the HBV capsid as a vaccine carrier, and as a target for antiviral therapy. ß

show abstract

“…The fulllength RT requires the assistance of the host cell chaperone proteins in order to establish and maintain a conformation that is competent to recognize the ε RNA and to initiate protein priming (9,10,13,15,17,18,41,42). However, a truncated DHBV RT protein, MiniRT2, with deletion of the entire RNase H domain, the N-terminal third of the TP domain, and most of the spacer, retains ε RNA binding and protein priming activity but no longer requires the host chaperones (55).…”

mentioning

confidence: 99%

Cryptic Protein Priming Sites in Two Different Domains of Duck Hepatitis B Virus Reverse Transcriptase for Initiating DNA Synthesis In Vitro

Boregowda

Zhu

et al. 2011

J Virol

View full text Add to dashboard Cite

Initiation of reverse transcription in hepadnaviruses is accomplished by a unique protein-priming mechanism whereby a specific Y residue in the terminal protein (TP) domain of the viral reverse transcriptase (RT) acts as a primer to initiate DNA synthesis, which is carried out by the RT domain of the same protein. When separate TP and RT domains from the duck hepatitis B virus (DHBV) RT protein were tested in a transcomplementation assay in vitro, the RT domain could also serve, unexpectedly, as a protein primer for DNA synthesis, as could a TP mutant lacking the authentic primer Y (Y96) residue. Priming at these other, so-called cryptic, priming sites in both the RT and TP domains shared the same requirements as those at Y96. A mini RT protein with both the TP and RT domains linked in cis, as well as the full-length RT protein, could also initiate DNA synthesis using cryptic priming sites. The cryptic priming site(s) in TP was found to be S/T, while those in the RT domain were Y and S/T. As with the authentic TP Y96 priming site, the cryptic priming sites in the TP and RT domains could support DNA polymerization subsequent to the initial covalent linkage of the first nucleotide to the priming amino acid residue. These results provide new insights into the complex mechanisms of protein priming in hepadnaviruses, including the selection of the primer residue and the interactions between the TP and RT domains that is essential for protein priming.The Hepadnaviridae family includes the hepatitis B virus (HBV), a global human pathogen that chronically infects hundreds of millions and causes a million fatalities yearly, and related animal viruses such as the duck hepatitis B virus (DHBV) (40). Hepadnaviruses contain a small (ϳ3-kb), partially double-stranded DNA genome that is replicated through an RNA intermediate, called pregenomic RNA (pgRNA) by reverse transcription (39, 43). The virally encoded reverse transcriptase (RT) is unique among known RTs in its structure and function (14). RT is composed of four domains. The Nterminal TP (terminal protein) is conserved among all hepadnaviruses but absent from all other known RTs and is required for viral reverse transcription. The spacer domain, which does not have any known role in RT functions, connects TP to the central RT domain and the C-terminal RNase H domain. Both the RT and the RNase H domains share sequence homology with other RTs, including the RT active-site motif YMDD and the catalytic RNase H residues (4, 5, 35, 57).A prerequisite for the initiation of reverse transcription in hepadnaviruses is the specific interaction between RT and a short RNA signal called ε located at the 5Ј end of pgRNA (33, 51). RT-ε interaction is required to activate the polymerase activity of RT and ε also serves as the template for the initial stage of viral reverse transcription (13,16,44,46,47,49).Instead of relying on an RNA primer to prime DNA synthesis, as is the case with most other RTs and DNA polymerases in general, the hepadnavirus RT uses a specific Y residue in the TP ...

show abstract

Hepadnavirus assembly and reverse transcription require a multi-component chaperone complex which is incorporated into nucleocapsids

Cited by 298 publications

References 80 publications

Inhibition of Hepatitis B Virus Dna Replication by Imino Sugars Without the Inhibition of the Dna Polymerase: Therapeutic Implications

Inhibition of Hepatitis B Virus Dna Replication by Imino Sugars Without the Inhibition of the Dna Polymerase: Therapeutic Implications

Packaging of up to 240 subunits of a 17 kDa nuclease into the interior of recombinant hepatitis B virus capsids

Cryptic Protein Priming Sites in Two Different Domains of Duck Hepatitis B Virus Reverse Transcriptase for Initiating DNA Synthesis In Vitro

Contact Info

Product

Resources

About