The Tudor Domain Protein Spindlin1 Is Involved in Intrinsic Antiviral Defense against Incoming Hepatitis B Virus and Herpes Simplex Virus Type 1

Ducroux, Aurélie; Benhenda, Shirine; Rivière, Lise; Semmes, O. John; Benkirane, Monsef; Neuveut, Christine

doi:10.1371/journal.ppat.1004343

Cited by 51 publications

(35 citation statements)

References 55 publications

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“…Thus, cccDNA is persistent throughout the cycle of infectivity. cccDNA is decorated with the usual proteins of euchromatin with the addition of two HBV proteins: X and Cp (Belloni et al, 2009; Bock et al, 2001; Buendia and Neuveut, 2015; Ducroux et al, 2014; Fallot et al, 2012; Levrero et al, 2009; Lucifora et al, 2011; Pollicino et al, 2006). The interaction of Cp with core protein is poorly understood and this information is just beginning to accumulate.…”

Section: Cp and Cccdnamentioning

confidence: 99%

Core protein: A pleiotropic keystone in the HBV lifecycle

et al. 2015

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Hepatitis B Virus (HBV) is a small virus whose genome has only four open reading frames. We argue that the simplicity of the virion correlates with a complexity of functions for viral proteins. We focus on the HBV core protein (Cp), a small (183 residue) protein that self-assembles to form the viral capsid. However, its functions are a little more complicated than that. In an infected cell Cp modulates every step of the viral lifecycle. Cp is bound to nuclear viral DNA and affects its epigenetics. Cp correlates with RNA specificity. Cp assembles specifically on a reverse transcriptase-viral RNA complex or, apparently, nothing at all. Indeed Cp has been one of the model systems for investigation of virus self-assembly. Cp participates in regulation of reverse transcription. Cp signals completion of reverse transcription to support virus secretion. Cp carries both nuclear localization signals and HBV surface antigen (HBsAg) binding sites; both of these functions appear to be regulated by contents of the capsid. Cp can be targeted by antivirals -- while self-assembly is the most accessible of Cp activities, we argue that it makes sense to engage the broader spectrum of Cp function. This article forms part of a symposium in Antiviral Research on “From the discovery of the Australia antigen to the development of new curative therapies for hepatitis B: an unfinished story.”

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Section: Cp and Cccdnamentioning

confidence: 99%

Core protein: A pleiotropic keystone in the HBV lifecycle

et al. 2015

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“…First, we demonstrate that mcHBV-GLuc cccDNA formed minichromosome in transfected cells, a key feature of cccDNA, by binding to known histone proteins and histone associated proteins (Fig. 4a)1819202122233840. Second, the mcHBV-GLuc cccDNA remained active for more than three weeks in HepG2 cells (Fig.…”

Section: Discussionmentioning

confidence: 72%

“…The HBV viral rebound was observed even after decades of successful HBV suppression associated with robust anti-HBV immune response after acute infection14151617 or after IFNα treatment11, indicating that episome cccDNA can persist stably in an occult status. As minichromosomes, cccDNA has been identified to be associated with histone proteins and its function is regulated by epigenetic “writers”, “readers” and “erasers”181920212223. However, the structure and the regulation of HBV cccDNA minichromosome is still unclear.…”

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confidence: 99%

Minicircle HBV cccDNA with a Gaussia luciferase reporter for investigating HBV cccDNA biology and developing cccDNA-targeting drugs

Liu

Murphy

et al. 2016

Sci Rep

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Chronic Hepatitis B Virus (HBV) infection is generally not curable with current anti-viral drugs. Virus rebounds after stopping treatment from the stable HBV covalently-closed-circular DNA (cccDNA). The development of drugs that directly target cccDNA is hampered by the lack of robust HBV cccDNA models. We report here a novel HBV cccDNA technology that will meet the need. We engineered a minicircle HBV cccDNA with a Gaussia Luciferase reporter (mcHBV-GLuc cccDNA), which serves as a surrogate to measure cccDNA activity. The mcHBV-GLuc cccDNA was easily produced in bacteria, and it formed minichromosomes as HBV cccDNA episome DNA does when it was transfected into human hepatocytes. Compared to non-HBV minicircle plasmids, mcHBV-GLuc cccDNA showed persistent HBV-GLuc activity and HBx-dependent gene expression. Importantly, the mcHBV-GLuc cccDNA showed resistance to interferons (IFN) treatment, indicating its unique similarity to HBV cccDNA that is usually resistant to long-term IFN treatment in chronic HBV patients. Most importantly, GLuc illuminates cccDNA as a surrogate of cccDNA activity, providing a very sensitive and quick method to detect trace amount of cccDNA. The mcHBV-GLuc cccDNA model is independent of HBV infection, and will be valuable for investigating HBV cccDNA biology and for developing cccDNA-targeting drugs.

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“…Chromatin was subjected to immunoprecipitation overnight at 4°C with 3 g of nonspecific immunoglobulins (Sigma) as a negative control, an anti-H4 antibody (Active Motif) as a positive control, or an anti-DDB1 antibody (Santa Cruz). Immunoprecipitated chromatins were processed and analyzed by realtime qPCR (29).…”

Section: Methodsmentioning

confidence: 99%

DDB1 Stimulates Viral Transcription of Hepatitis B Virus via HBx-Independent Mechanisms

Kim

Lee

Son

et al. 2016

J Virol

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HBx, a small regulatory protein of hepatitis B virus (HBV), augments viral DNA replication by stimulating viral transcription. Among numerous reported HBx-binding proteins, DDB1 has drawn attention, because DDB1 acts as a substrate receptor of the Cul4-DDB1 ubiquitin E3 ligase. Previous work reported that the DDB1-HBx interaction is indispensable for HBx-stimulated viral DNA replication, suggesting that the Cul4-DDB1 ubiquitin E3 ligase might target cellular restriction factors for ubiquitination and proteasomal degradation. To gain further insight into the DDB1-HBx interaction, we generated HBx mutants deficient for DDB1 binding (i.e., R96A, L98A, and G99A) and examined whether they support HBx-stimulated viral DNA replication. In contrast to data from previous reports, our results showed that the HBx mutants deficient for DDB1 binding supported viral DNA replication to nearly wild-type levels, revealing that the DDB1-HBx interaction is largely dispensable for HBx-stimulated viral DNA replication. Instead, we found that DDB1 directly stimulates viral transcription regardless of HBx expression. Through an HBV infection study, importantly, we demonstrated that DDB1 stimulates viral transcription from covalently closed circular DNA, a physiological template for viral transcription. Overall, we concluded that DDB1 stimulates viral transcription via a mechanism that does not involve an interaction with HBx. IMPORTANCEDDB1 constitutes a cullin-based ubiquitin E3 ligase, where DDB1 serves as an adaptor linking the cullin scaffold to the substrate receptor. Previous findings that the DDB1-binding ability of HBx is essential for HBx-stimulated viral DNA replication led to the hypothesis that HBx could downregulate host restriction factors that limit HBV replication through the cullin ubiquitin E3 ligase that requires the DDB1-HBx interaction. Consistent with this hypothesis, recent work identified Smc5/6 as a host restriction factor that is regulated by the viral cullin ubiquitin E3 ligase. In contrast, here we found that the DDB1-HBx interaction is largely dispensable for HBx-stimulated viral DNA replication. Instead, our results clearly showed that DDB1, regardless of HBx expression, enhances viral transcription. Overall, besides its role in the viral cullin ubiquitin E3 ligase, DDB1 itself stimulates viral transcription via HBx-independent mechanisms. H epatitis B virus (HBV) infection represents a major global public health concern, with over 300 million chronically infected patients worldwide. Chronic HBV infection carries a great risk of developing into severe liver diseases, including cirrhosis and liver cancer, which result in a million deaths annually (1). HBV carries a small (ca. 3.2-kb), relaxed circular (RC), partially double-stranded DNA. Following entry into the host cell, the viral RC DNA traffics to the nucleus, where it is converted into a covalently closed circular DNA (cccDNA), the template for viral transcription (2). Four viral RNAs are transcribed from their respective promoters and serve a...

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The Tudor Domain Protein Spindlin1 Is Involved in Intrinsic Antiviral Defense against Incoming Hepatitis B Virus and Herpes Simplex Virus Type 1

Cited by 51 publications

References 55 publications

Core protein: A pleiotropic keystone in the HBV lifecycle

Core protein: A pleiotropic keystone in the HBV lifecycle

Minicircle HBV cccDNA with a Gaussia luciferase reporter for investigating HBV cccDNA biology and developing cccDNA-targeting drugs

DDB1 Stimulates Viral Transcription of Hepatitis B Virus via HBx-Independent Mechanisms

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