Ducroux Aurélie, Benhenda Shirine, Rivière Lise, Semmes O John, Benkirane Monsef, Neuveut Christine
Unité des Hépacivirus et Immunité Innée, Institut Pasteur, Paris, France; UMR CNRS 3569, Paris, France.
The Leroy T. Canoles Jr Cancer Research Center and Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia, United States of America.
PLoS Pathog. 2014 Sep 11;10(9):e1004343. doi: 10.1371/journal.ppat.1004343. eCollection 2014 Sep.
Hepatitis B virus infection (HBV) is a major risk factor for the development of hepatocellular carcinoma. HBV replicates from a covalently closed circular DNA (cccDNA) that remains as an episome within the nucleus of infected cells and serves as a template for the transcription of HBV RNAs. The regulatory protein HBx has been shown to be essential for cccDNA transcription in the context of infection. Here we identified Spindlin1, a cellular Tudor-domain protein, as an HBx interacting partner. We further demonstrated that Spindlin1 is recruited to the cccDNA and inhibits its transcription in the context of infection. Spindlin1 knockdown induced an increase in HBV transcription and in histone H4K4 trimethylation at the cccDNA, suggesting that Spindlin1 impacts on epigenetic regulation. Spindlin1-induced transcriptional inhibition was greater for the HBV virus deficient for the expression of HBx than for the HBV WT virus, suggesting that HBx counteracts Spindlin1 repression. Importantly, we showed that the repressive role of Spindlin1 is not limited to HBV transcription but also extends to other DNA virus that replicate within the nucleus such as Herpes Simplex Virus type 1 (HSV-1). Taken together our results identify Spindlin1 as a critical component of the intrinsic antiviral defense and shed new light on the function of HBx in HBV infection.
乙型肝炎病毒感染（HBV）是肝细胞癌发生的主要危险因素。HBV从共价闭合环状DNA（cccDNA）进行复制，该cccDNA作为附加体保留在受感染细胞的细胞核内，并作为HBV RNA转录的模板。在感染的情况下，调节蛋白HBx已被证明对cccDNA转录至关重要。在这里，我们鉴定出细胞Tudor结构域蛋白Spindlin1是HBx的相互作用伴侣。我们进一步证明，在感染的情况下，Spindlin1被招募到cccDNA并抑制其转录。Spindlin1基因敲低导致HBV转录增加以及cccDNA上组蛋白H4K4三甲基化增加，这表明Spindlin1影响表观遗传调控。对于缺乏HBx表达的HBV病毒，Spindlin1诱导的转录抑制作用比对HBV野生型病毒更大，这表明HBx可抵消Spindlin1的抑制作用。重要的是，我们表明Spindlin1的抑制作用不仅限于HBV转录，还扩展到在细胞核内复制的其他DNA病毒，如单纯疱疹病毒1型（HSV-1）。综上所述，我们的结果确定Spindlin1是内在抗病毒防御的关键组成部分，并为HBx在HBV感染中的功能提供了新的线索。
