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Basic Characteristics of Mutations
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Mutation Site
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P101S |
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Mutation Site Sentence
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We found that only the hbx2 derivatives containing Ser-101 instead of Pro-101 (hbx 2P101S and hbx 2P101S/M130K) downregulated the β-catenin level, to the level obtained with HBX3 (Fig. 2a, bF2). |
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Mutation Level
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Amino acid level |
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Mutation Type
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Nonsynonymous substitution |
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Gene/Protein/Region
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X |
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Standardized Encoding Gene
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X
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Genotype/Subtype
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- |
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Viral Reference
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-
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Functional Impact and Mechanisms
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Disease
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Hepatitis B Virus Infection
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Immune
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- |
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Target Gene
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TP53
SIAH1
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Clinical and Epidemiological Correlations
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Clinical Information
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- |
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Treatment
|
- |
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Location
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- |
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Literature Information
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PMID
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17622616
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Title
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Hepatitis B virus X protein differentially affects the ubiquitin-mediated proteasomal degradation of beta-catenin depending on the status of cellular p53
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Author
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Jung JK,Kwun HJ,Lee JO,Arora P,Jang KL
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Journal
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The Journal of general virology
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Journal Info
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2007 Aug;88(Pt 8):2144-2154
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Abstract
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Abnormal accumulation of beta-catenin is considered to be a strong driving force in hepatocellular carcinogenesis; however, the mechanism of beta-catenin accumulation in tumours is unclear. Here, it was demonstrated that hepatitis B virus X protein (HBx) differentially regulates the level of beta-catenin through two ubiquitin-dependent proteasome pathways depending on p53 status. In the presence of p53, HBx downregulated beta-catenin through the activation of a p53-Siah-1 proteasome pathway. For this purpose, HBx upregulated Siah-1 expression at the transcriptional level via activation of p53. In the absence of p53, however, HBx stabilized beta-catenin through the inhibition of a glycogen synthase kinase-3beta-dependent pathway. Interestingly, HBx variants with a Pro-101 to Ser substitution were unable to activate p53 and thus could stabilize beta-catenin irrespective of p53 status. Based on these findings, a model of beta-catenin regulation by HBx is proposed whereby the balance between the two opposite activities of HBx determines the overall expression level of beta-catenin. Differential regulation of beta-catenin by HBx depending on host (p53 status) and viral factors (HBx sequence variation) helps not only to explain the observation that cancers accumulating beta-catenin also exhibit a high frequency of p53 mutations but also to understand the contradictory reports on the roles of HBx during hepatocellular carcinogenesis.
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Sequence Data
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-
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