Hepatitis B virus transcriptional interference and liver cancer-related mutations

乙型肝炎病毒转录干扰与肝癌相关突变

• 批准号: 8969082
• 负责人: SHUPING TONG
• 金额: $ 20.13万
• 依托单位: RHODE ISLAND HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2017-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8969082
• 关键词: Address; Biological; CMV promoter; Capsid; Cell Proliferation; Chronic; Chronic Hepatitis B; Circular DNA; Core Protein; DNA biosynthesis; Development; Epidemiologic Studies; Genetic Transcription; Genome; Glycine decarboxylase; Hepatitis B; Hepatitis B Surface Antigens; Hepatitis B Virus; Hepatitis B e Antigens; Hepatocarcinogenesis; Hepatocyte; Immune Tolerance; Infection; Length; Link; Malignant neoplasm of liver; Medical; Molecular Biology; Monitor; Mutation; Nature; Patients; Phase; Polyadenylation; Polymerase; Positioning Attribute; Primary carcinoma of the liver cells; Production; Protein S; Proteins; RNA; Risk; Signal Transduction; Specific qualifier value; Staging; Testing; Time; Trans-Activators; Transcript; Transcriptional Regulation; Transgenic Mice; Translating; Translations; Up-Regulation; Viral; Viral Genome; Virion; Virus; Work; ds-DNA; env Gene Products; immune clearance; immunogenic; in vivo; mutant; novel; overexpression; particle; promoter; protein expression; public health relevance; vector; viral RNA

 DESCRIPTION (provided by applicant): Establishment of chronic hepatitis B virus (HBV) infection requires induction of immune tolerance by hepatitis B e antigen (HBeAg) and excess envelope proteins in the form of subviral particles. The subsequent immune clearance phase rather selects for core promoter mutations and SPII promoter deletions. Both types of mutations and HBx protein, a transcriptional transactivator, have been implicated in the development of hepatocellular carcinoma (HCC). The core promoter drives transcription of the 3.5-kb pc RNA for HBeAg and slightly shorter pg RNA for genome replication, while the SPII promoter drives the 2.1-kb RNA for the middle and small (S) envelope proteins. Core promoter mutations diminish HBeAg expression but enhance genome replication through transcriptional up regulation of pg RNA at the expense of pc RNA. Surprisingly, mutations conferring the highest level of genome replication reduced S protein level. Since all the four classes of HBV transcripts are unidirectional and co-terminal at the 3' end, our interpretation is that the 3.5-kb RNAs interfere with transcription of the 2.1-kb RNA by promoter occlusion. To verify this hypothesis, the impact of deleting the core promoter or replacing it with the strong CMV promoter on transcription of the 2.1-kb RNA will be determined. To examine whether the 2.1-kb RNA interferes with transcription of the 0.7-kb RNA for HBx protein, we will establish whether SPII promoter deletions found in HCC patients up regulate HBx transcript. Finally, since the 3' end of all the transcripts overlaps with the 5' end of the terminally redundant 3.5-kb RNAs, the abundant 2.1-kb RNA has the potential to inhibit transcription of the 3.5-kb RNAs. This will be verified by examining the replication impact of SPII promoter deletions in the context of a circularized HBV genome in contrast to vector-linked dimeric construct. We propose that bidirectional transcriptional interference allows HBV to effectively coordinate its genome replication with envelope and HBx protein expression. We previously found that core promoter mutations enable the HBx protein expressed alone (and at high level) to trigger cell proliferation. Transcriptional interference will allow SPII promoter deletions to markedly augment HBx protein expression from the intact genome. Thus, the two types of mutations could work synergistically with HBx protein to promote hepatocarcinogenesis. In summary, this application explores a novel mechanism of HBV transcriptional regulation and at the same time connects the three viral factors in HCC development.

 描述（通过应用提供）：建立慢性丙型肝炎病毒（HBV）感染需要通过丙型肝炎（HBEAG）诱导免疫耐受性，并以皮下颗粒的形式超过包膜蛋白。随后的免疫清除阶段是为核心启动子突变和SPII启动子缺失选择。两种类型的突变和HBX蛋白（一种转录反式激活剂）在肝细胞癌（HCC）的发展中均隐含。核心启动子驱动用于HBEAG的3.5-KB PC RNA的转录，用于基因组复制的PG RNA略短，而SPII启动子则驱动中间和小（S）包膜蛋白的2.1-kb RNA。核心启动子突变减少了HBEAG表达，但通过转录以PC RNA为代价来增强基因组复制。令人惊讶的是，突变会导致最高水平的基因组复制降低了S蛋白水平。由于所有四个类别的HBV转录本在3'末端都是单向和共末端，因此我们的解释是3.5-kb RNA会通过启动子闭塞干扰2.1-kb RNA的转录。为了验证这一假设，将确定删除核心启动子或用强CMV启动子对2.1-kb RNA转录进行替换的影响。干扰了HBX蛋白0.7-Kb RNA的转录，我们将确定在HCC患者中发现的SPII启动子缺失是否会调节HBX转录本。最后，由于所有转录本的3'末端与终端冗余3.5-kb RNA的5'端重叠，因此大量的2.1-kb RNA具有抑制3.5-kb RNA的转录的潜力。这将通过检查SPII启动子缺失的复制影响在我们先前发现的核心启动子突变使HBX蛋白可以单独表达（并在高水平上）触发细胞增殖的复制影响来验证这一点。 转录干扰将使SPII启动子缺失从完整的基因组中显着增强HBX蛋白表达。这两种突变可以与HBX蛋白协同起作用，以促进肝癌发生。总而言之，该应用程序探讨了HBV转录调控的一种新型机制，同时又连接了HCC发育中的三个病毒因素。