Initiation of Hepatitis B Virus Replication

描述(申请人提供)：乙肝病毒感染是一个世界性的健康问题。据估计，世界上有2亿至5亿慢性乙肝病毒携带者，到目前为止，还没有可靠的治疗方法。乙肝病毒可导致急性和慢性肝病，慢性乙肝携带者患原发性肝细胞癌(PHC)的估计相对风险约为未感染患者的100倍。因此，需要对慢性乙肝病毒感染进行有效的治疗。在这些研究中，将探讨调节乙肝病毒脱氧核糖核酸(HBVDNA)合成的初始步骤的机制(S)。HBVDNA的合成是通过病毒聚合酶与位于HBV前基因组RNA 5‘端的茎环结构epsilon结合来启动的。首先，以聚合酶的氨基末端结构域为引物，以epsilon的隆起区为模板，合成了乙肝病毒负链DNA的前三个核苷酸。带有共价连接的三核苷酸序列的乙肝病毒聚合酶随后被转移到前基因组RNA 3‘端的DR1序列。然后，通过反转录前基因组RNA来进行乙肝病毒负链DNA的合成。调控易位步骤的机制(S)尚不清楚。最近，一个调控序列元件Phi被发现，它位于DR1序列的上游，位于怀孕RNA的3‘端，对病毒的有效复制非常重要，并与epsilon的5’-一半互补。这一发现表明，负链引物从epsilon到DR1的易位可能是由前基因组RNA的构象变化所介导的，使该引物与前基因组RNA 3‘端的DR1序列接近。土拨鼠肝炎病毒(WHV)和鸭乙型肝炎病毒(DHBV)基因组中epsilon和phi之间的互补性的保守性也支持这一观点。因此，通过对这些序列元件的突变分析，将直接检验epsilon和Phi之间的互补性在调节乙肝病毒复制中的作用。该方法旨在确定慢性乙肝病毒感染治疗干预的可能靶点。

DESCRIPTION (provided by applicant): Hepatitis B virus (HBV) infection is a worldwide health problem. It is estimated that there are 200 to 500 million HBV chronic carriers in the world for whom, to date, there is no reliable treatment. HBV causes both acute and chronic liver disease and the estimated relative risk of primary hepatocellular carcinoma (PHC) in chronic HBV carriers is approximately 100 times greater than in uninfected individuals. Therefore, effective treatments for chronic HBV infection are required. In these studies, the mechanism(s) regulating the initial steps in the synthesis of hepatitis B virus (HBV) DNA will be investigated. HBV DNA synthesis is initiated by binding of the viral polymerase to a stem-loop structure, epsilon, located at the 5'-end of the HBV pregenomic RNA. Initially, the first three nucleotides of HBV minus-strand DNA are synthesized utilizing the amino-terminal domain of the polymerase as a primer and the bulge region of epsilon as a template. The HBV polymerase with the covalently attached trinucleotide sequence is subsequently translocated to the DR1 sequence at the 3'-end of the pregenomic RNA. HBV minus-strand DNA synthesis then proceeds by the reverse transcription of the pregenomic RNA. The mechanism(s) regulating the translocation step are unknown. Recently, a regulatory sequence element, phi, located immediately upstream of the DR1 sequence at the 3'-end of the pregnomic RNA that is important for efficient viral replication and is complementary to the 5'-half of epsilon was identified. This finding suggests that the translocation of the minus-strand primer from epsilon to DR1 might be mediated by a conformational change in the pregenomic RNA that brings the primer into proximity with the DR1 sequence at the 3'-end of the pregenomic RNA. The conservation of the complementarity between epsilon and phi in the woodchuck hepatitis virus (WHV) and the duck hepatitis B virus (DHBV) genomes also supports this contention. Therefore, the role of the complementarity between epsilon and phi in regulating HBV replication will be examined directly by mutational analysis of these sequence elements. This approach is aimed at identifying possible targets for therapeutic intervention in chronic HBV infection.