McArdle Laboratory for Cancer Research, University of Wisconsin School of Medicine and Public Health, 1400 University Ave., Madison, WI 53706, USA.
J Virol. 2011 Feb;85(3):1298-309. doi: 10.1128/JVI.01957-10. Epub 2010 Nov 17.
The carboxy-terminal domain (CTD) of the core protein of hepatitis B virus is not necessary for capsid assembly. However, the CTD does contribute to encapsidation of pregenomic RNA (pgRNA). The contribution of the CTD to DNA synthesis is less clear. This is the case because some mutations within the CTD increase the proportion of spliced RNA to pgRNA that are encapsidated and reverse transcribed. The CTD contains four clusters of consecutive arginine residues. The contributions of the individual arginine clusters to genome replication are unknown. We analyzed core protein variants in which the individual arginine clusters were substituted with either alanine or lysine residues. We developed assays to analyze these variants at specific steps throughout genome replication. We used a replication template that was not spliced in order to study the replication of only pgRNA. We found that alanine substitutions caused defects at both early and late steps in genome replication. Lysine substitutions also caused defects, but primarily during later steps. These findings demonstrate that the CTD contributes to DNA synthesis pleiotropically and that preserving the charge within the CTD is not sufficient to preserve function.
乙型肝炎病毒核心蛋白的羧基末端结构域（CTD）对于衣壳组装并非必需。然而，CTD 确实有助于前基因组 RNA（pgRNA）的包裹。CTD 对 DNA 合成的贡献不太明确。这是因为 CTD 内的一些突变会增加被包裹和逆转录的剪接 RNA 与 pgRNA 的比例。CTD 包含四个连续精氨酸残基簇。各个精氨酸簇对基因组复制的贡献尚不清楚。我们分析了核心蛋白变体，其中单个精氨酸簇被替换为丙氨酸或赖氨酸残基。我们开发了在基因组复制过程中的特定步骤分析这些变体的检测方法。我们使用未剪接的复制模板来研究仅 pgRNA 的复制。我们发现，丙氨酸取代在基因组复制的早期和晚期步骤都引起缺陷。赖氨酸取代也会引起缺陷，但主要发生在后期步骤。这些发现表明，CTD 多效性地参与 DNA 合成，并且在 CTD 内保持电荷不足以维持功能。
