Perri S, Ganem D
Department of Microbiology and Immunology, University of California, San Francisco 94143-0414, USA.
J Virol. 1997 Nov;71(11):8448-55. doi: 10.1128/JVI.71.11.8448-8455.1997.
The viral polymerase and several cis-acting sequences are essential for hepadnaviral DNA replication, but additional host factors are likely to be involved in this process. We previously identified two sequences, UBS and DBS (upstream and downstream binding sites), present in multiple copies in and adjacent to the pregenomic RNA (pgRNA) terminal redundancy, that were specifically recognized by a 65-kDa host factor, p65. The possible roles of these two sequences in hepatitis B virus (HBV) replication were investigated in the context of the intact viral genome. UBS is contained within the terminal redundancy of pgRNA, and the 5' copy of this sequence is essential for viral replication. Mutations within the central core of UBS ablate p65 binding and selectively block synthesis of plus-strand DNA, without affecting RNA packaging or minus-strand synthesis. The DBS sequence, which is located downstream of the pgRNA polyadenylation site, overlaps the core (C) protein coding region. All mutations introduced into this site severely affected viral replication. However, these effects were shown to result from dominant negative effects of mutant core polypeptides rather than from cis-acting effects on RNA recognition. Thus, the 5' UBS but not DBS sites play important cis-acting roles in HBV DNA replication; however, the involvement of p65 in these roles remains a matter for investigation.
病毒聚合酶和几个顺式作用序列对嗜肝DNA病毒的DNA复制至关重要，但这一过程可能还涉及其他宿主因子。我们之前鉴定出两个序列，即上游结合位点（UBS）和下游结合位点（DBS），它们以多个拷贝存在于前基因组RNA（pgRNA）末端冗余区及其附近，可被一个65 kDa的宿主因子p65特异性识别。在完整病毒基因组的背景下研究了这两个序列在乙型肝炎病毒（HBV）复制中的可能作用。UBS包含在pgRNA的末端冗余区内，该序列的5'拷贝对病毒复制至关重要。UBS中央核心区域内的突变会消除p65结合并选择性地阻断正链DNA的合成，而不影响RNA包装或负链合成。位于pgRNA聚腺苷酸化位点下游的DBS序列与核心（C）蛋白编码区重叠。引入该位点的所有突变都严重影响病毒复制。然而，这些效应被证明是由突变核心多肽的显性负效应引起的，而不是对RNA识别的顺式作用效应。因此，5' UBS而非DBS位点在HBV DNA复制中发挥重要的顺式作用；然而，p65在这些作用中的参与情况仍有待研究。
