University of Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan 430071, PR China.
J Gen Virol. 2021 Mar;102(3). doi: 10.1099/jgv.0.001517. Epub 2021 Jan 18.
Baculoviruses are large DNA viruses that replicate within the nucleus of infected host cells. Therefore, many viral proteins must gain access to the nucleus for efficient viral genome replication, gene transcription and virion assembly. To date, the global protein localization pattern of baculoviral proteins is unknown. In this study, we systematically analysed the nuclear localization of 154 ORFs encoded by the prototypic baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), either during transient expression or with super-infection of the virus. By transient expression of vectors containing -fused ORFs, we found that in the absence of virus infection, 25 viral proteins were localized in the nucleus. Most of these, which we called 'auto-nuclear localization' proteins, are related to virus replication, transcription or virion structure, and 20 of them contain predicted classical nuclear localization signal. Upon virus infection, 11 proteins, which originally localized in the cytoplasm or both cytoplasm and nucleus in the transfection assays, were completely translocated into the nucleus, suggesting that their nuclear import is facilitated by other viral or host proteins. Further co-transfection experiments identified that four of the 11 proteins, including P143, P33, AC73 and AC114, were imported into the nucleus with the assistance of the auto-nuclear localization proteins LEF-3 (for P143), TLP (for P33) and VP80 (for both AC73 and AC114). This study presents the first global nuclear localization profile of AcMNPV proteins and provides useful information for further elucidation of the mechanisms of baculovirus nuclear entry and gene functions.
杆状病毒是在感染宿主细胞的核内复制的大型 DNA 病毒。因此，许多病毒蛋白必须进入细胞核，以实现有效的病毒基因组复制、基因转录和病毒粒子组装。迄今为止，杆状病毒蛋白的全球蛋白质定位模式尚不清楚。在这项研究中，我们系统地分析了模式杆状病毒——苜蓿银纹夜蛾多核多角体病毒（AcMNPV）的 154 个 ORF 的核定位情况，这些 ORF 或在瞬时表达期间，或在病毒的超感染时进行分析。通过瞬时表达含有 -融合 ORF 的载体，我们发现，在没有病毒感染的情况下，有 25 种病毒蛋白定位于细胞核内。其中大多数，我们称之为“自动核定位”蛋白，与病毒复制、转录或病毒粒子结构有关，其中 20 个含有预测的经典核定位信号。在病毒感染后，11 种原本在转染试验中定位于细胞质或细胞质和细胞核中的蛋白完全被转运到细胞核内，这表明它们的核输入是由其他病毒或宿主蛋白促进的。进一步的共转染实验表明，这 11 种蛋白中的 4 种，包括 P143、P33、AC73 和 AC114，在自动核定位蛋白 LEF-3（用于 P143）、TLP（用于 P33）和 VP80（用于 AC73 和 AC114）的协助下被转运到细胞核内。这项研究首次呈现了 AcMNPV 蛋白的全局核定位图谱，并为进一步阐明杆状病毒核进入和基因功能的机制提供了有用的信息。
