Chen Yali, Ciustea Mihai, Ricciardi Robert P
Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, 19104, USA.
Virology. 2005 Sep 30;340(2):183-91. doi: 10.1016/j.virol.2005.06.017.
Kaposi's sarcoma-associated human herpesvirus (KSHV) encodes a processivity factor (PF-8, ORF59) that forms homodimers and binds to viral DNA polymerase (Pol-8, ORF9). PF-8 is essential for stabilizing Pol-8 on template DNA so that Pol-8 can incorporate nucleotides continuously. Here, the intracellular interaction of these two viral proteins was examined by confocal immunofluorescence microscopy. When individually expressed, PF-8 was observed exclusively in the nucleus, whereas Pol-8 was found only in the cytoplasm. However, when co-expressed, Pol-8 was co-translocated with PF-8 into the nucleus. Mutational analysis revealed that PF-8 contains a nuclear localization signal (NLS) as well as domains located at the N-terminus and the C-proximal regions that are required for Pol-8 binding. This study suggests that the mechanism that enables PF-8 to transport Pol-8 into the nucleus is the first critical step required for Pol-8 and PF-8 to function processively in KSHV DNA synthesis.
卡波西肉瘤相关的人类疱疹病毒（KSHV）编码一种持续性因子（PF-8，开放阅读框59），该因子形成同源二聚体并与病毒DNA聚合酶（Pol-8，开放阅读框9）结合。PF-8对于在模板DNA上稳定Pol-8至关重要，从而使Pol-8能够连续掺入核苷酸。在此，通过共聚焦免疫荧光显微镜检查了这两种病毒蛋白的细胞内相互作用。单独表达时，仅在细胞核中观察到PF-8，而仅在细胞质中发现Pol-8。然而，当共表达时，Pol-8与PF-8共转运到细胞核中。突变分析表明，PF-8包含一个核定位信号（NLS）以及位于N端和C近端区域的结构域，这些结构域是Pol-8结合所必需的。这项研究表明，使PF-8将Pol-8转运到细胞核中的机制是Pol-8和PF-8在KSHV DNA合成中进行持续性功能所需的第一个关键步骤。
