Gill Michael B, Kutok Jeffery L, Fingeroth Joyce D
Divison of Infectious Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA.
J Virol. 2007 Jun;81(12):6523-35. doi: 10.1128/JVI.00147-07. Epub 2007 Apr 11.
The thymidine kinase (TK) encoded by Epstein-Barr virus (EBV) differs not only from that of the alphaherpesviruses but also from that of the gamma-2 herpesvirus subfamily. Because cellular location is frequently a determinant of regulatory function, to gain insight into additional role(s) of EBV TK and to uncover how the lymphocryptovirus and rhadinovirus enzymes differ, the subcellular localizations of EBV TK and the related cercopithecine herpesvirus-15 TK were investigated. We show that in contrast to those of the other family members, the gamma-1 herpesvirus TKs localize to the centrosome and even more precisely to the periphery of the centriole, tightly encircling the tubulin-rich centrioles in a microtubule-independent fashion. Centrosomal localization is observed in diverse cell types and occurs whether the protein is expressed independently or in the context of lytic EBV infection. Surprisingly, analysis of mutants revealed that the unique N-terminal domain was not critical for targeting to the centrosome, but rather, peptide sequences located C terminal to this domain were key. This is the first herpesvirus protein documented to reside in the centrosome, or microtubule-organizing center, an amembranous organelle that regulates the structural biology of the cell cycle through control of chromosome separation and cytokinesis. More recently, proteasome-mediated degradation of cell cycle regulatory proteins, production and loading of antigenic peptides onto HLA molecules, and transient homing of diverse virion proteins required for entry and/or egress have been shown to be coordinated at the centrosome. Potential implications of centrosomal localization for EBV TK function are discussed.
爱泼斯坦-巴尔病毒（EBV）编码的胸苷激酶（TK）不仅与甲型疱疹病毒的胸苷激酶不同，也与γ-2疱疹病毒亚科的胸苷激酶不同。由于细胞定位常常是调节功能的一个决定因素，为了深入了解EBV TK的其他作用，并揭示淋巴细胞隐病毒和嗜瘤病毒的酶之间的差异，我们研究了EBV TK和相关的猕猴疱疹病毒15 TK的亚细胞定位。我们发现，与其他家族成员的胸苷激酶不同，γ-1疱疹病毒的胸苷激酶定位于中心体，甚至更精确地定位于中心粒的外周，以一种不依赖微管的方式紧密环绕富含微管蛋白的中心粒。在多种细胞类型中都观察到了中心体定位，无论该蛋白是独立表达还是在EBV裂解感染的情况下表达，都会出现这种定位。令人惊讶的是，对突变体的分析表明，独特的N末端结构域对于靶向中心体并不关键，相反，位于该结构域C末端的肽序列才是关键。这是首个被证明存在于中心体或微管组织中心的疱疹病毒蛋白，中心体是一种无膜细胞器，通过控制染色体分离和胞质分裂来调节细胞周期的结构生物学。最近的研究表明，蛋白酶体介导的细胞周期调节蛋白降解、抗原肽在HLA分子上的产生和加载，以及病毒进入和/或释放所需的多种病毒粒子蛋白的短暂归巢，都在中心体处协调进行。本文讨论了中心体定位对EBV TK功能的潜在影响。
