Hijacking of the nucleolar protein fibrillarin by TGB1 is required for cell-to-cell movement of Barley stripe mosaic virus
Hijacking of the nucleolar protein fibrillarin by TGB1 is required for cell-to-cell movement of Barley stripe mosaic virus
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TGB1 劫持核仁蛋白纤维蛋白是大麦条纹花叶病毒细胞间移动所必需的
DOI：
10.1111/mpp.12612
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发表时间：
2018-05-01
影响因子：
4.9
通讯作者：
Li, Dawei
中科院分区：
文献类型：
--
作者：
Li, Zhenggang;Zhang, Yongliang;Li, Dawei
大麦条纹花叶病毒（Barley stripe mosaic virus，BSMV）三重基因块1（Triple Gene Block 1，TGB 1）是一种多功能运动蛋白，具有RNA结合、ATP酶和解旋酶活性，主要定位于细胞胞间连丝（Plasmodesmata，PD）上。在这里，我们表明，TGB 1定位于细胞核和核仁，以及细胞质，和TGB 1的核质运输所需的BSMV细胞到细胞的运动。预测分析和激光扫描共聚焦显微镜（LSCM）实验证实TGB 1具有核仁定位信号（NoLS）（氨基酸95-104）和核定位信号（NLS）（氨基酸227-238）。NoLS突变显著减少了BSMV细胞间的运动，而NLS突变几乎完全消除了运动。此外，无论是NoLS还是NLS突变体病毒都不能全身感染本氏烟草，尽管NoLS突变体病毒能够建立大麦的全身感染。蛋白质相互作用实验表明，TGB 1直接与核仁蛋白原纤蛋白（Fibrillarin，Fib 2）的富含甘氨酸精氨酸（GAR）结构域相互作用。此外，在BSMV感染的细胞中，Fib 2积累增加约60%-70%，并与TGB 1共定位在胞间连丝中。此外，fib 2敲除转基因植物中BSMV细胞间的运动减少到非转基因植物的三分之一以下。Fib 2还与TGB 1和BSMV RNA共定位，TGB 1和BSMV RNA是核糖核蛋白（RNP）运动复合物的主要成分。总的来说，这些结果表明，TGB 1-Fib 2相互作用在细胞间运动中发挥直接作用，我们提出Fib 2被BSMV TGB 1劫持，形成BSMV RNP，在细胞间运动中发挥作用。
Barley stripe mosaic virus (BSMV) Triple Gene Block1 (TGB1) is a multifunctional movement protein with RNA-binding, ATPase and helicase activities which mainly localizes to the plasmodesmata (PD) in infected cells. Here, we show that TGB1 localizes to the nucleus and the nucleolus, as well as the cytoplasm, and that TGB1 nuclear-cytoplasmic trafficking is required for BSMV cell-to-cell movement. Prediction analyses and laser scanning confocal microscopy (LSCM) experiments verified that TGB1 possesses a nucleolar localization signal (NoLS) (amino acids 95-104) and a nuclear localization signal (NLS) (amino acids 227-238). NoLS mutations reduced BSMV cell-to-cell movement significantly, whereas NLS mutations almost completely abolished movement. Furthermore, neither the NoLS nor NLS mutant viruses could infect Nicotiana benthamiana systemically, although the NoLS mutant virus was able to establish systemic infections of barley. Protein interaction experiments demonstrated that TGB1 interacts directly with the glycine-arginine-rich (GAR) domain of the nucleolar protein fibrillarin (Fib2). Moreover, in BSMV-infected cells, Fib2 accumulation increased by about 60%-70% and co-localized with TGB1 in the plasmodesmata. In addition, BSMV cell-to-cell movement in fib2 knockdown transgenic plants was reduced to less than one-third of that of non-transgenic plants. Fib2 also co-localized with both TGB1 and BSMV RNA, which are the main components of the ribonucleoprotein (RNP) movement complex. Collectively, these results show that TGB1-Fib2 interactions play a direct role in cell-to-cell movement, and we propose that Fib2 is hijacked by BSMV TGB1 to form a BSMV RNP which functions in cell-to-cell movement.