Department of Biochemistry and Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Virology. 2011 Feb 5;410(1):257-67. doi: 10.1016/j.virol.2010.11.002. Epub 2010 Dec 9.
Cardioviruses have a unique 2A protein (143 aa). During genome translation, the encephalomyocarditis virus (EMCV) 2A is released through a ribosome skipping event mitigated through C-terminal 2A sequences and by subsequent N-terminal reaction with viral 3C(pro). Although viral replication is cytoplasmic, mature 2A accumulates in nucleoli shortly after infection. Some protein also transiently associates with cytoplasmic 40S ribosomal subunits, an activity contributing to inhibition of cellular cap-dependent translation. Cardiovirus sequences predict an eIF4E binding site (aa 126-134) and a nuclear localization signal (NLS, aa 91-102), within 2A, both of which are functional during EMCV infection. Point mutations preventing eIF4E:2A interactions gave small-plaque phenotype viruses, but still inhibited cellular cap-dependent translation. Deletions within the NLS motif relocalized 2A to the cytoplasm and abrogated the inhibition of cap-dependent translation. A fusion protein linking the 2A NLS to eGFP was sufficient to redirect the reporter to the nucleus but not into nucleoli.
冠状病毒具有独特的 2A 蛋白（143 个氨基酸）。在基因组翻译过程中，脑心肌炎病毒（EMCV）2A 通过核糖体跳跃事件释放，该事件通过 C 末端 2A 序列和随后与病毒 3C(pro)的 N 末端反应得到缓解。尽管病毒复制是细胞质的，但成熟的 2A 在感染后不久就积累在核仁中。一些蛋白也会短暂地与细胞质 40S 核糖体亚基结合，这种活性有助于抑制细胞帽依赖性翻译。在 2A 内，冠状病毒序列预测存在 eIF4E 结合位点（aa126-134）和核定位信号（NLS，aa91-102），这两者在 EMCV 感染过程中均具有功能。阻止 eIF4E:2A 相互作用的点突变产生小斑块表型病毒，但仍抑制细胞帽依赖性翻译。NLS 基序内的缺失将 2A 重新定位到细胞质中，并消除了对帽依赖性翻译的抑制。将 2A 的 NLS 与 eGFP 融合蛋白足以将报告蛋白重新定向到细胞核，但不能进入核仁。
