Two aromatic residues in the PB2 subunit of influenza A RNA polymerase are crucial for cap binding
Two aromatic residues in the PB2 subunit of influenza A RNA polymerase are crucial for cap binding
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DOI：
10.1074/jbc.m300130200
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发表时间：
2003-05-30
影响因子：
4.8
通讯作者：
Brownlee, GG
中科院分区：
文献类型：
--
作者：
Fechter, P;Mingay, L;Brownlee, GG
mRNA在其5 '端被含有N-7-甲基鸟嘌呤的独特帽结构加帽。帽结构的识别在基因表达的一些最核心的过程中以及在一些病毒过程中是至关重要的，例如流感病毒转录的引发。最近对三种进化上不相关的帽结合蛋白（牛痘病毒蛋白VP 39、真核翻译因子eIF 4 E和核帽结合蛋白CBP 20）的结构的解析表明，帽结构的识别是通过相同的一般机制实现的，即通过两个芳香族氨基酸残基之间的帽结构的N-7-甲基鸟嘌呤的“重叠”。本研究的目的是测试流感病毒的RNA聚合酶是否独立进化出类似的帽识别机制。结合体内和体外方法，我们表征了病毒RNA聚合酶PB 2亚基中两个关键的芳香族氨基酸Phe（363）和Phe（404），这两个氨基酸对于帽结合是必需的。这两个残基的芳香性在甲型、B和C型流感中是保守的，甚至在不同的Thogoto病毒PB 2亚基中也是保守的。因此，我们的研究结果支持与进化无关的VP 39、eIF 4 E和CBP 20中类似的流感RNA聚合酶帽结合机制。
mRNAs are capped at their 5'-end by a unique cap structure containing N-7-methyl guanine. Recognition of the cap structure is of paramount importance in some of the most central processes of gene expression as well as in some viral processes, such as priming of influenza virus transcription. The recent resolution of the structure of three evolutionary unrelated cap binding proteins, the vaccinia viral protein VP39, the eukaryotic translation factor eIF4E, and the nuclear cap-binding protein CBP20 showed that the recognition of the cap structure is achieved by the same general mechanism, i.e. by "sandwiching" of the N-7-methyl guanine of the cap structure between two aromatic amino acid residues. The purpose of the present study was to test whether a similar cap recognition mechanism had independently evolved for the RNA polymerase of influenza virus. Combining in vivo and in vitro methods, we characterized two crucial aromatic amino acids, Phe(363) and Phe(404), in the PB2 subunit of the viral RNA polymerase that are essential for cap binding. The aromaticity of these two residues is conserved in influenza A, B, and C and even in the divergent Thogoto virus PB2 subunits. Thus, our results favor a similar mechanism of cap binding by the influenza RNA polymerase as in the evolutionary unrelated VP39, eIF4E, and CBP20.