The positive transcription elongation factor activity of the vaccinia virus J3 protein is independent from its (nucleoside-2′-O-) methyltransferase and poly(A) polymerase stimulatory functions
The positive transcription elongation factor activity of the vaccinia virus J3 protein is independent from its (nucleoside-2′-O-) methyltransferase and poly(A) polymerase stimulatory functions
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DOI：
10.1006/viro.2002.1538
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发表时间：
2002-09-15
期刊：
影响因子：
3.7
通讯作者：
Condit, RC
中科院分区：
文献类型：
--
作者：
Latner, DR;Thompson, JM;Condit, RC
先前的遗传学和生物化学实验表明，牛痘病毒J3蛋白在mRNA合成和修饰中具有三种不同的作用。首先，J3是（核苷-2 '-O-）甲基转移酶，其甲基化第一个转录核苷酸的2'位置，从而在mRNA的5'末端将帽-0转化为帽-1结构。第二，J3是病毒编码的poly（A）聚合酶的持续合成因子。第三，J3最近已被证明在体内具有中期和晚期基因正转录延伸因子活性。先前的实验已经表明，聚（A）聚合酶刺激活性和（核苷-2 '-O-）甲基转移酶活性是蛋白质的两个独立功能，其可以通过定点诱变进行遗传分离。在这篇文章中，J3介导的转录延伸活性和蛋白质的其他两个功能之间的关系进行了研究，通过构建几个定点突变病毒，含有甲基转移酶或聚（A）聚合酶的持续合成功能的特定缺陷。结果表明，J3正转录延伸因子活性是蛋白质的第三个独立功能，其在mRNA修饰中与其其他两个功能在遗传上是可分离的。结果还表明，无论是聚（A）聚合酶的刺激，也不是J3蛋白的甲基转移酶的活动是必不可少的病毒在细胞培养物中的生长。(C)2002 Elsevier Science（美国）。
Previous genetic and biochemical experiments have shown that the vaccinia virus J3 protein has three different roles in mRNA synthesis and modification. First, J3 is a (nucleoside-2'-O-)methyltransferase which methylates the 2' position of the first transcribed nucleotide, thus converting a cap-0 to a cap-1 structure at the 5' ends of mRNAs. Second, J3 is a processivity factor for the virus coded poly(A) polymerase. Third, J3 has recently been shown to have intermediate and late gene positive transcription elongation factor activity in vivo. Previous experiments have shown that the poly(A) polymerase stimulatory activity and the (nucleoside-2'-O-)methyltransferase activity are two independent functions of the protein that can be genetically separated through site-directed mutagenesis. In this article, the relationship between the J3-mediated transcription elongation activity and the two other functions of the protein was investigated by constructing several site-directed mutant viruses that contain specific defects in either methyltransferase or poly(A) polymerase processivity functions. The results demonstrate that the J3 positive transcription elongation factor activity is a third independent function of the protein that is genetically separable from its two other functions in mRNA modification. The results also show that neither the poly(A) polymerase stimulatory nor the methyltransferase activities of the J3 protein is essential for virus growth in cell culture. (C) 2002 Elsevier Science (USA).