cis-acting elements at opposite ends of the Citrus tristeza virus genome differ in initiation and termination of subgenomic RNAs
cis-acting elements at opposite ends of the Citrus tristeza virus genome differ in initiation and termination of subgenomic RNAs
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DOI：
10.1016/j.virol.2004.01.005
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发表时间：
2004-04-25
期刊：
影响因子：
3.7
通讯作者：
Dawson, WO
中科院分区：
文献类型：
--
作者：
Ayllón, MA;Gowda, S;Dawson, WO
柑橘衰退病毒（Citrus tristeza virus，CTV）是梭状病毒科（Closteroviridae）的成员，其基因组RNA为约20 kb的正链RNA，产生10个3 '-coteminal subgenomic（sg）RNA，作为其内部基因的信使（m）RNA。此外，约700 nt的5 '末端sgRNA群体在感染细胞中高度丰富。先前的分析表明，控制器元件（CE）负责3 '末端mRNA，并且小的5'末端sgRNA在产生的额外sgRNA的数量上不同。两种类型的CE的特征是产生5 '和3'末端正链sgRNA，但3'CE另外产生3'末端mRNA的负链互补物。在此，我们发现5'CE相对于3' CE的终止（对于5 '-末端sgRNA）和起始（对于3'-末端sgRNA）位点发生在相应最小活性CE的相对末端。主要外壳蛋白基因的3' CE起始位点，可能还有p20和p23基因的起始位点，都在最小单位之外（就基因组RNA而言为3'），而终止位点位于最小CE内，起始位点上游30-50 nt（指正链序列）。相比之下，5' CE的起始位点在最小单元的5'区域中，终止位点在下游20-35 nt（参考正链序列）。此外，CE在起始核苷酸和对该核苷酸的诱变的响应方面不同。3' CE起始于尿苷酸的sgRNA合成，而5' CE起始于胞苷酸。我们以前发现，3'CE是不寻常的耐受诱变的起始位点，与起始进行从替代位点。5' CE起始位点的突变阻止了5'-或3 '-末端sgRNA的合成。因此，基因组两端的顺式作用元件是显著不同的，可能来自不同的起源和/或在该病毒的生命周期中具有不同的功能。(C)2004年爱思唯尔公司All rights reserved.
Citrus tristeza virus (CTV), a member of the Closteroviridae with a plus-stranded genomic RNA of approximately 20 kb, produces 10 3'-coterminal subgenomic (sg) RNAs that serve as messenger (m)RNAs for its internal genes. In addition, a population of 5'-terminal sgRNAs of approximately 700 nts are highly abundant in infected cells. Previous analysis demonstrated that the controller elements (CE) are responsible for the 3'-terminal mRNAs and the small 5'-terminal sgRNAs differ in the number of additional sgRNAs produced. A feature of both types of CE is production of 5'- and 3'-terminal positive-stranded sgRNAs, but the 3' CEs additionally produce a negative-stranded complement of the 3'-terminal mRNAs. Here, we found that the termination (for 5'-terminal sgRNAs) and initiation (for 3'-terminal sgRNAs) sites of the 5' vs. the 3' CEs occur at opposite ends of the respective minimal active CEs. The initiation site for the 3' CE of the major coat protein gene, and probably those of the p20 and p23 genes, was outside (3' in terms of the genomic RNA) the minimal unit, whereas the termination sites were located within the minimal CE, 30-50 nts upstream of the initiation site (referring to the positive-strand sequence). In contrast, the initiation site for the 5' CE was in the 5' region of the minimal unit, with the termination sites 20-35 nts downstream (referring to the positive-strand sequence). Furthermore, the CEs differ in initiation nucleotide and response to mutagenesis of that nucleotide. The 3' CE initiates sgRNA synthesis from a uridylate, whereas the 5' CE initiates from a cytidylate. We previously found that the 3' CEs were unusually tolerant to mutagenesis of the initiation sites, with initiation proceeding from alternative sites. Mutagenesis of the initiation site of the 5' CE prevented synthesis of either the 5'- or 3'-terminal sgRNAs. Thus, the cis-acting elements at opposite ends of the genome are remarkably different, perhaps having arisen from different origins and or with different functions in the life cycle of this virus. (C) 2004 Elsevier Inc. All rights reserved.