Characterization of the cis-acting elements controlling subgenomic mRNAs of Citrus tristeza virus:: Production of positive- and negative-stranded 3′-terminal and positive-stranded 5′-terminal RNAs
Characterization of the cis-acting elements controlling subgenomic mRNAs of Citrus tristeza virus:: Production of positive- and negative-stranded 3′-terminal and positive-stranded 5′-terminal RNAs
复制标题
DOI：
10.1006/viro.2001.0987
复制
发表时间：
2001-07-20
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：
Gowda, S;Satyanarayana, T;Dawson, WO
柑橘 tristeza 病毒 (CTV) 是长线病毒科的一员，具有类似于 20 kb 的正义 RNA 基因组，具有从基因组 RNA 翻译的两个 5' ORF 和通过九个或十个 3' 末端亚基因组 (sg) RNA 表达的 10 个 3' 基因。 3'基因的表达似乎具有介于“甲病毒超群”的较小病毒和冠状病毒科的较大病毒之间的特性。 sgRNA 与基因组相邻，没有共同的 5' 前导序列，并且与大量互补 sgRNA 相关。不同 sgRNA 的产生受到时间和数量上的调节，高表达的基因在 ORF 的 5' 端具有非编码区 (NCR)。对控制高表达的主要外壳蛋白（CP）基因和中间表达的次要外壳蛋白（CPm）基因的顺式作用元件进行了定位和比较。突变分析表明，CP sgRNA控制元件映射在转录起始位点上游的-47至-5 nts内，完全在NCR内，而CPm控制区映射在上游ORF内的57 nt序列内。尽管预计这两个区域都会折叠成两个茎环结构，但诱变表明一级结构可能比二级结构更重要。由于每个控制元件产生大量的 3' 端正链和负链 sgRNA，因此我们无法区分顺式作用元件是否充当启动子或终止子，或两者兼而有之。控制元件的逆转意外地产生了大量负链 sgRNA，这显然是通过终止负链基因组 RNA 合成来实现的。对控制元件天然方向的进一步检查表明，正常产生大量延伸至 5' 末端附近的正链 sgRNA，对应于每个控制元件的终止。因此，每个控制元件产生三个 sgRNA，一条 5' 端正链以及正链和负链 3' 端 RNA。因此，理论上CTV可以在感染细胞中产生30-33种RNA。 (C) 2001 年学术出版社。
Citrus tristeza virus (CTV), a member of the Closteroviridae, has an similar to 20-kb positive-sense RNA genome with two 5' ORFs translated from the genomic RNA and 10 3' genes expressed via nine or ten 3'-terminal subgenomic (sg) RNAs. The expression of the 3' genes appears to have properties intermediate between the smaller viruses of the "alphavirus supergroup" and the larger viruses of the Coronaviridae. The sgRNAs are contiguous with the genome, without a common 5' leader, and are associated with large amounts of complementary sgRNAs. Production of the different sgRNAs is regulated temporally and quantitatively, with the highly expressed genes having noncoding regions (NCR) 5' of the ORFs. The cis-acting elements that control the highly expressed major coat protein (CP) gene and the intermediately expressed minor coat protein (CPm) gene were mapped and compared. Mutational analysis showed that the CP sgRNA controller element mapped within nts -47 to -5 upstream of the transcription start site, entirely within the NCR, while the CPm control region mapped within a 57 nt sequence within the upstream ORF Although both regions were predicted to fold into two stem-loop structures, mutagenesis suggested that primary structure might be more important than the secondary structure. Because each controller element produced large amounts of 3'-terminal positive- and negative-stranded sgRNAs, we could not differentiate whether the cis-acting element functioned as a promoter or terminator, or both. Reversal of the control element unexpectedly produced large amounts of a negative-stranded sgRNA apparently by termination of negative-stranded genomic RNA synthesis. Further examination of controller elements in their native orientation showed normal production of abundant amounts of positive-stranded sgRNAs extending to near the 5'-terminus, corresponding to termination at each controller element. Thus, each controller element produced three sgRNAs, a 5'-terminal positive strand and both positive- and negative-stranded 3'-terminal RNAs. Therefore, theoretically CTV could produce 30-33 species of RNAs in infected cells. (C) 2001 Academic Press.