Huang Ying-Wen, Hu Chung-Chi, Lin Chih-An, Liu Yu-Ping, Tsai Ching-Hsiu, Lin Na-Sheng, Hsu Yau-Heiu
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan, ROC.
Virology. 2009 Mar 30;386(1):139-53. doi: 10.1016/j.virol.2009.01.019. Epub 2009 Feb 7.
The 3'-untranslated region (UTR) of RNA genomes of viruses and satellite RNAs plays essential roles in viral replication and transcription. The structural features of the 3'-UTR of the satellite RNA of Bamboo mosaic virus (satBaMV) involved in its replication were analyzed in this study. By the use of enzymatic probing, the secondary structure of satBaMV 3'-UTR was confirmed to comprise two small stem-loops (SLA and SLB), one large stem-loop (SLC), and a poly(A) tail of mainly 75-200 adenylate residues, which is similar to those on the genomic RNA of the helper virus, BaMV. Five sets of mutants of satBaMV were constructed to analyze the biological functions of the structural elements of the 3'-UTR. The data revealed that both the polyadenylation signal and poly(A) tail are required for satBaMV RNA replication. The structural conservation of SLA, SLB, and SLC is also important for efficient satBaMV accumulation, whereas the nucleotides in these regions may also possess sequence-specific functions. In contrast to the requirement for the accumulation of BaMV genomic RNA, mutations in the conserved hexanucleotide (ACCUAA) in the loop region of SLC had limited effect on the accumulation of satBaMV RNA. In addition, replacing the 5'-, 3'-UTR, or both regions of satBaMV by those of BaMV greatly decreased the accumulation of satBaMV RNA. Taken together, these data indicate that satBaMV might have adopted a 3'-UTR structure similar to that of BaMV but may have evolved distinct features for its efficient replication.
病毒和卫星RNA的RNA基因组3'非翻译区（UTR）在病毒复制和转录中发挥着重要作用。本研究分析了参与竹花叶病毒卫星RNA（satBaMV）复制的3'-UTR的结构特征。通过酶促探测，证实satBaMV 3'-UTR的二级结构由两个小茎环（SLA和SLB）、一个大茎环（SLC）和一个主要由75 - 200个腺苷酸残基组成的多聚（A）尾组成，这与辅助病毒BaMV的基因组RNA上的结构相似。构建了五组satBaMV突变体，以分析3'-UTR结构元件的生物学功能。数据显示，多聚腺苷酸化信号和多聚（A）尾对于satBaMV RNA复制都是必需的。SLA、SLB和SLC的结构保守性对于satBaMV的高效积累也很重要，而这些区域的核苷酸可能也具有序列特异性功能。与BaMV基因组RNA积累的要求相反，SLC环区保守六核苷酸（ACCUAA）中的突变对satBaMV RNA的积累影响有限。此外，用BaMV的5'-、3'-UTR或两者替换satBaMV的相应区域会大大降低satBaMV RNA的积累。综上所述，这些数据表明satBaMV可能采用了与BaMV相似的3'-UTR结构，但可能已经进化出了不同的特征以实现其高效复制。
