Mirkov T E, Mathews D M, Du Plessis D H, Dodds J A
Department of Plant Pathology, University of California, Riverside 92521.
Virology. 1989 May;170(1):139-46. doi: 10.1016/0042-6822(89)90361-9.
Satellite tobacco mosaic virus (STMV) is a plant virus with a 17-nm icosahedral particle encapsidating a 0.3 X 10(6) Mr ssRNA genome that depends on tobamoviruses for its replication. The complete nucleotide sequence of STMV RNA deduced in the experiments described here was 1059 nucleotides in length. The efficiency of labeling viral RNA with [gamma-32P]ATP using T4 polynucleotide kinase was not affected by treatment with tobacco acid pyrophosphatase and/or bacterial alkaline phosphatase, indicating that the majority of the 5' termini of encapsidated STMV RNAs were not phosphorylated. The 240 3'-terminal nucleotides of STMV RNA and either tobacco mosaic virus (TMV) U1 RNA or TMV U2/U5 RNA had greater than 65% overall sequence similarity, with two nearly identical regions of 40 and 50 bases, respectively. There were no other regions of sequence relatedness to TMV RNA. The 19 5'-terminal nucleotides of STMV RNA had greater than 65% sequence similarity with the 16 5'-terminal nucleotides of brome mosaic virus (RNA 3 and 50% sequence similarity with the 12 5'-terminal nucleotides of the Q strain of cucumber mosaic virus RNA 3. The first open reading frame (ORF) beginning at base 53 encoded a 6800 Mr protein that corresponded in size to a major in vitro translation product directed by STMV RNA. A second ORF, beginning at nucleotide 163, had the capacity to code for a protein that corresponded in size (17,500 Mr) to the other major in vitro translation product. The first 12 codons of this ORF corresponded to the sequence of the N-terminal amino acids of the capsid protein. Western-blot analysis of the in vitro translation products revealed that the 17,500 Mr protein had the same electrophoretic mobility as the authentic capsid protein; it was also antigenically related to the capsid protein, but the 6800 Mr protein was not. Time course analysis of in vitro translation demonstrated that the 6800 Mr protein was synthesized at the same time as the capsid protein and did not arise by the proteolytic cleavage of a larger precursor polypeptide. These results suggest that the genome of STMV functioned as a polycistronic messenger RNA. It has not been determined if the 6800 Mr protein is synthesized in vivo. STMV RNA had untranslated regions of 52 and 418 nucleotides at its 5' and 3' termini, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
卫星烟草花叶病毒（STMV）是一种植物病毒，其17纳米的二十面体颗粒包裹着一个0.3×10⁶道尔顿的单链RNA基因组，它依赖烟草花叶病毒进行复制。在此处描述的实验中推导得出的STMV RNA的完整核苷酸序列长度为1059个核苷酸。用T4多核苷酸激酶以[γ-³²P]ATP标记病毒RNA的效率不受烟草酸性焦磷酸酶和/或细菌碱性磷酸酶处理的影响，这表明被包裹的STMV RNA的5'末端大部分未被磷酸化。STMV RNA的240个3'末端核苷酸与烟草花叶病毒（TMV）U1 RNA或TMV U2/U5 RNA的总体序列相似性大于65%，分别有两个40个碱基和50个碱基的几乎相同区域。与TMV RNA没有其他序列相关区域。STMV RNA的19个5'末端核苷酸与雀麦花叶病毒的16个5'末端核苷酸序列相似性大于65%，与黄瓜花叶病毒Q株系RNA 3的12个5'末端核苷酸序列相似性为50%。从第53个碱基开始的第一个开放阅读框（ORF）编码一个6800道尔顿的蛋白质，其大小与由STMV RNA指导的主要体外翻译产物相对应。第二个ORF从核苷酸163开始，能够编码一个大小（17,500道尔顿）与另一个主要体外翻译产物相对应的蛋白质。这个ORF的前12个密码子与衣壳蛋白N端氨基酸序列相对应。对体外翻译产物的蛋白质免疫印迹分析表明，17,500道尔顿的蛋白质与 authentic 衣壳蛋白具有相同的电泳迁移率；它也与衣壳蛋白有抗原相关性，但6800道尔顿的蛋白质没有。体外翻译的时间进程分析表明，6800道尔顿的蛋白质与衣壳蛋白同时合成，并非由更大的前体多肽的蛋白水解切割产生。这些结果表明STMV的基因组起着多顺反子信使RNA的作用。尚未确定6800道尔顿的蛋白质是否在体内合成。STMV RNA在其5'和3'末端分别有52个和418个核苷酸的非翻译区。（摘要截短至400字）
