Renaudin J, Pascarel M C, Bové J M
Laboratoire de Biologie Cellulaire et Moléculaire, I.N.R.A., Pont de la Maye, France.
J Bacteriol. 1987 Nov;169(11):4950-61. doi: 10.1128/jb.169.11.4950-4961.1987.
The replicative form (RF) of spiroplasma virus 4 (SpV4) has been cloned in Escherichia coli, and the cloned RF has been shown to be infectious by transfection (M. C. Pascarel-Devilder, J. Renaudin, and J.-M. Bové, Virology 151:390-393, 1986). The cloned SpV4 RF was randomly subcloned and was fully sequenced by the dideoxy chain termination technique, using the M13 cloning and sequencing system. The nucleotide sequence of the SpV4 genome contains 4,421 nucleotides with a G+C content of 32 mol%. The triplet TGA is not a termination codon but, as in Mycoplasma capricolum (F. Yamao, A. Muto, Y. Kawauchi, M. Iwami, S. Iwagani, Y. Azumi, and S. Osawa, Proc. Natl. Acad. Sci. USA 82:2306-2309, 1985), probably codes for tryptophan. With these assumptions, nine open reading frames (ORFs) were identified. All nine are characterized by an ATG or GTG initiation codon, one or several termination codons, and a Shine-Dalgarno sequence upstream of the initiation codon. The nine ORFs are distributed in all three reading frames. One of the ORFs (ORF1) corresponds to the 60,000-dalton capsid protein gene. Analysis of codon usage showed that T- and A-terminated codons are preferably used, reflecting the low G+C content (32 mol%) of the SpV4 genome. The viral DNA contains two G+C-rich inverted repeat sequences. One could be involved in transcription termination and the other in initiation of cDNA strand synthesis. The SpV4 genome was found to contain at least three promoterlike sequences quasi-identical to those of eubacteria. These results fully support the bacterial origin of spiroplasmas.
螺旋体病毒4（SpV4）的复制形式（RF）已在大肠杆菌中克隆，并且通过转染已证明克隆的RF具有感染性（M.C.帕斯卡雷尔 - 德维尔德、J.雷诺丹和J.-M.博韦，《病毒学》151:390 - 393，1986年）。克隆的SpV4 RF被随机亚克隆，并使用M13克隆和测序系统通过双脱氧链终止技术进行了全序列测定。SpV4基因组的核苷酸序列包含4421个核苷酸，G + C含量为32摩尔％。三联体TGA不是终止密码子，而是如在山羊支原体中一样（F.山尾、A.武藤、Y.川内、M.岩见、S.岩贺、Y.安积和S.大泽，《美国国家科学院院刊》82:2306 - 2309，1985年），可能编码色氨酸。基于这些假设，鉴定出了九个开放阅读框（ORF）。所有九个都以ATG或GTG起始密码子、一个或几个终止密码子以及起始密码子上游的Shine - Dalgarno序列为特征。这九个ORF分布在所有三个阅读框中。其中一个ORF（ORF1）对应于60,000道尔顿的衣壳蛋白基因。密码子使用情况分析表明，以T和A结尾的密码子更受青睐，这反映了SpV4基因组低G + C含量（32摩尔％）的特点。病毒DNA包含两个富含G + C的反向重复序列。一个可能参与转录终止，另一个参与cDNA链合成的起始。发现SpV4基因组包含至少三个与真细菌的启动子样序列几乎相同的序列。这些结果充分支持了螺旋体的细菌起源。
