Replicative form of Semliki Forest virus RNA contains an unpaired guanosine
Replicative form of Semliki Forest virus RNA contains an unpaired guanosine
复制标题
塞姆利基森林病毒 RNA 的复制形式含有未配对的鸟苷
作者：
G. Wengler;G. Wengler;H. Gross
含有感染性单链RNA的动物病毒基因组的复制机制尚不清楚。甲病毒含有约4.2 × 106分子量的感染性单链基因组RNA，其在蔗糖密度梯度1 -4上以约42 S沉淀。因此，它们被命名为（+）链RNA病毒5。大多数关于甲病毒结构或复制的研究都是使用辛德毕斯（SIN）或塞姆利基森林（SF）病毒进行的。除了感染性的42 S正链RNA外，在甲病毒感染的细胞中还合成了正极性的26 S单链RNA 3，4，6。26 S RNA序列与42 S RNA 3′末端区域的序列相同7，8。42 S RNA作为mRNA用于合成非结构蛋白，包括RNA聚合酶9 -11。26 S RNA是所有病毒结构蛋白的mRNA 12 -15。42 S SIN病毒基因组RNA具有5′末端结构m7 GpppApUpYpGp（参考文献16），SIN病毒特异性26 S RNA中存在含有m71，m2，72 G或m2，2，73 G的帽结构（参考文献17）。对相应SF病毒特异性核酸的5′-末端的类似研究尚未报道。在甲病毒感染的细胞中检测到的负极性的病毒特异性RNA的唯一种类在蔗糖密度梯度上在约42 S处沉积，并且与感染性病毒基因组RNA 18 -21互补。位于病毒特异性42 S和26 S RNA分子3′-末端的多聚腺苷酸序列22 -24是从互补的多聚腺苷酸序列20转录而来的。我们现在报告，我们已经确定了SF病毒特异性（+）链RNA的含帽寡核苷酸的结构，以及在感染细胞中合成的（-）链RNA的3′-末端的23个核苷酸的序列。我们的研究表明，SF病毒的复制型在（-）链的3′端含有一个未配对的鸟苷。
The mechanism of replication of the genome of animal viruses containing infectious single-stranded RNA is not understood in detail. Alphaviruses contain an infectious single-stranded genome RNA of about 4.2 × 106 molecular weight, which sediments at about 42S on sucrose density gradients1–4. Accordingly they are designated as (+)strand RNA viruses5. Most studies on the structure or replication of alphaviruses have been made using either Sindbis (SIN) or Semliki Forest (SF) viruses. Besides the infectious 42S plus-strand RNA, a 26S single-stranded RNA of positive polarity is synthesised in alphavirus-infected cells3,4,6. The 26S RNA sequences are identical to the sequences present in the 3′terminal region of the 42S RNA7,8. The 42S RNA functions as mRNA for the synthesis of nonstructural proteins including an RNA poly–merase9–11. The 26S RNA is the mRNA for all viral structural proteins12–15. The 42S SIN virus genome RNA has the 5′terminal structure m7GpppApUpYpGp (ref. 16), and a cap structure containing m71, m2,72 G or m2,2,73G is present in SIN virus-specific 26S RNA (ref. 17). Analogous studies on the 5′-termini of the corresponding SF-virus-specific nucleic acids have not been reported. The only species of virus-specific RNA of negative polarity detected in alphavirus-infected cells sediments at about 42S on sucrose density gradients and is complementary to the infectious viral genome RNA18–21. The poly(A) sequences present at the 3′-termini of the virus-specific 42S and 26S RNA molecules22–24 are transcribed from a complementary poly(U) sequence20. We now report that we have identied the structures of cap containing oligonucleotides of the SF virus-specific (+)strand RN As, and the sequence of 23 nucleotides at the 3′-terminus of the (−)strand RNA synthesised in infected cells. Our studies show that the replicative form of SF virus contains an unpaired guanosine at the 3′-end of the (−)strand.