The vaccinia virus A18R DNA helicase is a postreplicative negative transcription elongation factor.
The vaccinia virus A18R DNA helicase is a postreplicative negative transcription elongation factor.
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痘苗病毒 A18R DNA 解旋酶是一种复制后负转录延伸因子。
DOI：
10.1128/jvi.72.9.7012-7023.1998
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发表时间：
1998
影响因子：
5.4
通讯作者：
Condit,RC
中科院分区：
文献类型：
--
作者：
Xiang,Y;Simpson,DA;Spiegel,J;Zhou,A;Silverman,RH;Condit,RC
痘苗病毒A18R基因功能的丧失会导致一种称为混杂转录的异常转录模式，其定义是在感染后期通常转录沉默的基因组区域内的转录。错配转录导致细胞内双链核糖核酸浓度增加，进而导致细胞2-5A途径的激活，随后核糖核酸酶L催化病毒和细胞RNA的降解。三个假说之一可以解释杂乱转录：(I)感染后期早期启动子的重新激活，(Ii)随机转录起始，(Iii)上游启动子的直读转录。这里给出的几个病毒基因的转录分析强烈反对前两个假设。我们通过对痘苗病毒基因组的一个区域进行详细的转录分析来检验通读假说，该区域包含三个早期基因(M1L、M2L和K1L)，位于中间基因K2L的正下游。结果表明，A18R基因突变导致来源于K2L中间启动子的M1L基因的通读转录增加。A18R突变株感染核糖核酸酶L基因敲除的小鼠成纤维细胞不会导致2-5A途径的激活，但该病毒突变株存在晚期病毒基因表达缺陷，并对温度敏感。这些结果表明，A18R基因产物是复制后病毒基因的负转录延伸因子。
Loss of vaccinia virus A18R gene function results in an aberrant transcription profile termed promiscuous transcription, defined as transcription within regions of the genome which are normally transcriptionally silent late during infection. Promiscuous transcription results in an increase in the intracellular concentration of double-stranded RNA, which in turn results in activation of the cellular 2-5A pathway and subsequent RNase L-catalyzed degradation of viral and cellular RNAs. One of three hypotheses could account for promiscuous transcription: (i) reactivation of early promoters late during infection, (ii) random transcription initiation, (iii) readthrough transcription from upstream promoters. Transcriptional analysis of several viral genes, presented here, argues strongly against the first two hypotheses. We have tested the readthrough hypothesis by conducting a detailed transcriptional analysis of a region of the vaccinia virus genome which contains three early genes (M1L, M2L, and K1L) positioned directly downstream of the intermediate gene, K2L. The results show that mutation of the A18R gene results in increased readthrough transcription of the M1L gene originating from the K2L intermediate promoter. A18R mutant infection of RNase L knockout mouse fibroblast (KO3) cells does not result in 2-5A pathway activation, yet the virus mutant is defective in late viral gene expression and remains temperature sensitive. These results demonstrate that the A18R gene product is a negative transcription elongation factor for postreplicative viral genes.