Poxviruses encode a multisubunit DNA-dependent RNA polymerase (vRNAP) that carries out viral gene expression in the host cytoplasm. We report cryo-EM structures of core and complete vRNAP enzymes from Vaccinia virus at 2.8 Å resolution. The vRNAP core enzyme resembles eukaryotic RNA polymerase II (Pol II) but also reveals many virus-specific features, including the transcription factor Rap94. The complete enzyme additionally contains the transcription factor VETF, the mRNA processing factors VTF/CE and NPH-I, the viral core protein E11, and host tRNAGln. This complex can carry out the entire early transcription cycle. The structures show that Rap94 partially resembles the Pol II initiation factor TFIIB, that the vRNAP subunit Rpo30 resembles the Pol II elongation factor TFIIS, and that NPH-I resembles chromatin remodeling enzymes. Together with the accompanying paper (Hillen et al., 2019), these results provide the basis for unraveling the mechanisms of poxvirus transcription and RNA processing.

中文翻译：

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痘病毒转录的结构基础：牛痘RNA聚合酶复合物。

痘病毒编码一种多亚基 DNA 依赖性 RNA 聚合酶 (vRNAP)，可在宿主细胞质中进行病毒基因表达。我们报告了来自痘苗病毒的核心和完整 vRNAP 酶的冷冻电镜结构，分辨率为 2.8 Å。vRNAP 核心酶类似于真核 RNA 聚合酶 II (Pol II)，但也揭示了许多病毒特异性特征，包括转录因子 Rap94。完整的酶还包含转录因子 VETF、mRNA 加工因子 VTF/CE 和 NPH-I、病毒核心蛋白 E11 和宿主 tRNAGln。这种复合体可以进行整个早期转录周期。结构显示 Rap94 部分类似于 Pol II 起始因子 TFIIB，vRNAP 亚基 Rpo30 类似于 Pol II 延伸因子 TFIIS，并且 NPH-I 类似于染色质重塑酶。