Vaccinia virion protein I8R has both DNA and RNA helicase activities: Implications for vaccinia virus transcription
Vaccinia virion protein I8R has both DNA and RNA helicase activities: Implications for vaccinia virus transcription
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DOI：
10.1128/jvi.70.2.794-800.1996
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发表时间：
1996-02-01
影响因子：
5.4
通讯作者：
Smith, GL
中科院分区：
文献类型：
--
作者：
Bayliss, CD;Smith, GL
从痘苗病毒粒子中纯化出一种核酸依赖性 ATP 酶，并显示出具有 DNA:DNA 和 RNA:RNA 解旋酶活性，这只是已鉴定的第三种解旋酶，可以解旋 DNA 和 RNA 双链体，与核苷三磷酸磷酸水解酶 II (NPHII)（一种由基因 I8R 编码的 RNA 解旋酶）共纯化的 DNA 解旋酶活性 (S. S human, Proc, Natl, Acad, Sci, USA 89:10935-10939, 1992)，用两种 NPHII 抗血清进行免疫耗竭并分析重组 NPHII 蛋白(C. H. Gross 和 S. S human, J. Virol, 69:4727-4736, 1995)证实 DNA 解旋酶活性是由 I8R 编码的基因。 I8R DNA 解旋酶仅以 3' 至 5' 方向解开 DNA，解开 35 bp 但不解开 45 bp 的双链体，并且可以被大肠杆菌单链 DNA 结合蛋白刺激解开更长的双链体。 DNA 解旋酶活性不受盐刺激，并且对 100 mM NaCl 或 KCI 敏感。I8R 蛋白与人 RNA 解旋酶 A 和核 DNA 解旋酶 II（一种牛 DNA 和 RNA 解旋酶）具有氨基酸相似性。根据 I8R 温度敏感突变体的表型，有人提出 I8R 蛋白不是 DNA 复制所必需的，但可能有助于早期 mRNA 从病毒核心中挤出。 ISR 蛋白的 DNA 解旋酶活性允许对突变表型进行另一种解释，即 I8R DNA 解旋酶活性是痘苗病毒颗粒内早期转录起始所必需的。
A nucleic acid-dependent ATPase was purified from vaccinia virions and shown to have both DNA:DNA and RNA:RNA helicase activities, This is only the third helicase to be identified that can unwind both DNA and RNA duplexes, The DNA helicase activity copurified with nucleoside triphosphate phosphohydrolase II (NPHII), an RNA helicase encoded by gene I8R (S. Shuman, Proc, Natl, Acad, Sci, USA 89:10935-10939, 1992), Immunodepletion with two antisera to NPHII and analysis of recombinant NPHII protein (C. H. Gross and S. Shuman, J. Virol, 69:4727-4736, 1995) confirmed that the DNA helicase activity was encoded by the I8R gene. The I8R DNA helicase unwound DNA in a 3'-to-5' direction only, unwound duplexes of 35 bp but not 45 bp, and could be stimulated to unwind longer duplexes by the Escherichia coli single-stranded DNA-binding protein. DNA helicase activity was not stimulated by salt and was sensitive to 100 mM NaCl or KCI, The I8R protein has amino acid similarity to human RNA helicase A and to nuclear DNA helicase II, a bovine DNA and RNA helicase. On the basis of the phenotype of I8R temperature-sensitive mutants, it was suggested that the I8R protein is not required for DNA replication but might aid in the extrusion of early mRNA from the virus core. The DNA helicase activity of the ISR protein allows another interpretation of the mutant phenotype, namely, that the I8R DNA helicase activity is required for initiation of early transcription from within vaccinia virions.