Center for Infectious Disease Dynamics, Millennium Science Complex, Pennsylvania State University, University Park, PA, USA.
New England Biolabs, Inc, Ipswich, MA, USA.
Mol Biol Evol. 2021 Oct 27;38(11):5082-5091. doi: 10.1093/molbev/msab235.
The RNA-dependent RNA polymerase (RdRp) of all known double-stranded RNA viruses is located within the viral particle and is responsible for the transcription and replication of the viral genome. Through an RT-PCR assay, we determined that purified virions, in vitro translated RdRp proteins, and purified recombinant RdRp proteins of partitiviruses also have reverse transcriptase (RT) function. We show that partitivirus RdRps 1) synthesized DNA from homologous and heterologous dsRNA templates; 2) are active using both ssRNA and dsRNA templates; and 3) are active at lower temperatures compared to an optimal reaction temperature of commercial RT enzymes. This finding poses an intriguing question: why do partitiviruses, with dsRNA genomes, have a polymerase with RT functions? In comparison, 3Dpol, the RdRp of poliovirus, did not show any RT activity. Our findings lead us to propose a new evolutionary model for RNA viruses where the RdRp of dsRNA viruses could be the ancestor of RdRps.
所有已知双链 RNA 病毒的 RNA 依赖性 RNA 聚合酶（RdRp）都位于病毒粒子内，负责病毒基因组的转录和复制。通过 RT-PCR 检测，我们确定纯化的病毒粒子、体外翻译的 RdRp 蛋白和纯化的部分病毒重组 RdRp 蛋白也具有逆转录酶（RT）功能。我们表明，部分病毒 RdRps：1）从同源和异源 dsRNA 模板合成 DNA；2）使用 ssRNA 和 dsRNA 模板均具有活性；3）与商业 RT 酶的最佳反应温度相比，在较低温度下具有活性。这一发现提出了一个有趣的问题：为什么具有 dsRNA 基因组的部分病毒会拥有具有 RT 功能的聚合酶？相比之下，脊髓灰质炎病毒的 3Dpol（RdRp）没有显示出任何 RT 活性。我们的研究结果促使我们提出了一个新的 RNA 病毒进化模型，其中 dsRNA 病毒的 RdRp 可能是 RdRps 的祖先。
