College of Veterinary Medicine, Qingdao Agricultural University, Qingdao 266109, China.
College of Veterinary Medicine, Shandong Agricultural University, Tai'an 271018, China.
Vet Microbiol. 2023 May;280:109717. doi: 10.1016/j.vetmic.2023.109717. Epub 2023 Mar 2.
Picornavirus possesses one positive-sense, single-stranded RNA genome, in which a cis-acting replication element (cre) is located. The cre is a stem-loop structure that harbors a conserved AAACA motif within its loop region. This motif functions as a template for adding two U residues to the viral VPg, therefore generating a VPg-pUpU that is required for viral RNA synthesis. Senecavirus A (SVA) is an emerging picornavirus. Its cre has not been identified as yet. In the present study, one putative cre containing a typical AAACA motif was computationally predicted to exist within the VP2-encoding sequence of SVA. To test the role of this putative cre, 22 SVA cDNA clones with different point mutations in their cre-formed sequences were constructed in an attempt to rescue replication-competent SVAs. A total of 11 viruses were rescued from their individual cDNA clones, implying that some mutated cres exerted lethal impacts on SVA replication. To eliminate these impacts, an intact cre was artificially inserted into those SVA cDNA clones without ability of recovering virus. The artificial cre was proven to be able of compensating for some, but not all, defects caused by mutated cres, leading to successful recovery of SVAs. These results indicated that the putative cre of SVA was functionally similar to those of other picornaviruses, perhaps involved in the uridylylation of VPg.
小核糖核酸病毒拥有一条正链、单链 RNA 基因组，其中包含一个顺式作用复制元件 (cre)。cre 是一种茎环结构，其环区含有一个保守的 AAACA 基序。该基序作为在病毒 VPg 上添加两个 U 残基的模板，从而生成 VPg-pUpU，这是病毒 RNA 合成所必需的。塞内卡病毒 A (SVA) 是一种新兴的小核糖核酸病毒。其 cre 尚未被鉴定。在本研究中，计算预测在 SVA 的 VP2 编码序列内存在一个包含典型 AAACA 基序的假定 cre。为了测试这个假定 cre 的作用，构建了 22 个具有不同 cre 形成序列点突变的 SVA cDNA 克隆，试图拯救复制能力完整的 SVA。从它们各自的 cDNA 克隆中总共拯救出 11 种病毒，这意味着一些突变的 cres 对 SVA 复制产生了致命影响。为了消除这些影响，将一个完整的 cre 人工插入那些没有恢复病毒能力的 SVA cDNA 克隆中。人工 cre 被证明能够补偿一些，但不是所有，由突变 cres 引起的缺陷，导致 SVA 的成功恢复。这些结果表明，SVA 的假定 cre 在功能上与其他小核糖核酸病毒相似，可能参与 VPg 的尿苷酰化。
