Senecavirus A (SVA), formerly known as Seneca Valley virus, is classified into the genus Senecavirus in the family Picornaviridae. Mature virion harbors an approximately 7 300-nt-long, positive-sense, and single-stranded RNA genome, which contains 5′ and 3′ untranslated regions (UTRs). Internal ribosome entry site (IRES) is identified in the SVA 5′ UTR, and includes a RNA pseudoknot upstream of the start codon. This pseudoknot contains two stem structures, pseudoknot stem I and II (PKS-I and -II). The PKS-I is composed of two base-paired motifs (PKS-Ia and -Ib), between which there is an unpaired spacing (UpS). We reported previously that motif mutation in the PKS-II did not abolish the IRES activity, but interfered with SVA recovery from cDNA clone. In this study, we constructed five SVA minigenomes with point mutations in the PKS-I motif. Dual-luciferase reporter assay showed that motif mutations in PKS-I did not significantly interfere with the IRES activity to initiate protein expression. Correspondingly, we constructed five SVA cDNA clones with point mutations in the PKS-I motif. These genetically modified cDNA clones were separately transfected into BSR-T7/5 cells in attempting to rescue competent SVAs. However, only two viruses, namely PKS-Ia- and UpS-mutated recombinants, could be recovered from their individual cDNA clones. It can be concluded that the PKS-Ib is indispensable for viral growth.

Senecavirus A（SVA），原名塞内卡谷病毒，分为属Senecavirus在家庭中的小核糖核酸病毒. 成熟的病毒粒子包含大约 7 300 nt 长的正链单链 RNA 基因组，其中包含 5' 和 3' 非翻译区 (UTR)。内部核糖体进入位点 (IRES) 位于 SVA 5' UTR 中，包括起始密码子上游的 RNA 假结。该假结包含两个茎结构，即假结茎 I 和 II（PKS-I 和 -II）。PKS-I 由两个碱基配对的基序（PKS-Ia 和 -Ib）组成，它们之间有一个未配对的间距（UpS）。我们之前报道过 PKS-II 中的基序突变不会消除 IRES 活性，但会干扰从 cDNA 克隆中恢复 SVA。在这项研究中，我们构建了五个在 PKS-I 基序中具有点突变的 SVA 小基因组。双荧光素酶报告基因分析表明，PKS-I 中的基序突变不会显着干扰 IRES 活性以启动蛋白质表达。相应地，我们构建了五个在 PKS-I 基序中具有点突变的 SVA cDNA 克隆。这些基因修饰的 cDNA 克隆被分别转染到 BSR-T7/5 细胞中，以试图拯救有能力的 SVA。然而，只有两种病毒，即 PKS-Ia 和 UpS 突变的重组体，可以从它们各自的 cDNA 克隆中回收。可以得出结论，PKS-Ib 对于病毒生长是必不可少的。即 PKS-Ia 和 UpS 突变的重组体，可以从它们各自的 cDNA 克隆中回收。可以得出结论，PKS-Ib 对于病毒生长是必不可少的。即 PKS-Ia 和 UpS 突变的重组体，可以从它们各自的 cDNA 克隆中回收。可以得出结论，PKS-Ib 对于病毒生长是必不可少的。