DEAD-box helicase 23 (DDX23) is a host nuclear helicase, which is a part of the spliceosomal complex and involved in pre-mRNA splicing. To investigate whether DDX23, an internal ribosomal entry sites transacting factor (ITAF) affects foot-and-mouth disease virus (FMDV) replication and translation through internal ribosome entry site (IRES)-dependent manner. For this, we utilized a pull-down assay, Western blotting, quantitative real-time PCR, confocal microscopy, overexpression and small interfering RNA knockdown, as well as the median tissue culture infective dose. Our findings showed that FMDV infection inhibited DDX23 expression and the overexpression of DDX23 reduced viral replication, however, CRISPR Cas9 knockout/small interfering RNA knockdown increased FMDV replication. FMDV IRES domain III and IV interacted with DDX23, whereas DDX23 interacted with FMDV 3C proteinase and significantly degraded. The enzymatic activity of FMDV 3C proteinase degraded DDX23, whereas FMDV degraded DDX23 via the lysosomal pathway. Additionally, IRES-driven translation was suppressed in DDX23-overexpressing cells, and was enhanced in DDX23 knocked down. Collectively, our results demonstrated that DDX23 negatively affects FMDV IRES-dependent translation, which could be a useful target for the design of antiviral drugs.

中文翻译：

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DDX23负调控口蹄疫病毒的翻译和复制，并被3C蛋白酶降解

DEAD-box解旋酶23（DDX23）是宿主核解旋酶，它是剪接体复合体的一部分，参与mRNA的前期剪接。若要调查DDX23，内部核糖体进入位点交易因子（ITAF）是否通过依赖内部核糖体进入位点（IRES）的方式影响口蹄疫病毒（FMDV）复制和翻译。为此，我们利用了下拉测定，蛋白质印迹，实时定量PCR，共聚焦显微镜，过表达和小干扰RNA敲减以及组织培养中值感染剂量。我们的发现表明，FMDV感染抑制了DDX23的表达，而DDX23的过表达降低了病毒的复制，但是，CRISPR Cas9敲除/小干扰RNA敲除增加了FMDV的复制。FMDV IRES域III和IV与DDX23相互作用，而DDX23与FMDV 3C蛋白酶相互作用并显着降解。FMDV 3C蛋白酶的酶促活性降解了DDX23，而FMDV通过溶酶体途径降解了DDX23。此外，IRES驱动的翻译在过表达DDX23的细胞中受到抑制，而在DDX23敲低的细胞中得到增强。总的来说，我们的结果表明DDX23对FMDV IRES依赖性翻译产生负面影响，这可能是抗病毒药物设计的有用目标。