Comparison of the Regulatory Effects of Host Factors on Viral Internal Ribosomal Entry Sites

Host factors play critical roles in viral IRES-mediated translation by modulating the efficiency and specificity of viral protein synthesis. In this study, we used small interfering RNA (siRNA) treatment to silence and plasmid-based expression to overexpress PKD1L3 and USP31. Silencing PKD1L3 and USP31 suppressed IRES activity in FMDV and CSFV RNAs, whereas the overexpression of PKD1L3 did not have a significant effect, and USP31 overexpression resulted in only a modest increase in CSFV-IRES activity. Silencing PKD1L3 significantly reduced EMCV-IRES activity but had no significant effect on HCV- or DENV-IRES activity, and silencing USP31 had no significant effect on the activities of these three IRESs. Notably, the combined overexpression of PKD1L3 and USP31 significantly suppressed HCV-IRES activity, suggesting potential context-dependent interactions. These findings indicated that PKD1L3 and USP31 contribute more prominently to CSFV-, FMDV-, and EMCV-IRES-mediated translation than to HCV- or DENV-IRES-driven translation. Collectively, our results provide new insights into the host factors involved in IRES-mediated viral translation, establish a foundation for future in vivo studies to elucidate the specific roles of PKD1L3 and USP31 during viral infection, and indicate potential strategies for mitigating these viruses.