ITAF ₄₅ is a Pervasive Trans Acting Factor for Picornavirus Type II IRES Elements

Viruses have evolved elaborate mechanisms to hijack the host mRNA translation machinery to direct viral protein synthesis. Picornaviruses, whose RNA genomes lack a cap structure, inhibit cap-dependent mRNA translation, and utilize an internal ribosome entry site (IRES) in the RNA 5′-UTR to recruit the 40S ribosomal subunit. IRES activity is stimulated by a set of host proteins termed IRES trans -acting factors (ITAFs). The cellular protein ITAF ₄₅ (also known as PA2G4 and EBP1) was identified as an essential ITAF for foot-and-mouth disease virus (FMDV), with no apparent role in cell-free systems for the closely related viruses harboring similar IRES elements such as encephalomyocarditis virus (EMCV) and Theiler’s murine encephalomyelitis virus (TMEV). Here, we demonstrate that ITAF ₄₅ is a pervasive host factor within cells for picornaviruses containing a Type II IRES. CRISPR/Cas9 knockout of ITAF ₄₅ in several human cell lines conferred resistance to infection with FMDV, EMCV, TMEV, and equine rhinitis A virus (ERAV). We show that ITAF ₄₅ enhances initiation of translation on type II IRESs in cell line models. This is mediated by the C-terminal lysine-rich region of ITAF ₄₅ known to enable binding to viral RNA. These findings challenge previous reports of a unique role for ITAF ₄₅ in FMDV infection, positioning ITAF ₄₅ as a promising antiviral target for various animal viruses and emerging human cardioviruses.