Diverse Strategies Deployed by Poliovirus to Cope with Host Antiviral Responses

In the following document, I will describe two distinct strategies that poliovirus

(PV) deploys to manage host antiviral responses. In the first section, I report on a role of

the constitutive repressor of eIF2α phosphorylation (CReP) in translation of PV and the

endoplasmic reticulum (ER)-resident chaperone binding immunoglobulin protein (BiP)

at the ER. Functional, proximity-dependent labeling and cell fractionation studies

revealed that CReP, through binding of the eukaryotic translation initiation factor eIF2α,

anchors translation initiation machinery at the ER and enables protein synthesis in this

compartment. This ER site was protected from the suppression of cytoplasmic protein

synthesis by acute stress responses. I propose that partitioning of translation initiation

machinery at the ER enables cells to maintain active translation of PV during stress.

In the second section, I report that PV 2A protease cleaves all three members of

the YTHDF protein family, cytosolic N6-methyladenosine (m6A) ‘readers’ that regulate

target mRNA fate. These cleavages occurred early during infection, and preemptive

YTHDF3 depletion enhanced viral replication. This corresponded with diminished type-

I interferon (IFN) receptor (IFNAR) expression and IFN-stimulated gene induction,

while IFN production was not significantly changed. I propose that 2A protease cleaves

YTHDF proteins, in part, to interfere with IFNAR expression and antagonize the host

antiviral response.