Ataxin-2-like promotes translation of nonpolyadenylated reovirus mRNA

Mammalian orthoreovirus (reovirus) nonstructural protein μNS nucleates viral factories (VFs), which are sites of viral genome replication, protein synthesis, and particle assembly. Reovirus mRNAs are not polyadenylated, yet these transcripts are efficiently translated. To identify host factors associated with translation in VFs, we conducted a proteomics screen and identified ataxin-2-like (ATXN2L) as a μNS-interacting protein. CRISPR-mediated gene knockout (KO) of ATXN2L impairs reovirus replication. The ATXN2L RNA-binding domains are required for reovirus replication and association with the 3' terminus of nonpolyadenylated reovirus mRNAs. Synthesis of viral proteins is diminished in ATXN2L-KO cells following reovirus infection. Translation of a reovirus reporter construct is diminished following transfection of ATXN2L-KO cells with nonpolyadenylated mRNA but not with polyadenylated mRNA. These data identify ATXN2L as an essential mediator of translation of nonpolyadenylated reovirus mRNA.