KSHV lytic mRNA is efficiently translated in the absence of eIF4F

Herpesvirus genomes are decoded by host RNA polymerase II, generating messenger ribonucleic acids (mRNAs) that are post-transcriptionally modified and exported to the cytoplasm. These viral mRNAs have 5'-m7GTP caps and poly-adenylate (polyA) tails that should permit assembly of canonical eukaryotic initiation factor 4F (eIF4F) cap-binding complexes to initiate protein synthesis. However, we have shown that chemical disruption of eIF4F does not impede KSHV lytic replication, suggesting that alternative translation initiation factors (TIFs) support viral protein synthesis. Here we show that eIF4F and an alternative TIF known as eIF3d both contribute to the accumulation of viral proteins during KSHV lytic replication, with eIF3d supporting accumulation of viral proteins when eIF4F is depleted and vice-versa. However, eIF3d depletion greatly diminished release of infectious virions even when eIF4F was available to compensate for lost translation initiation capacity. This viral replication failure in the absence of eIF3d correlated with diminished accumulation of many enzymes in the cholesterol biosynthetic pathway and reduced accumulation of intracellular cholesterol. Moreover, we demonstrated that eIF3d was required to support efficient translation of essential cholesterol biosynthesis enzymes SQLE and MVK during lytic replication. These findings position eIF3d as a critical TIF not only required to support efficient translation of KSHV lytic mRNAs during times of need, but also to support the accumulation of intracellular cholesterol required to successfully complete an infectious cycle.