Vaccinia and influenza A viruses select rather than adjust tRNAs to optimize translation

Transfer RNAs (tRNAs) are central to protein synthe-sis and impact translational speed and fidelity by their abundance. Here we examine the extent to which viruses manipulate tRNA populations to favor translation of their own genes. We study two very different viruses: influenza A virus (IAV), a medium-sized (13 kB genome) RNA virus; and vaccinia virus (VV), a large (200 kB genome) DNA virus. We show that the total cellular tRNA popula-tion remains unchanged following viral infection, whereas the polysome-associated tRNA population changes dramatically in a virus-specific manner. The changes in polysome-associated tRNA levels reflect the codon usage of viral genes, suggesting the existence of local tRNA pools optimized for viral translation