Human cytomegalovirus (HCMV) induces numerous changes to the host metabolic network that are critical for high-titer viral replication. We find that HCMV
infection substantially induces de novo
pyrimidine biosynthetic flux. This activation is important for HCMV replication because inhibition of
pyrimidine biosynthetic
enzymes substantially decreases the production of infectious virus, which can be rescued through medium supplementation with
pyrimidine biosynthetic intermediates. Metabolomic analysis revealed that
pyrimidine biosynthetic inhibition considerably reduces the levels of various
UDP-
sugar metabolites in HCMV-infected, but not mock-infected, cells. Further,
UDP-
sugar biosynthesis, which provides the
sugar substrates required for glycosylation reactions, was found to be induced during HCMV
infection.
Pyrimidine biosynthetic inhibition also attenuated the glycosylation of the envelope
glycoprotein B (gB). Both glycosylation of gB and viral growth were restored by medium supplementation with either
UDP-
sugar metabolites or
pyrimidine precursors. These results indicate that HCMV drives de novo-synthesized
pyrimidines to
UDP-
sugar biosynthesis to support virion protein glycosylation. The importance of this link between
pyrimidine biosynthesis and
UDP-sugars appears to be partially shared among diverse virus families, because
UDP-
sugar metabolites rescued the growth attenuation associated with
pyrimidine biosynthetic inhibition during
influenza A and
vesicular stomatitis virus infection, but not murine hepatitis virus
infection. In total, our results indicate that viruses can specifically modulate
pyrimidine metabolic flux to provide the glycosyl subunits required for protein glycosylation and production of high titers of infectious progeny.