HSV-1 UL42 and UL47 hijack cellular nucleotide synthetic enzyme CAD to promote lytic replication

Cellular metabolic enzymes are well defined for their roles in metabolism, and their function beyond metabolism is poorly defined. Here, we report that herpes simplex virus 1 (HSV-1) couples evasion of the inflammatory response to metabolic activation to promote lytic replication. Specifically, HSV-1 activates carbamoyl-phosphate synthetase, aspartate transcarbamoylase, and dihydroorotase (CAD), which catalyzes the rate-limiting steps of de novo pyrimidine synthesis. Activated CAD not only fuels de novo nucleotide synthesis but also deamidates RelA. RelA deamidation suppresses NF-κB activation and the inflammatory response while simultaneously upregulating key glycolytic enzymes to promote aerobic glycolysis. Further affinity purification and functional assays identified HSV-1 UL42 and UL47 that interact with and activate CAD, recapitulating the phenotypes of RelA deamidation. Collectively, our work uncovers a role for a metabolic enzyme in coupling immune evasion to metabolic activation through its protein deamidase activity during HSV-1 infection, highlighting a potential therapeutic target.IMPORTANCEHost immune defense and cellular metabolism are two fundamental processes that shape viral pathogenesis. Here, we revealed that herpes simplex virus 1 (HSV-1) activates a nucleotide synthetic enzyme not only to support nucleotide synthesis but also to exploit its unconventional activity for immune evasion and metabolic reprogramming, highlighting a potential therapeutic target.