GTF3A mutations predispose to herpes simplex encephalitis by disrupting biogenesis of the host-derived RIG-I ligand RNA5SP141 .

Herpes simplex virus 1 (HSV-1) infects several billion people worldwide and can cause life-threatening herpes simplex encephalitis (HSE) in some patients. Monogenic defects in components of the type I interferon system have been identified in patients with HSE, emphasizing the role of inborn errors of immunity underlying HSE pathogenesis. Here, we identify compound heterozygous loss-of-function mutations in the gene encoding for transcription factor IIIA (TFIIIA), a component of the RNA polymerase III complex, in a patient with common variable immunodeficiency and HSE. Patient fibroblasts and gene-edited cells displayed impaired HSV-1-induced innate immune responses and enhanced HSV-1 replication. Chromatin immunoprecipitation sequencing analysis identified the 5 ribosomal RNA pseudogene 141 (), an endogenous ligand of the RNA sensor RIG-I, as a transcriptional target of TFIIIA. mutant cells exhibited diminished expression and abrogated RIG-I activation upon HSV-1 infection. Our work unveils a crucial role for TFIIIA in transcriptional regulation of a cellular RIG-I agonist and shows that genetic defects lead to impaired cell-intrinsic anti-HSV-1 responses and can predispose to HSE.