Human DBR1 deficiency impairs stress granule-dependent PKR antiviral immunity.

The molecular mechanism by which inborn errors of the human RNA lariat-debranching enzyme 1 (DBR1) underlie brainstem viral encephalitis is unknown. We show here that the accumulation of RNA lariats in human DBR1-deficient cells interferes with stress granule (SG) assembly, promoting the proteasome degradation of at least G3BP1 and G3BP2, two key components of SGs. In turn, impaired assembly of SGs, which normally recruit PKR, impairs PKR activation and activity against viruses, including HSV-1. Remarkably, the genetic ablation of PKR abolishes the corresponding antiviral effect of DBR1 in vitro. We also show that Dbr1Y17H/Y17H mice are susceptible to similar viral infections in vivo. Moreover, cells and brain samples from Dbr1Y17H/Y17H mice exhibit decreased G3BP1/2 expression and PKR phosphorylation. Thus, the debranching of RNA lariats by DBR1 permits G3BP1/2- and SG assembly-mediated PKR activation and cell-intrinsic antiviral immunity in mice and humans. DBR1-deficient patients are prone to viral disease because of intracellular lariat accumulation, which impairs G3BP1/2- and SG assembly-dependent PKR activation.