Presenter of 1 Presentation
GTF3A DEFICIENCY IN HUMANS PREDISPOSES TO HERPES SIMPLEX ENCEPHALITIS BY ABROGATING TRANSCRIPTION OF THE HOST-DERIVED RIG-I LIGAND RNA5SP141
Abstract
Background and Aims
Monogenic defects in type I interferon (IFN-I) signaling components have been identified in patients with herpes simplex encephalitis (HSE), emphasizing inborn errors of immunity underlying pathogenesis. In vitro studies demonstrate that the cytoplasmic RNA sensor RIG-I, which is well known to restrict RNA viruses, also critically contributes to the innate immune responses to DNA viruses including HSV-1.
Methods
We identified compound heterozygous mutations in the gene GTF3A in a family afflicted by HSE in early childhood. We studied primary patient cells as well as several CRISPR/Cas9-edited GTF3A mutant cells.
Results
GTF3A encodes for the transcription factor TFIIIA, which is part of the Pol III complex. We confirmed that the patient TFIIIA mutants have an impaired promoter-binding ability. We tested HSV-1 replication in the patient fibroblasts and GTF3A mutant cells and observed enhanced viral replication. To understand the underlying mechanism, we took an unbiased approach and searched for novel transcriptional targets of TFIIIA by ChIP-seq analysis and identified the pseudogene RNA5SP141, previously described as a RIG-I agonist. We found that RNA5SP141 is upregulated following HSV-1 infection and that this induction is abrogated in primary patient cells, in GTF3A gene-edited mutant cells, and upon targeted knockdown using siRNA. Finally, we explored the downstream effects of impaired RNA5SP141 expression on anti-herpesviral immunity and found abrogated RIG-I activation and markedly diminished induction of antiviral genes during HSV-1 infection.
Conclusions
Our work unveils a novel role for TFIIIA, acting as a moonlighting protein that regulates innate immune responses to HSV-1 by transcriptional regulation of the host-derived RNA5SP141 RIG-I ligand.