RNA Polymerase III Suppresses Varicella Zoster Virus in Human Neurons

Varicella zoster virus (VZV) is a ubiquitous human alphaherpesvirus, latently present in the majority of the population. Knowledge on the molecular mechanisms underlying VZV reactivation from peripheral ganglia is incomplete, as is our understanding of why only a small number of individuals develop life-threatening complications following reactivation. Previously, we have reported a pathogenic mutation in the POLR3F subunit of the cytosolic DNA sensor RNA polymerase III in 2 monozygotic twins diagnosed with recurring encephalitis and vasculitis, caused by VZV reactivation.

The main objective of this study was to determine the role of POLR3F mutations in VZV pathogenesis in a model of viral reactivation.

We generated human SH-SY5Y (POLR3F+/-) knockout cells. We determined the impact of POLR3F heterozygosity on VZV control during acute infection of differentiated SH-SY5Y neuronal cells by quantifying gene expression by RT-qPCR. We also established a quiescent infection model and quantified spontaneous reactivation by detection of viral proteins fused to fluorophores.

Varicella zoster virus infection of undifferentiated as well as terminally differentiated early passage SH-SY5Y cells resulted in higher viral gene expression and more VZV reactivation in the POLR3F neuronal heterozygous (POLR3F+/-) knockout cells, reflecting the patient phenotype, compared with wild-type cells.

This work identifies a novel role for POLR3F as a sentinel for VZV reactivation in neuronal cells and lends further support to the hypothesis that polymerase III (POL III) plays a role in immunity to VZV mainly upon reactivation in humans and that POL III defects predispose to VZV central nervous system infection.