The HSV-1 Latency-Associated Transcript Functions to Repress Latent Phase Lytic Gene Expression and Suppress Virus Reactivation from Latently Infected Neurons

Herpes simplex virus 1 (hsv-1) establishes life-long latent infection within sensory neurons,during which viral lytic gene expression is silenced. the only highly expressed viral gene product during latent infection is the latency-associated transcript (lat),a non-protein coding rna that has been strongly implicated in the epigenetic regulation of hsv-1 gene expression. we have investigated lat-mediated control of latent gene expression using chromatin immunoprecipitation analyses and lat-negative viruses engineered to express firefly luciferase or β-galactosidase from a heterologous lytic promoter. whilst we were unable to determine a significant effect of lat expression upon heterochromatin enrichment on latent hsv-1 genomes,we show that reporter gene expression from latent hsv-1 genomes occurs at a greater frequency in the absence of lat. furthermore,using luciferase reporter viruses we have observed that hsv-1 gene expression decreases during long-term latent infection,with a most marked effect during lat-negative virus infection. finally,using a fluorescent mouse model of infection to isolate and culture single latently infected neurons,we also show that reactivation occurs at a greater frequency from cultures harbouring lat-negative hsv-1. together,our data suggest that the hsv-1 lat rna represses hsv-1 gene expression in small populations of neurons within the mouse tg,a phenomenon that directly impacts upon the frequency of reactivation and the maintenance of the transcriptionally active latent reservoir. © 2016 nicoll et al.