Counteracting FOX proteins epigenetically control the herpesvirus lytic-latent balance.

The lytic-latent balance is a major viral persistence strategy and obstacle to curing viral diseases, yet its mechanisms remain poorly understood. Following lytic infection in non-neuronal cells, herpes simplex virus (HSV) establishes latency specifically in neurons and is reactivated by stresses. Here we identify forkhead box (FOX) transcription factors that can strongly activate or repress replication of HSV-1 and other alphaherpesviruses, and show that neurons express activating Fox (e.g., Foxf) genes poorly but repressive Fox (Foxk) genes abundantly while non-neuronal or stressed neuronal cells exhibit higher expression of activating Fox genes. Remarkably, knockdown of Foxk1 or overexpression of activating Fox genes induces reactivation from latency in male mouse neuronal culture and in vivo. Of note, FOX proteins bind the viral genome globally and nonsequence-specifically and interact with epigenetic cofactors for gene regulation. FOXF1 interacts with CBP and P300 to acetylate and open viral chromatin. FOXK1 works with SIN3A, a cofactor of histone deacetylation, and MAX to suppress HSV-1 and antagonize activating FOX proteins. Therefore, the viral lytic-latent balance is controlled by the relative abundance of counteracting host transcription factors that recruit different epigenetic regulators to the viral genome.