To set apart the euchromatin of LAT promoter/enhancer region from the heterochromatin of ICP0 promoter region in the latent infection, HSV evolves to contain chromatin insulator CTCCC repeats within the LAT intron, which recruits the CTCF protein and marks the boundary between the euchromatin and heterochromatin of latent HSV DNA [40]. The gene discussed is LAT; the disease is disease arising from reactivation of latent virus.