Schematic representation of the various recombinant HSV-1 bacterial artificial chromosome (BAC) and viral genomes. (A) pYEbac102 contains wild-type HSV-1 genome, and the BAC vector sequence was flanked by two loxP sites. pYEbacPC8 was subsequently derived from pYEbac102 by a two-step homologous recombination of BAC DNA. (B) In the first step, the infected cell protein 6 (ICP6) coding region in pYEbac102 was replaced by galactokinase (galK) cassette to generate pYEbacgalK. (C) In the second step, galK cassette was replaced by the cell cycle regulatory elements (consisted of cytomegalovirus promoter (CMVp), fusion protein of Gal4 DNA binding domain with nuclear factor Y, alpha (Gal4 NF-YA), synthetic poly A (P(A)), 8 × Gal4-binding site (Gal4 bs), cyclin A promoter (CycAp) and luciferase reporter gene (Luc)) to generate pYEbacPC8. (D) YE-102 recombinant viruses were derived from pYEbac102 by Cre-digestion to remove the BAC vector sequence. (E) Likewise, the BAC vector sequence in pYEbacPC8 was removed to generate YE-PC8 recombinant viruses. (F) YE-CMV-Luc was used as a control virus where the cell cycle-dependent promoter from Gal4 NF-YA to CycAp was removed using the similar strategy to construct YE-PC8.