Interestingly, HSV-1 does not require cells to be in the S-phase and even arrests the cell cycle at the G1/S transition step (Shadan et al., 1994; Song et al., 2000) , which partly explains why it can grow in non-dividing neurons. While the precise mechanism of this arrest is unclear, it is known that the viral ICP0 protein and the VP16 cellular partner HCF modulate the cell cycle (Hobbs and DeLuca, 1999; Lomonte and Everett, 1999; Piluso et al., 2002) .