Effects of the D286R mutation in UL31 on HSV-1 nuclear egress in HeLa cells. HeLa cells were infected with wild-type HSV-1(F), YK726 (UL31-D286R), or YK727 (UL31-D286R-repair) at an MOI of 10, fixed at 24 h postinfection, and examined by transmission electron microscopy. Arrowheads indicate membranous structures in the nucleus. N, nucleus; C, cytoplasm; NM, nuclear membrane. Bars, 500 nm.