RAD21 and infection: To determine whether the replicating HSV-1 genomes interact with the Cohesin complex, we first did double immunostaining with antibodies against the viral protein ICP4 to label the viral replication compartments and antibodies against SMC1, SMC3, and Rad21 in human primary fibroblast BJ cells at 6 h post-infection, a time point when HSV-1 replication centers are well organized.