Immunofluorescence samples were examined using a Zeiss LSM 510 or 710 Laser Scanning confocal microscope. The systems were carefully tested for the overlap of optical channels (Fig. S1). Image files were processed with Adobe Photoshop or Zen software and the profile plots of fluorescence intensity peaks along profiles spanning the viral DNA center were examined using Image J software. SIM microscopy was performed using a Nikon N-SIM microscope at the UIC confocal microscopy center.