The accessibility of HSV-1 DNA changes throughout the lytic infection cycle. Nuclei of infected cells isolated at 2, 4, 5, or 9 hpi were digested for 0.5, 2.5, 5, 15, 30, or 60 min (

) with 0.05 U MCN per 1 × 10
7 nuclei. The DNA was analyzed by Southern blot hybridization with HSV-1 or cellular probes. (A) Images of the ethidium bromide-stained gels (Total) or membranes hybridized with cellular (Cellular) or HSV-1 (HSV)-specific probes. M, molecular weight marker. Two different hybridizations representing the different patterns observed at 2 hpi are shown [2 hpi (
i) and (
ii)]. For HSV-1 DNA, standard and overexposures (bottom panels), in which the absence of nucleosome-sized HSV-1 DNA is more obvious, are shown. To achieve comparable signal intensities, only 67% of each sample was loaded for 0.5-min digestions. (B and C) Line graphs of the quantitated Southern blot hybridizations presenting the levels of cellular (B) or HSV-1 (C) DNA against digestion time, as percentages of DNA at time zero. Results from one experiment (4 and 9 hpi) or averages ± ranges for two [2 (
i), 2 (
ii), and 5 hpi] are shown.