Figure 4.

Alkaline sucrose density gradient centrifugation (ASDG) profiles of replication products after UV irradiation in (a) MCF‐7, (b) HepG2, (c) WiDr (= HT‐29), (d) CCRF‐CEM, (e) Mewo, or (f) RPMI8226 cells (effects of proteasome inhibitors or caffeine.) Adherent cells synchronized in the mid‐S phase were UV (10 J/m²)‐irradiated, incubated in the normal medium for 30 min, pulse‐labeled with 10 µCi/mL of [¹⁴C]thymidine for 1 h, washed twice with phosphate‐buffered saline (PBS), and incubated for 4–8 h at 37°C in a normal medium containing 50 µM MG‐132, 200 µM lactacystin, 5.0 µM MG‐262, or 5 mM caffeine. CCRF‐CEM and RPMI8226 cells were not synchronized, and pulse‐labeling was conducted for 30 min. Sedimentation is from right to left. The average fragment length (in Mb) of each profile is shown in square brackets. cpm, counts per minute.