Figure S3. A Defect in Damage-Induced Sister Chromatid Exchange in UBC13-/-

The impaired post-replication repair of UBC13-/- deficient DT40 cells. Top panels:Wild-type cells or UBC13-/- cells were pulse labeled with [14C] thymidine (10 µCi/ml) for 10 min (open circles). In a pulse chase experiment, the pulse-labeled cells were incubated further for one hour (open triangles) in fresh medium containing 10 µM unlabeled thymidine. Samples were separated on 5-20 % alkaline sucrose gradients sedimention from right to left. Bottom panels: Wild-type and UBC13-/- cells were irradiated with UV light (5 J/m2), incubated for 20 min, and then pulse-labeled with [14C] thymidine (10 µCi/ml) for 20 min (open circles). In a pulse-chase experiment, the pulse-labeled cells were incubated further for one hour (open triangles) or 3 hour (closed squares) in the chase medium. Left: wild-type cells. Right: Ubc13 deficient cells. The arrow indicates the positions of T4 phage DNA (166 kb), which was [14C]-labeled and sedimented in a parallel run. Labeled E.coli DNA (about 4 megabase) had sediment near the bottom (fraction No.3-6) (Yamada et al., 1996)