Nucleolin Participates in DNA Damage Response Figure 6. Nucleolin contributes to MDC1-dependent damage responses and histone eviction. (A) Nucleolin is required for IR-induced accumulation of HR factors into chromatin fraction. U2OS cells were transfected by nucleolin siRNA. After 2 days, these cells were irradiated by 10 Gy of c-ray and were harvested at indicated times after IR. Nucleoplasm (nuclear sup) and chromatin extracts were prepared as described in Materials and Methods, and analyzed by Western blot using indicated antibodies. (B) Nucleolin is required for RNF168 focus formation. U2OS cells were transfected by nucleolin siRNA or negative control siRNA, and after 2 days these cells were irradiated by 5 Gy of c-ray. After 30 minutes, their cells were fixed and immuno-staining was performed using indicated antibodies. (C) Nucleolin interacts with MDC1. Extracts from normal lymphoblastoid PLOS ONE | www.plosone.org 8 November 2012 | Volume 7 | Issue 11 | e49245