Nucleolin Participates in DNA Damage Response Figure 5. Nucleolin participates in DSB repair. (A) Nucleolin interacts with HR factors, RPA34 and NBS1 in response to DNA damage. The extracts from normal lymphoblastoid cells were immunoprecipitated with anti-nucleolin antibody or normal rabbit IgG, and then the immuno- complexes were detected by Western blot analysis. (B) NHEJ and HR activity in nucleolin-knockdown cells. HeLa-DRGFP, NBS-DRGFP or MRC5-pEJ cells were transfected by nucleolin siRNA. After 2 days I-SceI expression plasmid were introduced to these cells by electroporation and analyzed by flowcytometer. Open column: control, closed column: nucleolin siRNA. (C, D and E) 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 indicated times, their cells were fixed and immuno-staining was performed using anti-Rad51 antibody (C), anti-RPA 34 antibody (D) or anti-c-H2AX antibody (E). Then, percentages of foci-positive cell were counted under fluorescence microscope. Open column: control, closed column: nucleolin siRNA. doi:10.1371/journal.pone.0049245.g005 PLOS ONE | www.plosone.org 7 November 2012 | Volume 7 | Issue 11 | e49245