In response to DNA damage, several signaling pathways that arrest the cell cycle in G 1 and G 2 are activated. The downregulation of mitotic genes contributes to the stable maintenance of the G 2 arrest. The human LINC or DREAM complex, together with the B-MYB transcription factor, plays an essential role in the expression of G 2 -M genes. Here, we show that DNA damage results in the p53-dependent binding of p130 and E2F4 to LINC and the dissociation of B-MYB from LINC. We find that B-MYB fails

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... to dissociate from LINC in p53 mutant cells, that this contributes to increased G 2 -M gene expression in response to DNA damage in these cells, and, importantly, that B-MYB is required for recovery from the G 2 DNA damage checkpoint in p53-negative cells. Reanalysis of microarray expression data sets revealed that high levels of B-MYB correlate with a p53 mutant status and an advanced tumor stage in primary human breast cancer. Taken together, these data suggest that B-MYB/LINC plays an important role in the DNA damage response downstream of p53. [Cancer Res 2009;69(9):4073-80] Figure 2 . The p53 > p21 pathway is necessary to switch LINC from B-MYB to p130. A, MCF-7 cells were treated with doxorubicin, as described in Fig. 1A . LIN9 was immunoprecipitated, and bound p130 protein and inputs (10%) were analyzed by immunoblotting. The asterisk denotes the slower migrating, hyperphosphorylated form of p130 in untreated cells. B, HCT-116 wt and p21 À/À cells were treated with doxorubicin for 2 h. At the indicated time points, LIN9 was immunoprecipitated. Bound p130 and input levels of p130, p21, and h-tubulin were detected by immunoblotting. C, MCF-7 cells were treated with 4.3 Amol/L Nutlin-3 for the indicated times. LIN9 was immunoprecipitated, and bound proteins and input protein levels (10%) were analyzed by immunoblotting. D, HCT-116 p53 +/+ and p53 À/À cells were treated with doxorubicin and analyzed as described in B. Cell cycle profiles of doxorubicin and Nutlin-3-treated genes are shown in Supplementary Fig. S1 .