E2F1 and breast cancer: In contrast, analysis of the genes transactivated in TKO HCC and the genes bound by haemagglutinin (HA)-tagged exogenous E2f1 in breast cancer cells25 identified 549 genes at the intersection of both data sets (P-value<10−55; Fig. 7j), suggesting that ChIP-Seq experiments performed by pulling-down endogenous proteins may only detect high-affinity binding target genes and ignore a significant fraction of target genes bound by E2f1 with low affinity.