Eight E2F family members have been identified so far, E2F1 to E2F8, whereas E2F1 to E2F6 share the same structure: conserved DNA binding and dimerization domains, and, except for E2F6, have domains for transactivation and binding Pocket Proteins (PP): p107, p130 and Rb (Retinoblastoma) (reviewed in Tsantoulis and Gorgoulis, 2005; DeGregori and Johnson, 2006). This evidence concerns the gene E2F1 and retinoblastoma.