Fig. 2. dE2F1^su89 mutation blocked RBF-mediated inhibition of E2F target gene expression and S phase entry in the second mitotic wave (SMW). (A–D) In situ hybridization of PCNA, an E2F target gene, in eye discs of various genotypes is shown. The genotypes are (A) wild-type, (B) +/GMRRBF-280², (C) dE2F1^su89/GMRRBF-280² and (D) dE2F1^su89. Expression of RBF-280 in the dE2F1^su89/+ background did not inhibit PCNA expression in SMW. Note that a high level of PCNA expression was observed in the furrow of the dE2F1^su89/GMRRBF-280² discs, an expression pattern that was similar to that of the dE2F1^su89 discs (D). (E–H) BrdU incorporation by eye discs from various genotypes is shown. The genotypes are (E) wild-type, (F) +/GMRRBFDap, (G) dE2F1^su89/GMRRBFDap and (H) dE2F1^su89. GMRRBFDap expresses both RBF and Dap in the posterior part of the eye, which delayed and partially inhibited S phase in SMW (F). Introducing one copy of dE2F1^su89 into a GMRRBFDap background suppressed the inhibition of S phase entry in SMW (G). Arrowheads indicate the second mitotic wave.