Figure 4.

E2F transcriptional activation and Dp loss are highly similar, except for specific genes that require E2F activity for expression after exit. Using microarrays, we compared gene expression in E2F1–DP-expressing wings (ap-Gal4/UAS-E2F1, UAS-DP, tub-Gal80^TS) with controls (ap-Gal4/UAS, tub-Gal80^TS) and Dp mutant wings (w;Dp^a1/a2) with controls (w) at three time points. (A) Heat map of transcript changes (color range indicates the log₂ ratio of expression compared with controls). All transcripts with a fold change of 1.5 or more (>log₂ ± 0.6) at one or more time points are shown. Gray bars indicate transcripts that were removed from analysis because of high variability among independently replicated experiments (n = 4 for E2F; n = 3 for Dp^−/−). Transcripts were clustered using Genesis software for hierarchical clustering. Representative genes from each major cluster are listed on the right. Typical group transcripts are up-regulated in E2F-expressing and Dp^−/− wings at 24 and 36 h APF, whereas other transcripts are repressed or inversely regulated. Arrays for E2F and Dp^−/− at 24 and 36 h were highly similar with a correlation coefficient of 0.74. (B) A group of 162 genes was up-regulated >1.75-fold (>log₂ 0.82) by E2F activity at one or both time points APF but was not significantly increased in Dp^−/− (change <1.3-fold; <log₂ 0.4). Asterisks indicate examples of genes that regulate cyclin–Cdk activity or mitosis.