Fig. 4

Compromising G0 disrupts D1, HP1 and Polycomb body clustering and leads to partial de-repression of select PcG targets. E2F was co-expressed with GFP or RFP in the posterior wing to delay cell cycle exit. At 26–28 h wings were dissected and immunostained for the indicated heterochromatin binding proteins and DAPI to label nuclei (A–I). J Overall fluorescence intensities were measured for 319–1270 nuclei for each chromatin modification. The distribution of individual focus intensity (L, M), foci number per nucleus section (K) all indicate that delaying cell cycle exit disrupts heterochromatin clustering and formation of large Polycomb bodies in wing cell nuclei. N Chromosome compaction was measured using the distance of the AACAC repeats to the chromocenter. When cell cycle exit is delayed, chromosome compaction is also compromised. For J, N, P values were determined by an unpaired t test. *< 0.05; **< 0.01; ***< 0.001; ****< 0.0001. O Microarray analysis revealed specific PcG target genes that become temporarily de-repressed in wings expressing E2F at 24 h when cell cycle exit is delayed. P values were determined by ANOVA *< 0.05. Scale bars = 10 μm in A–I except for anterior (A) and posterior (P) zoomed images where the bar = 2 μm (e.g., B_A, B_P)