Figure 6.

The absence of Acf1 leads to a faster S phase in larval neuroblasts. (A) S phase progression was monitored by the incorporation of BrdU in replicating larval neuroblasts. Dissected neuroblasts were incubated with BrdU for 2, 4, or 6 h, and then blocked in mitosis by incubation with Colcemid for 1 h. The pattern of BrdU incorporation was scored as “No Labeling,” “Heterochromatin Only,” or “Euchromatin and Heterochromatin.” (B) Mitotic chromosomes with BrdU labeling of pericentric heterochromatin only. DNA, blue; BrdU, red; scale bar, 15 μm. (C) Mitotic chromosomes with BrdU labeling of euchromatin and heterochromatin. DNA, blue; BrdU, red. (D) Summary of the effects of the loss of Acf1 on the progression of larval neuroblasts through the cell cycle. (E) Neuroblasts lacking Acf1 exhibit a faster progression through S phase compared with isogenic controls (acf1³/acf1³), as judged by the earlier appearance of Euchromatin and Heterochromatin labeling. The colored bars represent the relative numbers of chromosomes with a particular type of BrdU staining: Euchromatin and Heterochromatin (blue), Heterochromatin Only (red), or No Labeling (green). The numbers at the left are the total numbers of chromosomes scored for BrdU incorporation in each experiment. (F) Heterozygous deficiency Df(2L)DS6 uncovering the entire histone gene cluster leads to a faster S phase relative to an isogenic control.