H3K4 trimethylation is severely reduced in ash2I1mutants. (a) Colocalization of trimethylated H3K4 (red) with ASH2 (green) in the polytene chromosome 2L arm. (b) Detection by western blot of H3K4 trimethylation on wt and ash2I1 histone extracts. H3 was used as a loading control. (c) Detection of H3K4 trimethylation (red) in wt (bright green), heterozygous (green) and ash2I1 homozygous (black) wing disc cells. Note that in the latter cells H3K4 trimethylation is severely reduced. Antibodies used were anti-HA (for ASH2-HA detection), anti-trimethylated H3K4 and anti-H3. Nuclei are labelled with DAPI (blue).