Histone H3 modifications at the BIM locus. (A) ChIP was carried out for the activating marks H3AcK9 and H3K4Me3 and the inactive mark H3K27Me3 on a representative sensitive (ALL-3) and resistant (ALL-2) xenograft. ChIP material was applied to customized tiling arrays to provide a comprehensive view of the BIM locus as described in “ChIP and ChIP-chip arrays.” (B) ChIP was carried out for H3K9Ac in 2 representative sensitive (ALL-3 and -11) and 3 representative resistant (ALL-2, -10, and -19) xenografts and visualized at the BIM, NOXA, PUMA and GAPDH genomic loci by PCR followed by polyacrylamide gel electrophoresis and SYBR staining. Splicing of samples within a single representative gel is indicated by dividing spaces. (C) ChIP was carried out for H3K9Ac at the BIM locus and quantified relative to the GAPDH locus. Relative BIM acetylation was plotted against the amount of Bim protein induced in each xenograft after treatment with dexamethasone (1μM, 16 hours) as previously published.¹⁸  The color-code alongside the y-axis designates the in vivo LGD in days for each xenograft (see supplemental Table 1); LGD indicates leukemia growth delay; nd, not determined. (D) H3K9 acetylation of BIM was evaluated by ChIP analysis of primary ALL samples in 2 independent patient cohorts (green, Australian; blue, Italian). Data from the Australian cohort were normalized to LMO2, whereas those from the Italian cohort to GAPDH. Individual results represent the mean of 4 experiments; red bar, mean of each subgroup. (E) Basal BIM mRNA expression was determined by RT²-PCR and grouped as for Figure 3D.