STAT5 constitutively occupies BCL10-SBR in vivo in Kit225, MT2 and Hut102 cells. Kit225 cells (A) were made quiescent in medium without IL-2 for 24 h, MT2 (B) and Hut102 (C) cells were grown until exhaustion. Cells were then stimulated with medium (-) or IL-2 (+) for 30 min at 37°C, then fixed with 1% formaldehyde for 10 min at room temperature and then chromatin immuno-precipitated with antibodies to Acetyl-Histone 4, C-terminal STAT5 or control IgG. The eluted DNA was amplified with primers corresponding to PRR III (black bars) or BCL10-SBR (grey bars). Representative data for MT2, Hut102 (n = 2), and Kit225 cells (n = 3) are shown. Input material represents 5% of immuno-precipitated chromatin.