Stable Transfections of a BAC reporter construct containing Bcl11b and Major Peak confirm the T-cell specific enhancer activity of Major Peak in a chromatin context. (A) Generation of BAC-Bcl11b-YFP-MP construct. A YFP cassette replaced the Exon 1 of Bcl11b. Major Peak was cloned into the BAC at 9.8-kb downstream of 3′UTR of Bcl11b. (B) Stable transfections of the BAC constructs into P2C2 and Raw264.7 cells: histograms of YFP fluorescence in individual subcultures after selection are shown. Results are representative of two independent experiments.