Conventional CD4+ T cells were sort-purified from WT C57BL/6 mice, and the Lef1-deficient CD4+ T cells were sorted from CD4-Cre+ Lef1 fl/fl mice. The cells were then fixed and sonicated to generate chromatin fragments, followed by immunoprecipitation with an anti-Lef1 antibody (C18A7, Cell Signaling Technology), which were then properly washed and immunoprecipitated DNA extracted. The DNA segments from ChIP were end-repaired and ligated to indexed Illumina adaptors, followed by amplification by PCR with a low number of cells (18-21 cycles). The resulting libraries were seqeunced with Illumina Hiseq-2000 platform.