Splenic CD8 T cells were sort-purified from WT or Tcf1/Lef1-deficient mice, the cells were then fixed and sonicated to generate chromatin fragments, followed by immunoprecipitation with antibodies against Sin3A, 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.