We thus generated Pax5Jak2/+Rosa26BirA/+ mice and used in vitro cultured pro‐B cells from young mice (expressing Pax5) or B‐ALL tumors (lacking Pax5) to determine the genome‐wide DNA‐binding pattern of Pax5‐Jak2 by streptavidin‐mediated chromatin precipitation coupled with deep sequencing (Bio‐ChIP‐seq; Revilla‐i‐Domingo et al, 2012). This evidence concerns the gene JAK2 and acute lymphoblastic leukemia.