Four sites, which exhibited differential binding of Pax5 and Pax5‐Jak2 in the Bio‐ChIP‐seq data (Appendix Fig S5A), were selected for validation by Bio‐ChIP‐qPCR analysis of independently prepared Pax5Bio/Bio pro‐B cell, Pax5Jak2/+Rosa26BirA/+ pro‐B cell, and Pax5Jak2/+Rosa26BirA/+ B‐ALL samples (Appendix Fig S5B). Here, JAK2 is linked to acute lymphoblastic leukemia.