Lymphoid/myeloid-specific binding of transcription factors to the E box, ISRE, and κB site of β₂m.

Schematic representation of the β₂m promoter and transcription factors binding to the 3 adjacent regulatory sites in the promoter region upstream of the SXY regulatory module. The E box is bound by ubiquitous factors USF1 and USF2. The ISRE is a binding site for IRF1 and IRF2 and the lymphoid/myeloid factors IRF4 and IRF8. Because IRF3 is also a potent transactivator of β₂m, also IRF3 is likely to bind the ISRE. The κB site is bound by the NF-κB subunits p50 and p65, and in B cells also marginally by c-Rel and RelB.