The human and murineJAK3promoters share an 88-bp region of homology but use different transcription factor binding sites within that region to activate transcription ofJAK3. The sequence alignment of the human and murine Jak3 promoters is shown. The sequence of the human Jak3 promoter has been described in Aringer et al.¹⁴  The Stat binding site that is necessary for transcription of the murine Jak3 gene in myeloid cells and the AP-1 and ETS sites that are necessary for maximal transcription of the human JaK3 gene in T cells are highlighted. Stat and ETS binding sites are in boldface, and the AP-1 binding sites are boxed. Positions -45A and -46A of the murine Jak3 promoter are denoted with capital letters. When these 2 bases are mutated together (-45 and -46 A to C), activity of the Jak3 promoter in M1 cells is markedly reduced.