Murine MR 5′ flanking region. Both strands of the flanking region were sequenced by the dideoxy method. The translation start site ATG is indicated in bold letters, followed by some translated sequence in small letters. The transcription start site is indicated by a large arrow. The boxes indicate potential and experimentally verified transcription factor binding sites (see Results). The location of the four potential PU.1 sites (P177, P164, P32, and P22) and the single Sp1 site as well as the initiator (Inr) element are portrayed.