Map of the distal regulatory region responsible for IFN inducibility of the Ly-6E promoter in B cells. (A) Various constructs used to characterize this region and their response to IFN-γ assayed by luciferase activity is shown as well as the HaeIII 150-bp fragment showing maximum IFN inducibility. Computer analysis of this sequence identified potential sites for three DNA binding proteins: a CAT box, NF-κB, and a GMb site defined in the promoter of the GM-CSF gene. Constructs κB, κB*, −κB, and GMb* were designed to address their function. Astericks represent mutated sites and −κb construct lacks NF-κB site. BG1 and BG2 sequences were generated by PCR to further define the functional sites. BG2 contains additional 8 bp relative to BG1 and an insertion of a nucleotide (C) 3′ toNlaIII site to generate SalI site. BG1 was fully inducible, whereas BG2 was completely devoid of inducibility. The increase in luciferase activity is shown on the right and is representative of five experiments. (B) At the bottom, the minimal sequence required for IFN-γ inducibility is shown.