Downstream Activation of a TATA-less Promoter by Oct-2, Bob1, and NF-κB Directs Expression of the Homing Receptor BLR1 to Mature B Cells

The chemokine receptor, BLR1, is a major regulator of the microenvironmental homing of B cells in lymphoid organs. In vitro studies identify three essential elements of the TATA-less blr1 core promoter that confer cell type- and differentiation-specific expression in the B cells of both humans and mice, a functional promoter region (−36 with respect to the transcription start site), a NF-κB motif (+44), and a noncanonical octamer motif (+157). The importance of these sites was confirmed by in vivo studies in gene-targeted mice deficient of either Oct-2, Bob1, or both NF-κB subunits p50 and p52. In all of these animals, the expression of BLR1 was reduced or absent. In mice deficient only of p52/NF-κB, BLR1 expression was unaffected. Thus our data demonstrate that BLR1 is a target gene for Oct-2, Bob1, and members of the NF-κB/Rel family and provides a link to the impaired B cell functions in mice deficient for these factors.