Transcriptional regulation of the murine 3 ' IgH enhancer by OCT-2

Targeted disruption of either of the B cell-specific transcription factors Oct-2 or OCA-B/BOB-1/OBF-1 dramatically affects B cell terminal differentia tion. The 3' enhancer of immunoglobulin heavy chain (IgH) locus is importan t for transcription of the locus in terminal plasma cells. Allele-specific suppression of mutant Oct-2 binding sites in this enhancer by a variant Oct -2 protein revealed that in a mature B cell line this enhancer was specific ally dependent upon Oct-2, as contrasted to the closely related Oct-1 trans cription factor. Phosphorylation of the Oct-2 protein was important for thi s activation and was synergistic for coactivation by the OCA-B factor. Thes e results indicate that Oct-2 and OCA-B interact with the 3' enhancer in re gulation of the IgH locus during B cell activation.