Identification of novel factors which bind specifically to the core promoter of the immunoglobulin heavy chain gene.

Nuclear extracts from HeLa cells and the B-cell line, BJA-B, generated two protein-DNA complexes which bound specifically to sequences in the TATA box of the immunoglobulin heavy chain gene (IgH) promoter. Complex A also bound the core promoter of a retroviral long terminal repeat but did not bind to five other promoters including the adenovirus major late promoter. Of these seven promoters, complex B bound only to the IgH promoter. Footprinting analysis revealed that both complexes A and B bound sequences which include the TATA element, and complex A additionally contacted sequences downstream to +28. Mutation of the IgH TATA element from ATTAATATA to GCTA-TAAAA, the optimal TATA sequence as found in the major late promoter, resulted in a 10-fold decrease in binding to complex A and a 25-fold decrease in binding complex B. Surprisingly, both transfection experiments in HeLa cells and in vitro transcription experiments with whole nuclear extract demonstrated that mutation of the TATA box in the core IgH promoter to this consensus sequence resulted in a 2-fold decrease in the level of transcription. These data suggest that the specific sequence of the TATA region is important, and factors which recognize these sequences, such as complex A and B, may modulate the level of transcription from the IgH promoter.