Pax-5 (BSAP) recruits Ets proto-oncogene family proteins to form functional ternary complexes on a B-cell-specific promoter.
The paired box transcription factor Pax-5 (B-cell-specific activator protein) is a key regulator of lineage-specific gene expression and differentiation in B-lymphocytes. We show that Pax-5 functions as a cell type-specific docking protein that facilitates binding of the early B-cell-specific mb-1 promoter by proteins of the Ets proto-oncogene family. Transcriptional activity of the mb-1 promoter in pre-B-cells is critically dependent on binding sites for Pax-5:Ets complexes. Ternary complex assembly requires only the Pax-5 paired box and ETS DNA-binding domains. Mutation of a single base pair in the ternary complex binding site allows for independent binding by Ets proteins but, conversely, inhibits the binding of Pax-5 by itself. Strikingly, the mutation reverses the pattern of complex assembly: Ets proteins recruit Pax-5 to bind the mutated sequence. Recruitment of Net and Elk-1, but not SAP1a, by Pax-5 defines a functional difference between closely related Ets proteins. Replacement of a valine (V68) in the ETS domain of SAP1a by aspartic acid (as found in c-Ets-1, Elk-1, and Net) enhanced ternary complex formation by more than 60-fold. Together, these observations define novel transcription factor interactions that regulate gene expression in B cells.
Fitzsimmons
D
D
Division of Basic Immunology, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
Hodsdon
W
W
Wheat
W
W
Maira
S M
SM
Wasylyk
B
B
Hagman
J
J
D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000235:genetics*; D001402:B-Lymphocytes; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D051925:CD79 Antigens; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000378:metabolism*; D015513:Oncogene Proteins; D051757:PAX5 Transcription Factor; D010957:Plasmids; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014176:Protein Biosynthesis; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000276:immunology / Q000378:metabolism*; D050783:Proto-Oncogene Proteins c-ets; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*; D011995:Recombination, Genetic; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors / Q000276:immunology / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D050807:ets-Domain Protein Elk-1
D015703:Antigens, CD; D051925:CD79 Antigens; C497881:CD79A protein, human; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; C086924:Elk3 protein, mouse; C000715470:MAS1 protein, human; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D011947:Receptors, Antigen, B-Cell; C085981:Sap1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1