Involvement of the Ets family factor PU.1 in the activation of immunoglobulin promoters.
The B cell-specific expression of immunoglobulin (Ig) genes is controlled by the concerted action of variable (V) region promoters and intronic or 3' enhancers, all of which are active in a lymphoid-specific manner. A crucial highly conserved element of the V region promoters is the octamer site -ATTTGCAT-, which can be bound by ubiquitous (Oct-1) as well as B cell-specific (Oct-2) factors. Another less conserved element found in many Ig promoters is pyrimidine-rich and has been shown to be functionally important, in particular for those Ig promoters that have only an imperfect octamer site. In this study we have analyzed the factors binding specifically to the pyrimidine-rich motif of the V kappa 19 promoter, a light chain gene promoter with an imperfect octamer site. Using nuclear extracts prepared from B cells, we detected two sets of specific complexes in electrophoretic mobility shift experiments. One complex appears to be ubiquitous but enriched in lymphoid cells and represents the binding of a potentially novel factor with an apparent molecular mass of approximately 50 kDa. The other complex was found only with extracts from pre-B or B cells as well as from a macrophage cell line and appears to be caused by the binding of PU.1, a factor of the Ets family. We show that on this Ig promoter Oct factors (Oct-1 or Oct-2) and PU.1 can bind concomitantly but without synergism. By transfection experiments in non-B cells we demonstrate that PU.1 is indeed able to activate this promoter in concert with Oct-2. Furthermore, we show that PU.1 can bind with varying affinities to the pyrimidine-rich elements of several other Ig promoters. These data suggest a more general role for PU.1 or other members of the Ets family in the activation of Ig promoters.
Schwarzenbach
H
H
Friedrich Miescher Institute, Basel, Switzerland.
Newell
J W
JW
Matthias
P
P
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051863:Host Cell Factor C1; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; D010618:Phenanthrolines; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011743:Pyrimidines / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; C497693:Hcfc1 protein, mouse; D051863:Host Cell Factor C1; D007147:Immunoglobulin Light Chains; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; D010618:Phenanthrolines; C494166:Pou2f1 protein, mouse; C489206:Pou2f2 protein, mouse; D011743:Pyrimidines; D015682:Retroviridae Proteins, Oncogenic; D014157:Transcription Factors; C062022:v-Spi-1 protein, Friend spleen focus-forming virus; C025205:1,10-phenanthroline