A novel B cell-derived coactivator potentiates the activation of immunoglobulin promoters by octamer-binding transcription factors.
A novel B cell-restricted activity, required for high levels of octamer/Oct-dependent transcription from an immunoglobulin heavy chain (IgH) promoter, was detected in an in vitro system consisting of HeLa cell-derived extracts complemented with fractionated B cell nuclear proteins. The factor responsible for this activity was designated Oct coactivator from B cells (OCA-B). OCA-B stimulates the transcription from an IgH promoter in conjunction with either Oct-1 or Oct-2 but shows no significant effect on the octamer/Oct-dependent transcription of the ubiquitously expressed histone H2B promoter and the transcription of USF- and Sp1-regulated promoters. Taken together, our results suggest that OCA-B is a tissue-, promoter-, and factor-specific coactivator and that OCA-B may be a major determinant for B cell-specific activation of immunoglobulin promoters. In light of the evidence showing physical and functional interactions between Oct factors and OCA-B, we propose a mechanism of action for OCA-B and discuss the implications of OCA-B for the transcriptional regulation of other tissue-specific promoters.
Luo
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Y
Laboratory of Biochemistry and Moelcular Biology, Rockefeller University, New York, New York 10021.
Fujii
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H
Gerster
T
T
Roeder
R G
RG
D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D051863:Host Cell Factor C1; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics*; D008969:Molecular Sequence Data; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000302:isolation & purification*; D014157:Transcription Factors; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D007136:Immunoglobulins; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; D015534:Trans-Activators; D014157:Transcription Factors