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Interaction and functional interference of C/EBPbeta with octamer factors in immunoglobulin gene transcription

Item Type:Article
Title:Interaction and functional interference of C/EBPbeta with octamer factors in immunoglobulin gene transcription
Creators Name:Hatada, E.N. and Chen-Kiang, S. and Scheidereit, C.
Abstract:The ubiquitous transcription factor C/EBP{beta} functions as an activator or inhibitor depending on the ratios of three isoforms translated from in-frame AUG. We have identified C/EBP binding sites in both light and heavy chain immunoglobulin (Ig) promoters. Of the two C/EBP sites present in the light chain promoter, the upstream site is essential for promoter function. Mutation of this element drastically decreases promoter activity, despite the presence of an intact octamer element. Both light and heavy chain promoters were activated or inhibited by C/EBP{beta} isoforms in transfected cells according to the transactivation ability of these isoforms. Endogenous IgM mRNA and protein were repressed by the inhibitory form, C/EBP{beta}-3, indicating a general role of C/EBP{beta} in the regulation of Ig genes. We show that C/EBP{beta}-3 forms ternary complexes with Oct-1 and Oct-2 on heavy and light chain promoters, and also interacts with both octamer-binding proteins in the absence of DNA. This suggests that interference of Oct-1/Oct-2 function by C/EBP{beta}-3 may account for the observed repression. Inhibition by C/EBP{beta}-3 occurs not only through a C/EBP{beta} site, but also through the octamer element, as shown by co-transfection experiments with heterologous promoter constructs. Thus, C/EBP{beta} regulates Ig promoter transcription by modulating octamer factor activity.
Keywords:C/EBP{beta} Interaction with Oct-1/Oct-2, Essential C/EBP Element, Immunoglobulin Promoter, Transcriptional Activation, Transcriptional Repression
Source:European Journal of Immunology
Page Range:174-184
Date:1 January 2000
Official Publication:https://doi.org/10.1002/1521-4141(200001)30:1<174::AID-IMMU174>3.0.CO;2-T
PubMed:View item in PubMed

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