Publication

Regulation of Immunoglobulin Germline ε Transcripts by IL-4, CD40 Ligand and Lipopolysaccharide via Stat6, AP-1 and NF-кB Transcription Factors: A Dissertation

Shen, Ching-Hung
Citations
Altmetric:
Student Authors
Faculty Advisor
Academic Program
Immunology and Virology
Document Type
Doctoral Dissertation
Publication Date
2000-07-01
Subject Area
Embargo Expiration Date
Link to Full Text
Abstract

Induction of germline (GL) ε transcripts, an essential step preceding immunoglobulin (Ig) isotype switching to IgE, requires activation of transcription factors by IL-4 and a B cell activator, e.g. CD40 ligand (CD40L). AP-1 (Fos and Jun), induced transiently by CD40L, binds a DNA element in the mouse GL ε promoter. AP-1 synergizes with Stat6 to activate both the intact GL ε promoter and a minimal heterologous promoter driven by the AP-1 and Stat6 sites of the mouse GL ε promoter. By contrast, C/EBPβ, which transactivates the human GL ε promoter, inhibits IL-4 induction of the mouse promoter, probably by attenuating the synergistic interaction between AP-1 and Stat6. Furthermore, AP-1 does not transactivate the human GL ε promoter. Thus, due to selective binding of either AP-1 or C/EBP proteins, induction of GL ε transcripts in mouse and human may be regulated differently. In addition to AP-1, NF-кB activity is also induced by CD40L stimulation in normal B cells. Using GST pulldown assays and coimmunoprecipitation techniques I show that NF-кB and tyrosine-phosphorylated Stat6 can directly bind each other in vitro and in vivo. When Stat6 and NF-кB proteins are co-expressed in human embryonic kidney 293 (HEK 293) cells, an IL-4-inducible reporter gene containing both cognate binding sites in the promoter is synergistically activated in the presence of IL-4. Furthermore, the same IL-4-inducible reporter gene is also synergistically activated by the endogenous Stat6 and NF-кB proteins in IL-4-stimulated B lymphoma cells I.29μ. Consistently, by using nuclear extracts from transfected HEK 293 cells and from I.29μ B cells in electrophoretic mobility shift assays (EMSAs), I show that Stat6 and NF-кB bind cooperatively to a DNA probe containing both sites, and the presence of a complex formed by their cooperative binding correlates with the synergistic activation of the promoter by Stat6 and NF-кB. I conclude that the direct interaction between Stat6 and NF-кB may provide the basis for synergistic activation of the GL ε promoter. Finally, although mouse GL ε transcripts have a half-life of approximately 100 min, the RNA level continues to increase for up to 24 h and the promoter appears to be active for at least 2 days after B cell activation. These data suggest that induction of AP-1 and NF-кB activities by CD40L, although transient, is required for activation of the mouse GL ε promoter by IL-4-induced Stat6.

Source
Year of Medical School at Time of Visit
Sponsors
Dates of Travel
DOI
PubMed ID
Other Identifiers
Notes

In the process of seeking author's permission to provide full text.

Funding and Acknowledgements
Corresponding Author
Related Resources
Related Resources
Repository Citation
Rights
Copyright is held by the author, with all rights reserved.
Distribution License