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Updated: Aug 20, 2026

Using an Automated Cell Counter to Simplify Gene Expression Studies: siRNA Knockdown of IL-4 Dependent Gene Expression in Namalwa Cells
Published on: April 14, 2010
Repression of an interleukin-4-responsive promoter requires cooperative BCL-6 function
Miera B Harris1, Justin Mostecki, Paul B Rothman
1Integrated Program in Cellular, Molecular, and Biophysical Sciences and the Departments of Medicine and Microbiology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Abstract:
BCL-6 functions as a potent transcriptional repressor that binds with specificity to DNA elements bearing marked similarity to STAT recognition sequences. Previous studies have demonstrated that BCL-6 and Stat6 can both bind and regulate the Iepsilon promoter that controls immunoglobulin heavy chain class switching to IgE. Examination of BCL-6-/- and BCL-6-/-Stat6-/- mice has demonstrated that BCL-6 is a repressor of IgE and that Stat6 is still required for the interleukin-4 (IL-4) induction of class switching to IgE in B cells lacking BCL-6. To define the mechanisms by which BCL-6 represses IL-4 function, we analyzed the role of BCL-6 in repressing the Iepsilon promoter. There are three BCL-6-binding sites within this IL-4-responsive promoter. Analysis of Iepsilon promoters that have mutated BCL-6-binding sites demonstrates that at least two of these sites are required for maximal BCL-6 repression of this locus. Footprinting analysis demonstrates that BCL-6 binds cooperatively to the two upstream binding sites in the Iepsilon promoter. This cooperative binding requires the POZ domain of BCL-6. Furthermore, activated Stat6 molecules can displace BCL-6 from one of these binding sites. These data demonstrate that cooperative interaction between BCL-6 molecules is required for repression of the Iepsilon promoter.
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