A critical control element for interleukin-4 memory expression in T helper lymphocytes

Area of Science:

• Immunology
• Molecular Biology
• Epigenetics

Background:

• Naive T helper (Th) lymphocytes require T cell receptor and IL-4 receptor signaling to express the interleukin-4 (IL-4) gene.
• Preactivated Th lymphocytes can re-express IL-4 independently of IL-4 receptor signaling upon restimulation.
• This memory of IL-4 gene expression is linked to epigenetic modifications and increased GATA-3 transcription factor levels.

Purpose of the Study:

• To identify and characterize a regulatory element involved in the memory of IL-4 gene expression.
• To investigate the role of GATA-3 binding to this element.
• To understand the epigenetic mechanisms governing IL-4 memory.

Main Methods:

• Identification of a conserved intronic regulatory element (CIRE) in the IL-4 gene.
• In vitro and in vivo binding assays for GATA-3 to the CIRE.
• Analysis of DNA demethylation and histone acetylation at the CIRE during Th2 differentiation.
• Gene deletion studies by replacing IL-4 gene regions with GFP.

Main Results:

• A conserved intronic regulatory element with a tandem GATA-3 binding site was identified in the IL-4 gene.
• GATA-3 binds to this element in a sequence- and orientation-dependent manner.
• DNA demethylation and histone acetylation of the CIRE occur early in differentiating Th2 cells.
• Deletion of the CIRE impairs the establishment of IL-4 expression memory, requiring exogenous IL-4 for re-expression.

Conclusions:

• The conserved intronic regulatory element acts as a genetic control element for IL-4 memory expression.
• This element links initial epigenetic modifications of the IL-4 gene locus to GATA-3.
• The CIRE is essential for sustained IL-4 production in memory Th2 cells.