Transcription Factor Ets-2 Acts as a Preinduction Repressor of Interleukin-2 (IL-2) Transcription in Naive T Helper Lymphocytes

Ioannis Panagoulias,Tassos Georgakopoulos,Ioanna Aggeletopoulou,Marios Agelopoulos,Dimitris Thanos,Athanasia Mouzaki

doi:10.1074/jbc.m116.762179

Ioannis Panagoulias, Tassos Georgakopoulos + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m116.762179

Copy DOI

Abstract

IL-2 is the first cytokine produced when naive T helper (Th) cells are activated and differentiate into dividing pre-Th0 proliferating precursors. IL-2 expression is blocked in naive, but not activated or memory, Th cells by the transcription factor Ets-2 that binds to the antigen receptor response element (ARRE)-2 of the proximal IL-2 promoter. Ets-2 acts as an independent preinduction repressor in naive Th cells and does not interact physically with the transcription factor NFAT (nuclear factor of activated T-cells) that binds to the ARRE-2 in activated Th cells. In naive Th cells, Ets-2 mRNA expression, Ets-2 protein levels, and Ets-2 binding to ARRE-2 decrease upon cell activation followed by the concomitant expression of IL-2. Cyclosporine A stabilizes Ets-2 mRNA and protein when the cells are activated. Ets-2 silences directly constitutive or induced IL-2 expression through the ARRE-2. Conversely, Ets-2 silencing allows for constitutive IL-2 expression in unstimulated cells. Ets-2 binding to ARRE-2 in chromatin is stronger in naive compared with activated or memory Th cells; in the latter, Ets-2 participates in a change of the IL-2 promoter architecture, possibly to facilitate a quick response when the cells re-encounter antigen. We propose that Ets-2 expression and protein binding to the ARRE-2 of the IL-2 promoter are part of a strictly regulated process that results in a physiological transition of naive Th cells to Th0 cells upon antigenic stimulation. Malfunction of such a repression mechanism at the molecular level could lead to a disturbance of later events in Th cell plasticity, leading to autoimmune diseases or other pathological conditions.

Highlights

IL-2 is the first cytokine produced when naive T helper (Th) cells are activated and differentiate into dividing pre-Th0 proliferating precursors
Ets-2 mRNA was expressed in Peripheral Blood Mononuclear Cell (PBMC) ex vivo or when cultured in plain culture medium (CM) at similar levels, and its expression was slightly decreased when PBMCs were activated with the mitogens phorbol myristate acetate and ionomycin (P/I) (Fig. 1A, PBMC)
These results strongly suggest that Ets-2 expression is differentially regulated in the various PBMC populations with T-cells showing a negative correlation between Ets-2 and IL-2 expression

Summary

Introduction

IL-2 is the first cytokine produced when naive T helper (Th) cells are activated and differentiate into dividing pre-Th0 proliferating precursors. We propose that Ets-2 expression and protein binding to the ARRE-2 of the IL-2 promoter are part of a strictly regulated process that results in a physiological transition of naive Th cells to Th0 cells upon antigenic stimulation Malfunction of such a repression mechanism at the molecular level could lead to a disturbance of later events in Th cell plasticity, leading to autoimmune diseases or other pathological conditions. IL-2 gene repression occurs at two stages, the preinduction and the postinduction, i.e. when T-cells are in the resting state and after TCR signaling when a feedback inhibition of cell activation takes place to cease the expression of IL-2 gene and terminate T-cell activation [7, 8] These known negative regulators of IL-2 expression act either directly by binding to the IL-2 promoter or indirectly to repress IL-2 transcription [7, 8]. PBMC, peripheral blood mononuclear cell; CM, culture medium; P/I, phorbol myristate acetate and ionomycin; Treg, regulatory T cell; CsA, cyclosporine A; CAT, chloramphenicol acetyltransferase; MM, multiple myeloma; POLII, polymerase II; ␤2-m, ␤2-microglobulin; CB, cord blood; PE, phycoerythrin; qPCR, quantitative PCR; Ab, antibody; ANOVA, analysis of variance; ETS, E26 transformation-specific; DREAM, downstream regulatory element antagonist modulator; ChIP, chromatin immunoprecipitation; OCT, octamer-binding transcription factor; TCEd, distal T-cell element

Objectives

Results

Conclusion