FOXP3 interactions with histone acetyltransferase and class II histone deacetylases are required for repression

Abstract

The forkhead family protein FOXP3 acts as a repressor of transcription and is both an essential and sufficient regulator of the development and function of regulatory T cells. The molecular mechanism by which FOXP3-mediated transcriptional repression occurs remains unclear. Here, we report that transcriptional repression by FOXP3 involves a histone acetyltransferase-deacetylase complex that includes histone acetyltransferase TIP60 (Tat-interactive protein, 60 kDa) and class II histone deacetylases HDAC7 and HDAC9. The N-terminal 106 -190 aa of FOXP3 are required for TIP60 -FOXP3, HDAC7-FOXP3 association, as well as for the transcriptional repression of FOXP3 via its forkhead domain. FOXP3 can be acetylated in primary human regulatory T cells, and TIP60 promotes FOXP3 acetylation in vivo. Overexpression of TIP60 but not its histone acetyltransferase-deficient mutant promotes, whereas knockdown of endogenous TIP60 relieved, FOXP3-mediated transcriptional repression. A minimum FOXP3 ensemble containing native TIP60 and HDAC7 is necessary for IL-2 production regulation in T cells. Moreover, FOXP3 association with HDAC9 is antagonized by T cell stimulation and can be restored by the protein deacetylation inhibitor trichostatin A, indicating a complex dynamic aspect of T suppressor cell regulation. These findings identify a previously uncharacterized complex-based mechanism by which FOXP3 actively mediates transcriptional repression.A central theme that has emerged over the last 25 years is that a process of self-regulation of the immune response occurs to limit self-reactivity. Biochemical details of how the immune system distinguishes and regulates self and non-self remain to be fully documented (1). A recently characterized CD4 ϩ CD25 ϩ regulatory T cell subset expresses the Foxp3 transcription factor. As a transcriptional repressor of cytokine gene expression (2), Foxp3 was subsequently identified as an essential and sufficient regulator of natural regulatory T cell development and function (3-5).Mammalian transcriptional repressors can execute their function by either passive or active mechanisms (6, 7). FOXP3 may, for example, function as a passive transcriptional repressor in the case of its association with 9). In this study, we explore the role of FOXP3 as an active transcriptional repressor by revealing the dynamic FOXP3 ensemble formation with a specific histone acetyltransferase (HAT) and certain class II histone deacetylases (HDACs) in expanded human CD4 ϩ CD25 ϩ regulatory T cells (10, 11).Histone acetylation and histone deacetylation affect chromatin remodeling during T cell development and differentiation (12, 13). HAT and HDAC abnormalities have been associated with leukemia (14, 15), diabetes (16) and other diseases of the immune system (17-19). The linkage of HAT and HDAC as components of a single complex permits dynamic responsiveness to extracellular stimulation (18,20). The HAT TIP60 (Tat-interactive protein, 60 kDa), originally isolated as an HIV-1 TAT-interactive protein (21), functions as eith...

Loss of FOXP3 expression in natural human CD4+CD25+ regulatory T cells upon repetitive in vitro stimulation

“…Recently, FOXP3 was shown to directly repress IL-2 as well as IFN-g gene expression after TCR-mediated stimulation by its binding to the promoter/enhancer regions of the respective genes, as part of a FOXP3-histone deacetylase-histone acetyltransferase complex that induces chromatin remodeling through histone deacetylation [31,32]. Any reduction in FOXP3 expression is therefore likely to interfere with correct assembly of such complexes and ultimately leads to loss of their repressive activity [31]. Interestingly, we and others recently identified putative binding sites for several transcription factors, including the transcriptional activator CREB/activating transcription factor (ATF) within the TSDR of the foxp3 locus [18,33].…”

Unravelling the molecular basis for regulatory T‐cell plasticity and loss of function in disease

“…The modifiable mediators of this regulation include methylation,37, 38, 39, 40, 41, 42, 43, 44 acetylation45, 46, 47 and microRNA‐mediated control of transcript translation 28, 48, 49, 50, 51, 52, 53, 54, 55. The global regulation of FOXP3 is influenced by chromatin organises, including SATB1 acts both during development and in mature cells 48, 58.…”

Class IIa histone deacetylases: regulating the regulators

“…During the past few years, class IIa HDACs have been shown to repress an increasing number of transcriptional regulators through direct or indirect interaction. Interestingly, many of these are important regulators of key genetic programs during development, such as members of the GATA (Ozawa et al, 2001;Watamoto et al, 2003), Forkhead (Li et al, 2007), NK-2 homeodomain-containing and signal transducer and activator of transcription (Xiao et al, 2003) families of transcription factors.…”