Cd8 enhancer E8 _I and Runx factors regulate CD8α expression in activated CD8 ⁺ T cells

Abstract

Cd8a and Cd8b1 coreceptor gene (Cd8) expression is tightly controlled during T-cell development by the activity of five Cd8 enhancers (E8 I -E8 V ). Here we demonstrate a unique transcriptional program regulating CD8 expression during CD8 + effector T-cell differentiation. The Cd8 enhancer E8 I and Runx/core-binding factor-β (CBFβ) complexes were required for the establishment of this regulatory circuit, because E8 I -, Runx3-, or CBFβ-deficient CD8 + T cells down-regulated CD8α expression during activation. This finding correlated with enhanced repressive histone marks at the Cd8a promoter in the absence of E8 I , and the down-regulation of CD8α expression could be blocked by treating E8 I -, Runx3-, or CBFβ-deficient CD8 + T cells with the histone deacetylase inhibitor trichostatin A. Moreover, Runx/CBFβ complexes bound the Cd8ab gene cluster in activated CD8 + T cells, suggesting direct control of the Cd8a locus. However, CD8 + effector T cells maintained high levels of CD8α when CBFβ was conditionally deleted after activation. Thus, our data suggest an E8 I -and Runx3/CBFβ-dependent epigenetic programming of the Cd8a locus during T-cell activation, leading to Runx/ CBFβ complex-independent maintenance of CD8α expression in effector T cells.epigenetic marks | transcriptional control | cytotoxic T lymphocytes T he expression of the CD4 and CD8 coreceptors is linked with the functional phenotype of mature T cells. On conventional T cells, CD8 usually consist of CD8α and CD8β heterodimers (encoded by the closely linked Cd8a and Cd8b1 genes, respectively), and the expression of the Cd8 genes during T-cell development is regulated by the activity of at least five different cisregulatory elements (1). The first Cd8 enhancer identified, designated E8 I , is active in mature CD8 single-positive thymocytes and in CD8 + T cells, and in innate-like CD8αα + intraepithelial lymphocyte (IEL) of the gut (2, 3). The generation of E8 I -deficient mice revealed that E8 I is essential for CD8αα expression in γδTCR (T-cell receptor) IEL, while CD8 expression on conventional T cells was not impaired (4, 5). The Cd8 enhancer E8 II directs expression of a reporter transgene in double-positive (DP) thymocytes and CD8 + T cells (4), while E8 II -deficient mice have normal CD8 expression (6). Combined deletion of E8 I and E8 II leads to variegated expression of CD8 in DP thymocytes (6), and subsequent studies showed that CD8 variegation correlates with an epigenetic "off" state (7). A similar variegation phenotype is also observed in mice lacking the Cd8 enhancer E8 V (8). Another enhancer, E8 III , is active in DP thymocytes (4), and combined deletion of E8 II and E8 III resulted in a mild CD8 variegation phenotype in DP thymocytes, but E8 II ,E8 III -deficient mice have normal levels of CD8 on peripheral T cells (9). Taken together, these studies revealed a complex network of cis-regulatory elements, and link Cd8 enhancer functions with chromatin

In Vitro Induction of Regulatory CD4+CD8α+ T Cells by TGF-β, IL-7 and IFN-γ

“…Runx3 is a transcription factor implicated in the expression of CD8α [17], which in CD8α + IEL and activated T cells is dependent on the CD8α enhancer E8 I [18]. To determine whether expression of CD8α in in vitro differentiated CD4 + CD8α + T cells correlates with Runx3 expression, we determined Runx3 mRNA levels.…”

cAMP Responsive Element Modulator (CREM) α Mediates Chromatin Remodeling of CD8 during the Generation of CD3+CD4−CD8− T Cells

“…Interestingly, RUNX3 and the Runx/core binding factor-␤ are necessarily required for CD8 co-receptor expression in activated CD8 ϩ T cells through the recruitment to the E8 I enhancer (31). The absence of E8 I resulted in chromatin remodeling of the entire CD8 cluster with enhanced H3K27me3 and reduced histone H3 acetylation, both reflecting a "closure" of the murine CD8a gene (31). This is of special interest, because E8 I maps to our CNS6 and -7, and is in close proximity to CNS8, all of which undergo CREM␣-instructed epigenetic remodeling in response to TCR activation.…”

Cytotoxic CD4 T Cells: Differentiation, Function, and Application to Dengue Virus Infection

“…Ectopic expression of ThPOK in CD8 T cells results in reduced expression of CD8, the T-box transcription factor eomesodermin (Eomes), as well as effector molecules such as IFN-γ, granzyme B, and perforin, further supporting the notion that ThPOK restricts the initiation of cytotoxic T lymphocyte (CTL) differentiation program in CD4 T cells (51). In contrast, Runx3 promotes CD8 expression by binding its enhancer regions (52, 53) and also cooperates with Eomes and another T-box transcription factor, T-bet, to induce the manufacture of IFN-γ, perforin, and granzyme B (54, 55). Intriguingly, a portion of CD4 T cells downregulates their expression of ThPOK in the intestine, especially in the intraepithelial lymphocyte (IEL) compartment, under unimmunized conditions or following activation with their cognate antigen (24, 25).…”