A Common Promoter Variant of TBX21 is Associated with Allele Specific Binding to Yin‐Yang 1 and Reduced Gene Expression

Abstract

T‐bet is a key regulator for the lineage commitment in CD4 T helper (Th) 1 cells by activating the hallmark production of interferon‐γ, and its expression level is linked to autoimmune, infectious, and allergic diseases. A T to C base substitution has been identified at position ‐1993 in the TBX21 (encoding T‐bet) promoter and has been associated with asthma and systemic lupus erythematosus. This study aimed to investigate the molecular mechanisms responsible for the influence of the T‐1993C polymorphism on transcription and its functional effect by luciferase reporter, EMSAs, Chromatin immunoprecipitation assay, and flow cytometric analysis of intracellular T‐bet, IFN‐γ and IL‐4 expression in activated CD4+ T cells. The presence of a ‐1993T allele obviously increases promoter activity compared with that of a promoter with a ‐1993C allele. TBX21 promoter carrying ‐1993C allele possesses significantly stronger binding affinity to the Yin Yang 1 (YY1) transcription factor than that carrying ‐1993T allele. YY1 overexpression decreased TBX21 promoter function in a T cell line, demonstrating that this element functions as a repressor. The C to T base exchange relieves the repression mediated by YY1. The individuals carrying ‐1993C allele were determined to have significantly diminished expression of TBX21 and IFN‐γ and increased IL‐4 production in cells compared with the individuals carrying ‐1993T allele (P < 0.05). These findings demonstrate that the TBX21 T‐1993C polymorphism represses TBX21 expression and Th1 cytokine production through control of YY1, which might result in the imbalance between Th1 and Th2 immune responses in autoimmune or allergic diseases.

TBX21-1993T/C (rs4794067) polymorphism is associated with increased risk of chronic periodontitis and increased T-bet expression in periodontal lesions, but does not significantly impact the IFN-g transcriptional level or the pattern of periodontophatic bacterial infection

“…In this aspect our result are in accordance with published evidence. 25,26 However, it is important to notice that despite the strong influence of T allele/genotypes over T-bet expression ( 2 fold), the subsequent impact over IFN-g expression was significantly lower (1.21-fold), and proved statistically non-significant.…”

The role of upstream stimulatory factor 1 in the transcriptional regulation of the human TBX21 promoter mediated by the T-1514C polymorphism associated with systemic lupus erythematosus

“…Jurkat cells (a CD4 + human T lymphoblast cell line) and THP-1 cells (a human monocytic cell line) were cultured as described previously (Li et al 2011). …”

“…The EMSA was performed based on the method described previously (Li et al 2011). Synthesized oligonucleotides, 5′-ATATATTTGTGCATGTGTGCAAAAGAC-3′ (corresponding to −1527/−1501 of the human TBX21 gene with −1514 T) and 5′-ATATATTTGTGCACGTGTGCAAAAGAC-3′ (-1514C), labeled with biotin at the 5′-end were annealed with each complementary oligonucleotide labeled with biotin at the 5′-end.…”

“…The TBX21 gene promoter is polymorphic, and promoter-reporter studies have identified several positive and negative regulatory promoter sequences within the 2-kb region upstream of the transcription start site (Yu et al 2007;Li et al 2011;Shin et al 2009). Three single nucleotide polymorphisms (SNPs) at −1993(C/T), −1514(C/T), −999(G/A) upstream of the transcription start site have been identified (Suttner et al 2009).…”

“…For example, the associations between SNP haplotypes at −1514 and −1993 and SLE (You et al 2010), between T-1993C polymorphism and autoimmune hepatitis , and between T-1514C polymorphism and RA have been reported (Chae et al 2009). We previously analyzed the effect of a T-1993C polymorphism on the function of the TBX21 gene and found that the occurrence of an additional Yin Yang 1 (YY1) motif in the −1993C allele resulted in higher affinity to YY1, which subsequently caused lower transactivation of the promoter (Li et al 2011). The aim of the current study was to investigate the functional significance of T-1514C polymorphism in the TBX21 promoter by observing its association with TBX21 expression and CD4 + T lymphocytes activation in response to ex vivo mitogens stimulation and its direct effect on cis-acting transcriptional regulation of TBX21.…”