A CTLA-4 gene polymorphism at position −318 in the promoter region affects the expression of protein

Abstract

Sweden CTLA-4 is an important negative regulator of the immune system. The regulation of the CTLA-4 gene (Ctla-4) transcription is poorly understood. A single nucleotide polymorphism (SNP) at −318 in the Ctla-4 promoter region is associated with certain autoimmune diseases. Since the −318 SNP occurs in a potential regulatory region, it is conceivable that the CЈ T transition may affect the expression of In the present study, we show that the −318T allele is associated with a higher promoter activity than the −318C allele (8.13 ± 0.46 vs 6.87 ± 0.49 CTLA-4 plays an important role in the immune system as a T cell inhibitory factor. This inhibitory signal not only determines whether T cells become activated, but also affects the clonal representation in an immune response. CTLA-4 regulates cell cycle progression rather than directly the induction of apoptosis. 1 CTLA-4 Ig and anti-CTLA-4 have been applied for the treatment of both autoimmune diseases and cancers.Little is known about the regulatory mechanism for CTLA-4 expression. Polymorphisms in the Ctla-4 are associated with several autoimmune diseases, and polymorphisms at certain locations of the Ctla-4 might conceivably affect its expression. We have described a higher prevalence of thymine at position −318 of the Ctla-4 promoter (−318T) in patients with Wegener's granulomatosis. 2 Recently, Ligers and colleagues reported that individuals carrying −318T exhibited significantly increased expression both of cell-surface CTLA-4 in activated cells and of Ctla-4 mRNA in non-stimulated cells, 3 suggesting a potential role for the CЈ T transition in the regulation of expression. In the present study, we examined the effect of CЈ T switch at −318 on the Ctla-4 promoter activity. Our results demonstrated that the −318T allele was associated with a significantly higher promoter activity than the −318C allele. Results and discussionTo determine whether the CЈ T transition at position −318 transcriptionally regulates the Ctla-4 gene expression, we made two Ctla-4 promoter reporter constructs which contained C and T alleles, respectively. As shown in Figure 1, the −318T allele was associated with a higher promoter activity than the −318C allele (8.13 ± 0.46 vs 6.87 ± 0.49). This result was also confirmed in the THP-1 cell line transfected with these two reporter constructs, and stimulated with IFN-␥ (5 mg/ml) and PMA (10 ng/ml).Our allele-specific transcription data indicate that the −318T allele is associated with higher transcriptional activity than the −318C allele. The -318T allele could be considered as protective against autoimmune reactions. Our results could explain the increased expression of CTLA-4 3 and the observed associations of the −318T allele to some diseases. 4 Homozygosity for −318/T in the promoter of Ctla-4 is rarely present in a Caucasian population. [4][5][6][7] In our previous study, the frequencies of individuals with genotypes −318C/C, C/T, and T/T were 86%, 17% and 0%, respectively, in healthy individuals (n = 122) and 69%, 31%, 0%, respective...

Allelic effects on gene regulation at the autoimmunity-predisposing CTLA4 locus: a re-evaluation of the 3′ +6230G>A polymorphism

“…This SNP is the only one of the CTLA4 5 0 -flanking SNPs that is located in a phylogenetically conserved region and its undertransmitted T allele (frequency ¼ 0.09) is predicted to disrupt a response element for TCF1/LEF1, a pair of transcription factors important in lymphocyte development. 7 We found that this genetic effect is independent of the þ 6230 SNP and we confirmed a previous report 8 of increased in vitro transcription of the À318T allele. 9 This transcriptional effect is relevant in vivo as we showed that, in heterozygous subjects, there was increased CTLA4 mRNA transcribed from the T allele, 9 an effect we hypothesized may be mediated by the disruption of the predicted TCF1/LEF1 site.…”

Association of CTLA-4 gene promoter polymorphisms with systemic sclerosis in Iranian population

“…In this regard, an association between CTLA-4 promoter genotypes at position À318 and levels of CTLA-4 molecule has been demonstrated. 25,26 However, the two variants of this SNP were not predicted to be a binding site for homo sapiens transcription factors (http://mbs.cbrc.jp/research/db/TFSEARCH.html). Alternatively, the associations observed here might Association of CTLA-4 gene promoter polymorphisms S Almasi et al be related to linkage disequilibrium between the CTLA-4 alleles at these positions and those of a putative locus for SSc.…”

Evidence for CTLA4 as a susceptibility gene for dilated cardiomyopathy

“…29,30 The human CTLA4 gene is known to contain polymorphisms in three distinct regions: a C4T single-base substitution in the promoter at position À318, an A/G dimorphism in exon 1 at position 49, and a multiallelic dinucleotide repeat in the 3¢ untranslated region. 12,31,32 When we screened the four coding exons and the promoter of the CTLA gene for genetic variability in DCM patients and healthy controls, we confirmed the presence of known SNPs in the promoter and in exon 1. We observed that the allelic distribution of the promoter SNP was not associated with the prevalence of DCM.…”