Abstract
IntroductionRegulatory factor X-box 1 (RFX1) can interact with DNA methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1), and RFX1 down-regulation contributes to DNA hypomethylation and histone H3 hyperacetylation at the cluster of differentiation (CD) 11a and CD70 promoters in CD4+ T cells of patients with systemic lupus erythematosus (SLE). This leads to CD11a and CD70 overexpression, thereby triggering autoimmune responses. In order to provide more insight into the epigenetic mechanisms leading to the deregulation of autoimmune-related genes in SLE, we asked whether RFX1 is involved in regulating histone 3 lysine 9 (H3K9) tri-methylation at the CD11a and CD70 promoters in SLE CD4+ T cells.MethodsCD4+ T cell samples were isolated from 15 SLE patients and 15 healthy controls. H3K9 tri-methylation levels were measured by chromatin immunoprecipitation (ChIP) and real-time quantitative PCR. CD4+ T cells were transfected with plasmids using the Human T cell Nucleofector Kit. RFX1 and histone methyltransferase suppressor of variegation 3-9 (Drosophila) homolog 1 (SUV39H1) interaction was determined by co-immunoprecipation (co-IP) and Western blot and immunofluorescence staining. CD11a and CD70 mRNA levels were measured by real-time RT-PCR.ResultsH3K9 tri-methylation levels were significantly reduced within the CD11a and CD70 promoter regions in SLE CD4+ T cells. RFX1 co-immunoprecipitated with SUV39H1 at the CD11a and CD70 promoters in healthy control CD4+ T cells. Overexpressing or knocking-down RFX1 revealed that RFX1 expression correlated with H3K9 tri-methylation levels, as well as CD11a and CD70 expression levels in CD4+ T cells.ConclusionsRFX1 recruits SUV39H1 to the promoter regions of the CD11a and CD70 genes in CD4+ T cells, thereby regulating local H3K9 tri-methylation levels. These findings shed further light on the central role of RFX1 down-regulation in the epigenetic de-repression of auto-immune genes in SLE.
Highlights
Regulatory factor X-box 1 (RFX1) can interact with DNA methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1), and RFX1 down-regulation contributes to DNA hypomethylation and histone H3 hyperacetylation at the cluster of differentiation (CD) 11a and CD70 promoters in CD4+ T cells of patients with systemic lupus erythematosus (SLE)
We demonstrated that RFX1 forms a stable complex with HDAC1 and DNMT1 in the nucleus of CD4+ T cells, and that down-regulating RFX1 in these cells increases histone acetylation and decreases DNA methylation at the CD11a and CD70 promoter regions, epigenetic changes that lead to the de-repression of CD11a and CD70 [10]
chromatin immunoprecipitation (ChIP)-quantitative polymerase chain reaction (qPCR) analysis revealed that the lysine of histone H3 (H3K9) in the promoter regions of CD11a and CD70 are significantly hypomethylated in SLE CD4+ T cells compared with control CD4+ T cells (Figure 1)
Summary
Regulatory factor X-box 1 (RFX1) can interact with DNA methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1), and RFX1 down-regulation contributes to DNA hypomethylation and histone H3 hyperacetylation at the cluster of differentiation (CD) 11a and CD70 promoters in CD4+ T cells of patients with systemic lupus erythematosus (SLE). This leads to CD11a and CD70 overexpression, thereby triggering autoimmune responses. We demonstrated that RFX1 forms a stable complex with HDAC1 and DNMT1 in the nucleus of CD4+ T cells, and that down-regulating RFX1 in these cells increases histone acetylation and decreases DNA methylation at the CD11a and CD70 promoter regions, epigenetic changes that lead to the de-repression of CD11a and CD70 [10]
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