IL-6/STAT3 pathway induced deficiency of RFX1 contributes to Th17-dependent autoimmune diseases via epigenetic regulation.

Epigenetic modifications affect the differentiation of T cell subsets and the pathogenesis of autoimmune diseases, but many mechanisms of epigenetic regulation of T cell differentiation are unclear. Here we show reduced expression of the transcription factor RFX1 in CD4+ T cells from patients with systemic lupus erythematosus, which leads to IL-17A overexpression through increased histone H3 acetylation and decreased DNA methylation and H3K9 tri-methylation. Conditional deletion of Rfx1 in mice exacerbates experimental autoimmune encephalomyelitis and pristane-induced lupus-like syndrome and increases induction of Th17 cells. In vitro, Rfx1 deficiency increases the differentiation of naive CD4+ T cells into Th17 cells, but this effect can be reversed by forced expression of Rfx1. Importantly, RFX1 functions downstream of STAT3 and phosphorylated STAT3 can inhibit RFX1 expression, highlighting a non-canonical pathway that regulates differentiation of Th17 cells. Collectively, our findings identify a unique role for RFX1 in Th17-related autoimmune diseases.

Distinct epigenomes in CD4+ T cells of newborns, middle-ages and centenarians.

Age-related variations in genes and microRNAs expression and DNA methylation have been reported respectively; however, their interactions during aging are unclear. We therefore investigated alterations in the transcriptomes, miRNAomes and DNA methylomes in the same CD4+T cells from newborn (NB), middle-aged (MA) and long-lived (LL) individuals to elucidate the molecular changes and their interactions. A total 659 genes showed significantly expression changes across NB, MA and LL individuals, in which we identified four age-related co-expression modules with three hub networks of co-expressed genes and non-coding RNAs. Moreover, we identified 9835 differentially methylated regions (DMRs) including 7015 hypermethylated and 2820 hypomethylated DMRs in the NB compared with the MA, and 12,362 DMRs including 4809 hypermethylated and 7553 hypomethylated DMRs in the MA compared with the LL. The integrated analysis revealed a potential relationship between genes transcription and DNA methylation for many age- or immune-related genes, suggesting that DNA methylation-dependent transcription regulation is involved in development and functions of T cells during aging. Our results reveals age-related transcription and methylation changes and their interactions in human T cells from the cradle to the grave. Longitudinal work is required to establish the relationship between identified age-associated genes/DNA methylation and T cells aging phenotypes.

The role of microRNA-1246 in the regulation of B cell activation and the pathogenesis of systemic lupus erythematosus.

BACKGROUND: The pathogenesis of systemic lupus erythematosus (SLE) has not yet been completely elucidated. One of the hallmarks of SLE is the production of autoantibodies by uncontrolled over-activated B cells. Early B cell factor 1 (EBF1) contributes to the development, activation, and proliferation of B cells through activation of the AKT signaling pathway. Accumulating evidence has demonstrated that several microRNAs (miRNAs) contribute to the pathogenesis of autoimmune diseases through the regulation of B cells in SLE. We aim to investigate the expression patterns of miR-1246 in B cells and its contribution to pathogenesis of SLE. RESULTS: Our results showed that the expression of miR-1246 was significantly decreased in B cells from SLE patients. We verified that miR-1246 specifically targeted the EBF1 messenger RNA (mRNA) by interacting with its 3'-untranslated region (3'-UTR) and regulated the expression of EBF1. Transfection of miR-1246 inhibitors into healthy B cells upregulated the expression of EBF1, enhanced B cell function, and increased the production of B cell surface co-stimulatory molecules CD40, CD80, and CD86. We also observed that abnormal activation of the AKT signaling pathway was associated with decreased P53 expression, leading to the downregulation of the miR-1246 expression; and upregulation of the miR-1246 expression reversed the responsiveness of B cells by inhibiting EBF1 expression. CONCLUSIONS: Activated B cells in lupus could decrease the expression of miR-1246 through the AKT-P53 signaling pathway, which in turn enhances the expression of EBF1, thereby promoting further activation of B cells. Conversely, upregulation of miR-1246 could interrupt this amplification pathway. Our findings thus provide a theoretical framework towards the research of novel biological targets in SLE treatment.

The effect of mycophenolic acid on epigenetic modifications in lupus CD4+T cells.

Systemic lupus erythematosus (SLE) is a complex systemic autoimmune disease involving multiple organs and characterized by overproduction of autoantibodies and T and B cell abnormalities. The treatment for SLE has been restricted to immunosuppressants and corticosteroids. Mycophenolate mofetil (MMF), as a relatively new immunosuppressant, is now widely used in the treatment of SLE patients, particularly those with nephritis. However, it is unclear whether mycophenolic acid (MPA) could modulate the reported disorders of epigenetic status in CD4(+)T cells from SLE patients. In this study, we demonstrated that MPA can upregulate the histone H3/H4 global acetylation status by regulating HATs and HDACs in lupus CD4(+)T cells. Furthermore, we found that MPA also affected the histone H4 acetylation and histone H3K4 tri-methylation levels in CD40L promoter region that inhibited the expression of CD40L. These findings indicate the potential epigenetic mechanism of therapeutic effects of MPA in SLE.

Peripheral whole blood FOXP3 TSDR methylation: a potential marker in severity assessment of autoimmune diseases and chronic infections.

Immune dysregulation is a cardinal feature of autoimmune diseases and chronic microbial infections. In particular, regulatory T cells are downregulated in autoimmune diseases while upregulated in chronic microbial infections. FOXP3 is the master regulator of Treg development. Treg-specific demethylated region (TSDR) is a highly conserved locus on the FOXP3 gene that is fully demethylated in natural Tregs but methylated in effector T cells. In our study, we used high resolution melt-polymerase chain reaction (HRM-PCR) to determine the FOXP3 TSDR methylation status in autoimmune diseases and chronic microbial infections. We found that FOXP3 TSDR to have the highest mean melting temperature (highly methylated) in active SLE patients compared to all the other groups (p < 0.001). The psoriasis group also had a significantly high mean melting temperature (78.62 ± 0.20) when compared with the inactive SLE group (78.49 ± 0.29, p < 0.05) and control group (78.44 ± 0.25, p < 0.01). There was no significant difference in melting temperature between inactive SLE and healthy controls. Disease activity in SLE was directly associated with methylation of the FOXP3 TSDR. On the other hand, patients with chronic microbial infections had significantly lower FOXP3 TSDR mean melting temperature (demethylated) when compared with healthy controls (78.28 ± 0.21 vs 78.44 ± 0.25, p < 0.05). Our results suggest that the use of HRM-PCR to detect FOXP3 TSDR methylation status is a reliable and easy method to predict natural regulatory T cell levels in peripheral blood in different disease conditions. Determining FOXP3 TSDR methylation status can be a useful tool in diagnosis, and monitoring the severity of autoimmune diseases and chronic microbial infections.

Up-regulation of microRNA-210 induces immune dysfunction via targeting FOXP3 in CD4(+) T cells of psoriasis vulgaris.

Psoriasis vulgaris (PV) is a chronic inflammatory and T cell-mediated autoimmune skin disease. An immune dysfunction that is manifested by abnormally activated T cells and defective regulatory T (Treg) cells may play an important role in the pathogenesis of PV. However, the precise mechanism of the immune dysfunction in PV patients still remains unclear. In this study, we found that miR-210 expression is increased significantly in CD4(+) T cells from patients with PV and confirmed that FOXP3 is a target gene of miR-210. We also found that overexpression of miR-210 inhibits FOXP3 expression and impairs the immunosuppressive functions of Treg cells in CD4(+) T cells from healthy controls. In contrast, inhibition of miR-210 increases FOXP3 expression and reverses the immune dysfunction in CD4(+) T cells from patients with PV. Our data demonstrates that increased miR-210 induces immune dysfunction via by FOXP3 in CD4(+) T cells from patients with PV.

A possible role of HMGB1 in DNA demethylation in CD4+ T cells from patients with systemic lupus erythematosus.

The aberrant activity of CD4(+) T cells in patients with systemic lupus erythematosus (SLE) is associated with DNA hypomethylation of the regulatory regions in CD11a and CD70 genes. Our previous studies demonstrated that Gadd45a contributes to the development of SLE by promoting DNA demethylation in CD4(+) T cells. In this study, we identified proteins that bind to Gadd45a in CD4(+) T cells during SLE flare by using the method of co-immunoprecipitation and mass spectrometry, High mobility group box protein 1 (HMGB1) is one of identified proteins. Furthermore, gene and protein expression of HMGB1 was significantly increased in SLE CD4(+) T cells compared to controls, and HMGB1 mRNA was correlated with CD11a and CD70 mRNA. A significant, positive correlation was found between HMGB1 mRNA and SLEDAI for SLE patients. Our data demonstrate that HMGB1 binds to Gadd45a and may be involved in DNA demethylation in CD4(+) T cells during lupus flare.

[DNA methylation status of miR-126 and its host gene EGFL7 in CD4+ T cells from patients with systemic lupus erythematosus].

OBJECTIVE: To explore the mechanisms by which DNA methylation regulates miR-126 and its host gene EGFL7 in CD4+ T cells from patients with systemic lupus erythematosus (SLE). METHODS: We analyzed the expression and the DNA methylation status within promoter region of EGFL7 and miR-126 by real-time qPCR and bisulfite genomic sequencing analysis. RESULTS: miR-126 and EGFL7 mRNA expression was upregulated in CD4+ T cells from SLE compared with that from healthy controls (P<0.01). EGFL7 mRNA level was positively correlated with miR-126 expression in CD4+ T cells from SLE (r=0.538, P=0.015). The average methylation level of EGFL7 promoter in CD4+ T cells from SLE was lower than that from healthy controls (P<0.05). CONCLUSION: The upregulation of miR-126 and its host gene EGFL7 expression in CD4+ T cells from SLE is associated with the hypomethylation of the EGFL7 promoter.

Aberrant histone modification in peripheral blood B cells from patients with systemic sclerosis.

OBJECTIVES: To investigate alterations in histone modifications in B cells and their role in the pathogenesis of systemic sclerosis (SSc). METHODS: Global histone H3/H4 acetylation and H3K4/H3K9 methylation in B cells of SSc were tested by EpiQuik™ assay kits. Related histone modifier enzymes were measured by RT-PCR and Western blot. RESULTS: Global histone H4 hyperacetylation and global histone H3K9 hypomethylation were observed in SSc B cells compared with controls. Expression of JHDM2A was significantly increased but HDAC2, HDAC7, and, SUV39H2 were significantly down-regulated in SSc B cells relative to controls. Global histone H4 acetylation and the expression of HDAC2 were negatively correlated. Global histone H3K9 methylation and the expression of SUV39H2 protein were positively correlated. Global H4 acetylation was positively correlated with disease activity and expression of HDAC2 protein was negatively correlated with skin thickness. CONCLUSIONS: Histone modifications were altered in B cells in SSc correlating with skin thickness and disease activity.

[Construction of special reporter to detect DNA methylation regulatory activity in FCER1G gene promoter through patch-methylation].

OBJECTIVE: To construct a special luciferase reporter to detect DNA methylation regulatory activity in FCER1G gene promoter regulatory element. METHODS: We constructed special full and mock methylated FCER1G gene promoter regulatory luciferase reporters by patch-methylation, and detected DNA methylation regulatory activity by comparing the luciferase activity of full-methylated luciferase reporters with mock-methylated reporters. RESULTS: We successfully constructed the full and mock methylated FCER1G gene promoter regulatory luciferase reporters. The ratio of luciferase activity between the full methylated and the mock methylated was (0.36±0.07):1 (P<0.001). CONCLUSION: FCER1G promoter activity is methylation-sensitive and is regulated by DNA methylation.

Whole-genome DNA methylation in skin lesions from patients with psoriasis vulgaris.

Psoriasis, a chronic inflammatory skin disorder, is characterized by aberrant keratinocyte proliferation and differentiation in the epidermis. Although the pathogenesis of psoriasis is still incompletely understood, both genetic susceptibilities and environmental triggers are known to act as key players in its development. Several studies have suggested that DNA methylation is involved in the pathogenesis of psoriasis. However, the precise mechanisms underlying the regulation and maintenance of the methylome as well as their relationship with this disease remain poorly characterized. Herein, we used methylated DNA immunoprecipitation sequencing (MeDIP-Seq) to characterize whole-genome DNA methylation patterns in involved and uninvolved skin lesions from patients with psoriasis. The results of our MeDIP-Seq analyses identified differentially methylated regions (DMRs) covering almost the entire genome with sufficient depth and high resolution, showing that the number of hypermethylated DMRs was considerably higher than that of hypomethylated DMRs in involved psoriatic skin samples. Moreover, gene ontology analysis of MeDIP-Seq data showed that the aberrantly methylated genes belonged to several different ontological domains, such as the immune system, cell cycle and apoptosis. The results of the bisulfite-sequencing experiments for the genes PDCD5 and TIMP2 confirmed the methylation status identified by MeDIP-Seq, and the mRNA expression levels of these two genes were consistent with their DNA methylation profiles. To our knowledge, the present study constitutes the first report on MeDIP-Seq in psoriasis. The identification of whole-genome DNA methylation patterns associated with psoriasis provides new insight into the pathogenesis of this complex disease and represents a promising avenue through which to investigate novel therapeutic approaches.

Aberrant histone modifications in peripheral blood mononuclear cells from patients with Henoch-Schönlein purpura.

Henoch-Schönlein purpura (HSP), the most common type of leukocytoclastic vasculitis, is caused by T cell-mediated autoimmune reactions. In this study, we analyze histone modification patterns in peripheral blood mononuclear cells (PBMCs) of HSP patients, and investigate the expression levels of inflammatory cytokines (IFN-γ, IL-2, IL-4, IL-6 and IL-13), transcription factors (T-bet, GATA-3 and TIM-1) and chemokines (CXCL4 and CXCL10) in HSP patients. Our results show that histone H3 acetylation and methylation are significantly enhanced in PBMCs from HSP patients. We also demonstrate specifically that marked increases in histone H3 acetylation and H3 lysine 4 trimethylation occur at the IL-4 loci in these patients. In addition, the expression levels of IL-4, IL-6, IL-13, GATA-3, TIM-1 and CXCL4 are also increased. These findings suggest that abnormal histone modifications are present in the PBMCs of patients with HSP, possibly contributing to the activation of pathological immune responses associated with HSP.

E4BP4 overexpression: a protective mechanism in CD4+ T cells from SLE patients.

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease characterized by various immunological abnormalities, including dysregulated activation of T and B lymphocytes, which trigger autoantibody production and immune-complex deposition. E4BP4, also known as NFIL3, has emerged as a major transcription factor that regulates the development and function of immune cells in a number of lineages. E4BP4 has been shown to regulate cytokines expression, and its synthesis is in turn controlled by various cytokines. To date, the roles of E4BP4 in immune dysregulation and autoimmune disorders are unclear. In this study, we demonstrated that E4BP4 expression is increased in CD4(+) T cells isolated from patients with active systemic lupus erythematosus (SLE), especially in patients treated with glucocorticoid (GC). Increased expression of E4BP4 inhibited the activation and self-reactivity of T cells stimulated by anti-CD3/CD28 antibodies. In contrast, the self-reactivity was enhanced in CD4(+) T cells from SLE patients following E4BP4 gene silencing and the production of autoantibody was increased in autologous B cells. We further demonstrated that E4BP4 directly regulated CD40L expression by binding to the promoter region and altering histone acetylation and methylation of the CD40L loci. Taken together, our data provide evidence that E4BP4 can inhibit CD40L expression through epigenetic modifications in the promoter region of CD40L, thus negatively regulating self-reactivity of SLE CD4(+) T cells. Furthermore, our data demonstrate that overexpression of E4BP4 initiates a protective mechanism in SLE CD4(+) T cells, which may be a promising target in the therapy for SLE.

[Effect of total glucosides of peony on expression and DNA methylation status of ITGAL gene in CD4(+) T cells of systemic lupus erythematosus].

OBJECTIVE: To investigate the effect of total glucosides of peony (TGP) on expression and DNA methylation status of ITGAL gene (CD11a) in CD4(+) T cells from patients with systemic lupus erythematosus (SLE). METHODS: CD4(+) T cells were isolated by positive selection using CD4 beads. CD4(+) T cells were treated by TGP at 0, 62.5, 312.5 and 1562.5 mg/L for 48 h. The MTT method was used to assess cell viability; mRNA expression level was measured by realtime-PCR; protein level of CD11a was measured by flow cytometric analysis; DNA methylation status was assayed by bisulfite sequencing. RESULTS: No significant change in cell viability was found in CD4(+) T cells among the different concentration groups (P>0.05). Compared with control, the mRNA and protein levels of ITGAL were down-regulated significantly in SLE CD4(+) T cells treated with TGP (1562.5 mg/L) (P< 0.01). Furthermore, the extent of DNA methylation of ITGAL promoter was increased in TGP (1562.5 mg/L) treated CD4(+) T cells compared with control group (P<0.01). CONCLUSION: TGP can repress CD11a gene expression through enhancing DNA methylation of ITGAL promoter in CD4(+) T cells from patients with SLE. This observation represents a preliminary step in understanding the mechanism of TGP in SLE therapy.

Decreased microRNA-142-3p/5p expression causes CD4+ T cell activation and B cell hyperstimulation in systemic lupus erythematosus.

OBJECTIVE: To examine the role of microRNA-142-3p/5p (miR-142-3p/5p) in the development of autoimmunity in patients with systemic lupus erythematosus (SLE). METHODS: MicroRNA-142-3p/5p expression levels were determined by real-time quantitative polymerase chain reaction, and potential target genes were verified using luciferase reporter gene assays. The effects of miR-142-3p/5p on T cell function were assessed by transfection with miR-142-3p/5p inhibitors or mimics. Histone modifications and methylation levels within a putative regulatory region of the miR-142 locus were detected by chromatin immunoprecipitation assay and bisulfite sequencing, respectively. RESULTS: We confirmed that miR-142-3p and miR-142-5p were significantly down-regulated in SLE CD4+ T cells compared with healthy controls and observed that miR-142-3p/5p levels were inversely correlated with the putative SLE-related targets signaling lymphocytic activation molecule-associated protein (SAP), CD84, and interleukin-10 (IL-10). We demonstrated that miR-142-3p and miR-142-5p directly inhibit SAP, CD84, and IL-10 translation, and that reduced miR-142-3p/5p expression in CD4+ T cells can significantly increase protein levels of these target genes. Furthermore, inhibiting miR-142-3p/5p in healthy donor CD4+ T cells caused T cell overactivation and B cell hyperstimulation, whereas overexpression of miR-142-3p/5p in SLE CD4+ T cells had the opposite effect. We also observed that the decrease in miR-142 expression in SLE CD4+ T cells correlated with changes to histone modifications and DNA methylation levels upstream of the miR-142 precursor sequence. CONCLUSION: The results of this study indicate that reduced expression of miR-142-3p/5p in the CD4+ T cells of patients with SLE causes T cell activity and B cell hyperstimulation.

Total glucosides of paeony induces regulatory CD4(+)CD25(+) T cells by increasing Foxp3 demethylation in lupus CD4(+) T cells.

Total glucosides of paeony (TGP), an active compound extracted from Paeony root, has been used in therapy for autoimmune diseases. However the molecular mechanism of TGP in the prevention of autoimmune response remains unclear. In this study, we found that TGP treatment significantly increased the percentage and number of Treg cells in lupus CD4(+) T cells. Further investigation revealed that treatment with TGP increased the expression of Foxp3 in lupus CD4(+) T cells by down-regulating Foxp3 promoter methylation levels. However, we couldn't observe similar results in healthy control CD4(+) T cells treated by TGP. Moreover, our results also showed that IFN-γ and IL-2 expression was enhanced in TGP-treated lupus CD4(+) T cells. These findings indicate that TGP inhibits autoimmunity in SLE patients possibly by inducing Treg cell differentiation, which may in turn be due to its ability to regulate the methylation status of the Foxp3 promoter and activate IFN-γ and IL-2 signaling.

Inhibited expression of hematopoietic progenitor kinase 1 associated with loss of jumonji domain containing 3 promoter binding contributes to autoimmunity in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by T cell overactivation and B cell hyper-stimulation. Hematopoietic progenitor kinase 1 (HPK1, also called MAP4K1) negatively regulates T cell-mediated immune responses. However, the role of HPK1 and the mechanisms that regulate HPK1 expression in SLE remain poorly understood. Using chromatin immunoprecipitation (ChIP) microarray data, we identified markedly increased histone H3 lysine 27 trimethylation (H3K27me3) enrichment at the HPK1 promoter of SLE CD4+ T cells relative to controls, and confirmed this observation using ChIP and real-time PCR experiments. We further found that HPK1 mRNA and protein levels were significantly decreased in CD4+ T cells of patients with SLE, and that this decrease was not caused by exposure to standard SLE medications. Down-regulating HPK1 in healthy CD4+ T cells significantly accelerated T cell proliferation and production of IFNγ and IgG. Consistent with these findings, overexpressing HPK1 in SLE CD4+ T cells caused a significant decrease in T cell reactivity. In addition, we observed a striking decrease in jumonji domain containing 3 (JMJD3) binding, but no marked change in enhancer of zeste homolog 2 (EZH2) binding, at the HPK1 promoter region in SLE CD4+ T cells compared to healthy controls. SiRNA knock down of JMJD3 in healthy CD4+ T cells led to decreased JMJD3 binding and increased H3K27me3 enrichment at the HPK1 promoter region, thus inhibiting the expression of HPK1. Concordantly, plasmid-induced overexpression of JMJD3 in SLE CD4+ T cells led to increased JMJD3 binding, decreased H3K27me3 enrichment, and up-regulated HPK1 expression. Our results show for the first time that inhibited HPK1 expression in SLE CD4+ T cells is associated with loss of JMJD3 binding and increased H3K27me3 enrichment at the HPK1 promoter, contributing to T cell overactivation and B cell overstimulation in SLE. These findings suggest that HPK1 may serve as a novel target for effective SLE therapy.

Abnormal DNA methylation in CD4+ T cells from people with latent autoimmune diabetes in adults.

Aberrant DNA methylation in T cells has been linked to pathogenesis of autoimmune diseases. To investigate genomic and gene-specific DNA methylation levels in CD4(+) T cells from patients with latent autoimmune diabetes in adults (LADA), and to investigate changes in the expression of genes that regulate methylation as well as the autoimmune-related gene FOXP3 in these patients. Global CD4(+) T cell DNA methylation was measured in 15 LADA patients and 11 healthy controls using a methylation quantification kit. mRNA levels of DNA methytransferases (DNMTs), methyl-DNA binding domain proteins (MBDs) and FOXP3 were measured by real time PCR. Methylation of a FOXP3 regulatory element region was determined by bisulphite genomic sequencing. Genomic DNA methylation in CD4(+) T cells from LADA patients was significantly increased compared to controls. DNMT3b mRNA levels were higher in CD4(+) T cells from LADA patients than in controls. DNMT3b expression positively correlated with global DNA methylation in LADA CD4(+) T cells. FOXP3 expression was decreased, and the FOXP3 promoter region was hypermethylated in CD4(+) T cells from LADA patients compared with controls. DNA methylation levels are altered in CD4(+) T cells from LADA patients, which may contribute to disease onset and progression by affecting the expression of autoimmune-related genes.

RFX1 regulates CD70 and CD11a expression in lupus T cells by recruiting the histone methyltransferase SUV39H1.

INTRODUCTION: 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. 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. METHODS: CD4(+) 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. RESULTS: H3K9 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. CONCLUSIONS: RFX1 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.