Background/Purpose:  Recently, accumulating studies have documented that up-regulated cAMP responsive element modulator α (CREMα) which can inhibit IL-2 and induce IL-17A in T cells plays a critical role in the pathogenesis of systemic lupus erythematosus (SLE). The aim of this research is to investigate the mechanisms that regulate CREMα expression in SLE.

Methods:  Histone H3 lysine 4 trimethylation (H3K4me3, a hallmark correlated with transcription activation) amounts at various gene promoters in CD4+ T cells from SLE patients and healthy controls were assayed by chromatin immunoprecipitation (ChIP) microarray. Numbers of H3K4me3, H3K4 methyltransferases SET domain containing 1 (Set1) and mixed-lineage leukemia 1 (MLL1), H3ac and H4ac (both are marks of gene activation), and DNA methyltransferase (DNMT) 3a within the CREMα promoter were measured by ChIP and real-time PCR. DNA methylation (a hallmark of gene silencing) abundance at the CREMα promoter was tested by methylated CpG-DNA immunoprecipitation (MeDIP) and real-time PCR. Levels of CREMα and Set1 mRNA and protein were quantified by real-time RT-PCR and western blotting, respectively. IL-2 and IL-17A productions were detected by enzyme-linked immunosorbent assay (ELISA).

Results:  From the ChIP microarray data, we found sharply increased H3K4me3 amount at the CREMα promoter in SLE CD4+ T cells compared to controls. Then by ChIP and real-time PCR, we confirmed this result. Moreover, H3K4me3 amount at the promoter was positively correlated with CREMα mRNA level in SLE CD4+ T cells. In addition, a striking increase was observed in Set1 enrichment, but no marked change in MLL1 enrichment at the CREMα promoter in SLE CD4+ T cells. We also proved Set1 enrichment was positively correlated with H3K4me3 amount at the CREMα promoter, and positively correlated with CREMα mRNA level in SLE CD4+ T cells. Knocking down Set1 with siRNA in SLE CD4+ T cells decreased Set1 and H3K4me3 enrichments, and elevated the levels of DNMT3a and DNA methylation, while the amounts of H3ac and H4ac didn’t alter greatly at the CREMα promoter. All these inhibited the expression of CREMα, then augmented IL-2 and down-modulated IL-17A productions. Subsequently, we observed that DNMT3a enrichment at the CREMα promoter was down-regulated significantly in SLE CD4+ T cells, and H3K4me3 amount was negatively correlated with both DNA methylation level and DNMT3a enrichment at the CREMα promoter in SLE CD4+ T cells.

Conclusion:  Our findings suggest for the first time that in SLE CD4+ T cells, increased Set1 enrichment up-regulates H3K4me3 amount at the CREMα promoter, which antagonizes DNMT3a and suppresses DNA methylation within this region. All these factors induce CREMα overexpression, consequently result in IL-2 under-expression and IL-17A overproduction, and contribute to the development of SLE at last.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/aberrant-epigenetic-alterations-at-the-promoter-up-regulate-camp-responsive-element-modulator-alpha-in-cd4-t-cells-from-patients-with-systemic-lupus-erythematosus/